Papers

The Global Ecology and Oceanography of Harmful Algal Blooms (GEOHAB) programme was initiated in 1999 by the Scientific Committee on Oceanic Research (SCOR) and the Intergovernmental Oceanographic Commission (IOC) of UNESCO, to develop a research programme on the ecological and oceanographic mechanisms underlying the population dynamics of harmful algal blooms (HABs). The ultimate goal of this research is to allow the development of observation systems and models that will enable prediction of HABs, thereby reducing their impact on the health of humans and marine organisms, as well as their economic impact on society. The GEOHAB Implementation Plan (GEOHAB, 2003) specifies the formation of Core Research Projects (CRPs) related to four ecosystems types: upwelling systems, fjords and coastal embayments, eutrophic systems and stratified systems. These CRPs are initiated through small, focused open science meetings. The first Open Science Meeting (OSM)—HABs in Upwelling Systems, Lisbon, Portugal, 17–20 November 2003—focused on meso-scale hydrodynamic features (coastal upwelling zones). The second OSM— HABs in Fjords and Coastal Embayments, Viña del Mar, Chile, 26–30 April 2004—dealt with HAB events and their monitoring in semi-enclosed coastal systems, particularly non-eutrophied systems. The third OSM— HABs and Eutrophication, Maryland, USA, 7–10 March 2005—focused on high biomass HABs and their potential link with anthropogenic inputs. The fourth and last OSM—HABs in Stratified Systems, Paris, France, 5–8 December 2005—concentrated on small scale hydrographic features which may be encountered in any of the above mentioned environments. The present report outlines the justification and research priorities for the study of relationships between HABs and stratification, as well as some of the new approaches and advanced instrumentation that may be considered.

Keywords: subduction channel; velocity inversion; fluid overpressure; grain deformation

We use two high-quality pre-stack depth-migrated multichannel seismic profiles acquired to quantify physical properties variations of underthrust sediments along the first ~ 30 km of subduction off the erosional southern Ecuadorian margin. Seismic data show three zones along the subduction channel (referred to as Zones I, II and III) characterized by distinct velocity and velocity-derived physical properties, which are in agreement with values estimated from experimental results of deformation in granular media. These three zones result from transformational changes of underthrust sediments governed by fundamentally different physical processes that control their mechanical behavior at increasing confining pressures. Based on our observations and its comparison with experimental results, we argue that the transformations undergone by underthrust sediments as they dip into the subduction zone are the following: within Zone I, progressively increasing velocity (and decreasing velocity-derived porosity) indicates continuous sediment compaction, which must be accompanied by effective fluid drainage along the décollement and/or across the accretionary wedge. The underthrust material is here unconsolidated from a mechanical point of view. Laboratory experiments indicate that the dominant processes at this range of pressures are grain rolling, particle rotation and frictional slip at grain contacts. Within Zone II, velocity (and porosity) remains constant for ~ 16 km (SIS-72) and ~ 12 km (SIS-18). This suggests undrained conditions resulting in growing fluid overpressure at the subduction channel. Grain deformation is similar to Zone I. Within Zone III, velocity increases and porosity falls rapidly, indicating sediment compaction and subsequent release of over-pressured fluids, where grain deformation is likely to be elastic. This might be the dominant process until the grains attain their crushing strength, resulting in granular cataclasis and, eventually, in the collapse of the system. We suggest that over-pressured fluid release may induce hydrofracturation and it is likely to increase inter-plate coupling down from Zone III.

Keywords: grazing, herbivory, microzooplankton, oligotrophy, primary production, upwelling

Microzooplankton (here defined as <200 µm grazers) are key components of marine foodwebs. Their grazing significantly affects primary producers and usually exceeds that of mesozooplankton. However, our knowledge of the detailed roles that microzooplankton taxa play in marine ecosystems is surprisingly limited. Here, I identify the main protists responsible for most of the grazing impact on phytoplankton in two contrasting marine ecosystems: oligotrophic waters and productive waters, such as upwelling systems, spring blooms, and other blooms in nearshore and estuarine systems. Evidence indicates that pico- and nano-sized flagellates, which are routinely included with the microzooplankton size class of protists, appear to be the main grazers of phytoplankton in oligotrophic habitats, whereas heterotrophic and mixotrophic dinoflagellates are candidates for the dominant grazing impact in upwelling and other productive ecosystems. Microzooplankton are also important contributors to mesozooplankton diet, especially in oligotrophic areas, although the strength of the mesozooplankton–microzooplankton link is traditionally overlooked in plankton studies. As a final remark, this review emphasizes the need to develop suitable methods for studying the role of microbial grazers in the dynamics of marine ecosystems.

Keywords: Size-fractionated dilutions · Microzooplankton · Nanograzers · Microbial grazers · Phytoplankton · NW Mediterranean

Grazing by microzooplankton is typically assessed by dilution experiments of the whole natural community. However, in many ecosystems these experiments actually include not only micrograzers but also nanograzers. We discerned the relevance of micro- and nanograzers under contrasting trophic situations in the coastal NW Mediterranean throughout a seasonal cycle. We measured the grazing upon total, <10 µm, and >10 µm chlorophyll a in 11 standard dilution experiments. We also conducted simultaneous dilution experiments with the <10 µm planktonic community, to assess the potential impact of <10 µm grazers when released of predatory pressure by larger consumers. From September 2005 to May 2006 the microbial grazers consumed less than half of the total phytoplankton production. From June 2006 and for the whole summer period, the grazing on total phytoplankton increased, ranging from 76 to 104% of the primary production consumed per day. On annual average, microbial grazers consumed 56% of the total primary production. Grazing on <10 µm phytoplankton was very variable, from not significant (January and March) to >100% of the primary production consumed daily in July and August (the average impact for the whole study period was 58%). Grazing impact on >10 µm cells was very low, only significant in 5 out of 11 experiments (average impact of 23% of the >10 µm primary production consumed daily, range 23 to 71%). When the entire microbial community was size-fractioned by 10 µm, the potential impact of <10 µm nanograzers was evident for most of the year, although during the spring the differences between the impact on phytoplankton <10 µm measured in these experiments and in standard (unfiltered) dilutions were higher. During the warmer months (July and August) the size distribution of the grazers’ community slightly shifted towards <10 µm organisms (72 to 88% of the biomass of grazers were <10 µm cells). Heterotrophic flagellates stood out as very relevant grazers in this system. In summary, the data suggest that the coastal NW Mediterranean is a system in which microzooplankton (>10 µm organisms) weakly control the primary producers during the cold season (winter and most of the autumn), switch to nano-sized heterotrophic prey during spring, partially suppressing the impact of this group on phytoplankton, and finally are replaced by nanograzers during the warmer months (end of the summer period), heavily impacting the dominant small primary producers.

This work describes the main effects that have to be taken into account to model the sea surface emission at L-band, and the existing approaches to perform the sea surface salinity retrieval from multiangular radiometric measurements. This manuscript reviews the activities carried out in these fields during the past years by the Universitat Polite`cnica de Catalunya (UPC) in collaboration with the Institut de Cie`ncies del Mar (ICM - CSIC). They cover the precise measurement of the dielectric permittivity of the seawater at L-band, the sea surface emissivity (including the effect of wind-driven waves, swell, currents, rain, and oil spills), the comparison of experimental data with numerical models, and the development of sea surface salinity retrieval algorithms for SMOS using multiangular radiometric data. The first salinity retrievals using 2D aperture synthesis radiometry are also presented.

Keywords: Dimethylsulfide (DMS); Dimethylsulfoniopropionate (DMSP); Picophytoplankton; Oceanic eddies; Modelling

The major source of reduced sulfur in the remote marine atmosphere is the biogenic compound dimethylsulfide (DMS), which is ubiquitous in the world's oceans and released through food web interactions. Relevant fluxes and concentrations of DMS, its phytoplankton-produced precursor, dimethylsulfoniopropionate (DMSP) and related parameters were measured during an intensive Lagrangian field study in two mesoscale eddies in the Sargasso Sea during July–August 2004, a period characterized by high mixed-layer DMS and low chlorophyll—the so-called ‘DMS summer paradox’. We used a 1-D vertically variable DMS production model forced with output from a 1-D vertical mixing model to evaluate the extent to which the simulated vertical structure in DMS and DMSP was consistent with changes expected from field-determined rate measurements of individual processes, such as photolysis, microbial DMS and dissolved DMSP turnover, and air–sea gas exchange. Model numerical experiments and related parametric sensitivity analyses suggested that the vertical structure of the DMS profile in the upper 60 m was determined mainly by the interplay of the two depth-variable processes—vertical mixing and photolysis—and less by biological consumption of DMS. A key finding from the model calibration was the need to increase the DMS(P) algal exudation rate constant, which includes the effects of cell rupture due to grazing and cell lysis, to significantly higher values than previously used in other regions. This was consistent with the small algal cell size and therefore high surface area-to-volume ratio of the dominant DMSP-producing group—the picoeukaryotes.

Keywords: Sediment dynamics; Sea level; Seiches; Coastal currents; Modelling; Harbours; Mediterranean Sea

The variability of suspended sediments in a Mediterranean harbour was studied using high-frequency moored instruments. Data analysis revealed that the fundamental mode of oscillation or seiche is the main contribution to the sea level variability and currents. Yet a direct relation between the seiche and suspended sediment was not clear. To study the sediment dynamics, a coupled hydrodynamic-sediment one-dimensional vertical model for sand and non-cohesive mud was implemented. Results showed good agreement between most of the observed and simulated resuspension events. Indeed, the vertical extension and the duration of these events were satisfactorily simulated for mud class. Model simulations were used to determine the time delay between suspended sediment and currents, which improved the correlation between the seiche and suspended sediment to some degree. Scarce events of sediment advection from outside waters and fresh water discharges from land-based sources were identified. It is suggested that phytoplankton species detected in the harbour were responsible for discrepancies between observations and simulations.

Keywords: Bay of Fundy, model simulations, gyre climatology.

The characteristics of a persistent gyre in the mouth of the Bay of Fundy are studied using model simulations. A set of climatological runs are conducted to evaluate the relative importance of the different forcing mechanisms affecting the gyre. The main mechanisms are tidal rectification and density-driven circulation. Stronger circulation of the gyre occurs during the later part of the stratified season (July-August and September-October). The density-driven flow around the gyre is set up by weak tidal mixing in the deep basin in the central Bay of Fundy and strong tidal mixing on the shallow flanks around Grand Manan Island and western Nova Scotia. Spring river discharge has an important influence on near-surface circulation but only a small effect when averaged over the entire water column. Retention of particles in the gyre is controlled by the residual tidal circulation, increased frontal retention during stratified periods, wind stress, and interactions with the adjacent circulation of the Gulf of Maine. Residence times longer than 30 days are predicted for particles released in the proximity of the gyre.

Keywords: Submarine canyon; Gulf of Lions

Previous work in the Gulf of Lions (western Mediterranean Sea) has suggested that significant amounts of sediment escape through the western part of this tectonically passive margin, despite it being far removed from the primary sediment source (the Rhone River, not, vert, similar160 km to the NE). The primary mechanism behind this export is hypothesized to be the interaction of a regional, southwestward sediment-transport path with a canyon deeply incising the southwestern part of the shelf, Cap de Creus Canyon. To understand the pattern of off-shelf sediment export from the western Gulf of Lions, and more specifically, the role of Cap de Creus Canyon in this transport, box cores were collected within the canyon and on the adjacent shelf during five cruises from November 2003 to April 2005. Geochronology (210Pb-derived accumulation rates), grain-size distributions, and sedimentary structures (X-radiography) were analyzed to assess temporal and spatial sedimentation patterns. Results indicate two mid-shelf depocenters (30–90 m water depth) in the northern and southern portions of the study area, separated by a zone of bypassing due to current acceleration around a headland (Cap Bear). Estimates of a sediment budget indicate that not, vert, similar6–8% of the sediment input to the Gulf is sequestered on the shelf region. Within the Cap de Creus Canyon, there is a significant spatial asymmetry in both grain size and accumulation rates. The northern flank is a modern depocenter of fine-grained sediments, while the southern flank is primarily non-depositional for mud and includes locations of apparent erosion. This suggests the influence of multiple oceanographic processes supplying sediment to the canyon: advection of nepheloid layers from the northern rim that provide a relatively continuous sediment supply (over decadal timescales), and episodic strong currents affecting the southern rim, which can scour sediment from the southern flank. The mid-depth thalweg has an ephemeral mud layer, overlying sand and consolidated mud. The mud layer appears to be flushed down canyon periodically. The canyon head contains coarse material, suggesting reworked sands may be entering. The 100-year sediment budget, based on accumulation rates for the fine-grained fraction in the upper canyon, indicates that not, vert, similar1% of the total sediment input to the Gulf is accumulating in upper Cap de Creus Canyon. However, this number may significantly underestimate the total sediment entering the canyon because water-column measurements show that sediment is likely moving through the upper canyon during major dense-water cascading events from the shelf and being deposited deeper in the canyon system. The ephemeral mud layer also indicates rapid deposition and frequent flushing of sediment through the upper canyon. Overall, this study shows that Cap de Creus Canyon is an active conduit of sediment past the shelf break, despite its location distal to the primary sediment source to the Gulf.

Keywords: Suspended sediment transport; Off-shelf export; Submarine canyon; Storm events; Dense shelf water cascading; Resuspension; Gulf of Lions; Cap de Creus

Shelf-to-canyon suspended sediment transport during major storms was studied at the southwestern end of the Gulf of Lions. Waves, near-bottom currents, temperature and water turbidity were measured on the inner shelf at 28-m water depth and in the Cap de Creus submarine canyon head at 300 m depth from November 2003 to March 2004. Two major storm events producing waves Hs>6 m coming from the E–SE sector took place, the first on 3–4 December 2003 (max Hs: 8.4 m) and the second on 20–22 February 2004 (max Hs: 7 m). During these events, shelf water flowed downcanyon producing strong near-bottom currents on the canyon head due to storm-induced downwelling, which was enhanced by dense shelf water cascading in February 2004. These processes generated different pulses of downcanyon suspended sediment transport. During the peak of both storms, the highest waves and the increasing near-bottom currents resuspended sediment on the canyon head and the adjacent outer shelf causing the first downcanyon sediment transport pulses. The December event ended just after these first pulses, when the induced downwelling finished suddenly due to restoration of shelf water stratification. This event was too short to allow the sediment resuspended on the shallow shelf to reach the canyon head. In contrast, the February event, reinforced by dense shelf water cascading, was long enough to transfer resuspended sediment from shallow shelf areas to the canyon head in two different pulses at the end of the event. The downcanyon transport during these last two pulses was one order of magnitude higher than those during the December event and during the first pulses of the February event and accounted for more than half of the total downcanyon sediment transport during the fall 2003 and winter 2004 period. Major storm events, especially during winter vertical mixing periods, produce major episodes of shelf-to-canyon sediment transport at the southwestern end of the Gulf of Lions. Hydrographic structure and storm duration are important factors controlling off-shelf sediment transport during these events.

Keywords: Submarine canyon; anthropogenic trace metals; shelf–slope transfer, marine sediment record; Mediterranean Sea; Barcelona; industrial times contamination

Anthropogenic trace-metal concentrations and inventories were studied on the Llobregat continental margin, from the Llobregat river mouth to the Foix submarine canyon. A prodelta sedimentary depocentre was identified along with a previously known canyon depocentre. Significant upward increases in trace-metal contents were detected in sediment cores of the prodelta and upper part of the canyon (down to 860 m depth). Metal enrichment factors ranged between 1.8 and 10 on the continental shelf and between 1.2 and 2.7 in the submarine canyon. These metal enrichments occurred during the 20th century and can be correlated with the period of maximum increase of population and industrial activities in the Barcelona area and the consequent anthropogenic metal inputs. Maximum trace-metal enrichments are located in the prodelta depocentre and significant enrichments were also measured in the southern prodelta and in the Foix upper canyon as a consequence of efficient shelf–canyon sediment and metal transfer. Deeper in the canyon, at 1370 m depth, no metal enrichments were detected, probably because of particle dispersion and dilution with uncontaminated sediment within the canyon. This study shows that, in some Mediterranean sedimentation systems, anthropogenic trace metal contamination is affecting not only the littoral and the continental shelf, but also the adjacent continental slope sediments through submarine canyons.

Keywords: Alexandrium; ITS; Mediterranean Sea; phylogeny; ribosomal genes; taxonomy

Phylogenetic relationships among the Mediterranean Alexandrium (Dinophyceae) species based on sequences of 5.8S gene and Internal Transcript Spacers of the rRNA operon Authors: Antonella Pennaa; Santiago Fragab; Mercedes Masc; Maria Grazia Giacobbed; Isabel Bravob; Esther Garcsc; Magda Vilac; Elena Bertozzinia; Francesca Andreonie; Antonella Luglif; Cristiano Vernesig Abstract A phylogenetic analysis of the genus Alexandrium, including both the most common and rare species from coastal areas of the Mediterranean Sea was carried out. Nucleotide sequences of 5.8 S gene and Internal Transcribed Spacer regions of the rRNA operon were examined and analysed together with isolates of Alexandrium spp. from elsewhere in the world. These rDNA ribosomal markers were useful in delineating the phylogenetic position of species in the genus, as well as in determining relationships among isolates within each species collected from different localities. Results of phylogeographical analyses within the \'Alexandrium tamarense\' species complex identified three lineages in the Mediterranean Sea: the Mediterranean (ME), Western European (WE) and Temperate Asian (TA) clades. The phylogenetic grouping of the isolates is consistent with the ribotype clades, but not with the morpho-species that constitute the complex. Additional non-toxic isolates were included in the ME clade. The NA (North Atlantic) clade is the fourth group within the \'Alexandrium tamarense\' species complex identified by phylogenetic analyses. Based on its higher genetic diversity and phylogeographical relationships, it can be hypothesized that the NA clade represents the ancestral group of the \'Alexandrium tamarense\' species complex. Alexandrium minutum isolates of the NW Mediterranean clustered with strains from Brittany and Australia. Alexandrium minutum constituted a sister clade of A. tamutum, which is another species strongly associated with the Mediterranean area. Another typical Mediterranean species, A. taylori, was placed as a sister clade of A. pseudogoniaulax by the phylogenetic analysis. Finally, the phylogenetic relationships of some Alexandrium morpho-species that were infrequently observed in the Mediterranean Sea have been resolved.

Keywords: Sardinella aurita · Engraulis encrasicolus · Larvae · Eggs · Microzooplankton · Vertical distribution · NW Mediterranean

In recent years a northward expansion of Sardinella aurita has been reported in the western Mediterranean. Considering the coexistence of its larvae with those of the dominant species Engraulis encrasicolus, the present study was conducted to compare their vertical distributions in 2 areas off the Catalan coast with different vertical environmental conditions. During summer, the water column was stratified with a deep chlorophyll maximum (DCM) beneath the pycnocline. However, the southern area, under the influence of the Ebro River, was characterized by a secondary surface chlorophyll maximum. Vertical distribution of larval food, nauplii and copepodites showed good agreement with the high chlorophyll layers. In the earliest stages of development, larvae of both species remained in the upper levels. From 6 mm standard length on they developed a day/night migratory behaviour to search for food during the day (feeding period). Therefore, in the south, where the abundance of potential food in the upper layers was relatively high, larvae of both species remained in the upper levels during the day. However, in the north, where food was restricted to the DCM, only E. encrasicolus larvae were able to reach these deep levels. The low temperatures (~15°C) detected at the DCM may restrict the vertical migration of S. aurita in accordance with their thermophilic character. This limitation might might represent a restriction for the northward expansion of this species in the western Mediterranean.

During winter 2005–2006, particle fluxes and near‐bottom currents were measured in and around the Lacaze‐Duthiers and Cap de Creus submarine canyons (western Gulf of Lion). Current anomalies show the occurrence of a major dense shelf water cascading event down to the slope, the latest recorded up to date in the area. Concomitant increased total mass fluxes highlight the ability of cascading waters to transport large amounts of coarse sediment and organic matter, which is predominantly of terrestrial origin. In addition, results reveal that the current regime and associated grain size sorting is the responsible for a geochemical gradient of settling organic particles along the slope.

Keywords: Sediment transport; Gulf of Lions; Dense-water cascading; Sediment resuspension; Canyon; Sedimentation

Multiple canyons incise the continental slope at the seaward edge of the continental shelf in the Gulf of Lions and are actively involved in the transfer of sediment from shelf to deep sea. Two canyons in the southwest region of the Gulf of Lions, Lacaze-Duthiers Canyon and Cap de Creus Canyon, were instrumented with bottom-boundary-layer tripods in their heads to evaluate the processes involved in sediment delivery, resuspension and transport. In both canyons, intense cold, dense-water flows carry sediment across the slope. In the Lacaze-Duthiers canyon head (located not, vert, similar35 km from the shoreline), dense-water cascading into the canyon was episodic. Currents were highly variable in the canyon head, and responded to interactions between the along-slope Northern Current and the sharp walls of the canyon. Inertial and other high-frequency fluctuations were associated with suspended-sediment concentrations of not, vert, similar5 mg/l. In Cap de Creus canyon head (located not, vert, similar14 km from the shoreline), downslope currents were higher in magnitude and more persistent than in Lacaze-Duthiers canyon head. Greater suspended-sediment concentrations (peaks up to 20 mg/l) were observed in Cap de Creus Canyon due to resuspension of the canyon seabed during dense-water cascading events. The similarities and contrasts between processes in these two canyon heads emphasize the importance of the interaction of currents with sharp canyon bathymetry. The data also suggest that cold, dense-water flows have more potential to carry sediment to the slope on narrow shelves, and may more efficiently transfer that sediment to the deep sea where a smooth transition between shelf and slope exists.

Multifractal formalism in the microcanonical framework has proved to be a valuable approach to understand and analyze complex signals, typically associated with natural phenomena in scale invariant systems. In this paper, we discuss the multifractal microcanonical formalism in a comprehensive, unified way, including new theoretical proofs and validation tests on real signals, so completing some known gaps in the foundations of this theory. We also review the latest advances and describe the present perspectives in this field. Some technical details on the implementation of involved algorithms and relevant open issues are also discussed

Keywords: Physical oceanography; Streamlines; Singularity analysis; Wavelet analysis; Multifractal; Pattern recognition

In the recent years, the power of employing singularity analysis of scalar variables to perform pattern recognition in complex images has been evidenced. This approach is particularly useful when the image under study corresponds to a scalar variable submitted to a turbulent flow because, in that case, the arrangement of singularity manifolds corresponds to the multifractal hierarchy from the underlying turbulent flow. In this paper we will show how this intimate connection between Image Processing and Physics, when applied to Microwave Sea Surface Temperature images, allows to uncover global circulation patterns in the ocean at a daily basis with the resolution of 1/4 of degree. Using this technique, details not evidenced in the non-processed image are revealed. The emerging patterns provide a description of the global oceanic currents much richer than the usual global circulation scheme; in particular, instabilities, eddy generation and filamentation are distinctly identified. A pattern extraction of this kind is useful in order to measure and track mesoscale oceanic phenomena, opening the way to many operational and reanalysis applications.

Three-dimensional numerical simulations of rotating, statically and inertially stable, mesoscale flows show that wave packets, with vertical velocity comparable to that of the balanced flow, can be spontaneously generated and amplified in the frontal part of translating vortical structures. These frontal wave packets remain stationary relative to the vortical structure (e.g., in the baroclinic dipole, tripole, and quadrupole) and are due to inertia–gravity oscillations, near the inertial frequency, experienced by the fluid particles as they decelerate when leaving the large speed regions. The ratio between the horizontal and vertical wavenumbers depends on the ratio between the horizontal and vertical shears of the background velocity. Theoretical solutions of plane waves with varying wavenumbers in background flow confirm these results. Using the material description of the fields it is shown that, among the particles simultaneously located in the vertical column in the dipole’s center, the first ones to experience the inertia–gravity oscillations are those in the upper layer, in the region of the maximum vertical shear. The wave packet propagates afterward to the fluid particles located below.

The concept of piecewise constant symmetric vortex in the context of threedimensional baroclinic balanced geophysical flows is explored. The pressure gradients generated by horizontal cylinders and spherical balls of uniform potential vorticity (PV), or uniform material invariants, are obtained either analytically or numerically, in the general case of Boussinesq and f -plane dynamics as well as under the quasigeostrophic and semigeostrophic dynamical approximations. Based on the order of magnitude of the different terms in the PV inversion equation, approximated PV equations are deduced. In some of these cases, radial solutions are possible and the interior and exterior solutions are found analytically. In the case of non-radial dependence, exterior solutions can be found numerically. Linear, and upper and lower bound approximations to the full PV inversion equations, and their respective solutions, are also included. However, the general solution for the pressure gradient in the vortex exterior does not have spherical symmetry and remains as an important theoretical challenge. It is suggested that, in order to maintain everywhere the inertial and static stability of the balanced geophysical flows, small balls of finite radius, rather than PV singularities, could become, specially in numerical applications, useful mathematical objects.

Keywords: Late Quaternary; turbidite; sedimentary processes; sedimentary instability; stratigraphy; Galicia Bank

Five main Pleistocene–Holocene lithofacies are defined in three different sedimentary environments (fault scarp, sedimentary lobe and inter-lobe channel) of the SW Galicia Bank: (1) turbidites (biogenous and terrigenous), (2) hemipelagites, (3) pelagites, (4) debrites, and (5) Heinrich sediments. In the sedimentary lobe and inter-lobe channel, the stratigraphic record consists mainly of turbidites interbedded with debrites and Heinrich sediments and hemipelagites that are covered by hemipelagites or pelagites. In the fault scarp, the stratigraphy comprises hemipelagites and turbidites covered by pelagites. Frequency of turbidite events has varied between 1/1.2 ka and 1/3.1 ka, since 31.3 ka BP. At least four turbidite events (1 to 4) between 9.1 and 31.3 ka BP, have been correlated between the different sedimentary environments. The downslope of turbidity flows prevailed until 9.1 ka; after which, vertical settling and slow lateral advection have controlled sedimentation. The source area of turbidites and debrites is the fault scarp. Erosion of the slope near-surface pelagites/hemipelagites and ancient outcropping deposits could explain the presence of biogenous turbidites and terrigenous turbidites respectively. The rhythmic development of turbidites interrupted by hemipelagites could represent the manifestation of different pulses of sedimentary instability induced by a combination of oversteepening (up to 29°) and occurrence of earthquakes.

This work illustrates the great potential of multichannel seismic reflection data to extract information from the finestructure of meddies with exceptional lateral resolution (10–15 m). We present seismic images of three meddies acquired in the Gulf of Cadiz (SW Iberian Peninsula), which consist of concentric reflectors forming oval shapes that sharply contrast with the background oceanic structure.The seismic images reveal the presence of different regions within the meddies that are consistent with those observed in historical temperature (T) and salinity (S) data. The core region, characterized by smooth T and S variations, is weakly reflective. The double-diffusive upper and lower boundaries and the lateral-interleaving outer edges, characterized by stronger T and S contrasts, display strong reflectivity bands. These new observations clearly show differences between layers developed at the upper and lower boundaries that can contribute to the knowledge of mixing processes and layering formation in oceans.

Keywords: Sea surface salinity Sensitivity experiments Regional ocean model Atmospheric forcing Eastern subtropical North-Atlantic

The surface salinity response to changes of various external forcings and model parameters is investigated in a regional 1/3º configuration of the NEMO-OPA model implemented over the eastern North-Atlantic subtropical Ocean. Fourteen realistic climatological simulations are run. By default, neither relaxation to climatological surface salinity nor temperature is included. Forcing fields and parameters expected to impact the surface salinity are modified. These include: the wind stress, the surface temperature, wind speed and relative humidity entering the bulk calculation for sensible and latent heat fluxes,the precipitation, the data specified at open boundaries, the lateral viscosity operator, the salt lateral diffusivity, the vertical mixing scheme, the on/off switch of the double diffusion parameterization, the river runoffs and the SSS/SST restoring terms. The SSS standard deviation over this ensemble of model simulations is of the order of 0.1 psu, which is also the order of the annual cycle of the surface salinity field in this area. In this experimental framework, the wind stress is found to have the largest impact on the model SSS, both in terms of mean field and annual variability. The sensitivity to the precipitation, atmospheric temperature, open boundary external data, and to the relaxation to climatological SSS and SST, is also significant. Of all the model parameterizations, the lateral salt diffusivity is the one associated to the strongest surface salinity model response. This work allows the identification of the main sources of error for model surface salinity. It paves the way for a more comprehensive investigation of SSS model error statistics, which is needed for future data assimilation experiments motivated by the close launch of the new SSS-observing SMOS and Aquarius satellite missions

Keywords: body size, consumer resource, energy transfer, food web, marine, transfer efficiency

Knowledge of relationships between predator size and prey size are needed to describe interactions of species and size classes in food webs. Most estimates of predator and prey sizes have been based on dietary studies and apply to small numbers of species in a relatively narrow size range. These estimates may or may not be representative of values for other groups of species and body sizes or for other locations. Marine predator and prey size data associated with published literature were identified and collated to produce a single data set. If predator or prey length of mass were not measured in the original study, the length or mass was calculated using length–mass relationships. The data set consists of 34931 records from 27 locations covering a wide range of environmental conditions from the tropics to the poles and for 93 types of predator with sizes ranging from 0.1 mg to over 415 kg and 174 prey types with sizes from 75 pg to over 4.5 kg. Each record includes: predator and prey scientific names, common names, taxa, life stages and sizes (length and mass with conversion details), plus the type of feeding interaction, geographic location (with habitat description, latitude, longitude) and mean annual environmental data (sea surface temperature and primary productivity).

Keywords: 16S rRNA gene, Bacteroidetes, Biodiversity, Clone libraries, DGGE, Ecology, Extremophiles, Fingerprinting, Gammaproteobacteria, Hypersaline Salar Salt lake, Tebenquiche

Lake Tebenquiche is one of the largest saline water bodies in the Salar de Atacama at 2,500 m above sea level in northeastern Chile. Bacteria inhabiting there have to deal with extreme changes in salinity, temperature and UV dose (i.e., high environmental dissimilarity in the physical landscape). We analyzed the bacterioplankton structure of this lake by 16S rRNA gene analyses along a spatio–temporal survey. The bacterial assemblage within the lake was quite heterogeneous both in space and time. Salinity changed both in space and time ranging between 1 and 30% (w/v), and total abundances of planktonic prokaryotes in the different sampling points within the lake ranged between two and nine times 106 cells mL−1. Community composition changed accordingly to the particular salinity of each point as depicted by genetic fingerprinting analyses (denaturing gradient gel electrophoresis), showing a high level of variation in species composition from place to place (beta-diversity). Three selected sites were analyzed in more detail by clone libraries. We observed a predominance of Bacteroidetes (about one third of the clones) and Gammaproteobacteria (another third) with respect to all the other bacterial groups. The diversity of Bacteroidetes sequences was large and showed a remarkable degree of novelty. Bacteroidetes formed at least four clusters with no cultured relatives in databases and rather distantly related to any known 16S rRNA sequence. Within this phylum, a rich and diverse presence of Salinibacter relatives was found in the saltiest part of the lake. Lake Tebenquiche included several novel microorganisms of environmental importance and appeared as a large unexplored reservoir of unknown bacteria.

Keywords: remote sensing, radiometry, SMOS, salinity measurements, oceanographic campaigns

In preparation for the European Space Agency SMOS (Soil Moisture and Ocean Salinity) satellite mission, radiometric and oceanographic measurements were performed in December 2000 and January 2001 and in November 2001 from a fixed platform in the NW Mediterranean to improve the modelling of the sea surface emissivity at L-band and new semi-empirical models were derived. Now one of these models has been used to retrieve sea surface salinity from L-band radiometric data acquired with a different instrument and different location. These data were acquired in August 2003 over the continental shelf within the influence of the Rio de la Plata, from Argentina to Brazil, southern Atlantic ocean with the STARRS airborne radiometer. Results show that the radiometer is capable of realistically detecting natural variations in surface salinity even though the model was derived in very different oceanographic conditions and from data collected by a different instrument.

Keywords: Alexandrium catenella · Ammonium · Urea · Interactions · Strain variability

Short-term experiments were carried out to investigate whether interactions between ammonium (NH4+) and urea uptake regulate the total nitrogen assimilation of the toxic dinoflagellate Alexandrium catenella. To test for strain variability, 5 strains of A. catenella from the NW Mediterranean were used: 3 strains from the Thau lagoon (southern France) and 2 strains from the Catalonia basin (Spain). For each strain, the uptake rate of 1 nutrient (NH4+ or urea) at a reference concentration (10 µgatN l–1) was measured as a function of the increasing concentration of the other nutrient (0 to 10 µgatN l–1). Simultaneous N uptake rates of the distinct nitrogen sources were obtained from 15N-NH4+ and 15N-urea incorporation measurements. A strong inhibition of urea uptake by NH4+ (maximum inhibition, Imax > 55%) was observed exclusively for the French strains. No influence of urea on the NH4+-uptake rate was noted for any strain. Estimation of total N uptake rates revealed that the N-urea uptake inhibition was not a competitive disadvantage for A. catenella cells considering that the reduced N-urea uptake was more than compensated for by NH4+ uptake. Furthermore, the computation of composite kinetic parameters from total N uptake data suggested that French strains were more competitive than the Spanish ones in an environment characterized by low NH4+ concentrations (≤5 µgatN l–1) and high urea concentrations (as 10 µgatN l–1). These N uptake characteristics may reflect particular metabolic adaptations by the strains to their respective environment.

Keywords: Alexandrium catenella, ammonium, ammonium release, temporal variability, uptake kinetics, urea

In batch cultures of four Mediterranean strains (from France, Italy, and Spain) of Alexandrium catenella (Whedon et Kof.) Balech growing on a daily light cycle, ammonium and urea uptake were estimated by the 15N tracer technique. Ammonium uptake could be described by Michaelis–Menten kinetics along a substrate gradient of 0.1–10 μgat N · L−1 for the four strains, while two different patterns were observed for urea uptake with Michaelis–Menten kinetics for one strain and linear kinetics for the others. In all cases, an increase in uptake rates with time was noted over the daylight period. This trend led to a net increase in the maximum uptake rate (Vmax; for saturable kinetics) and in the initial slope α. For ammonium, Vmax increased by a factor of 2–10 depending on the strain, and, for urea, the maximal uptake rates measured increased by a factor of 2–18. Temporal variations of half-saturation constants (Ks) for both nutrients did not show a clear trend. Increases in Vmax and α showed an acclimation of the cells’ uptake system over time to a N pulse, which may be explained by the light periodicity. For two strains, extensive ammonium release was observed during urea assimilation. This mechanism removes urea from the medium, so it is no longer available to other potential competitors, but supplies N back to the medium in the form of ammonium. From a methodological point of view, the phenomenon leads to considerable underestimates of the contribution of urea to phytoplankton growth.

Keywords: backscatter; deep-towed sidescan sonar TOBI; swath-bathymetry; high-resolution seismics; coral mounds; South Iberian Margin; Mediterranean Sea

An acoustic study of the Almería Margin (eastern Alboran Sea, SW Mediterranean) was carried out by means of an integrated dataset, comprising deep-towed TOBI sidescan sonar, swath-bathymetry, TOPAS high-resolution seismics and sediment gravity cores. The Almería Margin is a complex system dominated by volcanic and tectonic features shaped by recent sedimentary processes, in which a regional hemipelagic sedimentation is intercalated by sporadic gravitative events. The aim of this work is twofold. The first objective is to recognize the sedimentary and tectonic features that shape the Almeria Margin. The main morpho-sedimentary and morpho-structural elements observed are: the Almería canyon/channel Turbidite System, the Dalías Tributary Valley System, landslides, active faults and folds and volcanic banks. The second aim is to explore and quantify the surface and subsurface seafloor parameters that characterize the backscatter of the study area. Sedimentary, geomorphological and biological elements that play a role in the acoustic signature of the Almería Margin were detected. Nevertheless, it should be noted that seafloor acoustic backscatter is also affected by geometrical and instrumental factors. Despite the wide variability of the environments studied, a low average acoustic backscatter reflects a diffused draping of hemipelagic sedimentation in the area. Higher backscatter values were observed at the top of some volcanic banks, along the Almería canyon, and in the shallower sector of the Dalías tributary valley system. The influence of subseafloor properties in the acoustic signature of the area was revealed by backscatter-grain size correlations, which were carried out for different depth intervals in sediment cores collected in the Almería Turbidite System. A poor relationship was found between backscatter and superficial silty sediments of the area, whereas a higher correlation resulted in the upper 50 cm. The presence of subsurface turbidites in the cores associated with the higher backscatter values suggests volume interface scattering of these sandy layers as a controlling factor of the acoustic signature obtained in the Almería Margin. On the other hand, in rough settings such as the ones observed in the Dalías Tributary Valley System, topographic relief of up to 1–1.5 m strongly interacted with the TOBI acoustic pulse. This suggests that large-scale roughness is an additional parameter that characterizes the acoustic strength of the area. Extremely high reflective patches distributed along some of the volcanic banks (Chella and Pollux Banks) for depths ranging from 230 to 470 m coincide with areas where carbonate cold water coral mounds develop. In the TOBI images, coral facies reach the maximum value of acoustic backscatter, which is probably related to the rough morphology of coral ecosystems. The position of coral mounds in the banks suggests that the occurrence of strong bottom currents and reduced sedimentary inputs are environmental factors that favour their settling and development in the Almería Margin.

Keywords: Inner shelf; Gravel dunes; Sorted bedformsMediterranean Sea; Italy; Marettimo Island

Side scan sonar records, sediment textural characteristics, and in-situ field observations were used to study gravelly and pebbly dunes and sorted bedforms on the inner shelf of Marettimo Island, along the northwestern Sicilian shelf. The dunes are composed of coarse sands, gravels and pebbles (D50: 2–16 mm), displaying a symmetrical shape with a wavelength in the range of 1–2.5 m and a height of 0.15–0.30 m. The bedforms are distributed in a patchy pattern in a depth range of 10–50 m, and are described for the first time on a Mediterranean inner shelf. Sorted bedforms are linear morphological features developed almost perpendicular to the coast in the eastern sector of the island between 15 and 50 m water depth. Bottom shear stresses required for sediment entrainment and the generation of the shallower dunes can be reached during strong storms (Hs=5–6 m; Tp=9–11 s), which are not common in the Mediterranean Sea. However, wave storm events recorded in the study area during the last 17 years are not able to generate the coarsest and deeper dunes, suggesting that the stirring mechanism for dune formation is associated with severe storms that have a recurrence interval of more than 17 years. The long-term stability of the coarse bedforms is supported by the permanence of sorted bedforms without significant morphological changes for long periods (>13 years). Therefore, it is shown that processes forming coarse bedforms can occur in tideless and moderate-energy settings like those of the Mediterranean continental shelves, although the morphological features are probably less dynamic and remain unaltered for longer periods than on higher-energy shelves.

Posidonia oceanica is a widespread coastal Mediterranean seagrass which accumulates in its subsurface large quantities of organic material derived from its roots, rhizomes and leaf sheaths embedded in sandy sediments. These organic deposits may be up to several meters thick as they accumulate over thousands of years forming the matte, whose high content in organic carbon plays a major role in the global ocean carbon cycle. In this study, very high-resolution seismo-acoustic methods were applied to image the subsurface features of a P. oceanica seagrass meadow at Portlligat (Cadaqués, Girona, Spain), in the NW-Mediterranean Sea. Our findings yield fresh insights into the settling of the P. oceanica meadow in the study area, and define with unprecedented detail the potential volume occupied by the matte. A strong reflector, located from 4.3 to 11.7 m depth, was recognized in several seismo-acoustic profiles as the substratum on which P. oceanica first settled in the study area. A 3D bathymetric model of this substratum allowed us to reconstruct the Portlligat palaeo-environment prior to the settling of P. oceanica, which corresponded to a shallow coastal setting protected from the open sea. A core drilled in the meadow at Portlligat revealed the presence of a 6 m thick dense matte composed of medium to coarse sandy sediments mixed with plant debris and bioclasts. Radiocarbon datings revealed a constant accretion rate of the matte of about 1.1 m/kyr. Gravelly bioclastic deposits observed at the base of the core correspond to the base of the matte and gave a date of 5616 ± 46 Cal yr BP. For the first time, very high-resolution marine geophysical techniques allowed us to accurately define the volume occupied by P. oceanica matte, which in the study area reaches up to almost 220,000 ± 17,400 m3. This result is an important step forward in our efforts to estimate the size of the carbon sink represented by P. oceanica meadows along the Mediterranean coasts significantly contributing to the biosphere carbon cycle.

Keywords: eggshell, oocyte, teleost, ZP ultra-structure

The oocyte vitelline envelope (VE) of gilthead seabream is composed of four known zona pellucida (ZP) proteins, ZPBa, ZPBb, ZPC, and ZPX. We have previously shown that the gilthead seabream ZP proteins are differentially transcribed in liver and ovary, with the expression in liver being under estrogenic control. However, although mRNA was found in both liver and ovary, only low ZPBa protein levels were detected in liver and plasma. Using isoform-specific ZP antibodies we show that ZPBa and ZPX translation products are present in the cytosol of stage I and II oocytes. In addition, the zpBa and zpX mRNAs were detected in early developing oocytes. During oocyte growth (vitellogenesis), the VE increased in thickness (>10 µm), and we show that the four ZP isoforms are present in different regions of the VE. ZPX was detected closest to the oocyte plasma membrane while the intermediate region was composed of ZPBa, ZPBb, and ZPC. At the outer layer, only ZPC was detected. When oocytes reach the fully grown stage they resume meiosis and hydration. As the oocyte expands, thinning to 4 µm, the VE acquire a striped and compact appearance at the electron microscopy level. This study provides further evidence for the oocyte origin of some ZP proteins in the gilthead seabream and suggests that the ZP proteins are differentially distributed within the VE.

Keywords: Oceanic phytoplankton Satellite ocean color images Missing data Turbulence cascading Wavelet representation

Oceanic turbulent flows develop complicated patterns, with eddies, filaments and shear currents. Although usually referred as chaotic, their inner organization is strongly hierarchical: turbulent flows develop cascades, which transfer properties such as energy or scalar density from larger to smaller scales. In this work, we present a novel algorithm based on the cascade and able to fill data gaps in satellite images (particularly, chlorophyll concentration maps). The first step is to show that cascade processes for chlorophyll-a concentration images take a simple, explicit form when an appropriate wavelet (here Battle-Lemarié of order 3) representation is used. A reconstruction algorithm exploiting the cascade structure is then given with a detailed description. We discuss the validity and quality of this algorithm when applied to SeaWiFS and MODIS-Aqua ocean color images. An application to merging data from multiple satellite missions is presented together with a demonstration of the benefit of this algorithm over two other merging methods

Fluid distribution in convergent margins is by most accounts closely related to tectonics. This association has been widely studied at accretionary prisms, but at half of the Earth's convergent margins, tectonic erosion grinds down overriding plates, and here fluid distribution and its relation to tectonics remain speculative. Here we present a new conceptual model for the hydrological system of erosional convergent margins. The model is based largely on new data and recently published observations from along the Middle America Trench offshore Nicaragua and Costa Rica, and it is consistent with observations from other erosional margins. The observations indicate that erosional margins possess previously unrecognized distinct hydrogeological systems: Most fluid contained in the sediment pores and liberated by early dehydration reactions drains from the plate boundary through a fractured upper plate to seep at the seafloor across the slope, rather than migrating along the décollement toward the deformation front as described for accretionary prisms. The observations indicate that the relative fluid abundance across the plate‐boundary fault zone and fluid migration influence long‐term tectonics and the transition from aseismic to seismogenic behavior. The segment of the plate boundary where fluid appears to be more abundant corresponds to the locus of long‐term tectonic erosion, where tectonic thinning of the overriding plate causes subsidence and the formation of the continental slope. This correspondence between observations indicates that tectonic erosion is possibly linked to the migration of overpressured fluids into the overriding plate. The presence of overpressured fluids at the plate boundary is compatible with the highest flow rates estimated at slope seeps. The change from aseismic to seismogenic behavior along the plate boundary of the erosional margin begins where the amount of fluid at the fault declines with depth, indicating a control on interplate earthquakes. A previously described similar observation along accreting plate boundaries strongly indicates that fluid abundance exerts a first‐order control on interplate seismogenesis at all types of subduction zones. We hypothesize that fluid depletion with depth increases grain‐to‐grain contact, increasing effective stress on the fault, and modifies fault zone architecture from a thick fault zone to a narrower zone of localized slip.

Dense shelf water cascading in the northwestern Mediterranean Sea during winter 2005, which was shown to cause large erosion in the canyons and to influence deep benthic ecosystem, was investigated using numerical modeling validated with temperature and current observations. Intense dense water formation took place on the Gulf of Lion and Catalan shelves. Dense shelf water was transferred to the deep basin through three pathways. The Cap de Creus canyon in the western Gulf of Lion already identified as a huge pathway was shown to export about 1000 km3 of dense water during two months. The Palamós and Blanes canyons located on the Catalan margin were shown to be important pathways for water formed locally and for water transiting from the Gulf of Lion. After the cascading period, dense shelf water was transported mostly toward the Balearic Sea.

Keywords: Sediment transport; Sediment resuspension; Sediment budget; 3D sediment transport modeling; Continental margins; Northwestern Mediterranean Sea; Gulf of Lions

In situ observations were combined with 3D modeling to gain understanding of and to quantify the suspended sediment transport in the Gulf of Lions (NW Mediterranean Sea). The outputs of a hydrodynamic–sediment transport coupled model were compared to near-bottom current and suspended sediment concentration measurements collected at the head of seven submarine canyons and at a shallow shelf site, over a 6-month period (November 2003–May 2004). The comparisons provide a reasonable validation of the model that reproduces the observed spatial and time variations. The study period was marked by an unusual occurrence of marine storms and high river inputs. The major water and sediment discharges were supplied by the Rhone, the largest Mediterranean river, during an exceptional flood accompanying a severe marine storm in early December 2003. A second major storm, with moderate flooding, occurred in February 2004. The estimate of river input during the studied period was 5.9 Mt. Our study reveals (i) that most of the particulate matter delivered by the Rhone was entrapped on the prodelta, and (ii) that marine storms played a crucial role on the sediment dispersal on the shelf and the off-shelf export. The marine storms occurring in early December 2003 and late February 2004 resuspended a very large amount of shelf sediment (>8 Mt). Erosion was controlled by waves on the inner shelf and by energetic currents on the outer shelf. Sediment deposition took place in the middle part of the shelf, between 50 and 100 m depth. Resuspended sediments and river-borne particles were transported to the southwestern end of the shelf by a cyclonic circulation induced by these onshore winds and exported towards the Catalan shelf and into the Cap de Creus Canyon which incises the slope close to the shore. Export taking place mostly during marine storms was estimated to reach 9.1 Mt during the study period.

Penilia avirostris is a cosmopolitan marine cladoceran that inhabits coastal and shelf waters of most low and mid latitude ecosystems. In this study, we describe the life history and population dynamics of P. avirostris at a fixed coastal station in the NW Mediterranean Sea. This marine cladoceran was very seasonal, having population maxima in summer (2500–3000 ind m–3), and being practically absent from the water column for the rest of the year. The population typically collapsed in late summer–early autumn, and this decline was accompanied by a shift to gametogenetic reproduction, allowing the production of resting eggs to ensure the continuity of the species in the following season. Estimated birth rates of P. avirostris in the Catalan Sea ranged between 0.097 and 0.46 day–1 and seemed to be decoupled from changes in P. avirostris standing stocks. Birth rates were mainly dependent on the changes in abundance of embryo-carrying females and their brood size, because during the period of population plateau the temperature-dependent embryonic developmental time was rather similar (2.3–2.7 days). Neonates are like miniature adults and need a very short period of growth and moulting to reach the reproductive stage. This life-history trait can explain the fast blooming and dominance of plankton communities by P. avirostris under suitable conditions. Finally, the causes for the seasonal decline of P. avirostris populations are also discussed.

Keywords: Macrobenthos - Demersal fish - Antarctica - Disturbance

The long-term benthic disturbance experiment (BENDEX) was started on the eastern Weddell Sea shelf off Austasen (Antarctica) during ‘Polarstern’ cruise ANT XXI/2 in December 2003 to simulate the impact of grounding icebergs on the seabed and follow the steps and timescales of recovery of disturbed benthos and demersal fish communities. Here, we report the basic approach and first results for this experimental field study. By means of 11 densely-placed hauls with a modified bottom trawl, a seabed area of approximately 100 × 1000 m was artificially scoured to inflict a similar damage to the benthic habitats as a grounding iceberg. Before the disturbance event and 11 days after it, the seafloor communities were sampled (invertebrate assemblages by multibox corers, the fish fauna by trawl hauls) and comparatively analyzed. Sediment texture and chemistry was not significantly altered by the heavy disturbance inflicted by repeated trawling, whereas the fauna was negatively affected. Invertebrate benthic biomass was drastically reduced by a factor of 10, while mean abundances were only slightly reduced. Demersal fish biomass and abundance were slightly but not significantly smaller after the disturbance. Effects of disturbance became more evident in the composition of the fish fauna, with Trematomus pennelli and T. hansoni being dominant at disturbed sites, whereas Chionodraco myersi was the dominant species in trawl catches from undisturbed stations.

Keywords: gilthead seabream; SaAqp1a; SaAqp1b; functional expression; salinity; gastrointestinal tract

Aquaporin (AQP)-mediated intestinal water absorption may play a major osmoregulatory role in euryhaline teleosts, although the molecular identity and anatomical distribution of AQPs in the fish gastrointestinal tract is poorly known. Here, we have investigated the functional properties and cellular localization in the intestine of two gilthead seabream (Sparus aurata) homologs of mammalian aquaporin-1 (AQP1), named SaAqp1a and SaAqp1b. Heterologous expression in Xenopus laevis oocytes showed that SaAqp1a and SaAqp1b were water-selective channels. Real-time quantitative RT-PCR and Western blot using specific antisera indicated that abundance of SaAqp1a mRNA and protein was higher in duodenum and hindgut than in the rectum, whereas abundance of SaAqp1b was higher in rectum. In duodenum and hindgut, SaAqp1a localized at the apical brush border and lateral membrane of columnar enterocytes, whereas SaAqp1b was detected occasionally and at very low levels at the apical membrane. In the rectum, however, SaAqp1a was mainly accumulated in the cytoplasm of a subpopulation of enterocytes spread in groups over the surface of the epithelia, including the intervillus pockets, whereas SaAqp1b was detected exclusively at the apical brush border of all rectal enterocytes. Freshwater acclimation reduced the synthesis of SaAqp1a protein in all intestinal segments, but it only reduced SaAqp1b abundance in the rectum. These results show for the first time in teleosts a differential distribution and regulation of two functional AQP1 homologs in the intestinal epithelium, which suggest that they may play specialized functions during water movement across the intestine.

Keywords: Prestige; Heinrich Events; thermohaline circulation; Mn diagenesis; magnetic properties; turbidites

U-channel-based high-resolution magnetic and geochemical measurements supported by scanning electron microscopy, X-ray diffraction and fluorescence, and grain-size analyses of discrete samples were carried out on six sediment cores recovered from the SW flank of the Galicia Bank, at the Prestige's wreck area. Five magnetochemical facies, reflecting the different sedimentary environments (i.e. hemipelagic, contouritic, turbiditic), sediment provenances and early diagenetic redoxomorphic processes (i.e. Mn peaks) are defined on the basis of a cluster analysis. The records showed climatically forced detrital signatures of regional importance, associated with continental slope sedimentary processes. The chronostratigraphy and correlation of the cores is based on 20 14C AMS-dating, recognition of Heinrich like Events H1 to H3 and well-documented Holocene climatic features. From a geochemical and enviromagnetic perspective, the Late Pleistocene to Holocene evolution of the area shows two different sedimentation contexts. MIS 2 is dominated by down-slope depositional processes. The highest sedimentation rates (9.1 cm/ky) were achieved during this interval. The major turbidite activity is recorded between ≈ 31 000 yr BP and ≈ 13 500 yr BP. Successive arrivals of IRD (H1 to H3) are also identified during this period. In contrast, Holocene sedimentation was dominated by a mixture of pelagic, hemipelagic and along-slope depositional processes and presented considerable lower sedimentation rates (3 cm/ky). Bottom-currents intensification at 7000 yr BP and 4500 yr BP coinciding with Late Holocene warm events are also recognised during this stage.

There is now an increased awareness of the importance of polar regions in the Earth system, as well as their vulnerability to anthropogenic derived change, including of course global climate change. This new edition offers a concise but comprehensive introduction to polar ecology and has been thoroughly revised and updated throughout, providing expanded coverage of marine ecosystems and the impact of humans. It incorporates a detailed comparison of the Arctic and Antarctic systems, with a particular emphasis on the effects of climate change, and describes marine, freshwater, glacial, and terrestrial habitats. This breadth of coverage is unique in the polar biology literature. As with other titles in the Biology of Habitats Series , particular emphasis is placed on the organisms that dominate these extreme environments although pollution, conservation and experimental aspects are also considered. This accessible text is suitable for both senior undergraduate and graduate students taking courses in polar ecology, often as part of a wider marine biology degree program. It will also be of value and use to the many professional ecologists and conservation biologists requiring a concise overview of the topic.

Bacterivory was determined in surface waters of Franklin Bay, western Arctic, over a seasonal ice-covered period (winter–spring, 2003–2004). The objectives were to obtain information on the functioning of the microbial food web under the ice, during winter (from 21 December 2003 to 21 March 2004) and during spring (from 22 March 2004 to 29 May 2004), and to test whether bacterial losses would increase after the increase in bacterial production following the spring phytoplankton bloom. Chl a concentrations ranged from 0.04 to 0.36 µg L-1, increasing in March and reaching a peak in April. Bacterial biomass showed no consistent trend for the whole period, and protist biomass followed a pattern similar to that of Chl a. Bacterial production increased 1 week after Chl a concentrations started to increase, while bacterivory rates increased very slightly. Average bacterivory rates in winter (0.16 ± 0.07 µg C L-1 d-1) were not significantly different from those in spring (0.29 ± 0.24 µg C L-1 d-1). Average bacterial production, on the other hand, was similar to bacterivory rates in winter (0.19 ± 0.38 µg C L-1 d-1), but higher than bacterivory in spring (0.93 ± 0.28 µg C L-1 d-1). Therefore, bacterial production was controlled by grazers during winter and by substrate concentration in spring.

Keywords: flatfishes, mathematical modelling, morphometry, saccular otolith

A dimensionless measure of otolith mass asymmetry, χ, was calculated as the difference between the masses of the right and left paired otoliths divided by average otolith mass. Saccular otolith mass asymmetry was studied in eight flatfish species (110 otolith pairs) and compared with data from a previously published study on roundfishes. As in the case of symmetrical fishes, the absolute value of χin flatfishes does not depend on fish length and otolith growth rate, although otolith mass and the absolute value of otolith mass difference are correlated with fish length. The values of χwere between −0·2 and +0·2 in 96·4% of flatfishes studied. The mean ±s.e. value of χin flatfishes was significantly larger than in standard bilaterally symmetrical marine fishes (‘roundfishes’), respectively 0·070 ± 0·006 and 0·040 ± 0·006. The most prominent distinction is the existence of downside prevalence of saccular otolith mass in flatfishes, which contrasts with no right–left prevalence in roundfishes found in a previous study. In the right-eyed flatfishes (Soleidae), the left saccular otoliths are heavier than the right otoliths. In the left-eyed flatfishes (Bothidae and Citharidae), the right saccular otoliths are heavier than the left otoliths. Not all flatfishes, however, fit in this design: 11·8% of flatfishes studied had the heavier saccular otoliths in the upside labyrinth and 5·4% of flatfishes had no otolith mass asymmetry (within the accuracy of the analysis). At the same time, the more mobile flatfishes (bothids and citharids) have more symmetrical and, hence, more precisely organized saccular otolith organs than the bottom-associated flatfishes (soleids). It is possible to assume that the value of the otolith asymmetry is not only correlated with flatfish placement in a particular family, or position of eyes, but also may correlate with general aspects of their ecology. Mathematical modelling indicated that for most flatfishes one-side saccular prevalence had no substantial significance for sound processing. On the other hand, calculations showed that 49% of flatfishes (but only 14·5% of roundfishes) have |χ| which exceed the critical level and, in principle, could sense the difference between the static displacement of the large and small paired otoliths. At that, the number of the soleids that could sense this difference is greater than the number of the bothids and citharids, 84 and 27%, respectively.

Keywords: Pandalid shrimps · Diet · Reproduction · Seasonality · Environmental variables · Benthopelagic fauna · Stable isotope analysis

The feeding habits of the 2 Plesionika species occurring around the Balearic Islands (western Mediterranean) were examined. Samples were taken with a bottom trawl from depths between 247 and 752 m from August 2003 to June 2004 at 2 sites (Cabrera and Sóller) off the island of Mallorca. Both species preferentially exploited mesopelagic resources but the shallower living P. heterocarpus, which inhabits the shelf-slope break, also consumed benthic organisms (e.g. polychaetes, bivalves, tanaids). Spatio-temporal changes were evident in the diet of the 2 pandalids. In P. heterocarpus, 2 seasonal groups were revealed by nMDS analysis, one summer–autumn, the other winter–spring. Differences in prey consumption were observed between Cabrera and Sóller samples, with a temporal shift in the dominance of some prey between the 2 areas. The diet of P. heterocarpus was significantly correlated with geographical (e.g. latitude, depth), chemico-physical variables (mainly those related to sediment characteristics) and biological features (e.g. maturity stages, sex) of the species. Correlation between percentage of mature females and caloric content of prey in the stomach did not show any clear seasonal pattern; also trophic level did not change throughout the year (δ15N = 7.87‰ ± 0.17). Temporal changes in diet composition were stronger in the deeper pandalid P. martia and strictly related to its reproductive pattern. Three groups were revealed by multivariate analysis: (1) a summer group (August and September samples), (2) an autumn–winter group (November and February), characterized by high predation on gelatinous plankton, salps, hyperiids and pelagic molluscs and (3) a spring group, in which predation was directed to higher energy prey such as euphausiids and decapods. The higher percentage of mature females observed in spring was correlated with the increase in energy requirements in the pre-spawning period. Stable isotope analysis revealed a stronger seasonality for P. martia than for P. heterocarpus. An abrupt decrease in trophic level (δ15N) and an analogous enrichment in δ13C values were observed in February. This trend may be related to various factors, among others a higher consumption of refractory material (e.g. marine snow) in winter, when mesopelagic resources are scarcer, changes in the whole zooplanktonic and suprabenthic communities due to phytodetritus input of low δ15N /high δ13C values, and possible reproductive migration to deeper waters.

Very few studies have analysed the niches of pelagic protist in details. This is because for most protists, both an accurate species definition and methods for routine detection and quantification of cells are lacking. The morphospecies Micromonas pusilla, a marine unicellular green alga, is the most ubiquitous and cosmopolitan picoeukaryote described to date. This species comprises several independent genetic lineages or clades, which are not currently distinguishable based on comparison of their morphology or biogeographical distribution. Molecular probes were used to detect and quantify the genetic clades of M. pusilla in samples from temperate, polar and tropical environments in order to assess potential ecological niche partitioning. The three clades were detected in all biogeographical regions studied and were commonly found in sympatry. Cell abundances recorded for clades A and B were high, especially at coastal stations. Clade C, when detected, was always at low abundances and is suggested to be a low-light clade. Shifts in the contribution of clades to total M. pusilla abundance were observed along environmental gradients, both at local and basin-wide scales. This suggests that the phylogenetic clades occupy specific niches and confirms the existence of cryptic species within the morphospecies M. pusilla. Parameters which can precisely explain the distribution of these cryptic species remain to be elucidated.

Keywords: Alexandrium fundyense; Harmful algal blooms; Hemocyte; Histopathology; Immunology; Mytilus edulis

Mussels (Mytilus edulis) were exposed to cultures of the toxic dinoflagellate Alexandrium fundyense or the non-toxic alga Rhodomonas sp. to evaluate the effects of the harmful alga on the mussels and to study recovery after discontinuation of the A. fundyense exposure. Mussels were exposed for 9 days to the different algae and then all were fed Rhodomonas sp. for 6 more days. Samples of hemolymph for hemocyte analyses and tissues for histology were collected before the exposure and periodically during exposure and recovery periods. Mussels filtered and ingested both microalgal cultures, producing fecal pellets containing degraded, partially degraded, and intact cells of both algae. Mussels exposed to A. fundyense had an inflammatory response consisting of degranulation and diapedesis of hemocytes into the alimentary canal and, as the exposure continued, hemocyte migration into the connective tissue between the gonadal follicles. Evidence of lipid peroxidation, similar to the detoxification pathway described for various xenobiotics, was found; insoluble lipofuchsin granules formed (ceroidosis), and hemocytes carried the granules to the alimentary canal, thus eliminating putative dinoflagellate toxins in feces. As the number of circulating hemocytes in A. fundyense-exposed mussels became depleted, mussels were immunocompromised, and pathological changes followed, i.e., increased prevalences of ceroidosis and trematodes after 9 days of exposure. Moreover, the total number of pathological changes increased from the beginning of the exposure until the last day (day 9). After 6 days of the exposure, mussels in one of the three tanks exposed to A. fundyense mass spawned; these mussels showed more severe effects of the toxic algae than non-spawning mussels exposed to A. fundyense. No significant differences were found between the two treatments during the recovery period, indicating rapid homeostatic processes in tissues and circulating hemocytes.

Hydrodynamics and sediment resuspension events, induced at the shoreline by a deep-draft vessel passing nearby, are described. Measurements (pressure, currents and turbidity) were obtained at 4 Hz, on a lower beach ~50 m from a channel where large car ferries operate in Wootton Creek, Isle of Wight. The study focuses on a representative 8-min 32-s-long record, during which two large vessels passed the channel section. At the shore, the passage of each vessel induced a long-period water-level drawdown, followed by a water-level oscillation (seiche) of similar period, and the short-period waves of the wake. Both drawdowns were the main constituents of the prevailing wave pattern. The second drawdown was the largest in amplitude, in response to a higher speed of the ferry, and the influence of the seiche which had been activated during the preceding event. Two successive peaks of turbidity were observed shortly after this drawdown. Analyses of current velocity and direction indicate that the sediments resuspended originated from the shallower upper beach. Anthropogenically induced erosion of the foreshore is predicted at Wootton Creek.

Keywords: geomorphology; Galicia margin; Galicia Bank; half-graben structure; slope apron; mass-movements

Morphological analysis was carried out on the SW flank of the Galicia Bank, as part of detailed geological studies of the half-graben where the Prestige oil tanker wreckage is located. Broad multibeam echosounder (SIMRAD EM-12S-120) and seismic reflection (Airgun) data were collected on board RV Hespérides. Three groups of morphological features were identified as: tectonic, erosive and depositional. The main tectonic morphological feature is a N–S oriented fault scarp in the eastern part of the study area. Main erosive features are: gullies, slide scars, E–W oriented inter-lobe channels and a NNE–SSW oriented Main Channel. Dominant depositional morphologies comprise: thirteen E–W oriented sedimentary wedges, seven large E–W to NE–SW oriented sedimentary lobes, and the relatively smooth sedimentary layer covering the eastern and western ridges that comprise the Galicia Bank's SW flank. Characterization, classification and distribution of these features indicate that the study area constitutes a half-graben structure comprising a N–S oriented normal fault scarp abruptly connecting steep gradients in the eastern area with the gentle slope of the central area. A thick but narrow wedge of sediment has accumulated at the foot of the scarp as a result of mass-movement processes that govern the formation of a series of short-lived wedges, overlapping lobes and also channels. This particular kind of slope apron system corresponds to a tectonic-controlled drainage pattern from a sharply tilted, hanging wall block, supplied by sediment from the ridge. Finally we can conclude that the Prestige stern and bow are located at the steep fault scarp, close to a channel head, and at the axis of inter-lobe channels developed by mass-movement processes. Thus, morphologic, tectonic and sedimentary factors can be considered as potential hazards.

The present study analyses for the first time the diet of larvae of the clupeid Sardinella aurita in the NW Mediterranean. Gut contents of larvae from first feeding (3.9 mm) to early postflexion stages (14.7 mm) were analysed. The type and abundance of ingested prey were related to the plankton composition in the environment in order to determine prey-type selectivity. The feeding incidence observed was among the highest reported for clupeid larvae, with higher values during the day (68.6%) than at night (7.7%), indicating that Sardinella aurita larvae are diurnal predators. The mean number of ingested prey was 3.3 (±2.51). The width of the prey increased from <30 to 410 µm with the development of the larvae, but the niche breadth did not vary with the size of the larvae. The diet was based on different stages of copepods (nauplii and postnauplii) and cladocerans (mainly Evadne spp.), though the preference for each type of prey varied, with higher preference for copepod nauplii in larvae <8 mm and a higher preference for Evadne spp. in larvae ≥8 mm. The copepod based diet of S. aurita larvae is very similar to that reported for Engraulis encrasicolus larvae in the Mediterranean, indicating a possible competition for food between the first-feeding larvae in situations of low prey abundance.

Keywords: Bullet tuna larvae · Feeding ecology · Prey selection · Ontogeny · Vision · NW Mediterranean

The bullet tuna Auxis rochei, Risso 1810, is a small tuna widely distributed in tropical and temperate seas. The present study reports on the first attempt to jointly monitor diet and food selection in larvae of this species and to assess the influence of the ontogenetic development of feeding-related organs on the diet. A. rochei larvae from 2 to 7 mm long are diurnal feeders and highly active predators, with high values of feeding incidence, gut fullness and number of ingested prey items. The rate of change in prey item size in relation to larval size was higher than in other species. Only small, non-motile prey items are eaten at the onset of feeding. Rapid mouth development and the early appearance of teeth allow larvae from 3 to 5 mm long to ingest a wide range of prey. However, niche breadth decreases at 5 mm, when larvae avoid small prey items in favour of larger ones with a higher carbon content. Chesson’s selectivity index indicated that small larvae (from 2 to 3 mm long) selected a variety of small prey items, mainly copepod nauplii. Larvae measuring 3 to 5 mm selectively ate cladocerans and appendicularians, and larvae with lengths ≥5 mm preferred appendicularians and fish larvae. Precocious body development (mouth, teeth, and onset of stomach and caudal fin development) and improved visual acuity (larger lens diameter and angular cone density) are factors that contribute to the feeding success of larvae of this species.

Carbon fixation was analyzed in a series of stratified lakes with oxygen–sulfide interfaces following 14C- bicarbonate incorporation into oxygenic phototrophic, anoxygenic phototrophic (photosynthetic sulfur bacteria; PSB), and chemolithoautotrophic guilds (dark fixation processes), respectively. One of the lakes (Lake Ciso ́ , Banyoles) was studied in more detail using microautoradiography of 14C-labeled cells and microscopic observations during day and night. Dark carbon fixation was high for many of the depths sampled in all the lakes studied and there was a correspondence between carbon (C) fixation in the dark and abundance of photosynthetic purple sulfur bacteria (PSB). After in-situ dark incubations, microautoradiographies revealed labeled cells actively incorporating inorganic carbon belonging to both unidentified rod bacteria but also to PSB (Amoebobacter sp. and Thiocystis sp.). The concentration of labeled rod bacteria was very similar in light and dark incubations, as well as in day and night samplings, and had a tendency to increase in the anoxic dark hipolimnion. Surprisingly, PSB consistently incorporated inorganic carbon in dark incubations at high rates during the day but much less at night. This suggests that photosynthetic organisms are capable of substantial dark C fixation after being subjected to light, and that ‘‘light dependent’’ dark carbon-fixation activity is an issue that has to be carefully addressed in future experiments.

Keywords: Shoreface nourishment; Subtidal sandbars; Shoreline position; Video imagery; Bar switching

The response to a shoreface nourishment of the two-bar system at Noordwijk (the Netherlands) is analyzed based on a daily data set of time-exposure video images collected during about 6 years, complemented with topographic and bathymetric surveys. The 1.7 Mm3 nourishment, implemented as a 3 km alongshore bump seaward of the outer bar, migrated more than 300 m onshore in 4 years before losing its integrity. Furthermore, the nourishment interrupted the autonomous seaward migration of both bars for the entire duration of the study period and, allaying earlier fears, did not intensify the three-dimensional patterns in the bars, such as the crescentic plan-shape and rip channels. The nourishment did result in clear head effects on both flanks, with the bar becoming discontinuous and the flank section decaying or becoming attached to an offshore-located bar, while the section of bar landward of the nourishment became attached to a landward-located bar. This sequence of morphologies is known as bar switching. Each switching episode took almost one year to complete and can therefore not be ascribed to individual wave events. We suspect that shoreface nourishments enhance the possibility of bar switching by creating alongshore variability in the position and depth of the outer bar and in its cross-shore migration rate and direction. The Noordwijk nourishment did not influence the shoreline position as its trend did not undergo distinctive variations after 1998. Differences in the response of the Noordwijk sandbars to the shoreface nourishment compared with other Dutch nourishments are attributed to the location and size (volume per unit length) of the nourishment with respect to the sandbars and to the median grain size of the nourished material.

Keywords: beach rotation; nourishment; shoreline position; video imaging

Artificially embayed beaches are an increasingly common environment in retreating and urban coasts. The study of embayed beaches usually focuses on the concept of some equilibrium configuration of the shoreline caused by the wave approach and the location of protection structures, but detailed studies of their shoreline dynamics are scarce. The study reported herein monitored the shoreline dynamics of three artificial embayed beaches in Barcelona City during a three-year period using an Argus video system to examine the behaviour of the emerged beach in order to assess the main factors affecting the shoreline, and to analyze the processes causing beach rotation at different time-scales. The length and degree of protection of the three beaches were different and so were their morphological behaviours. Two of the beaches presented a general retreating trend with rapid/abrupt displacements of the shoreline caused by oblique wave incidence during storm events and to the effects of beach nourishment. After nourishment, slower changes at the beaches determined beach evolution which was also influenced by the formation of long-lasting megacusps. The third beach, the most protected one, showed an accretionary trend, no formation of megacusps and episodes of beach rotation related to the gradual recovery of the beach after storm events. It is concluded that factors controlling the evolution of Barcelona City beaches are associated with both natural processes and man-induced actions, resulting in a more complex pattern than would be expected for small embayed beaches. Beach rotation appears as a key process for understanding the morphodynamics of embayed beaches. It occurs as a fast response to storms but also as a medium-term adaptation of the shoreline configuration to morphological changes in the beach or to the recovery of a more stable orientation after storm events and man-made changes in the beach orientation resulting from nourishment or sand relocation.

The spontaneous generation and propagation of short-scale inertia–gravity waves (IGWs) during the merging of two initially balanced (void of IGWs) baroclinic anticyclones is numerically investigated. The IGW generation is analyzed in flows with different potential vorticity (PV) anomaly, numerical diffusion, numerical resolution, vortex aspect ratio, and background rotation. The vertical velocity and its vertical derivative are used to identify the IGWs in the total flow, while the unbalanced flow (the waves) is diagnosed using the optimal PV balance approach. Spontaneous generation of IGWs occurs in all the cases, primarily as emissions of discrete wave packets. The increase of both the vortex strength and vortex extent isotropy enhances the IGW emission. Three possible indicators, or theories, of spontaneous IGW generation are considered, namely, the advection of PV, the material rate of change of the horizontal divergence, and the three-dimensional baroclinic IGW generation analogy of Lighthill sound radiation theory. It is suggested that different mechanisms for spontaneous IGW generation may be at work. One mechanism is related to the advection of PV, with the IGWs in this case having wave fronts similar to the PV isosurfaces in the upper layers, and helical patterns in the deep layers. Trapped IGWs are ubiquitous in the vortex interior and have annular wave front patterns. Another mechanism is related to the spatially coherent motion of preexisting IGWs, which eventually cooperate to produce mean flow, in particular larger-scale horizontal divergence, and therefore larger-scale vertical motion, which in turns triggers the emission of new IGWs.

We used mesocosm experiments to study the bacterioplankton community in a highly dynamic coastal ecosystem during four contrasting periods of the seasonal cycle: winter mixing, spring phytoplankton bloom, summer stratification and autumn upwelling. A correlation approach was used in order to measure the degree of coupling between the dynamics of major bacterial groups, heterotrophic carbon cycling and environmental factors. We used catalysed reporter deposition-fluorescence in situ hybridization to follow changes in the relative abundance of the most abundant groups of bacteria (Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes). Bacterial carbon flux-related variables included bacterial standing stock, bacterial production and microbial respiration. The environmental factors included both, biotic variables such as chlorophyll-a concentration, primary production, phytoplankton extracellular release, and abiotic variables such as the concentration of dissolved inorganic and organic nutrients. Rapid shifts in the dominant bacterial groups occurred associated to environmental changes and bacterial bulk functions. An alternation between Alphaproteobacteria and Bacteroidetes was observed associated to different phytoplankton growth phases. The dominance of the group Bacteroidetes was related to high bacterial biomass and production. We found a significant, non-spurious, linkage between the relative abundances of major bacterial groups and bacterial carbon cycling. Our results suggest that bacteria belonging to these major groups could actually share a function in planktonic ecosystems.

Keywords: Auto- and heterotrophic picoplankton; Heterotrophic nanoflagellates; Bacterial production; Grazing; Central Atlantic Ocean

The role of microorganisms in the transfer of carbon of marine systems is very important in open oligotrophic oceans. Here, we analyze the picoplankton structure, the heterotrophic bacterioplankton activity, and the predator–prey relationships between heterotrophic bacteria and nanoflagellates during two large scale cruises in the Central Atlantic Ocean (not, vert, similar29°N to not, vert, similar40°S). Latitud cruises were performed in 1995 between March–April and October–November. During both cruises we crossed the regions of different trophic statuses; where we measured different biological variables both at the surface and at the deep chlorophyll maximum (DCM). The concentration of chlorophyll a varied between 0.1 and 0.8 mg m−3, the abundance of heterotrophic bacteria varied between <1.0 × 105 and >1.0 × 106 cells ml−1, and that of heterotrophic nanoflagellates between <100 and >1.0 × 104 cells ml−1. The production of heterotrophic bacteria varied more than three orders of magnitude between <0.01 and 24 μgC L−1 d−1; and the growth rates were in the range <0.01–2.1 d−1. In the Latitud-II cruise, Prochlorococcus ranged between <103 and >3 × 105 cells ml−1, Synechococcus between <100 and >1.0 × 104 cells ml−1, and picoeukaryotes between <100 and >104 cells ml−1. Two empirical models were used to learn more about the relationship between heterotrophic bacteria and nanoflagellates. Most bacterial production was ingested when this production was low, the heterotrophic nanoflagellates could be controlled by preys during Latitud-I cruise at the DCM, and by predators in the surface and in the Latitud-II cruise. Our results were placed in context with others about the structure and function of auto- and heterotrophic picoplankton and heterotrophic nanoplankton in the Central Atlantic Ocean.

Keywords: Flash-flood; Sediment transport; Hypopycnal river plume; Têt River; Gulf of Lions; Northwest Mediterranean

This paper describes an integrated study of a typical Mediterranean flood event in the Gulf of Lions. A flood with a 5-year return interval occurred in the Têt River basin and adjacent inner-shelf in the Gulf of Lions, northwest Mediterranean, during April 2004. Data were collected during this flood as part of event-response investigations of the EU-funded Eurostrataform (European Margin Strata Formation) project. Southeasterly storm winds led to a flood which directly modified the inner-shelf hydrodynamics. Sediment delivery to the coastal zone during this flood represented more than half of the mean annual discharge of the Têt River to the Gulf of Lions. This river transported a large amount of sand in suspension, representing 25% of the total suspended load, and as bedload representing 8% of the total load, during this event. Sand introduced in the nearshore was transported northwards during the peak storm and nourished a small delta. Fine sediments were separated from coarse sediments at the river mouth, and were advected southwards and seawards by the counter-clockwise general circulation. Fine-grained sediments were transported via a hypopycnal plume along the coast towards the southern tip of the Gulf of Lions and the Cap Creus canyon. The along-shore currents, which intensified from north to south of the Gulf of Lions, particularly between the Cap Creus promontory and the Cap Creus canyon, favoured the transfer of fine-grained sediments from the continental shelf of the Gulf of Lions towards the continental slope. Our results show that floods with a few-year return interval in small coastal rivers can play a significant role in the transport of sediments on microtidal continental margins and their export from the shelf through canyons.

Keywords: Galicia Bank; echo-character analysis; high-resolution seismic profiles; swath bathymetry; TOBI sidescan sonar; sedimentary process

An echo-character analysis of the oil tanker Prestige wreck area was undertaken using high-resolution marine geophysical methods (TOPAS and airgun seismic-reflection profiles, multibeam echosounder and TOBI sidescan sonar). Integration and comparison of the results using all these methods is presented given some practical applications for indirect near-surface and seafloor interpretations. Ten different echo types were identified and grouped into four main classes: I) distinct; II) indistinct; III) irregular and IV) hyperbolic. Echo-character distribution enabled us to determine recent sedimentary processes in the area. Two major depositional systems can be found through the identification of these sedimentary processes: a) a slope depositional system (SDS) located in the eastern and central area, where mass-movement processes are dominant and b) a turbiditic Main Channel depositional system (TDS) located in the western area where channel-related processes are dominant. Both of these interact over the half-graben structure of the southwestern sector of the Galicia Bank, where the Prestige wreck is located. Within the SDS, erosive and depositional mass-movement processes characterised a complex depositional system. Erosive processes occur on the fault scarp, channels head, inter-lobe channels and distal part of the sedimentary lobes. Moreover, depositional processes take place on the top of the fault scarp, sedimentary wedges, sedimentary lobes, and on the west flank of the Main Channel. Both depositional systems interact, but the SDS should be more active during fault-scarp reactivation periods, through relief rejuvenation and new exposed deposits. Microearthquake activity would favour the available materials, being weathered, eroded and transported by mass-movements. In such a situation, the TDS acts as the main collector of eroded sediment derived from the fault scarp throughout the SDS being responsible for its evacuation into the Iberian Abyssal Plain. However, outside of fault reactivation periods, the SDS is less active (such as during the present situation).

Keywords: Alboran Sea - Pliocene - Quaternary - Proximal margin evolution - Seismic stratigraphy - Sequence stratigraphy

The shelf-upper slope stratigraphy offshore and around the Guadalfeo River on the northern continental margin of the Alboran Sea, Western Mediterranean Basin, has been defined through the interpretation of a grid of Sparker seismic profiles. We tried to identify evolutionary trends in shelf growth, as well as to determine the regional/local factors that may modify the influence of glacio-eustatic fluctuations. Four major depositional sequences are identified in the sedimentary record by a detailed seismic interpretation, which defines three significant intervals of shelf-upper slope progradation, dominated by deposition of shelf-margin wedges, which resulted in uniform patterns of shelf-margin growth in response to significant sea-level falls. In contrast, the record of transgressive intervals is more variable, mainly as the result of distinct patterns of regressive-to-transgressive transitions. Major progradational wedges are internally composed of seaward-prograding, landward-thinning wedges, interpreted to represent shelf-margin deltaic deposits. In contrast, the last aggradational interval is composed of shelf-prograding wedges that show distinct characteristics, in terms of seismic facies, morphology and distribution when compared with previous shelf-margin wedges. These shelf wedges are thought to represent the particular case of Regressive Systems or Shelf Margin Systems Tracts, and their development seems to be controlled by a drastic change in main depocenter location, which moved from the upper slope to the shelf during the Pleistocene. The stacking pattern of seismic units, the shallowness of the acoustic basement and the migration of the shelf break are used to infer spatial and temporal changes in tectonic subsidence-uplift rates, which interact with low-order glacio-eustatic changes. For much of the Pliocene-Quaternary, uplifted sectors alternated laterally with sectors experiencing more subsidence. Subsequently, a significant change from lateral outgrowth to vertical accretion is recognised. This stratigraphic change could be related to the combined influence of increased subsidence rates on the shelf and the onset of higher-frequency glacio-eustatic cyclicity after the Mid Pleistocene Revolution that occurred around 1 Ma.

Keywords: XBT probes, operational oceanography, inverse method

A methodology for recovering salinity from expendable bathythermograph (XBT) data is presented. The procedure exploits climatological relationships between temperature, salinity and depth to build regional characteristic curves by fitting a polynomial function that minimises both the variance of residuals and unknowns. Hence, salinity is computed and recovered as a function of temperature and depth. Empirical formula are provided to recover the salinity field from temperature-depth measurements for the Cantabrian Sea and Galician Area. The method is validated and applied in the context of two marine rescue exercises carried out in the Bay of Biscay close to the north coast of Spain and in the Finisterre region, where a series of XBT and conductivity-temperature-depth (CTD) profiles were acquired during fast samplings. The results agree reasonably well with independent data in terms of the spatial structure, with the largest errors in the upper 100 m of the ocean and at intermediate levels. The first diagnoses of the surface geostrophic velocity fields obtained through the salinity reconstruction are coherent and may help in rescue and safety operations during marine emergencies. Hence, we recommend that a technical unit should consider this kind of expandable sampling strategy with both XBT and XCTD data during marine emergencies, since it provides useful and comprehensive information rapidly with minimal interference by means of formal operations on board search and rescue ships.

Keywords: Aristeus antennatus; Fisheries; NW Mediterranean; North Atlantic Oscillation

The fluctuations of catches of the deep-sea shrimp Aristeus antennatus (Risso, 1816) were analysed in the 6 ports of Catalonia where production is concentrated, based on monthly landings from 1988 to 2004. The 6 selected ports produced 300 t of red shrimp in 2004, or 80% of the total production in Catalonia. The series for each port showed clear interannual variability, with peaks of production in the early 1990s and more recently from 2001 to 2003. The time periods of the monthly data series, estimated by frequency analysis based on Fourier transform, varied around 7–8 years in the four central ports and 12–13 years in the two northern ports. Additionally, the different curves were not in phase: even in nearby ports, the maximum production is observed in different years. Since the North Atlantic Oscillation (NAO) index is an excellent proxy for long-term series of environmental variables, we aimed to explore relationships between the fluctuation of the NAO index and A. antennatus landings in the Catalan Sea. The correlation between the mean annual NAO index and the annual catches in each port was positive and significant with some time lags (from 1 to 3 years). The existence of clear patterns linking the NAO with marine ecological processes has been demonstrated in many studies, but the underlying ecological mechanisms are far from being well understood. The variations in environmental parameters linked to the NAO may act on biological organisms at different levels (individual, population) through physiology (metabolic and reproductive processes) or through trophic relationships, including ecological cascade effects. We propose that NAO-induced environmental variability may enhance food supply to A. antennatus and hence strengthen the reproductive potential of particular year classes, which result in increased catches 1 to 3 years later, although other possible effects of environmental variability on the population dynamics of this species are worth investigating.

Keywords: Aristeus antennatus · NAO · Deep-sea · Benthic–pelagic coupling

Recent studies have shown that the population dynamics of deep-sea organisms are affected by coupling between surface oceanic processes and energy, or trophic resources, reaching the sea floor. I analysed the correlation between the landings of a deep-sea shrimp (Aristeus antennatus) in Catalonia (NW Mediterranean) and the climatic indices of the annual North Atlantic Oscillation (NAO) and winter NAO between 1971 and 2007. I show that the size of landings is significantly correlated with the NAO and with the winter NAO, with 2 and 3 yr lags in both cases. Considering that around 60% of the landings comprise 2 to 3 yr old females, my results suggest that climatic conditions over the western Mediterranean (especially in winter) influence the year-class strength of this deep-sea shrimp, fished from 600 to 800 m depth.

We analyse the spatial structure of early developmental stages of three ecologically important small pelagic schooling fish species in the northwestern Mediterranean Sea: the anchovy Engraulis encrasicolus, the round sardinella Sardinella aurita, and the sardine Sardina pilchardus. We used data on egg and larval abundance (arranged by development stage), hydrographic data and potential prey biomass collected during two cruises in summer and autumn 2005. Our analysis is based on the computation of Lloyd's patchiness index during the ontogeny of early developmental stages, as well as the computation of spatial auto-correlograms and cross-correlograms with environmental variables. The combined analysis allowed determination of the relative role of behavioural traits and the influence of hydrographic conditions in shaping the spatial structure of the three clupeiforms. We show that the spawning and developmental strategies of the two summer-spawning species (E. encrasicolus and S. aurita) are different. Engraulis encrasicolus has relatively low patchiness for all early developmental stages, while the importance of trophic variables in determining spatial structure increases during development. Sardinella aurita spawns in a trophically favourable environment and the patchiness of its early developmental stages increases for older larvae, becoming decoupled from environmental variables. The autumn spawned S. pilchardus eggs and larvae showed a development strategy similar to S. aurita, with limited importance of environmental variables in determining their patchiness.

Keywords: Protist; Phytoplankton; Picoplankton; Diversity; Indian Ocean

Protists, and among them the picoeukaryotes (cells<3 μm), have been described as significant contributors to both carbon biomass and production in oligotrophic regions of the oceans. However, protist assemblages remain largely undescribed in pelagic ecosystems and in particular in the Indian Ocean. In the present work, we investigated protists along an eastward transect across the sub-tropical gyre of the Indian Ocean (from South Africa to Australia), with a particular focus on picoeukaryotes. We combined inverted and epifluorescence microscopy, flow cytometry, pigment analysis, denaturing gel gradient electrophoresis (DGGE), 18S rDNA clone libraries, and fluorescent in situ hybridization (FISH). Overall the picophytoplankton fraction contributed 88% and 90% of total Chl a at the surface and DCM, respectively, with picoeukaryotes accounting for 38% and 50% of total Chl a at the surface and DCM. Considering only the Indian South Subtropical Gyre (ISSG) province, we observed greater shifts in the picoeukaryotic assemblage throughout the upper 200 m of the water column than along the ca. 10,000 km cruise track. In terms of taxonomic diversity and contribution of each taxon to the picoeukaryotic community, prasinophytes were well represented at more coastal stations with the genus Micromonas reaching densities up to 750 cell mL−1 in coastal waters and less than 100 cell mL−1 at open ocean stations. Haptophytes (56% and 45% of picoeukaryotic pigments at surface and DCM, respectively) and possibly pelagophytes (28% and 40% of picoeukaryotic pigments at surface and DCM, respectively) appeared to be dominant at open ocean stations. Other groups and in particular organisms affiliated to chrysophytes, and to a lesser extent to cryptophytes, appear as clear targets for future qualitative and quantitative studies. Moreover, the occurrence of many sequences related to radiolarians (5% and 27% at surface and DCM, respectively) will require further investigation.

The morphology of the final phyllosoma larval stage of the slipper lobster Scyllarus pygmaeus is described and illustrated based on larvae captured from Mediterranean waters and compared with those described in other Scyllaridae. These larvae were always found in deep waters (>200 m). Nucleotide sequence analysis of a region of the nuclear 28S rDNA gene identified these larvae as S. pygmaeus, the morphology of which had been previously un-described. An intensive review revealed a misidentification of Scyllarus arctus larvae in the literature during the last 180 years, since the identification of S. pygmaeus larvae as Chrysoma mediterraneum. Detailed examination indicated that the final-stage larvae examined belonged to a clearly defined phyllosoma larval group within the genus Scyllarus, morphologically very similar to some phyllosoma larvae collected from Japan, Hawaiian Islands, New Zealand or Juan Fernandez Islands. This constitutes the first complete description of a phyllosoma stage of a member of the family Scyllaridae, with the specific identity of the larva being validated with molecular techniques.

Keywords: COI; Haplotype; Population differentiation; Coalescence time

The European spiny lobster (Palinurus elephas) is a suitable model organism to study the effects of past history and current oceanographic processes on the genetic diversity and population structure of marine species with a long-lived larval phase. A portion of the COI gene was sequenced in 227 individuals from 11 localities, covering most of the present distribution of the species. Divergence was found between Atlantic and Mediterranean regions, which could be explained by restricted gene flow between populations. Moreover, a principal component analysis detected differences within basins. The existence of genetic differentiation between Brittany and Ireland–Scotland populations could be accounted for by the large effect of the Gulf Stream, while mesoscale processes suffered by the incoming Atlantic waters could be responsible of genetic differentiation within the Mediterranean. Furthermore, historical processes could be responsible for a reduction on the overall genetic variability of P. elephas. The haplotypic distribution found in P. elephas, with the presence of one abundant haplotype and a large number of closely related haplotypes, is typical of species experiencing reduction in variability and subsequent expansions. Climatic fluctuations related to glacial cycles could explain the present level of variability and nucleotide diversity found. Interestingly, these glacial events do not seem to have the same impact in other species of the same genus. Our results indicate that recent glacial events could have had a lower impact on Palinurus mauritanicus, a congeneric species that presents an overlapping distribution area but is found in cooler waters than P. elephas.

Keywords: Le Danois Bank; Benthic communities; Demersal communities; Cantabrian Sea; Deep-sea; Faunal assemblages; Spatial distribution; Habitat characteristics

The purpose of this paper is to detect and describe general trends in the spatial distribution of epibenthic and demersal communities of Le Danois Bank (El Cachucho) in relation to the environmental variables that characterize their habitat by means of multivariate ordination. Data were derived from two multidisciplinary surveys carried out in October 2003 and April 2004 included in the ECOMARG project. The surveys were focused on the study of the physical scenario, including both geological (seabed characterization from bathymetry and backscatter data) and hydrographic features, and the different compartments of the benthic fauna (endobenthic, epibenthic, suprabenthic and demersal communities). For the present study, epibenthos and demersal species were sampled using two different gears, a 3.5 m beam trawl and a Porcupine 39/52 type baca otter trawl respectively. The total species richness combining both samplers ascended to 221, including 71 species of fishes, 65 crustaceans, 35 molluscs, 29 echinoderms, 10 cnidarians and 5 sponges. Multivariate methods were used for the study of the characteristics of communities and habitats. Hierarchical cluster analysis was applied to calculate and visualize similarities between samples in terms of species composition. To assess the amount of variation of faunal densities related to a set of eight environmental variables, a redundancy analysis (RDA) was used. The set of environmental variables used were: depth, near-bottom temperature and salinity, sedimentary typology (dry weight percentages of coarse sands, medium and fine sands, silt and organic matter) and seafloor reflectivity. Using the spatial distribution of the ranges of depth and seafloor reflectivity that characterize the habitats of the faunal assemblages we defined the spatial distribution of the different communities. The multivariate analysis of 18 beam-trawl samples and 15 otter trawl samples showed the existence of 4 main assemblages associated with the more characteristic habitats of the area. The Callogorgia–Chimaera community live mainly in the areas at the top of the Bank (425–550 m depth), where the sediment coverage is lower and there exists a high presence of rocky outcrops. The Gryphus–Galeus community were found in the areas at the top of the Bank covered by medium and fine sand sediments with low organic matter content. The Phormosoma–Trachyrincus community live on the sedimentary terraces that characterize the Bank break (550–800 m) and the Pheronema–Deania community occupy all the deeper (800–1050 m) sedimentary grounds of the inner basin.

Keywords: Cantabrian margin; Morphosedimentary features; Mass-movements; Contourite; Cap Ferret Fan; Depositional architecture

Multibeam bathymetry, high (sleeve airguns) and very high resolution (parametric system-TOPAS-) seismic records were used to define the morphosedimentary features and investigate the depositional architecture of the Cantabrian continental margin. The outer shelf (down to 180–245 m water depth) displays an intensively eroded seafloor surface that truncates consolidated ancient folded and fractured deposits. Recent deposits are only locally present as lowstand shelf-margin deposits and a transparent drape with bedforms. The continental slope is affected by sedimentary processes that have combined to create the morphosedimentary features seen today. The upper (down to 2000 m water depth) and lower (down to 3700–4600 m water depth) slopes are mostly subject to different types of slope failures, such as slides, mass-transport deposits (a mix of slumping and mass-flows), and turbidity currents. The upper slope is also subject to the action of bottom currents (the Mediterranean Water — MW) that interact with the Le Danois Bank favouring the reworking of the sediment and the sculpting of a contourite system. The continental rise is a bypass region of debris flows and turbidity currents where a complex channel-lobe transition zone (CLTZ) of the Cap Ferret Fan develops. The recent architecture depositional model is complex and results from the remaining structural template and the great variability of interconnected sedimentary systems and processes. This margin can be considered as starved due to the great sediment evacuation over a relatively steep entire depositional profile. Sediment is eroded mostly from the Cantabrian and also the Pyrenees mountains (source) and transported by small stream/river mountains to the sea. It bypasses the continental shelf and when sediment arrives at the slope it is transported through a major submarine drainage system (large submarine valleys and mass-movement processes) down to the continental rise and adjacent Biscay Abyssal Plain (sink). Factors controlling this architecture are tectonism and sediment source/dispersal, which are closely interrelated, whereas sea-level changes and oceanography have played a minor role (on a long-term scale).

Keywords: marine geology; Galicia Bank; Prestige disaster; geohazards

The geological characterization of the Galicia Bank Region, in the NW Iberian continental margin (Atlantic Ocean) was the marine geology community's response to the environmental risk posed by the sinking and oil spill of the Prestige tanker. This special volume of Marine Geology is a collection of papers that address themes of general interest for marine geohazard determination and assessment. A variety of topics associated with morphology, stratigraphy, sedimentology, tectonism and seismicity were considered in order to define the geohazards at the location of the Prestige wreck, which still has oil in its tanks. These studies have also served to provide greater detail and high-resolution datasets on the geological evolution of the Galicia Bank Region in general, and particularly its SW flank.

Keywords: Galicia Bank; high-resolution seismic profiles; stratigraphy; seismic facies; facies architecture; sedimentary evolution

The high-resolution seismic stratigraphy of the Galicia Bank Region and adjacent deposits of the neighbouring Iberian and Biscay Abyssal Plains was included as part of the geological studies conducted in the area where the oil-tanker Prestige wreck is located. This seismic stratigraphy is characterized by five seismic units (5 to 1, from oldest to youngest) lying above an irregular acoustic basement defined by a highly fractured system of horsts and grabens. These faulted systems have controlled the local depositional architecture, deforming, fracturing, relocating and distributing sediments since the Valanginian. Three depositional models of facies can be recognized on the Galicia Bank Region and surrounding abyssal plains: bank, escarpment, and abyssal plain facies. The bank facies reflects the depositional evolution from initial filling to obliterating stages of the horsts and grabens. The escarpment facies has a local distribution and represents deposition associated with active slopes of the faulted escarpments. The abyssal plain facies represents gravity flow deposits coming mostly from the bounded-fault flanks of the Galicia Bank Region. The Valanginian to Quaternary sedimentary evolution of the Galicia Bank Region reflects depositional responses to tectonic condition. The occurrence of mass-movements confirms that the syn-rift period (Valanginian to Aptian age) along the Galicia margin was diachronous, beginning in the Interior Basin and shifting later toward the west of the Galicia Bank Region (Deep Galicia Margin). The Albian to Quaternary post-rift evolution is characterized by a decrease in tectonic activity and sedimentary variations in the style of deposition (valley and related features, mass-movement deposits, contourites, and drape deposits) conditioned by changes in the sedimentary processes, paleoenvironments, and tectonic reactivation of the regional slopes. The effects of tectonic movements persist, as evidenced in areas where faulted escarpments and highs outcrop, and in areas of near-surface faulting. The syn-rift and post-rift stages have also conditioned the depositional architecture of the Prestige sinking area. The evolution of the surrounding abyssal plains does not reflect the same pattern to tectonic condition.

Keywords: zoea, megalopa, larval development

The complete larval development of the majoid crab Herbstia condyliata (Fabricius, 1787) from the western Mediterranean was obtained from laboratory culture. All larval stages (two zoeal stages and the megalopa) are described and illustrated in detail for the first time. The morphology of the zoeae and megalopa is compared with the corresponding stages of other known species of the family Pisidae. The zoeal stages of H. condyliata present a pleon with unusual characters within the Pisidae such as the presence of dorsolateral processes in pleomere 3, two dorsal setae in pleomeres 2–4 (second zoea) and the very long posterolateral processes in pleomeres 3–4. The megalopa can be differentiated from other Pisidae species by the presence of a very developed cardiac tubercle on the carapace and the absence of plumose setae on the basal segment of the first maxilliped exopod.

Keywords: Small-scale fisheries / Socioeconomics / Bioeconomic Simulation / Assessment

Trammel net is the main fishing gear used by artisanal fishers in Majorca Island (NW Mediterranean), and is representative of Mediterranean small-scale fisheries using static gear. The use of static gears close to the coast, where seasonal variability and spatial heterogeneity are high, promotes the diversification of fishing practices or metiers. We analyze the seasonal dynamics of the nets used, target species (red and black scorpionfish, red mullet and cuttlefish) exploitation patterns and the socio-economic conditions under which this fishery takes place, based on General Fisheries Directorate daily sale records (2002-2006). Additional personal socioeconomic interviews allowed the characterization of the trammel net fishery, its fishing behaviour, cost structure and conflicts. Catch and effort data and market surveys are used to evaluate the level of exploitation of the target species and allowed describing Majorca trammel net fishery as an activity based on a sustainable resource. The main target species were found to be near their maximum sustainable yield both by means of a surplus production model (with parameters estimated by CEDA-Catch Effort Data Analysis, software) and an age structured assessment model based on yield-per-recruit analysis. Management actions currently debated by local administration and fishers focus on improving fishers' economic situation, rather than on protecting a threatened resource. One of the management actions proposed is a one day effort reduction, which was analyzed here with the help of a bioeconomic simulation model. A 15-year (2005-2020) simulation allows providing advice to local managers to focus on the commercialization aspects, in order to obtain a higher value to the fish production, rather than expecting to obtain higher profits only by a reduction of the offer.

Keywords: Portunid crab; Prestige; Stomach content; Upwelling; NAO; Biomarkers; Spain; Galicia

Diet and feeding intensity of the portunid crab Polybius henslowii were studied during the spring of 2004 along Galician and Cantabrian continental shelves (NW Iberian Peninsula) between 78 and 287 m. The area had been affected by the Prestige oil spill in November 2002, with different sectors at different levels of pollution: highest in between Miño River and Cape Finisterre (MF) and from there to Estaca de Bares Point (FE) and lowest from Estaca to Cape Peñas (EP). From 37272 specimens collected in 59 bottom hauls, 342 were analysed for stomach fullness and diet composition. Stomach fullness was lower in FE, but with no significant differences among sectors. Diet was a mixture of pelagic and benthic prey: cephalopods (Ilex coindetti), brachyurans (P. henslowii) and polychaetes (Glycera sp.). Other prey were beloniform eggs and fish remains. Two stress markers were also studied in some specimens: Acetylcholinesterase (a neurotoxicity marker) varied among sampled areas, while lipid peroxidation (an oxidative stress marker) did not. Changes in trophic variables, distribution and density were analysed in relation to depth, surface and bottom T, surface Chl a from satellite imagery and tar aggregate concentration in sediments. Along Galician and Cantabrian coasts prey availability, linked to productivity level, seems to be the main factor affecting P. henslowii diet and distribution. Interannual abundance variability seems to be controlled by large-scale climatic conditions (NAO index). This natural variability masks possible effects induced by the oil spill.

A systematic search for methane-rich fluid seeps at the seafloor was conducted at the Pacific continental margin offshore southern Nicaragua and northern central Costa Rica, a convergent margin characterized by subduction erosion. More than 100 fluid seeps were discovered using a combination of multibeam bathymetry, side-scan sonar imagery, TV-sled observations, and sampling. This corresponds, on average, to a seep site every 4 km along the continental slope. In the northwestern part of the study area, subduction of oceanic crust formed at the East Pacific Rise is characterized by pervasive bending-induced faulting of the oceanic plate and a relatively uniform morphology of the overriding continental margin. Seepage at this part of the margin typically occurs at approximately cone-shaped mounds 50 - 100 m high and up to 1 km wide at the base. Over 60 such mounds were identified on the 240 km long margin segment. Some normal faults also host localized seepage. In contrast, in the southeast, the 220 km long margin segment overriding the oceanic crust formed at the Cocos-Nazca Spreading Centre has a comparatively more irregular morphology caused mainly by the subduction of ridges and seamounts sitting on the oceanic plate. Over 40 seeps were located on this part of the margin. This margin segment with irregular morphology exhibits diverse seep structures. Seeps are related to landslide scars, seamount-subduction related fractures, mounds, and faults. Several backscatter anomalies in side-scan images are without apparent relief and are probably related to carbonate precipitation. Detected fluid seeps are not evenly distributed across the margin but occur in a roughly margin parallel band centered 28 ± 7 km landward of the trench. This distribution suggests that seeps are possibly fed to fluids rising from the plate boundary along deep-penetrating faults through the upper plate.

Keywords: East African Great Lakes; flow cytometry; heterotrophic bacteria; large tropical lake; picoplankton; Synechococcus

1. We used flow cytometry to characterize freshwater photosynthetic picoplankton (PPP) and heterotrophic bacteria (HB) in Lake Kivu, one of the East-African great lakes. Throughout three cruises run in different seasons, covering the four major basins, phycoerythrin-rich cells dominated the PPP. Heterotrophic bacteria and PPP cell numbers were always high and spatial variations were modest. This represents an important difference from temperate and high latitude lakes that show high fluctuations in cell abundance over an annual cycle. 2. Three populations of picocyanobacteria were identified: one corresponded to single-cells (identified as Synechococcus by epifluorescence microscopy, molecular methods and pigment content), and the two other that most probably correspond to two and four celled colonies of the same taxon. The proportion of these two subpopulations was greater under stratified conditions, with stronger nutrient limitation. 3. High PPP concentrations (c. 105 cell mL−1) relative to HB (c. 106 cell mL−1) were always found. Lake Kivu supports relatively less bacteria than phytoplankton biomass than temperate systems, probably as a consequence of factors such as temperature, oligotrophy, nutrient limitation and trophic structure. 4. A review of PPP concentration across aquatic systems suggests that the abundance of Synechococcus-like cyanobacteria in large, oligotrophic, tropical lakes is very high. 5. Photosynthetic picoplankton cell abundances in the oligotrophic tropical lakes Kivu and Tanganyika are comparable to those of eutrophic temperate lakes. This apparently contradicts the view that PPP abundance increases with increasing eutrophy. More data on PPP in tropical lakes are needed to explore further this particular pattern.

In this article it is shown that the multifractal microcanonical formalism (herein referred to as MMF) has strong potential for bringing new solutions to a known problem in the analysis of some remotely sensed datasets: the determination of fire plumes in NOAA–AVHRR data. It has been proven that NOAA–AVHRR data can be used to detect plumes caused by fire accidents of different kinds. This work builds on previous studies and uses the MMF to introduce novel methods for the determination of plumes. The MMF can be used to derive geometrical superstructures (like certain multifractal topological manifolds and most importantly the so-called reduced signals) that are able to deal with the multiscale properties of turbulent geophysical fluid flows. These multiscale properties make use of the spatial distribution of grey-level values in the datasets and they are used in conjunction with previous pixel-based descriptors to enhance the determination of plume pixels.

Keywords: Antarctica, Fish larvae and juveniles, Salps, Krill , Distribution, Abundance, Size structure, Hydrography, Density front, Segregation

The spatial distribution, biomass and size structure of key mesozooplankton species and micronekton in the Bransfield Strait (Antarctica) are described in relation to environmental variables during the austral summer 2001. Stratified (BIONESS) biological sampling at five depth-ranges and CTD casts were performed at 40 stations, including a cross-Strait transect. Six families, 11 genera and 16 species composed the total catch of larval and juvenile fish, which were more abundant in the upper 75 m. Trematomus scotti was the most abundant fish and large individuals dominated at depths >75 m. The fish distribution patterns were associated with the main water masses in the area and with bottom depth. Spatial segregation in density and biomass of krill (Euphausia superba) and salps (Salpa thompsoni) was observed at a relatively small scale, in relation to the main water masses. Also, size-related spatial segregation was found in krill. The present study suggests that the spatial distribution of krill, salps and early life stages of fish, are influenced by the main water masses in the Strait, and that species may adapt their reproductive strategies not only to seasonal production peaks, but to transport processes within water bodies that maximise their fitness through optimum temperature and/or trophic.

Keywords: cold seeps; Costa Rica; side-scan sonar.

Quantification of fluid fluxes from cold seeps depends on accurate estimates of the spatial validity of flux measurements. These estimates are strongly influenced by the choice of geoacoustic mapping tools. Multibeam bathymetry, side-scan sonar, and Chirp subbottom profiler data of several mound-shaped cold seeps offshore central Costa Rica show great variety in morphology and structure although the features are only a few kilometers apart. Mound 11 (a 35 m high and 1000 m in diameter structure), situated in the SE of the study area, has an irregular morphology but a smooth surface on side-scan sonar data, while mound 12 (30 m high, 600 m across) is a cone of more regular outline but with a rough surface, and mound Grillo (5 m high, 500 m across) shows the same rough surface as mound 12 but without relief. Video observations and sediment cores indicate that the structures are formed by the precipitation of authigenic carbonates and indications for extensive mud extrusion are absent, except for one possible mudflow at mound 11. Different sonar frequencies result in variable estimates of the extent of these mounds with low frequencies suggesting much wider cold seeps, consequently overestimating fluid fluxes. The absence of mud volcanism compared to accretionary prisms where mud volcanism occurs is related to different tectonic styles: strong sediment overpressure and thrust faulting in typical accretionary prisms can generate mud volcanism, while subduction erosion and normal faulting (extension) of the overriding plate at the Costa Rican margin result in fluid venting driven by only slight fluid overpressures.

Keywords: Wide-angle seismics; Software; Signal processing; Plug-in; Object oriented programming

WASPAR (Wide-Angle reflection–refraction Seismic data Processing And Representation) is a new free multi-platform software tool to process and display wide-angle seismic data. It has been designed to read different raw data formats, construct record sections, process them using existing and newly developed algorithms, pick seismic phases and generate graphic files using a single, user-friendly interface. The main characteristics of WASPAR are its flexibility and expandability. It has been designed in a modular way using a plug-in architecture to manage raw data access and processing functionalities. We thus obtain a stable base easily maintainable and expandable. We have chosen the C++ programming language in combination with an object oriented methodology to facilitate the development of a multi-platform software tool, which is already available on Linux and MS Windows. In order to allow its expansion and upgrade, the program will be freely distributed under the terms of GPL license. The philosophy of this software tool is to leave it open to external contributions.

Keywords: beach morphodynamics; video imaging; morphodynamic modelling; Mediterranean Sea; wave forcing

In a recent study, Gómez-Pujol et al. [Gómez-Pujol, L., Orfila, A., Cañellas, B., Alvarez-Ellacuria, A., Méndez, F.J., Medina, R., Tintoré, J., 2007. Morphodynamic classification of sandy beaches in low energetic marine environment. Mar. Geol. 242, pp. 235–246] used the Wright and Short beach classification scheme fed with hindcasted wave and sediment settling velocity data to classify the morphodynamic states of a group of low-energy Mediterranean beaches (Mallorca, Spain). Here, we use morphodynamic data obtained from an Argus video station and a morphodynamic model to assess the validity of this type of model for predicting beach states under typical Mediterranean wave conditions. The results show that Ω-values alone do not provide a realistic prediction of beach states statistics and that the intensity of the forcing, represented by the wave energy level and the duration of the events, must also be taken into account.

Keywords: Fourier transforms, biology computing, feature extraction, geophysical signal processing, image classification, image representation

In computer based fish identification from otolith images, recent techniques such as Curvature Scale Space (CCS) and Wavelets have been used to locate the position of singular features. On the other hand, automated fish ageing methods use Fourier Transform (FT), Principal Component Analysis (PCA) or Peak Based Representation (PBR) to enhance classifier performance. In this work we use the Local Discriminant Bases algorithm (LDB). In ageing applications, is necessary to employ an optimization method to demodulate growth effects before using the LDB. LDB can also be used for fish identification after filtering and resampling the otolith contour. The proposed methods have been tested with otolith contours from a web-base database and with images of cod otolith sections. In both cases results show that only a few bases are needed to represent class features accurately.

The Encyclopedia of Global Warming and Climate Change is a collection of approximately 750 articles in a three-volume set, presented in an A to Z alphabetical format, exploring major topics related to global warming and climate change—ranging geographically from the North Pole to the South Pole, and thematically from social effects to scientific causes. Coverage includes the science and history of climate change, the polarizing controversies over climate-change theories, the role of societies, the industrial and economic factors, and the sociological aspects of climate change. The scope of the encyclopedia is focused on providing a primarily nonscientific resource to understanding the complexities of climate change for academic and public libraries, written by scholars and institutional experts in the geosciences.

Dynamics of biological processes on the deep-sea floor are traditionally thought to be controlled by vertical sinking of particles from the euphotic zone at a seasonal scale. However, little is known about the influence of lateral particle transport from continental margins to deep-sea ecosystems. To address this question, we report here how the formation of dense shelf waters and their subsequent downslope cascade, a climate induced phenomenon, affects the population of the deep-sea shrimp Aristeus antennatus. We found evidence that strong currents associated with intense cascading events correlates with the disappearance of this species from its fishing grounds, producing a temporary fishery collapse. Despite this initial negative effect, landings increase between 3 and 5 years after these major events, preceded by an increase of juveniles. The transport of particulate organic matter associated with cascading appears to enhance the recruitment of this deep-sea living resource, apparently mitigating the general trend of overexploitation. Because cascade of dense water from continental shelves is a global phenomenon, we anticipate that its influence on deep-sea ecosystems and fisheries worldwide should be larger than previously thought.

Keywords: Particle flux; Sediment transport; Advection; Temporal variability; Event-dominated; Cascading; Continental margin; NW Mediterranean

In the framework of the European project Eurostrataform, an array of six near-bottom mooring lines was deployed in the heads of the major submarine canyons incising the continental slope of the Gulf of Lions (NW Mediterranean). All moorings were equipped with sediment traps, current meters and turbidity Optical Backscatters Sensors (OBS) situated at few meters above the bottom. Particulate mass fluxes were recorded weekly by the sediment traps between November 2003 and May 2004 and compared with horizontal export fluxes obtained from the turbidity and current meters. Results show that near-bottom vertical particulate mass fluxes generally increase along slope between the northeastern-most and the southwestern region of the Gulf of Lions. Horizontal export fluxes also show some increase southwestward with flux in the southwestern-most canyon up to two-orders of magnitude higher than in northeast canyons. Furthermore, most of the export flux is driven by energetic and short events such as marine storms and dense shelf water cascading. Although the consequence of storms and cascading was obvious from traps and OBS measurements, substantial differences between vertical and horizontal fluxes appeared. While sediment traps recorded the largest vertical flux during the autumn storm (4 December) with contributions from river discharge and resuspended material, horizontal flux as obtained from OBS data was highest in winter (21–24 February). We believe that such discrepancies are partly due to measurement artifacts originating from the particle size effects and/or the different height above the bottom occupied by the traps and OBS which complicate comparisons between vertical and horizontal fluxes. However, different water-column conditions (stratified versus unstratified) together with the hydrodynamic regime during the two periods appear as a likely explanation for the flux differences between fall and winter storms.

Keywords: FSH; LH; Gonadotropin; Senegalese sole; Pituitary; In situ hybridization; Spermatogenesis

Pituitary gonadotropins (GTHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), are key regulators of vertebrate reproduction. However, in teleosts with testis of semi-cystic type and asynchronous spermatogenesis, as the flatfish Senegalese sole (Solea senegalensis), the physiological roles of FSH and LH are still not well understood. To gain insight into this mechanism, full-length complementary DNAs (cDNAs) encoding Senegalese sole FSHβ and LHβ subunits, and the common glycoprotein α subunit (CGα), were cloned and sequenced. The three cDNAs consisted of 550, 582 and 744 nucleotides encoding peptides of 120, 148 and 132 amino acids, respectively. Comparison of the deduced amino acid sequences of sole FSHβ, LHβ and CGα with those from other teleosts indicated that cysteine residues and potential N-linked glycosylation sites were fully conserved with respect to other percomorphs and salmonids. However, the primary structure of FSHβ and LHβ in pleuronectiforms appeared to be highly divergent. In situ hybridization of mature male pituitaries showed that fshb, lhb and cga mRNAs were localized in the proximal pars distalis and in the periphery of pars intermedia. Real-time quantitative reverse transcription-polymerase chain reaction indicated that the levels of all three transcripts in the pituitary of males increased during winter and spring, at the time when plasma levels of androgens raised and testicular germ cell development and spermatozoa production were stimulated. These results suggest that FSH and LH may regulate spermatogenesis in Senegalese sole similarly to that described for other teleosts with testis of cystic type and synchronous germ cell development.

Keywords: Suprabenthos; Zooplankton; Western Mediterranean; Bathyal communities; Trophic level; Aristeus antennatus

Dynamics of suprabenthos and zooplankton were analyzed in two areas located in the NW (off Sóller harbour) and S (off Cabrera Archipelago) of Mallorca (Balearic Islands, western Mediterranean) at depths ranging between 135–780 m. Four stations situated respectively at 150 m (shelf-slope break), and at bathyal depths of 350, 650 and 750 m were sampled at bi-monthly intervals during six cruises performed between August 2003 and June 2004. Suprabenthos showed maximum biomass in both areas from late spring to summer (April to August), while minimum biomass was found in autumn (September–November). Though variable, temporal dynamics of zooplankton showed peaks of biomass in late winter and summer (February and June), while minimals occurred in autumn (August–September) and, at bathyal depths, in April. Suprabenthos (abundance; MDS analyses) showed a sample aggregation as a function of depth (3 groups corresponding to the shelf-slope break, upper slope — over 350 m; and the middle, deeper part of the slope — over 650–750 m), without any separation of hauls by season. By contrast, zooplankton samples were separated by season and not by depth. There was evidence of three seasonal groups corresponding to summer (June 2004–August 2003), autumn–winter (September and November 2003, February 2004), and spring (April 2004), being especially well established off Sóller. In general, suprabenthos was significantly correlated with the sediment variables (e.g. total organic matter content (% OM), potential REDOX), whereas zooplankton was almost exclusively dependent on Chl a at the surface, which suggests two different food sources for suprabenthos and zooplankton. The increase of suprabenthos abundance in April–June was paralleled by a sharp increase (ca. 2.8 times) in the %OM on sediment during the same period, coupled ca. 1–2 months of delay with the peak of surface Chl a recorded in February–March (from satellite imagery data). Suprabenthos biomass was also correlated with salinity close to the bottom, suggesting a link between suprabenthos abundance and changes in the oceanographic condition of water masses close to the bottom. It is suggested that a higher suprabenthos biomass recorded off Sóller in comparison to that off Cabrera in June could, in turn, be related to a seasonal inflow of Levantine Intermediate Water (LIW) in April–June in this area at mid bathyal depths (350–650 m). This trend would be based on: 1) it was evident only at mid-slope depths between 350–750 m, coinciding with the LIW distribution, and 2) it was not recorded among zooplankton (collected throughout the water column). The possible effect of the fluctuations of suprabenthos and zooplankton on higher trophic levels has been explored studying the diet and food consumption rates of the red shrimp Aristeus antennatus, as indicator species by its dominance in bathyal communities. A. antennatus increased its food consumption from February to April–June 2004 off Sóller, which in the case of large (CL > 40 mm) specimens was found in both areas. In addition, there was a shift of diet from winter to spring–early summer. In this last period, A. antennatus preyed upon euphausiids and mesopelagic decapods and fish, while benthos (e.g. polychaetes and bivalves) decreased in the diet. This indicates an increase in the food consumption and probably in the caloric content of the diet in pre-spawning females in April–June 2004, which is synchronized with the period when gonad development begins in A. antennatus females (May–June). Anyway, macrozooplankton, and not suprabenthos, is crucial as a high energetic food source in the coupling between food intake and reproduction in the red shrimp.

Keywords: Feeding intensity; Trophic dynamics; Deep Sea; Decapoda; Benthic-Planktonic coupling; Reproductive cycle; Water masses; Daily migrations

Spatio-temporal variation of feeding intensity and diet in the red shrimp Aristeus antennatus was studied at two locations around the island of Mallorca (Balearic Islands, Western Mediterraean) in August, September, and November 2003, and in February, April and June 2004 at depths between 550 and 750 m. The two areas, with different oceanographic conditions, were respectively located in the northwest (Sóller) and the south (Cabrera) of Mallorca. Off Sóller, feeding intensity of A. antennatus showed a significant increase from February to April and June 2004 in all the three size-classes studied (small shrimps: CL < 30 mm; medium: CL between 30 and 40 mm; large: CL greater-or-equal, slanted 40 mm). Off Cabrera, the highest fullness was recorded in November 2003 among small and medium shrimp, while only large specimens showed patterns similar to that found off Sóller. Off Sóller, the diet of both small (CL < 34 mm) and large (CL greater-or-equal, slanted 34 mm) A. antennatus was mainly influenced by season, with three dietary groups corresponding to August–September 2003, to November 2003/February 2004, and to hauls from April to June 2004. Off Cabrera, hauls (representing diets) were grouped by depth, never by season. The most remarkable seasonal shift in the diet of A. antennatus off Sóller was the increase of mesopelagic prey in April–June relative to other months. In all size categories there was an increase off Sóller in the energy intake of prey ingested from February to June 2004, an increase not found off Cabrera. Degree of digestion of mesopelagic prey indicated nocturnal feeding on mesopelagic fauna. These prey probably have a shallower depth distribution at night than found in our daylight sampling, and possible migratory movements among prey and A. antennatus at night would explain the lack of correlation between prey abundance in guts and in the environment found during daylight periods for most micronekton mesopelagic prey (euphausiids, myctophids and sergestids). Off Sóller, fullness and diet were significantly linked to temporal changes in water column productivity (e.g., Chl a readings, fluorescence) and to changes in the shrimp biology (lipid content of hepatopancreas, Gonado-somatic Index, GSI). Off Cabrera, we found a higher dependence of fullness and diet with T and S, both variables in turn related to depth. The increase of stomach fullness and dietary energy intake in pre-reproductive females from February to April–June 2004 found off Sóller, coupled with the consumption of mesopelagic prey, was parallel to a significant increase of the gonad weight (GSI, fecundity) in June. Most individuals attain gonad development in the period May–June, after two months of the peak of primary production at the surface. The strong link found between pelagic resources and reproductive processes in a deep-sea species such as the shrimp Aristeus antennatus, situated near the top of the trophic web, suggests a rapid energy flow via mesopelagic fauna between surface primary production and bathyal megabenthic communities at oligotrophic insular areas. In contrast to mainland areas off the Catalan coasts submitted to the influence of submarine canyons, around the island of Mallorca the empoverishment of benthos biomass may enhance consumption of micronektonic prey and a possible accumulation of pre-reproductive females of A. antennatus in areas (e.g., steep slopes and persistent frontal systems found off Sóller) with high zooplankton aggregations.

Keywords: Particulate flux; Organic matter; Biomarkers; Seasonality; Storms; Cascading; Continental slope; NW Mediterranean Sea; Gulf of Lions

To investigate the role of coastal canyons in the transfer of organic matter from the shelf to the slope and basin, we deployed sediment trap/current meter pairs at the head of five canyons in the Gulf of Lions (GoL) between November 2003 and May 2004. Analysis of organic carbon, biogenic silica, Corg isotopic composition, Corg/total nitrogen, chloropigments, and amino acids clearly shows the seasonal influence and effect of extreme meteorological events on the composition of collected particles. The sampling period was divided into three “scenarios”. The first corresponded to a large easterly storm and flood of the Rhone river during stratified water column conditions; the composition of material collected during this event was influenced by increased transfer of riverine and coastal particulate matter, with a lower Corg content. During the second “fall-winter” scenario, northern and northwestern winds blowing over the shelf caused cooling and homogenization of the shelf water column; particles collected at this time reflected the homogeneous source of particulate matter transported through canyons; particles sitting in the vicinity of canyon heads are most likely swept downslope by the general south-westward circulation. Organic tracers indicate a degraded origin for organic matter transported during this period. A third “spring” scenario corresponded to northern winds alternating with eastward windstorms that triggered and/or enhanced the cascading of dense waters accumulated on the bottom of the shelf due to previous cooling. These conditions occurred in conjunction with increased phytoplankton productivity in shelf surface waters. Organic matter advected mainly by dense shelf water cascading was fresher due to the transport of newly produced particles and a variable terrestrial fraction; this fraction depended on the proportion of resuspended material accumulated during previous high discharge periods that was involved in each transport pulse. The tight link shown between meteorological conditions and organic matter transport is important for continental margin geochemical studies as future changes in climatic conditions may lead to dramatic changes in carbon sequestration capability and in the ecosystems of deep margin environments.

This chapter summarizes the main objectives and characteristics of the ESAs SMOS mission and its remote sensing applications. The SMOS payload is MIRAS, a new type of instrument in Earth observation: the first two-dimensional aperture synthesis interferometric radiometer. It operates at L-band, has multi-angular and multi-look imaging capabilities, and can be operated in dual-polarization or full-polarimetric modes. Due to its novelty, the principles of operation, imaging characteristics and its main performance parameters (spatial resolution and radiometric sensitivity and accuracy) are described, as well as the approach selected in the retrieval algorithms of sea surface salinity.

Keywords: Urban beaches, beach occupation, tourist season

Images from an Argus beach monitoring station were analyzed to count the number of people on two city beaches in Barcelona (NW Mediterranean) every hour for 4 years. Daily, weekly, seasonal, and interannual user distribution patterns were clearly established. Two different fit models were applied to the data based on a Fourier polynomial and nonlinear criteria, including external factors such as temperature and wind conditions, as well as predisposition factors. Finally, the evolution of beach users was compared with morphological beach changes caused by natural processes and human action. The results demonstrated that video observations provide a suitable method for counting people on the beach that could be useful for a number of coastal management applications.

Keywords: Biological roughness; Reworking rates; Ripples destruction; Wave dissipation

This work deals with the potential influence of benthic communities on the sediment dynamics of the coastal zone, and specifically with the modifications to bottom roughness caused by communities and their effects on wave propagation across the coastal profile. Time-series of video observations of the sea bottom on the Ebro delta coast were analysed in order to estimate the bottom roughness associated with physical and biological morphological components and the sediment reworking rates caused by epifaunal organisms. Biological roughness was mainly caused by ophiuroids and tanatocenosis of bivalve and gastropod shells, which changed their abundance during the study period. The total biological roughness (Kbio) ranged between 0.27 and 0.81 cm and represented a significant part (<20%) of the total form drag roughness. Flattening of ripples caused by bioturbation was observed under low-energy conditions. Surface sediment perturbation and bioturbation rates were also estimated. Based on these observations a wave propagation model was applied in order to carry out a sensitivity analysis of the significance of biological roughness on wave dissipation in the study area under different wave conditions.

Keywords: NW Mediterranean; Soil organic matter; Têt inner shelf; BIT index; Wet storm; Dry storm

River floods and storm waves are major processes for the dispersal and deposition of terrestrial organic matter (OM) in river-dominated coastal areas. A “wet storm” is connected to a flood with a high river discharge, while a “dry storm” is not associated with a flood. To better understand the sedimentation dynamics of terrestrial OM, especially soil OM, at the land–ocean interface during wet and dry storms, we studied sediment trap and core material collected on the Têt inner shelf (NW Mediterranean) using multiple organic proxies in combination with hydrodynamic parameters. The proportion of soil OM to the total OM in the trap material calculated based on the BIT (Branched and Isoprenoid Tetraether) index was higher during both wet (~ 40%) and dry (~ 30%) storms than during non-storm periods (~ 10%). However, only surface sediments (1-cm thick layers) recovered after December wet and moderate storms in 2003 showed enhanced soil OM percentages compared to the deeper sediments deposited during the last century. Given that the wet storm eroded 4-cm of seabed at the study site, flood-induced fresh soil OM was not deposited on the Têt inner shelf during the wet storm. However, the following moderate storm caused resuspension of flood-associated soil OM which was previously trapped nearshore. Accordingly soil OM was transported to the Têt inner shelf and stored there until the dry storm occurred.

Keywords: fisheries, fish ecophysiology, energy reserves, reproduction, condition indices

This study analyses for the first time the lipid (energy) reserves of European hake (Merluccius merluccius) in the north-western Mediterranean from an ecophysiological perspective. Results show that there is a progressive accumulation of lipids in the liver of maturing hake -where the bulk of the fat is stored- as individuals grow. Results also indicate that female pre-spawners expend much energy on reproductive activities since they present lower liver lipid reserves than juveniles and maturing individuals. Furthermore, results show that female pre-spawners with higher lipid reserves in their livers had a higher amount of lipids in their ovaries, suggesting that maternal condition (spawner quality) may affect the reproductive potential of hake. Overall, the results of this study suggest that the analysis of liver lipid reserves during pre-spawning, along with the evaluation of the gonadosomatic index and the consideration of the reproductive stage, can contribute to improve the estimation of the reproductive potential of gadoid species such as hake.

Keywords: deep-water formation, thermocline circulation, ocean physiology, Milankovitch cycles

One possible path for exploring the Earth’s far-from-equilibrium homeostasis is to assume that it results from the organisation of optimal pulsating systems, analogous to that in complex living beings. Under this premise it becomes natural to examine the Earth’s organisation using physiological-like variables. Here we identify some of these main variables for the ocean’s circulatory system: pump rate, stroke volume, carbon and nutrient arterial-venous differences, inorganic nutrients and carbon supply, and metabolic rate. The stroke volume is proportional to the water transported into the thermocline and deep oceans, and the arterial-venous differences occur between recently-upwelled deep waters and very productive high-latitudes waters, with atmospheric CO2 being an indicator of the arterial-venous inorganic carbon difference. The metabolic rate is the internal-energy flux (here expressed as flux of inorganic carbon in the upper ocean) required by the system’s machinery, i.e. community respiration. We propose that the pump rate is set externally by the annual cycle, at one beat per year per hemisphere, and that the autotrophic ocean adjusts its stroke volume and arterial-venous differences to modify the internal-energy demand, triggered by long-period astronomical insolation cycles (external-energy supply). With this perspective we may conceive that the Earth’s interglacial-glacial cycle responds to an internal organisation analogous to that occurring in living beings during an exercise-recovery cycle. We use an idealised double-state metabolic model of the upper ocean (with the inorganic carbon/nutrients supply specified through the overturning rate and the steady-state inorganic carbon/nutrients concentrations) to obtain the temporal evolution of its inorganic carbon concentration, which mimics the glacial-interglacial atmospheric CO2 pattern.

Keywords: continental margins; submarine canyon; sediment accumulation rates; trawling; Northwestern Mediterranean; Palamós Canyon (41–42°N, 3–4°E)

In order to study sediment accumulation rates in the Palamós submarine canyon (Northwestern Mediterranean) during the last century, three sediment cores were extracted from the canyon axis at depths of 450, 1200 and 1750 m respectively, where instrumented moorings were previously located. Estimated sedimentation rates based on 210Pb and 137Cs profiles suggest that the contemporary trends of sediment transfer and accumulation in the canyon may be different from secular trends. During the seventies, a two-fold increase of the sediment accumulation rate took place at the 1750 m depth site. This change has been associated to trawling activities and is attributed to the rapid technical development that the local trawling fleet underwent during the seventies. The surroundings and rims of submarine canyons are frequently targeted by commercial trawling fisheries, an activity that may enhance the input of resuspended particles into canyons, and eventually trigger sediment gravity flows. Our results suggest that the effects of trawling over the dynamics of the seafloor may extend further and deeper from the fishing grounds, eventually extending to bathyal depths. Hence the anthropogenic influence on the sedimentary budget of some deep submarine environments may be more important than previously thought.

Keywords: benthic hydroids; feeding; intracellular digestion; assimilation; herbivory

Previous evidence has shown that benthic hydroids capture all kinds of available prey and the only known constraint was prey size. Among the prey captured are phytoplankton cells but it is not known whether they are digested and assimilated. To test the hypothesis that benthic hydroids assimilate phytoplankton cells, a series of feeding experiments was carried out with the Mediterranean species Eudendrium racemosum. Ingestion rates and assimilation efficiency were determined by analysing the 14C incorporated from a labelled population of the diatom species Thalassiosira weissflogii. Eudendrium racemosum fed on T. weissflogii, after a period of starvation, and with the diatoms as the sole food item. In the presence of approximately 15,000 diatoms ml−1, Eudendrium fed at rates ranging from 16 to 55 diatoms polyp−1 hour−1. Accumulation of radioactivity in the hydrocaulus and the polyps of the hydroids were observed. A maximum ingestion of 31.6 diatoms per μgC of polyp (i.e. 175 diatoms per polyp) was observed in the experiments. Most of the diatom 14C ingested would have ended up in the Eudendrium tissue (efficiency 94%), and it was expected that a certain percentage would have been respired by the polyps. These data show that Eudendrium feed on phytoplankton, which can satisfy almost 100% of their energy demand when this type of food is sufficiently abundant.

We have reviewed the phytoplankton composition and succession in the East African Great Lakes, their response to environmental changes, and the communities of microorganisms of the microbial food web. Recent studies in some great lakes, as well as progress in understanding phytoplankton succession and response to environmental factors, enable us to update knowledge of the phytoplankton ecology of these lakes. In particular, we present information indicating that phytoplankton composition in lakes Tanganyika and Kivu may reflect recent changes as a result of global warming or species introduction. We also stress the importance of microbes (at the base of the food web) in these systems and suggest that the microbial food web, which has been mostly overlooked until recently, may play a very large role in determining productivity and nutrient cycling in these large lakes.

Keywords: Central America; Plate Tectonics; extension; magmatism; arc geochemistry

This study revisits the kinematics and tectonics of Central America subduction, synthesizing observations of marine bathymetry, high-resolution land topography, current plate motions, and the recent seismotectonic and magmatic history in this region. The inferred tectonic history implies that the Guatemala–El Salvador and Nicaraguan segments of this volcanic arc have been a region of significant arc tectonic extension; extension arising from the interplay between subduction roll-back of the Cocos Plate and the ~ 10–15mm/yr slower westward drift of the Caribbean plate relative to the North American Plate. The ages of belts of magmatic rocks paralleling both sides of the current Nicaraguan arc are consistent with long-term arc-normal extension in Nicaragua at the rate of ~ 5–10mm/yr, in agreement with rates predicted by plate kinematics. Significant arc-normal extension can ‘hide’ a very large intrusive arc-magma flux; we suggest that Nicaragua is, in fact, the most magmatically robust section of the Central American arc, and that the volume of intrusive volcanism here has been previously greatly underestimated. Yet, this flux is hidden by the persistent extension and sediment infill of the rifting basin in which the current arc sits. Observed geochemical differences between the Nicaraguan arc and its neighbors which suggest that Nicaragua has a higher rate of arc-magmatism are consistent with this interpretation. Smaller-amplitude, but similar systematic geochemical correlations between arc-chemistry and arc-extension in Guatemala show the same pattern as the even larger variations between the Nicaragua arc and its neighbors.

Keywords: physiography; morphostructure; tectonics; fault reactivation; Cenozoic; Galicia Bank

An analysis of Cenozoic tectonics was carried out on the Galicia Bank Region by means of 750 km of single-channel and 155 km of multi-channel vertical seismic profiles and multibeam bathymetry. This work forms part of a general study aimed at determining the geological risk in the wreck area of the Prestige oil tanker. Several structures affecting the post-rift sedimentary units were identified: I) Faults inherited from the Lower Cretaceous propagating rift (reactivated and non-reactivated), including reactivated normal (N–S, NW–SE) and transfer (NE–SW) faults; and II) Structures resulting from compressive episodes in the Paleogene to Upper Miocene and the Upper Miocene to the Present, including a) neotectonic normal faults decoupled from the basement structure, b) folds and flexures and c) reverse faults (NE–SW to ENE–SWS) related to the Bay of Biscay subduction, that are the most striking regional structures. The characterization of structural style, sedimentary post-rift unit deformation and morphological trends were used to carry out a detailed study of the morphostructure of the Galicia Bank Region. Six morphostructural provinces were differentiated, from E to W: 1) the Galicia Interior Basin related to a main graben; 2) the Transitional Zone, which is a horst and graben territory; 3) the Galicia Bank Main Horst; 4) the Half-Graben Domain; 5) the Deep Galicia Margin, whose structure shows rotated blocks; and 6) the Northwestern Flank, characterized by reverse faults. The Transitional Zone and the Galicia Bank provinces are assumed to be the two morphostructural provinces of the Galicia Bank marginal platform. The origin of the Cenozoic deformation must have been related to reactivation processes during the Pyrenean orogeny. We propose that the fault pattern observed in the study area is related to the phase of renewed Mesozoic fault activity. Polyphase extension in the rifting stage and Cenozoic movements have produced an extensional interference pattern that is evident in the physiography. The decouplage between basement tectonics and upper sedimentary unit tectonics suggests the presence of a viscous layer. A thrust-related main antiform related to the Bay of Biscay subduction is proposed to explain the origin of the Galicia Bank morphology.

Keywords: 11β-hydroxylase, androgen receptor, aromatasa, estradiol receptor, estrogen rec,eptor, gene expression patterns, Igf1, laser capture microdissection , sea bass

The role of genes implicated in the regulation of spermatogenesis and their patterns of expression is still poorly understood. In this study, we took advantage of the cystic arrangement of the teleost testis to set up a laser capture microdissection procedure to isolate cells from cysts containing spermatogonia, spermatocytes, spermatids, or spermatozoa. We then used quantitative PCR to determine the stage-specific expression patterns of the germ cell marker vasa; gonadal aromatase (cyp19a); estrogen receptors (ers) alpha, beta1, and beta2 (era, erb1, and erb2, respectively); 11beta-hydroxylase (cyp11b1); androgen receptor beta (arb); insulinlike growth factor 1 (igf1); and sox17. vasa had the highest mRNA levels, followed by genes involved in androgen metabolism (cyp11b1 and arb). Most genes associated with estrogen metabolism (cyp19a, era, and erb1) had a lower expression, whereas igf1 and sox17 exhibited the lowest mRNA levels. Comparison of changes in mRNA levels revealed five patterns of gene expression, in general with progressively lower expression seen as spermatogenesis advanced. igf1 and sox17 were exclusively expressed in spermatogonia-containing cysts, suggesting effects during the proliferative stage. Genes involved in androgen synthesis (cyp11b1) and action (arb) peaked during the early stages of spermatogenesis and then sharply decreased. In contrast, genes associated with estrogen action, particularly erb2 and era, showed a more gradual decrease. Together, these results demonstrate the usefulness of fish models and suggest that whereas androgens are required at high levels and may exert their major actions at the initial stages of spermatogenesis, estrogens are also essential, albeit required at lower levels, and with a more generalized influence.

Marine cyanobacteria of the genera Prochlorococcus and Synechococcus are important contributors to global primary production occupying a key position at the base of marine food webs. The genetically diverse nature of each genus is likely an important reason for their successful colonization of vast tracts of the world's oceans, a feature that has led to detailed analysis of the distribution of these genetic lineages at the local and ocean basin scale. Here, we extend these analyses to the global dimension, using new data from cruises in the Pacific, Indian and Arctic Oceans in combination with data from previous studies in the Atlantic Ocean, Arabian Sea, Red Sea and a circumnavigation of the southern hemisphere to form a data set which comprises most of the world's major ocean systems. We show that the distribution patterns of Prochlorococcus and Synechococcus lineages are remarkably similar in different ocean systems with comparable environmental conditions, but producing a strikingly different ‘signature’ in the four major ocean domains or biomes (the Polar Domain, Coastal Boundary Domain, Trade Winds Domain and Westerly Winds Domain). This clearly reiterates the idea of spatial partitioning of individual cyanobacterial lineages, but at the global scale.

Keywords: bacterioplankton - production - respiration - carbon - marine - seasonality - growth efficiency - coastal

Data from several years of monthly samplings are combined with a 1-year detailed study of carbon flux through bacteria at a NW Mediterranean coastal site to delineate the bacterial role in carbon use and to assess whether environmental factors or bacterial assemblage composition affected the in situ rates of bacterial carbon processing. Leucine (Leu) uptake rates [as an estimate of bacterial heterotrophic production (BHP)] showed high interannual variability but, on average, lower values were found in winter (around 50 pM Leu−1 h−1) as compared to summer (around 150 pM Leu−1 h−1). Leu-to-carbon conversion factors ranged from 0.9 to 3.6 kgC mol Leu−1, with generally higher values in winter. Leu uptake was only weakly correlated to temperature, and over a full-year cycle (in 2003), Leu uptake peaked concomitantly with winter chlorophyll a (Chl a) maxima, and in periods of high ectoenzyme activities in spring and summer. This suggests that both low molecular weight dissolved organic matter (DOM) released by phytoplankton, and high molecular weight DOM in periods of low Chl a, can enhance BHP. Bacterial respiration (BR, range 7–48 μg C l−1 d−1) was not correlated to BHP or temperature, but was significantly correlated to DOC concentration. Total bacterial carbon demand (BHP plus BR) was only met by dissolved organic carbon produced by phytoplankton during the winter period. We measured bacterial growth efficiencies by the short-term and the long-term methods and they ranged from 3 to 42%, increasing during the phytoplankton blooms in winter (during the Chl a peaks), and in spring. Changes in bacterioplankton assemblage structure (as depicted by denaturing gradient gel electrophoresis fingerprinting) were not coupled to changes in ecosystem functioning, at least in bacterial carbon use.

We collected surface samples in Franklin Bay (Western Arctic) from ice-covered to ice-free conditions, to determine seasonal changes in the identity and in situ activity of the prokaryotic assemblages. Catalysed reported fluorescence in situ hybridization was used to quantify the abundance of different groups, and combined with microautoradiography to determine the fraction of active cells taking up three substrates: glucose, amino acids and ATP. In surface waters, Archaea accounted for 16% of the total cell count in winter, but decreased to almost undetectable levels in summer, when Bacteria made up 97% of the total cell count. Alphaproteobacteria were the most abundant group followed by Bacteroidetes (average of 34% and 14% of total cell counts respectively). Some bacterial groups appearing in low abundances (< 10% of total cell counts), such as Betaproteo- bacteria, Roseobacter and Gammaproteobacteria, showed a high percentage of active cells. By contrast, more abundant groups, such as SAR11 or Bacteroidetes, had a lower percentage of active cells in the uptake of the substrates tested. Archaea showed low heterotrophic activity throughout the year. In comparison with temperate oceans, the percentage of active Bacteria in the uptake of the substrates was relatively high, even during the winter season.

Keywords: foraminifera; Mg/Ca; Ocean Drilling Program; electron microprobe; laser ablation; calcium carbonate

The advent of new microanalytical techniques such as electron microprobe mapping (EMP) and laser ablation microsamplers coupled to mass spectrometers (LA-ICP-MS) provides a new array of possibilities to explore in great detail the trace elements distribution in foraminiferal carbonates. Here we apply these techniques to characterize diagenetic phases present in foraminiferal shells from Ocean Drilling Program Site 1240 in the Panama Basin, a region characterized by the presence of manganese-rich minerals in the sediments. The combined application of these techniques allows us to characterize the elemental and spatial distribution on the surface and across the foraminiferal shells. Results illustrate the presence of at least two different Mn-rich contaminant phases in the foraminiferal carbonates: Mn-rich carbonates and ferromanganese oxides. Elemental maps also highlight the relevance of the foraminifera shell texture and porosity in the distribution and formation of these contaminant phases. In the case of Neogloboquadrina dutertrei, Mn phases form a continuous thin layer in the inner part of the chambers, whereas for Globigerinoides ruber, Mn phases have a rather patchy distribution and are usually found within the pores. Significant high magnesium concentrations are always associated with these Mn-rich phases. These new findings support the need of removing these Mn-rich contaminant phases in order to measure accurately the Mg/Ca ratios in the foraminifera shell and therefore obtain reliable Mg/Ca paleotemperature reconstructions.

Syndiniales are a parasitic order within the eukaryotic lineage Dinophyceae (Alveolata). Here, we analysed the taxonomy of this group using 43655 18S rRNA gene sequences obtained either from environmental data sets or cultures, including 6874 environmental sequences from this study derived from Atlantic and Mediterranean waters. A total of 5571 out of the 43655 sequences analysed fell within the Dinophyceae. Both bayesian and maximum likelihood phylogenies placed Syndiniales in five main groups (I–V), as a monophyletic lineage at the base of ‘core’ dinoflagellates (all Dinophyceae except Syndiniales), although the latter placement was not bootstrap supported. Thus, the two uncultured novel marine alveolate groups I and II, which have been highlighted previously, are confirmed to belong to the Syndiniales. These groups were the most diverse and highly represented in environmental studies. Within each, 8 and 44 clades were identified respectively. Co-evolutionary trends between parasitic Syndiniales and their putative hosts were not clear, suggesting they may be relatively ‘general’ parasitoids. Based on the overall distribution patterns of the Syndiniales-affiliated sequences, we propose that Syndiniales are exclusively marine. Interestingly, sequences belonging to groups II, III and V were largely retrieved from the photic zone, while Group I dominated samples from anoxic and suboxic ecosystems. Nevertheless, both groups I and II contained specific clades preferentially, or exclusively, retrieved from these latter ecosystems. Given the broad distribution of Syndiniales, our work indicates that parasitism may be a major force in ocean food webs, a force that is neglected in current conceptualizations of the marine carbon cycle.

Keywords: Merluccius merluccius, cascading events, spawning pattern, fecundity, western Mediterranean

The spawning cycle of the European hake (Merluccius merluccius, (Linnaeus, 1758)) was studied in two western Mediterranean areas, the Catalan Sea and the northern Tyrrhenian Sea, including observation of the monthly seasonal variation of the gonad maturity and the gonadosomatic index (GSI). The estimation of the maturity stages by GSI gave similar values in the two study areas: the spawning stage (IV) was easily distinguished from the other maturity stages and its range of variation showed a low overlap with stage III and no overlap with other stages. Although in both study areas active females were present during all the sampled months, the peak of reproductive activity was concentrated from February to May in the northern Tyrrhenian Sea but from August to December in the Catalan Sea, which was subjected to winter cascading events. Batch fecundity gave similar values in the Catalan and northern Tyrrhenian Seas: 204 and 202 eggs per gonad-free female gram, respectively. An asynchronous oocyte development is suggested for M. merluccius in the western Mediterranean.

Keywords: Aromatase; cyp19; Estrogens; Estrogen receptors; Sex differentiation; Sea bass; Dicentrarchus labrax

The present study addresses the role of aromatase and estrogen receptors in sex differentiation and development. With this purpose, a sea bass female- and a male-dominant group were obtained by successive size gradings since in this species females are already larger than males at the time of sex differentiation. Changes in cyp19a and cyp19b gene expression and enzymatic activity were monitored by a validated real-time PCR and a tritiated water assay, respectively, during early development and sex differentiation. Changes in mRNA expression of estrogen receptors, both erb1 and erb2, were also assessed during this period. Results show clear sex-related differences in cyp19a gene expression and enzymatic activity in gonads, with females exhibiting significantly higher levels than males at 150 days post hatching (DPH), when histological signs of sex differentiation were evident. cyp19b gene expression and activity in brain were detectable during early ontogenesis at 50 DPH but no clear sex-related differences were observed. Both erb1 and erb2 showed higher gene expression levels in testis than in ovaries around 200–250 DPH, corresponding with the time of testicular differentiation and precocious male maturation, but no sex-related differences were found in the brain. Together these results indicate that in the European sea bass high expression levels of cyp19a are associated with ovarian differentiation and thus cyp19a can be considered as a suitable molecular marker of ovarian differentiation. However, the involvement of cyp19b in sex differentiation cannot be concluded. In addition, the higher levels of erb1 and erb2 in males versus females during sex differentiation, coinciding with precocious male maturation in the sea bass, suggest an important role for these receptors in testicular development and maturation.

Keywords: Food-web modelling; Ecopath with Ecosim; Fishing impacts; Environmental factors; Ecosystem indicators; Trend analysis; Catalan Sea; NW Mediterranean

An ecosystem model representing the continental shelf and upper slope of the South Catalan Sea (NW Mediterranean) is calibrated and fitted to the available time series data from 1978 to 2003. We use a process-oriented model to explore the extent to which changes in marine resources and the ecosystem were driven by trophic interactions, environmental factors and fishing activities. Fishing effort and fishing mortality are used to drive the model, while observed (absolute and relative) biomasses and catches are compared with the predicted results. A reduction in the sum of the squared deviations of the observed and predicted values of the biomass is used as a metric for calibrating and assessing the fit of the model. A posteriori trophodynamic indicators are used to explore the ecosystem's structural and functional changes from 1978 to 2003, and a generalized least squares regression is used to assess the significance of the predicted trends. In general, a high proportion of the variability in the time series data is explained by the main trophic interactions (37–53%), fishing activities (14%), and indirectly by considering the environment (6–16%), as driving factors. The model's predictions match satisfactorily with the yearly data on the biomass for anglerfish, adult hake, demersal sharks, anchovy and mackerel, which show a statistically significant decrease over time, while the biomass of flatfish and seabirds are observed to increase. Catch data show a significant decrease in anglerfish, demersal sharks, anchovy and sardine, while there is an increase in red mullet, flatfish, juvenile hake and horse mackerel. These changes in biomass are predicted to have direct and indirect impacts on the ecosystem mediated by the trophic web, such as the proliferation of non-commercial species with lower trophic levels (e.g., benthic invertebrates) or higher turnover rates (e.g., cephalopods and benthopelagic fish). This is consistent with anecdotal information from the Mediterranean and is likely caused by trophic cascades due to the removal of demersal and pelagic higher trophic level organisms (predator release), and a decrease in small pelagic fish (competitor release). Trophodynamic indicators suggest a degradation pattern over time: both the mean trophic level of the community (mTLco, excluding primary producers and detritus) and a modified version of Kempton's index of biodiversity decrease with time, while the total flow to detritus and the loss of production due to fishing increase from 1978 to 2003. Additionally, the demersal/pelagic ratio increases due to an overall decrease in the abundance of small pelagic fish in the ecosystem.

Keywords: Trawl selectivity · Ecosystem management of fisheries · Trophodynamic model · Ecopath with Ecosim · Mediterranean Sea

We explored the potential ecosystem effects of improved selectivity in the South Catalan Sea demersal trawl fishery. A calibrated food web model representing current conditions of the ecosystem and selectivity data from recent fishing experiments were used to perform temporal dynamic simulations. This enabled the evaluation of direct and indirect impacts of fishing and provided insights into the sustainability of various management options for the trawl fishery. This fishery has the biggest fleet in the area, it is highly multispecies, and catches are largely composed of juveniles of target species and non-target species, which are often discarded in large quantities. Simulations indicate that improvement of trawl selectivity would have noticeable and complex direct and indirect effects on target and non-target demersal species. The biomass and catch of various commercial species (e.g. anglerfish, adult hake) would increase, while that of invertebrates (e.g. suprabenthos, Norway lobster) and juvenile and small-sized fish species (e.g. juvenile hake, blue whiting) would decrease due to higher predation mortalities and trophic cascades in the food web. Impacts on the pelagic compartment would also be noticeable. A slight increase in the mean trophic level of the community and of the catch is predicted, as well as of ecosystem biomass diversity. Generally, however, a greater reduction of fishing effort would be necessary for the recovery of highly exploited or overexploited demersal species. Trawling would experience moderate decreases in catches, while long-lining and bait-trolling would benefit. This work highlights the importance of including the mortality incurred during or post-escape from trawl nets when assessing the ecosystem effects of improved trawl selectivity.

Fisheries catches represent a net export of mass and energy that can no longer be used by trophic levels higher than those fished. Thus, exploitation implies a depletion of secondary production of higher trophic levels (here the production of mass and energy by herbivores and carnivores in the ecosystem) due to the removal of prey. The depletion of secondary production due to the export of biomass and energy through catches was recently formulated as a proxy for evaluating the ecosystem impacts of fishing–i.e., the level of ecosystem overfishing. Here we evaluate the historical and current risk of ecosystem overfishing at a global scale by quantifying the depletion of secondary production using the best available fisheries and ecological data (i.e., catch and primary production). Our results highlight an increasing trend in the number of unsustainable fisheries (i.e., an increase in the risk of ecosystem overfishing) from the 1950s to the 2000s, and illustrate the worldwide geographic expansion of overfishing. These results enable to assess when and where fishing became unsustainable at the ecosystem level. At present, total catch per capita from Large Marine Ecosystems is at least twice the value estimated to ensure fishing at moderate sustainable levels.

Keywords: Trawling disturbance; Benthic communities; Ecosystem-based management; Effort reduction; North-western and central Mediterranean Sea

Within the framework of ecosystem-based management, we focused on the use of seasonal closures as effective measures to minimise the degradation of benthic communities by trawling. These closures imply the complete cessation of trawling fleet activity and are commonly used in the Mediterranean to reduce the annual fishing effort, with the ultimate goal of effective resource management. In this study, we aimed to investigate how epibenthic communities respond to seasonal closures. The potential benefits of short-term annual closures in two Mediterranean fishing grounds were evaluated by analysing changes in community structure and composition that were linked to the closure. A decrease of faunal abundance was observed with the resumption of fishing activity after the closure at both fishing grounds. Remarkably, results indicated that some large and mobile fauna were able to respond to these closures. We concluded that the currently planned closures are too short to benefit benthic communities.

Este libro se gestó en el congreso sobre Ecología celebrado en Barcelona entre el 16 y 18 de Noviembre de 2005 bajo el título “La unidad en la diversidad. Un congreso sobre ecología tras el legado de Ramón Margalef”. El lema del congreso intentaba resumir la contribución más importante del profesor a la vez que servir de estímulo para una reflexión del estado actual de la ecología y sus posibilidades de afrontar de manera conjunta los desafíos que impone el cambio global y la crisis ambiental. La Ecología, como ciencia de síntesis, trata de explicar el funcionamiento de los sistemas ecológicos mediante la integración de conocimientos procedentes, en buena medida, de otras ciencias. Además de con la biología, la ecología interacciona con ciencias como la física, y más concretamente la termodinámica, que ofrece un contexto para explicar el funcionamiento de los ecosistemas, así como con las matemáticas, que proporcionan herramientas para plasmar las teorías ecológicas en expresiones manejables, y con la química, que establece las bases para la comprensión de los ciclos biogeoquímicos y la transformación de la materia y la energía en los procesos ecosistémicos.

Keywords: Alexandrium catenella; Copepods; Harmful algal blooms; NW Mediterranean; Phosphorus; Toxins

A microcosm approach was used to test whether: a) growth under unbalanced nutrient conditions (varying N:P ratios) affected the susceptibility of a phytoplankton community including the dinoflagellate Alexandrium catenella (a paralytic shellfish toxin producer) to mesozooplankton grazing, and b) the potential effects of unbalanced nutrient conditions were mediated by changes in toxicity of A. catenella or by other mechanisms. The experimental setup consisted of fifteen 30 l microcosms, filled with water from the Barcelona Harbour and subjected to treatments combining nutrient inputs at three different N:P ratios (Redfield N:P ratio or nutrient-balanced, high N:P and low N:P), addition or omission of A. catenella (an estimated initial concentration of 38 A. catenella cells ml− 1, a value typical for blooms in harbours of the Catalan coast), and selective addition of a cultured population of Acartia grani. P sufficiency had a strong positive effect on the growth of A. grani, both with or without A. catenella addition, presumably due to enhanced food quality of the prey community. The presence of this copepod resulted in lower concentrations of ciliates, A. catenella, and other dinoflagellates, suggesting active grazing by the copepods. No noxious effects of A. catenella on the copepods were detected at the relatively low cell concentrations of that dinoflagellate used in the experiment.

Keywords: erosive features; Mediterranean Outflow Water; Gulf of Cadiz; continental slope; contourites; neotectonics; Quaternary

Contourite depositional systems have been the focus of much recent research, but still relatively little is known about contourite erosive features and their associated processes. Based on multibeam bathymetry, side-scan imagery and different resolution seismic records, a detailed description and classification of the major erosive submarine valley features of the Contourite Depositional System of the Gulf of Cadiz middle slope is presented for the first time. Four types of erosive features have been differentiated, including contourite moats, contourite channels, marginal valleys and large isolated furrows, and interpreted in terms of their tectonic and oceanographic implications during the Quaternary. The study of the distribution and characteristics of erosive features is essential to better understand the present and past interaction of the Mediterranean Outflow Water (MOW) with the middle slope seafloor, and allows us to propose a new and more precise scheme for the MOW circulation patterns. This scheme includes a main along-slope circulation responsible for the excavation of the contourite moat and channels, and a secondary down-slope circulation responsible for the erosion of marginal valleys and isolated furrows. Three evolutionary stages have been observed in the development of the erosive system during the Quaternary, that can be related to changes in the distribution and splitting of the MOW as a consequence of the segmentation of the NE–SW diapiric ridges by neotectonic effects: 1) Early Pleistocene to Mid-Pleistocene: linear diapiric ridges; 2) Mid-Pleistocene to Late Pleistocene: diapiric reactivation and 3) Late Pleistocene to Holocene: main recent phase of diapiric ridges segmentation and rotation. This study provides important regional clues for establishing the evolution of the erosive features in relation with neotectonic effects, and represents a good example of the potential of erosive features as evidences for the reconstruction of the paleoceanography and recent tectonic changes.

Keywords: Antarctica; Bransfield Basin; glacial processes; glaciomarine processes; seismic stratigraphy

A seismic stratigraphic study of the Antarctic Peninsula margin of the Central Bransfield Basin was conducted using seismic and bathymetric data. The study focused on seismic sequences and units deposited after the basin opened, and yield a record of the evolution of the northern-most Antarctic Peninsula Ice Sheet. Two seismic sequences compose the post-rift stratigraphic succession on the Central Bransfield Basin slope platforms. Both sequences are composed of seismic units that record glacial/interglacial cycles and show evidence of the Antarctic Peninsula Ice Sheet having grounded on the continental shelf and slope platform on several occasions in the past. This evidence includes glacial and glaciomarine related sedimentary and erosional features within the seismic units (glacial unconformities, glacial troughs, till wedges, prograded wedges, trough mouth fans, glaciomarine sheet deposits and moraines), which are bounded by glacial unconformities. The Antarctic Peninsula lower slope also registered in its eastern sector the deposition of gravity flow deposits during ice sheet retreat and interglacial stages. The deposition of seismic units on the middle slope produced the present-day step-like profile of the margin composed of wide flat slope platforms and narrow and steep upper and lower slopes. Seismic units show changes in thickness and distribution that record the effect of the physiography and climatic changes on margin sedimentation. These variations produced an overall change from more line-sourced deposition to more point sourced deposition as ice streams evolved. The stacking of units shows a change in the stratigraphic architecture through time, from dominantly progradational (S2) to progradational/aggradational (S1). This change is correlated with a change in the frequency of ice sheet grounding events which was probably driven by a higher rate of eustatic rise and fall in relation with the Mid Pleistocene global climatic change.

Keywords: Oil-spill; Operational oceanography; Real-time; Forecast; Spanish waters

The ESEOO Project, launched after the Prestige crisis, has boosted operational oceanography capacities in Spain, creating new operational oceanographic services and increasing synergies between these new operational tools and already existing systems. In consequence, the present preparedness to face an oil-spill crisis is enhanced, significantly improving the operational response regarding ocean, meteorological and oil-spill monitoring and forecasting. A key aspect of this progress has been the agreement between the scientific community and the Spanish Search and Rescue Institution (SASEMAR), significantly favoured within the ESEOO framework. Important achievements of this collaboration are: (1) the design of protocols that at the crisis time provide operational state-of-theart information, derived from both forecasting and observing systems; (2) the establishment, in case of oil-spill crisis, of a new specialized unit, named USyP, to monitor and forecast the marine oceanographic situation, providing the required met-ocean and oil-spill information for the crisis managers. The oil-spill crisis scenario simulated during the international search and rescue Exercise 'Gijón-2006', organized by SASEMAR, represented an excellent opportunity to test the capabilities and the effectiveness of this USyP unit, as well as the protocols established to analyze and transfer information. The results presented in this work illustrate the effectiveness of the operational approach, and constitute an encouraging and improved base to face oil-spill crisis.

Past studies have shown that surface chlorophyll-a concentrations increase in the wake of hurricanes. Given the reported increase in the intensity of North Atlantic hurricanes in recent years, increasing chlorophyll-a concentrations, perhaps an indication of increasing biological productivity, would be an expected consequence. However, in order to understand the impact of variable hurricane activity on ocean biology, the magnitude of the hurricane-induced chlorophyll increase relative to other events that stir or mix the upper ocean must be assessed. This study investigates the upper ocean biological response to tropical cyclones in the North Atlantic from 1997–2005. Specifically, we quantitatively compare the anomalous chlorophyll-a concentrations created by cyclone activity to the total distribution of anomalies in the subtropical waters. We show that the cyclone-induced chlorophyll-a increase has minimal impact on the integrated biomass budget, a result that holds even when taking into consideration the lagged and asymmetrical response of ocean color.

Keywords: European hake; Recruitment; Environment; Condition indices; Energy allocation; Western Mediterranean

This study evaluates the link between the recruitment process of European hake (Merluccius merluccius L.) of the Balearic Islands (western Mediterranean) and the environmental and physiological conditions. Spatio-temporal variation of abundance and condition of fish were evaluated at two locations each with different oceanographic conditions, one in the north (Sóller, SO) and another in the south (Cabrera, CA) of Mallorca Island. Environmental variables explored were hydrography, sediment characteristics, phytoplankton pigment concentration (ppc) and the trophic resources of hake. Individuals were divided in three life stages: recruits, post-recruits and young adults. Hepatosomatic index (HSI), relative condition index (Kn), gonadosomatic index (GSI) and fullness index (FI) were analysed for the three life stages. Recruitment starts in February with the incorporation of smaller hakes, and it can be followed through spring and early summer with a peak in April. However, some spatial heterogeneity in the recruitment process has been found between north and south of the Island. The main pulse of recruitment occurred at a different time in the two areas. Spatial heterogeneity was also consistent with the condition of hake recruits, with higher values of Kn and HSI at SO than at CA. Maximum values of Kn were found in February at SO and in April at CA, coinciding with the start of the different recruitment pulses to the fishing grounds. Post-recruits and young adults also showed higher condition at SO than at CA. The arrival in spring of the Western Winter Intermediate Waters (WIW) drives the spatial-temporal variation in abundance and condition of hake. Ppc was highly correlated with recruit abundance with a time lag of two months, while for post-recruits the time lag was three months. The observed differences in the condition of hake between areas could be a consequence of the fact that the waters to the north of Mallorca are comparatively more under the seasonal influence of WIW which is formed in more productive areas. Thus, this study characterises the short temporal and spatial variability in the hake recruitment process off the Balearic Islands, both in terms of abundance and fish condition. This pattern is explained on the basis of the mesoscale environmental variability observed between north and south of Mallorca and the ecological adaptive strategy of recruiting in the optimal environmental season.

Keywords: Carbon flux · Microbial ecology · Ocean · Bacteria · Protists · Light · Genomics · Chemoautotrophy · Models

We now have a relatively good idea of how bulk microbial processes shape the cycling of organic matter and nutrients in the sea. The advent of the molecular biology era in microbial ecology has resulted in advanced knowledge about the diversity of marine microorganisms, suggesting that we might have reached a high level of understanding of carbon fluxes in the oceans. However, it is becoming increasingly clear that there are large gaps in the understanding of the role of bacteria in regulating carbon fluxes. These gaps may result from methodological as well as conceptual limitations. For example, should bacterial production be measured in the light? Can bacterial production conversion factors be predicted, and how are they affected by loss of tracers through respiration? Is it true that respiration is relatively constant compared to production? How can accurate measures of bacterial growth efficiency be obtained? In this paper, we discuss whether such questions could (or should) be addressed. Ongoing genome analyses are rapidly widening our understanding of possible metabolic pathways and cellular adaptations used by marine bacteria in their quest for resources and struggle for survival (e.g. utilization of light, acquisition of nutrients, predator avoidance, etc.). Further, analyses of the identity of bacteria using molecular markers (e.g. subgroups of Bacteria and Archaea) combined with activity tracers might bring knowledge to a higher level. Since bacterial growth (and thereby consumption of DOC and inorganic nutrients) is likely regulated differently in different bacteria, it will be critical to learn about the life strategies of the key bacterial species to achieve a comprehensive understanding of bacterial regulation of C fluxes. Finally, some processes known to occur in the microbial food web are hardly ever characterized and are not represented in current food web models. We discuss these issues and offer specific comments and advice for future research agendas

Keywords: gasteròpode, contaminació, tributilestany, masculinització, imposex.

El seguiment del fenomen de l’imposex (aparició de caràcters masculins en les femelles a causa de la presència del tributilestany (TBT) a l’aigua del mar) ha estat estudiat durant onze anys, de l999 a 2008, en el gasteròpode Bolinus brandaris, capturat principalment a la localitat de St. Carles de la Ràpita. Durant els primers set anys es van trobar anomalies anatòmiques en més d’un 90 % dels casos, malgrat les normes dictades per la Conselleria de Medi Ambient a partir de 1990 per evitar aquesta contaminació. Anatòmicament, es van observar petites diferències entre els conductes deferents i el penis del mascle respecte als de la femella. En els darrers tres anys aquest fenomen ha disminuït, i pràcticament ha desaparegut en els exemplars procedents de St. Carles de la Ràpita

Keywords: Satellite observations, Data assimilation, Remote sensing

The authors investigate the potential qualitative improvement brought by wide-swath, interferometry-based ocean altimetry measurements with respect to classical nadir altimeters in a coastal/shelf data assimilation system. In addition, particular attention is paid to roll errors, which could significantly reduce the expected benefits of wide-swath altimetry. A barotropic, nonlinear free-surface model is set up over the European shelf as part of an ensemble Kalman filter. Experiments assimilating simulated data are performed over the North Sea to test the ability of altimeter configurations to reduce model errors due to the action of meteorological forcing in the presence of bathymetric uncertainties. A simplified wide-swath observation scheme is used, composed of nadir altimeter height plus a nadir-centered cross-track sea level slope measurement. The simplified wide-swath measurements are found to be able to constrain events unsampled by a single nadir altimeter owing to a wider domain of influence in the cross-track direction and the ability to detect cross-track gradients. Since the satellite-borne interferometer is highly sensitive to the platform behavior, especially satellite roll, experiments taking roll errors into account are then carried out. Whereas observational errors are considered independent in most data assimilation studies, the roll of the platform correlates those errors along the path of the satellite. Despite the large amplitude of the roll errors, the contribution of the wide-swath altimeter in coastal zones remains valuable as long as the roll frequency is known (within Gaussian error) and the assimilation scheme is designed to take observational error correlations into account.

Metabolic diversity of heterotrophic bacterioplankton was tracked from early winter through spring with Biolog Ecoplates under the seasonally ice covered arctic shelf in the Canadian Arctic (Franklin Bay, Beaufort Sea). Samples were taken every 6 days from December 2003 to May 2004 at the surface, the halocline where a temperature inversion occurs, and at 200 m, close to the bottom. Despite the low nutrient levels and low chlorophyll a, suggesting oligotrophy in the winter surface waters, the number of substrates used (NSU) was greater than in spring, when chlorophyll a concentrations increased. Denaturing gradient gel electrophorisis analysis also indicated that the winter and spring bacterial communities were phylogenetically distinct, with several new bands appearing in spring. In spring, the bacterial community would have access to the freshly produced organic carbon from the early phytoplankton bloom and the growth of rapidly growing specialist phenotypes would be favoured. In contrast, in winter bacterioplankton consumed more complex organic matter originated during the previous year's phytoplankton production. At the other depths we tested the NSU was similar to that for the winter surface, with no seasonal pattern. Instead, bacterioplankton metabolism seemed to be influenced by resuspension, advection, and sedimentation events that contributed organic matter that enhanced bacterial metabolism.

Keywords: Marine fish; Cholinesterases; Lipid peroxidation; NW Mediterranean; Trophic level; Diet; Swimming capacity

We selected muscle tissue from nine commercial fish species, seven teleosts and two elasmobranchs, frequently caught in the NW Mediterranean trawling grounds in two different habitats (the continental shelf at 53 m and the slope at 660 m) for cholinesterases (ChEs) characterisation and activities determination, as well as the measure of lipid peroxidation (LP) levels. Acethyl- (AChE), butyryl- (BChE) and propionyl- (PrChE) cholinesterase were chosen as exposure markers of neurotoxic chemicals/molecules and LP as an effect marker of oxidative damage. The use of diagnose inhibitors: eserine sulphate, iso-OMPA and BW284c51 confirmed the measurement of true ChEs as well as the presence of pseudocholinesterases. The present study has evidenced the existence of interspecies differences, especially between teleosts and elasmobranchs but not in relation to depth. Moreover, the good correlation observed between all ChEs in most of the studied fish, supports the use of AChE as neurotoxic marker in field pollution monitoring. The non-metric multidimensional scaling analysis identified the commercial species hake Merluccius merluccius, among teleosts, and the shark, Galeus melastomus, as more adequate sentinel species in commercial fishing grounds. AChE activity showed a relationship with the fish trophic level, while all ChEs revealed a relationship with the feeding habits (benthic, suprabenthic, pelagic) and the stomach fullness. BChE activity and LP levels were the only markers to show a relationship with their swimming capacity.

The SMOS (Soil Moisture and Ocean Salinity) Mission is the second of the ESApsilas Living Planet Programme Earth Explorer Opportunity Missions and it is scheduled for launch on November 2008. Its objective is to provide global and frequent Soil Moisture (SM) and Sea Surface Salinity (SSS) maps. SMOSpsila single payload is the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS) sensor, an L-band two-dimensional aperture synthesis interferometric radiometer. To help in the retrieval process, auxiliary data must be used in combination with the brightness temperatures measured by MIRAS. The output products of SMOS at Level 3 will be SSS remote measurements with global coverage and an accuracy of 0.1-0.4 psu (practical salinity units) over 100 x 100 - 200 times 200 km2 in 30 - 10 days. In this study pseudo SMOS Level 3 Products have been obtained in order to test the impact at Level 3 of introducing ARGO salinity measurements in the SMOS data processing chain. To do so: 1) The Ocean Parallelise (OPA) Model has been run to provide geophysical parameters; 2) The SMOS End-to-end Processor Simulator (SEPS) has been used to compute the brightness temperatures as measured by the MIRAS; 3) The SMOS Level 2 Processor Simulator (SMOS-L2PS) has been applied to retrieve SSS values for each point and overpass. To asses also the possible impact of the coastal vicinity effect, two different zones have been simulated; the first one in open ocean and the second one in a coastal region, near the Canary islands (Spain) where SMOS and Aquarius CAL/VAL activities are foreseen. The results for both simulation scenarios are presented and discussed.

Keywords: Western Mediterranean; continental shelf; warming trends; sea level; NAO index

We analyse hydrographic, meteorological and sea level time series in the continental shelves of Málaga Bay and L'Estartit, in the South and North Western Mediterranean. We have detected an important reduction of the warming rates reported for the 90s decade, showing that the warming process of the Mediterranean is superimposed on several years lasting oscillations. These accelerations or interruptions, typically account for a fraction of the total trend, and therefore they are not able to obscure the warming detection if the time series are long enough. On the other hand, they can produce artificial results if the time series are short when compared with the length of these cycles. The warming of the shelf waters, its acceleration during the 90s and the reversal during the beginning of the XXI century, are also observed in air temperature time series along the Spanish Mediterranean. We have also checked the influence of the warming acceleration/disruption on the sea level rise. Mean sea level trends are around 1 mm/yr when long time series are analysed, but shorter time series can result in rising trends as large as 13 mm/yr, for accelerated warming periods, or even no sea level change for reversals of the warming trends. Another factor to study is the influence of the NAO on these warming/cooling periods as well as on the strength of upwelling favourable winds, which could have a great importance on shelf ecosystems.

Semi-enclosed and bounded by three continents, the Mediterranean sea is a region highly vulnerable to human activities, i.e.: the population surge along the coasts, the tourism pressure, the maritime traffic, the agriculture and the fishery exploitation, all have a potential impact on the Mediterranean environment. In addition, effective initiatives against the Global Climate Change need to be attempted in order to preserve our marine environment and to achieve a sustainable development of its resources. Prevention and adaptation to this new threat must be based on the rigorous and scientific knowledge accomplished through the systematic and continuous observation of the sea, and through the collection of multidisciplinary time-series and the subsequent analysis. This report responds to this necessity. The main goals of the Instituto Español de Oceanografía (IEO) are to generate scientific knowledge, as well as to assess and to inform the public about the state of the sea. The IEO is primary focussed on the study of the variety of phenomena influencing spanish coasts, including the process of Climate Change. To meet these objectives, a large set of actions have been planned. Some of them are already being implemented, such as a multidisciplinary observation system in the shelf and continental slope waters, or periodic scientific reports dealing with the detection and quantification of Climate Change effects and of other possible environmental impacts. The present report is the first of a series of future contributions. Besides the IEO, other Spanish institutions such as the ICM (CSIC), Puertos del Estado (PE), the IMEDEA (CSIC), the UMA, the UIB and the INM, involved in the monitoring, analysis and modelling of the Mediterranean sea, have also participated in it. The results show clear evidences of the effect of Climate Change in the physical properties of the mediterranean waters since 1948; in particular, the temperature and salinity increase of the deep waters, the accelerated rise of sea level since the early 1990s, and the air and sea surface temperature increase during the second half of the XX century.

We studied the seasonal variation of biotic and abiotic processes and the physico-chemical forcing factors involved in the production and consumption of dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) at a coastal sampling station in the northwestern Mediterranean. Monthly samplings of surface seawater for an 18-month period revealed that algal-associated DMSP and dimethylsulfoxide (DMSO) did not follow total phytoplankton biomass (measured as chlorophyll a [Chl a]). DMSP concentrations peaked 1 or 2 months later than the late winter Chl a bloom, following phytoplankton succession, whereas particulate DMSO was maximal in summer. Both Chl a–normalized concentrations (DMSP : Chl a and DMSO: Chl a) exhibited a clear seasonality with maxima in summer, which was indicative of concurrent phytoplankton succession and physiological acclimation toward higher dimethylated sulfur–producing taxa in summer. DMS concentrations also showed clear maxima in mid-summer and minima in winter, which is anticorrelated with Chl a. Gross DMS production rates were higher in summer, coinciding with higher DMSP-to-DMS conversion yields and exceeded microbial DMS consumption in this season. Heterotrophic bacteria and DMSP-assimilating phytoplankton only accounted for a portion (annual average 52%) of total DMSP transformations, suggesting that phytoplankton DMSP-lyases, either in stressed cells or upon grazing by herbivores, must play a more important role in DMS production than is generally believed. Calculated photolysis and measured microbial consumption alternated in dominance as DMS sinks over the year, with ventilation to the atmosphere generally being a minor loss process. Under higher solar radiation (from March to September), calculated photolysis followed variations of colored dissolved organic matter, a known DMS photosensitizer.

Keywords: Bacteria; DMSP; Leucine; Microautoradiography; FISH; Beaufort Sea; Franklin Bay; Arctic winter

The ability of bacteria to assimilate sulfur from dimethylsulfoniopropionate (DMSP) was examined in the western Arctic Ocean by combining microautoradiography and fluorescence in situ hybridization (FISH). Assimilation of leucine was also measured for comparative purposes since leucine is considered a universal substrate for bacteria, which use it for protein synthesis. Samples were collected at 3 m depth, through a hole in the ice, in the CASES (Canadian Arctic Shelf Ecosystem Study) overwintering station in Franklin Bay (eastern Beaufort Sea) in March and May 2004 to compare two contrasting situations: winter and early spring. FISH counts indicated that the bacterial assemblage consisted of α- (up to 60% of the EUB positive cells), β- (up to 10%) and γ-proteobacteria (around 20%), and Bacteroidetes (up to 60%). The β-proteobacteria were not active with any of the two substrates tested. The remaining groups were much less efficient at assimilating DMSP-sulfur (5% of the cells) than leucine (20–35%) both in winter and in spring. Only the Roseobacter group of α-proteobacteria showed a similar assimilation of both substrates.

Keywords: Coastal upwelling; Central waters; Frontal features; Double diffusion; Transport processes; Interleaving; Cape Verde; Geographic bounding coordinates (17–26°N) (22–14°W)

A historical data set is used to describe the coastal transition zone off Northwest Africa during spring 1973 and fall 1975, from 17° to 26°N, with special emphasis on the interaction between subtropical (North Atlantic Central Waters) and tropical (South Atlantic Central Waters) gyres. The near-surface geostrophic circulation, relative to 300 m, is quite complex. Major features are a large cyclonic pattern north of Cape Blanc (21°N) and offshore flow at the Cape Verde front. The large cyclone occurs in the region of most intense winds, and resembles a large meander of the baroclinic southward upwelling jet. The Cape Verde frontal system displays substantial interleaving that may partly originate as mesoscale features at the coastal upwelling front. Property–property diagrams show that the front is an effective barrier to all properties except temperature. The analysis of the Turner angle suggests that the frontal system is characterized by large heat horizontal diffusion as a result of intense double diffusion, which results in the smoothing of the temperature horizontal gradients. Nine cross-shore sections are used to calculate along-shore geostrophic water-mass and nutrient transports and to infer exchanges between the coastal transition zone and the deep ocean (import: deep ocean to transition zone; export: transition zone to deep ocean). These exchanges compare well with mean wind-induced transports and actual geostrophic cross-shore transport estimates. The region is divided into three areas: southern (18–21°N), central (21–23.5°N), and northern (23.5–26°N). In the northern area geostrophic import is roughly compensated with wind-induced export during both seasons. In the central area geostrophic import is greater than wind-induced export during spring, resulting in net import of both water (0.8 Sv) and nitrate (14 kmol s−1), but during fall both factors again roughly cancel. In the southern area geostrophy and wind join to export water and nutrients during both seasons, they increase from 0.6 Sv and 3 kmol s−1 during fall to 2.9 Sv and 53 kmol s−1 during spring.

Background In gonochoristic vertebrates, sex determination mechanisms can be classified as genotypic (GSD) or temperature-dependent (TSD). Some cases of TSD in fish have been questioned, but the prevalent view is that TSD is very common in this group of animals, with three different response patterns to temperature. Methodology/Principal Findings We analyzed field and laboratory data for the 59 fish species where TSD has been explicitly or implicitly claimed so far. For each species, we compiled data on the presence or absence of sex chromosomes and determined if the sex ratio response was obtained within temperatures that the species experiences in the wild. If so, we studied whether this response was statistically significant. We found evidence that many cases of observed sex ratio shifts in response to temperature reveal thermal alterations of an otherwise predominately GSD mechanism rather than the presence of TSD. We also show that in those fish species that actually have TSD, sex ratio response to increasing temperatures invariably results in highly male-biased sex ratios, and that even small changes of just 1–2°C can significantly alter the sex ratio from 1:1 (males:females) up to 3:1 in both freshwater and marine species. Conclusions/Significance We demonstrate that TSD in fish is far less widespread than currently believed, suggesting that TSD is clearly the exception in fish sex determination. Further, species with TSD exhibit only one general sex ratio response pattern to temperature. However, the viability of some fish populations with TSD can be compromised through alterations in their sex ratios as a response to temperature fluctuations of the magnitude predicted by climate change.

Keywords: lysosomal enzymes; yolk; egg

The aim of this study was to provide evidence on the modulation of lysosomal enzymes in terms of both gene expression and enzymatic activity during follicle maturation. For this purpose three lysosomal enzymes, cathepsins B, D, and L, were studied in relation to yolk formation and degradation, during the main phases of ovarian follicle growth in the pelagophil species, the sea bream Sparus aurata. Specific attention was focused on the gene expression quantification method, on the assay of enzymatic activities, and on the relationship between the proteolytic cleavage of yolk proteins (YPs), cathepsin gene expression and cathepsin activities. For the gene expression study, the cathepsins B-like and L-like mRNAs were isolated and partially or fully characterized, respectively; the sequences were used as design specific primers for the quantification of cathepsin gene expression by real-time PCR, in follicles at different stages of maturation. The enzymatic assays for cathepsins B, D, and L were optimized in terms of specificity, sensitivity and reliability, using specific substrates and inhibitors. In ovulated eggs, the lipovitellin I (LV I) was degraded and the changes in electrophoretic pattern were preceded by an increase in the activity of a cysteine proteinase, cathepsin L, and its mRNA. Cathepsin B did not appear to be involved in YP changes during the final maturation stage. Mol. Reprod. Dev. 75: 97–104, 2008. © 2007 Wiley-Liss, Inc.

Keywords: Engraulis encrasicolus; NW Mediterranean; Environmental conditions; Anchovy landings; GAM

Generalized additive models are proposed for a better understanding of the underlying mechanisms for anchovy variations in abundance. Environmental variables derived from satellite imagery (surface chlorophyll, sea surface temperature and wind-mixing index), river discharge (Rhône River and Ebre River) and anchovy landings (landings per unit of effort) as proxy for abundance were used, and three fishing zones were defined along the Catalan Coast. A time shift among wind index mixing, sea surface temperature and chlorophyll was observed for these variables to be significantly correlated with anchovy. Results pointed out to processes that appear to greatly influence species abundance and affect different life stages of anchovy (conditions preceding reproduction, larvae growth and survival and recruits growth). A high proportion of anchovy LPUE variability could be explained by environmental variables. Thus, some univariate models explained deviance are more than 50%, even up to around 70% of anchovy variability. In several cases the deviance explained by a given variable was even higher at the longer time-lags. Among all univariate and bivariate models fitted, the model that best explained anchovy LPUE variability, 79% of total deviance, was a model proposed for the central zone, based on the additive effect of surface chlorophyll and Rhône River discharge, considering time lags of 15 and 18 months, respectively, for each variable.

Keywords: Dense shelf water cascades; Sedimentary furrows; Submarine canyon; Mediterranean Sea

To investigate the processes by which sediment is transported through a submarine canyon incised in a continental margin affected by recurrent dense shelf water cascading events, several instrumented moorings were deployed in the Cap de Creus Canyon from September 2004 to September 2005. This was done as part of the EuroSTRATAFORM Program that investigated sediment transport and accumulation processes in the Gulf of Lions. Results obtained in this observational study confirm that major cascading events can effectively contribute to the rapid export of sediment from the shelf and upper slope to deeper environments, and suggest that the associated strong currents carrying coarse particles are able to erode the canyon floor and generate sedimentary furrows. During winter 2004–2005, persistent northerly winds and the absence of river floods contributed to decrease the buoyancy of coastal waters and to dramatically enhance the intensity of dense shelf water cascades in the Gulf of Lions. Under such conditions, cascading continuously affected the entire Cap de Creus upper canyon section for more than a month and sustained cold temperatures and down-canyon steady currents >60 cm/s (up to 100 cm/s), showing periodic fluctuations that lasted between 3 and 6 days. Increases in suspended sediment concentrations were associated with dense shelf water cascading outbursts, but the magnitude of the concentration peaks decreased with time, suggesting a progressive exhaustion of the resuspendable sediments from the shelf and canyon floor. Grain size analyses of the particles caught by a near-bottom sediment trap show that dense shelf water cascades are able to transport coarse sediments (up to 65% sand) in suspension (and presumably as bed load), which have the potential to abrade the seafloor and generate erosive bed forms. The orientation of a large field of “wide” (i.e., widths about 1/2 spacing indicative of erosive formation) sedimentary furrows recently observed in the Cap de Creus Canyon clearly coincides with the preferential direction of highest velocities measured by the moored current meters, indicating a causative relationship between contemporary dense shelf water cascades and furrow formation.

Cascading of dense shelf water from continental shelves is a global phenomenon whose effects have been largely underestimated. The north-western Mediterranean is one of the regions of the world where massive dense water formation occurs because of cooling and evaporation of surface waters during winter-time. Concurrent with the well known open-sea convection process over the MEDOC region, coastal surface waters over the wide shelf of the Gulf of Lions also become denser than the underlying waters and cascade downslope until reaching their equilibrium depth. Through this climate-driven phenomenon, dense shelf waters carrying large quantities of particles in suspension are rapidly advected hundreds of meters deep, mainly through submarine canyons. Recent observations within the frame of several research initiatives conducted in the north-western Mediterranean found that major dense shelf water cascades from the Gulf of Lions have a direct effect on the deep water (i.e. WMDW) thermohaline properties and on the long-term fluctuations of deep-sea fisheries, notably the shrimp Aristeus antennatus. Because of the flushing and recurrent behaviour of such cascading events, a continuous monitoring of this phenomenon under a system of Integrated Mediterranean Marine Observatories initiative could be conducted by means of establishing permanent real-time deep-sea observatories at specific key sites in the Mediterranean, in places where this process has been clearly identified (i.e. Gulf of Lions, southern Adriatic and Aegean shelves). Such infrastructures will allow studying this phenomenon using a transdisciplinary approach to assess in detail its effects and implications in the Mediterranean deep-sea ecosystem and living resources

Keywords: Loligo vulgaris; NW Mediterranean; GIS; GAM; Squid LPUE; Environment

We characterised the most productive areas for the commercial squid Loligo vulgaris off the Catalan Coast based on the combined integration of SST and PAR satellite data. We present the distribution of these areas during the most productive months in relation to the spatiotemporal presence of paralarvae of this species off the Catalan Coast. The work is based on Generalised Additive Models (GAMs) that combine the simultaneous analysis of the effect of different environmental explanatory variables from satellite imagery data to obtain the optimal model for paralarvae of the squid. The proposed model helped define the potential Essential Fish Habitat (EFH) for squid paralarvae recruitment, based on the best environmental conditions and is consistent with the higher LPUE observed four months later. The EFH defined for paralarvae recruitment by the model was detected every year in May in the areas both north and central of the Catalan Coast, the same areas where fishing ports evidence the highest commercial yield of squid.

Keywords: dinoflagellates; Parvilucifera; parasites; perkinsids; toxic phytoplankton

A new species of parasite, Parvilucifera sinerae sp. nov., isolated from a bloom of the toxic dinoflagellate Alexandrium minutum in the harbor of Arenys de Mar (Mediterranean Sea, Spain), is described. This species is morphologically, behaviourally, and genetically (18S rDNA sequence) different from Parvilucifera infectans, until now the only species of the genus Parvilucifera to be genetically analyzed. Sequence analysis of the 18S ribosomal DNA supported P. sinerae as a new species placed within the Perkinsozoa and close to P. infectans. Data on the seasonal occurrence of P. sinerae, its infective rates in natural and laboratory cultures, and intra-species strain-specific resistance are presented. Life-cycle studies in field samples showed that the dinoflagellate resting zygote (resting cyst) was resistant to infection, but the mobile zygote (planozygote) or pellicle stage (temporary cyst) became infected. The effects of light and salinity levels on the growth of P. sinerae were examined, and the results showed that low salinity levels promote both sporangial germination and higher rates of infection. Our findings on this newly described parasite point to a complex host–parasite interaction and provide valuable information that leads to a reconsideration of the biological strategy to control dinoflagellate blooms by means of intentional parasitic infections.

Keywords: Alexandrium peruvianum; Cysts; Nitrates; Phosphates; Sexuality; Life cycle

Alexandrium peruvianum (Balech et Mendiola) is a noxious phototrophic marine dinoflagellate. During the life cycle of this species, two kinds of cysts are produced: resting cysts, which are long-lasting and double-walled, and temporary cysts, which are short-lasting and thin-walled. In addition, short-lasting, but resting-like cysts can also be formed. Although it is crucial to identify sexual events in a dinoflagellate population, sexual and asexual cysts are morphologically very similar in this species. Therefore, we studied the complete life cycle and the nature of the cyst-like stages formed after individual isolation of specimens and crossing of clonal cultures established from germination of wild resting cysts. Asexual division in A. peruvianum takes place either in the motile stage by sharing of the theca (desmoschisis), or inside a vegetative cyst (temporary cyst), from which two, or at times four or six naked daughter cells can originate. The daughter cells completely synthesize new cell walls (eleutheroschisis). Sexuality was confirmed by the presence of fusing gamete pairs and longitudinally biflagellated planozygotes after out-crossing of compatible clonal strains. However, the clonal cultures had low levels of self-compatibility, since a flow cytometry analysis showed that synchronized self-crosses produced few zygotes (<5%). After isolation of individual cells, it was proved that the fate of the planozygotes depended on the nutritional status of the isolation media. Most of the planozygotes isolated to replete medium (L1) divided, whereas in medium lacking nitrates (L-N) or phosphates (L-P) they formed temporary, thin-walled cysts. Temporary cysts formed in L1 were always uninucleated and gave rise to one cell, while those formed in L-N or L-P produced 1–6 small cells. In addition, resting cysts were formed in culture, but never after individual planozygote isolation. Resting cysts were uninucleated and needed maturation time before entering dormancy. The resting cysts were considered sexual products, since longitudinally biflagellate germlings were liberated after germination in all cases studied. Mature resting cysts (52.3 ± 3.0 μm) had a dormancy period of 1–3 months, whereas temporary asexual cysts (32.5 ± 5.4 μm) germinated in less than 7 days.

The aim of this study was to explore the use of large-scale sequencing to better describe the genome content of naturally occurring, uncultured protists. We constructed a metagenomic fosmid library from a picoplanktonic assemblage (0.2–3 μm size cells) collected at the Blanes Bay Microbial Observatory (Western Mediterranean). Seven clones contained a small-subunit ribosomal RNA gene (SSU rDNA) affiliating with prasinophytes and uncultured alveolates. One clone (FBB25; 35 kb in size) was completely sequenced and found to be a tandem repeat array (5.5 times) of the rDNA operon, including three rRNA genes (SSU, large-subunit and 5.8S rDNAs) and three spacer regions (internal transcribed spacers 1, 2 and intergenic spacer). The SSU rDNA of FBB25 affiliated with the marine alveolates group I, cluster 1, and was almost identical to sequences retrieved only in marine surveys from a wide geographic and ecological range. Phylogenetic trees using the different rRNA genes showed FBB25 as an independent branch among the main alveolate groups, but their closest affiliation varied between the SSU tree (dinoflagellates) and the large-subunit and 5.8S trees (perkinsids). The spacer regions of FBB25 were particularly short when compared with other eukaryotes, indicating a possible genome streamlining in this picoeukaryote. Finally, not a single polymorphism was found in the rDNA repeat array, suggesting that the high SSU rDNA variability typically found in molecular surveys derives from organismal and not intragenomic diversity. This first report on the rDNA genomic structure of an uncultured marine alveolate improves their phylogenetic position and helps interpreting data generated during picoeukaryotic molecular surveys.

A decade after molecular techniques were used to discover novel bacteria and archaea in the oceans, the same approach has revealed a wealth of new marine eukaryotic microbes. The approach has been particularly successful with the smallest eukaryotes, where morphological and culture approaches frequently fail. Analysis of samples from the surface ocean, the most accessible and supposedly well-known oceanic region, reveals novel eukaryotic diversity at all different levels: from the highest taxonomic rank to the lowest microdiverse clusters. Moreover, marine eukaryotic assemblages show a large diversity with members belonging to many different lineages. The implication of this large and novel eukaryotic diversity for biodiversity surveys and ecosystem functioning opens new avenues for future research.

A SEA OF CLOUDS. Earth climate is closely linked to the chemistry of the atmosphere through the influence of the latter on the radiative balance. Greenhouse gases and aerosols cause heat retention at the earth surface and the lower atmosphere, and aerosols and clouds affect the atmospheric albedo (i.e., the amount of solar radiation that is reflected back to space and never reaches the surface). Aerosols, hence, play a multiple role in regulating climate, either by their optical properties or by seeding cloud formation. There are many sources of aerosols, but over the remote ocean, far from continents, most come from the oxidation of sulphur, carbon, nitrogen, and iodine gases emitted by the oceans’ microbiota. Since the industrial revolution, aerosols have been playing a significant role in slowing down global warming. Over the current century, the oceans are predicted to reduce their cooling capabilities by sequestering less CO2 and increasing too little their emission of aerosols and cloud precursors. Together with the expected reduction of anthropogenic aerosol loads due to the development of cleaner combustion technologies, these effects are predicted to accelerate temperature rise unless greenhouse gas emissions are dramatically reduced.

Keywords: Protists; Phytoplankton; Bacteria; Nutrients; Mixed layer; Sea ice; Light response

We measured the abundance and biomass of phototrophic and heterotrophic microbes in the upper mixed layer of the water column in ice-covered Franklin Bay, Beaufort Sea, Canada, from December 2003 to May 2004, and evaluated the influence of light and nutrients on these communities by way of a shipboard enrichment experiment. Bacterial cell concentrations showed no consistent trends throughout the sampling period, averaging (± SD) 2.4 (0.9) × 108 cells L− 1; integrated bacterial biomass for the upper mixed layer ranged from 1.33 mg C m− 3 to 3.60 mg C m− 3. Small cells numerically dominated the heterotrophic protist community in both winter and spring, but in terms of biomass, protists with a diameter > 10 µm generally dominated the standing stocks. Heterotrophic protist biomass integrated over the upper mixed layer ranged from 1.23 mg C m− 3 to 6.56 mg C m− 3. Phytoplankton biomass was low and variable, but persisted during the winter period. The standing stock of pigment-containing protists ranged from a minimum value of 0.38 mg C m− 3 in winter to a maximal value of 6.09 mg C m− 3 in spring and the most abundant taxa were Micromonas-like cells. These picoprasinophytes began to increase under the ice in February and their population size was positively correlated with surface irradiance. Despite the continuing presence of sea ice, phytoplankton biomass rose by more than an order of magnitude in the upper mixed layer by May. The shipboard experiment in April showed that this phototrophic increase in the community was not responsive to pulsed nutrient enrichment, with all treatments showing a strong growth response to improved irradiance conditions. Molecular (DGGE) and microscopic analyses indicated that most components of the eukaryotic community responded positively to the light treatment. These results show the persistence of a phototrophic inoculum throughout winter darkness, and the strong seasonal response by arctic microbial food webs to sub-ice irradiance in early spring.

Octopuses of the family Octopodidae adopt two major life-history strategies. The first is the production of relatively few, large eggs resulting in well-developed hatchlings that resemble the adults and rapidly adopt the benthic habit of their parents. The second strategy is production of numerous small eggs that hatch into planktonic, free-swimming hatchlings with few suckers, simple chromatophores and transparent musculature. These distinctive planktonic stages are termed para-larvae and differ from conspecific adults in their morphology, physiology, ecology and behaviour. This study aims to review available knowledge on this subject. In benthic octopuses with plank. tonic stages, spawning characteristics and duration of planktonic life seem to play an important role in their dispersal capacities. Duration of the hatching period of a single egg mass can range from 2 days to 11 wk, while duration of the planktonic stage can range from 3 wk to half a year, depending on the species and temperature. Thus these paralarvae possess considerable potential for dispersal. In some species, individuals reach relatively large sizes while living as part of the micronekton of oceanic, epipelagic waters. Such forms appear to delay settlement for an unknown period that is suspected to be longer than for paralarvae in more coastal, neritic waters. During the planktonic period, paralarval octopuses feed on crustaceans as their primary prey. In addition to the protein, critical to the protein-based metabolism of octopuses (and all cephalopods), the lipid and copper contents of the prey also appear important in maintaining normal growth. Littoral and oceanic fishes are their main predators and defence behaviours may involve fast swimming speeds, use of ink decoys, dive responses and camouflage. Sensory systems of planktonic stages include photo-, mechano- and chemoreceptors controlled by a highly evolved nervous system that follows the general pattern described for adult cephalopods. On settlement, a major metamorphosis occurs in morphology, physiology and behaviour. Morphological changes associated with the settlement process include positive allometric arm growth; chromatophore, iridophore and leucophore genesis; development of skin sculptural components and a horizontal pupillary response. At the same time, animals lose the Kölliker organs that cover the body surface, the 'lateral line system' and the oral denticles of the beaks. Strong positive phototaxis is a common response for hatchlings and some later paralarval stages but this response reduces, disappears or reverses after settlement. There are many gaps in our knowledge of the planktonic phases of benthic octopuses. Most of our understanding of octopus paralarvae comes from studies of just two species (Octopus vulgaris and Enteroctopus dofleini) and knowledge of the vast majority of benthic octopus species with planktonic stages is considered rudimentary or non-existent. Research is needed in a variety of fields, from taxonomy to ecology. Studies of feeding and nutrition are critical in order to develop the nascent aquaculture of key species and ageing studies are necessary to understand planktonic population dynamics, particularly in commercially valuable species targeted by fisheries. Current and potential anthropogenic impacts on these early life stages of octopuses, such as pollution, overfishing and global warming, are also identified.

Keywords: Alexandrium taylori; Coastal zone; Harmful algal bloom; LISST; Mediterranean Sea; Phytoplankton

Development of optical observation technologies provides new insights into harmful algal bloom (HAB) detection and assessment of HAB species dynamics. Based on preliminary laboratory tests, a laser in situ scattering and transmissometry instrument (LISST-100X) was used to monitor a high-biomass phytoplankton proliferation in the field. Short-term spatial and temporal changes in particle size distribution were measured during a recurrent Alexandrium taylori outbreak. Since the bloom was not monospecific, a size-fraction method to discriminate particular species from LISST-100X measurements was proposed. The results were validated to simultaneous microscopic counts of phytoplankton, and the significantly positive correlation obtained between the two methodologies confirmed the instrument's ability to discriminate phytoplankton at the group and species level. The LISST-100X obtains high-resolution in situ data, and is therefore a better alternative than the traditional microscope for assessing temporal and spatial evolution of HABs. Field observations showed high variability over a short time scale associated with diel vertical migration of A. taylori and the whole phytoplankton population (nanoplankton and microplankton). A numerical circulation model was used to investigate the influence of beach hydrodynamics in the observed horizontal variability. Simulations of the model suggested an important role of daily coastal circulation in determining the distribution of A. taylori in coastal environments.

Keywords: Fishing impacts · Ecosystem functioning · Loss in production · Primary production required · Trophic level · Overfishing · Ecosystem-based fisheries management

Exploited ecosystems are characterised by exports of secondary production from each fished trophic level that reduce the energy available for upper levels at the ecosystem scale, thus impinging on overall secondary production. Depletion in secondary production is proposed here as a proxy for quantifying the ecosystem effects of fishing. Theoretical analysis of trophic web interactions permits the quantification of the ‘loss in production’ and provides an ecological basis for defining a new synthetic index (L index) that takes into account both ecosystem properties (primary production and transfer efficiency) and features of fishing activities (trophic level of catches and primary production required). Quantitative meta-analysis of ecological models, representing 51 exploited ecosystems previously classified as overexploited or sustainably exploited, allows the association of a probability of the ecosystem being sustainably fished with each index value. Moreover, by fixing the reference level for this probability, the index provides a basis for estimating the maximum allowable catches. The L index is applied here to several ecosystems worldwide using landings data and ecological models, providing quantification of the disruption of energy flows for ecosystems subjected to different types and levels of fishing pressure. Its application to outputs of calibrated dynamic models enables the evaluation of sustainability of fisheries in past and future scenarios of alternative fisheries management policies. Results highlight the usefulness of this index for quantifying the impacts of fishing and providing directional advice for fisheries management. Thus, the L index may be used to support ecosystem-based management of fisheries.

Keywords: Sex differentiation; Protandry; Ambisexual gonads; Immunohistochemistry; Steroidogenic

To clarify the relationship between steroid hormones and sex differentiation of the protandrous anemonefish Amphiprion clarkii, we histologically examined its gonadal differentiation. From hatching to 30 days post hatching (dph), all of the gonads surveyed were sexually undifferentiated. The gonads of all fish first differentiated into ovaries at 60 dph, and the oocytes gradually developed and increased in number as the ovaries grew up until 183 dph. Some cysts of differentiated spermatogenic germ cells appeared in the ovaries at 214 dph, and ambisexual gonads with both ovarian and testicular tissues formed by 273 dph. Using immunohistochemistry, we then investigated the expression of cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), during gonadal sex differentiation. P450scc-immunopositive reactions first appeared in sexually undifferentiated gonads at 30 dph. Beginning at 60 dph, the number of strongly positive cells increased throughout the differentiation of the ovaries and continued to increase during the testicular differentiation until 210 dph. Immunopositive cells were observed more frequently in ovarian tissue than in testicular tissue in the ambisexual gonads at 270 dph. These results suggest that endogenous steroid hormones are important for the sex differentiation, including the primary sex differentiation and subsequent testicular differentiation, of the anemonefish.

A new one‐dimensional model of DMSP/DMS dynamics (DMOS) is developed and applied to the Sargasso Sea in order to explain what drives the observed dimethylsulfide (DMS) summer paradox: a summer DMS concentration maximum concurrent with a minimum in the biomass of phytoplankton, the producers of the DMS precursor dimethylsulfoniopropionate (DMSP). Several mechanisms have been postulated to explain this mismatch: a succession in phytoplankton species composition towards higher relative abundances of DMSP producers in summer; inhibition of bacterial DMS consumption by ultraviolet radiation (UVR); and direct DMS production by phytoplankton due to UVR‐induced oxidative stress. None of these hypothetical mechanisms, except for the first one, has been tested with a dynamic model. We have coupled a new sulfur cycle model that incorporates the latest knowledge on DMSP/DMS dynamics to a preexisting nitrogen/carbon‐based ecological model that explicitly simulates the microbial‐loop. This allows the role of bacteria in DMS production and consumption to be represented and quantified. The main improvements of DMOS with respect to previous DMSP/DMS models are the explicit inclusion of: solar‐radiation inhibition of bacterial sulfur uptakes; DMS exudation by phytoplankton caused by solar‐radiation‐induced stress; and uptake of dissolved DMSP by phytoplankton. We have conducted a series of modeling experiments where some of the DMOS sulfur paths are turned “off” or “on,” and the results on chlorophyll‐a, bacteria, DMS, and DMSP (particulate and dissolved) concentrations have been compared with climatological data of these same variables. The simulated rate of sulfur cycling processes are also compared with the scarce data available from previous works. All processes seem to play a role in driving DMS seasonality. Among them, however, solar‐radiation‐induced DMS exudation by phytoplankton stands out as the process without which the model is unable to produce realistic DMS simulations and reproduce the DMS summer paradox.

Keywords: Pseudo-nitzschia, bloom dynamics, phytoplankton community

The spatial and temporal variations in the composition of Pseudo-nitzschia during bloom events from August 2005 to February 2006 were characterised in two bays of the NW Mediterranean Sea (Alfacs and Fangar Bay) by means of scanning electron microscopy (SEM). The study provides detailed records of the Pseudo-nitzschia community at the species level and describes its relationship with both the surrounding environmental conditions and biotic factors such as the accompanying phytoplankton community. The size distributions of several species of Pseudo-nitzschia were monitored during the bloom events. These measurements may serve as indicators of the physiological status of the cells. The species observed in the two bays were Pseudo-nitzschia calliantha, P. delicatissima, P. fraudulenta, P. multistriata, and P. pungens. In Alfacs Bay, a mixed species bloom of P. calliantha and P. delicatissima began in late August 2005 and lasted 11 weeks. In Fangar Bay, the Pseudo-nitzschia bloom was limited to the period from early August to late September 2005 and comprised P. calliantha and P. delicatissima. Commonly, the proliferation of Pseudo-nitzschia was mono-specific or was accompanied by other diatoms. Two objectively defined groups were identified by the statistical analysis in Alfacs bay; the first was made up only of winter samples and the second of summer and autumn samples. The first group was defined by a high concentration of NO3¯ and low concentrations of NH4+, conditions associated with a high abundance of P. delicatissima and a low abundance of P. calliantha. The second group expressed the opposite characteristics. A succession of different blooming species of Pseudo-nitzschia lasting months in Alfacs Bay is described.

Keywords: diatoms, Pseudo-nitzschia, harmful algal blooms, autoecology, ITS morphology, pigments

Potentially toxic species of the genus Pseudo-nitzschia were studied along the Spanish NW Mediterranean coast from January 2005 to May 2006. Observation in electron microscopy revealed the presence of Pseudo-nitzschia brasiliana, P. calliantha, P. delicatissima, P. fraudulenta, P. multistriata and P. pungens. Several strains were isolated from coastal waters and their clonal cultures were compared by combined techniques, including light and electron microscopy and internal transcribed spacer (ITS-1, 5.8S and ITS-2) rDNA sequencing. Cultured isolates were submitted to HPLC analysis of pigments to evaluate the possibility of taxonomic discriminations by means of a simple chemotaxonomic approach. The genus Pseudo-nitzschia showed high cell concentrations during most of the year, but the population initiated a sharp decline at all stations in the period between April and May. P. delicatissima with P. calliantha were found at the northern stations between February and April, and at the southern stations between August and November. P. brasiliana and P. multistriata were only occasionally detected in the southern region. None of the environmental variables considered was significant to explain the observed spatial and temporal distributions of Pseudo-nitzschia species in the area studied. Differences in the growth rate and cell yield of the species indicate that biotic factors may play a role in the observed distributional patterns.

The distribution and population structure of the eurybathic gorgonian Corallium rubrum were studied off Cap de Creus (Costa Brava, Northwestern Mediterranean Sea). Red coral is endemic to the Mediterranean Sea and the adjacent NE Atlantic coast, where it has been over exploited for centuries. This study presents, the first quantitative data on the spatial distribution and structure of a population extending between 50 (common SCUBA limits) and 230 m depth, and compared it with shallow populations previously studied in the same area. Different remotely operated vehicles (ROV) and two methodological approaches were employed during four cruises between 2002 and 2006: 1-Extensive surveys: sea to coast transects in which red coral density and patch frequency were recorded; 2-Intensive surveys, in which parameters describing colony morphology were recorded. Most of the hard substrate between 50 and 85 m depth was inhabited by red coral colonies, showing a patch frequency of 8.3 ± 7.9 SD patches per 100 m-transect (total transect area: 34 m2), and within-patch colony densities of 16–376 colonies m−2 (mean of 43 ± 53 colonies m−2). Below 120 m depth red coral was less abundant, and rather than forming dense patches as in shallow water, isolated colonies were more common. The population structure differed between sites that are easily accessible to red coral fishermen, and remote ones (both at similar depth, 60–80 m), as colonies in easily accessible locations were smaller in height and diameter, and showed a less developed branching pattern. At shallower locations (10–50 m depth) the population structure was significantly different from those at deeper locations, due to the heavy harvesting pressure they are exposed to in the shallows. Twenty-five to forty-six percentage of the deeper colonies were taller than 6 cm, while only 7–16% of the shallow water colonies exceeded 6 cm colony height. Forty-six to seventy-nine percentage of the colonies in deeper waters were large enough to be legally harvested, while only 9–20% of the shallow water colonies met the 7 mm legal basal diameter to be collected. The branching pattern was also better developed in deeper colonies, as up to 16% of the colonies showed fourth order branches, compared to less than 1% of the shallow water colonies (of which 96% consisted of only one single branch). The results thus confirm that C. rubrum populations above 50 m depth are exposed to a higher harvesting intensity than deeper populations in the same area.

Keywords: adaptive filters, signal reconstruction, signal sampling, time-frequency analysis, wavelet transforms

The S-transform is becoming popular for time-frequency analysis and data-adaptive filtering thanks to its simplicity. While this transform works well in the continuous domain, its discrete version may fail to achieve accurate results. This paper compares and contrasts this transform with the better known continuous wavelet transform, and defines a relation between both. This connection allows a better understanding of the S-transform, and makes it possible to employ the wavelet reconstruction formula as a new inverse S-transform and to propose several methods to solve some of the main limitations of the discrete S-transform, such as its restriction to linear frequency sampling.

Keywords: Microwave radiometry, oceanography, salinity

The L-band interferometric radiometer onboard the Soil Moisture and Ocean Salinity mission will measure polarized brightness temperatures (Tb). The measurements are affected by strong radiometric noise. However, during a satellite overpass, numerous measurements are acquired at various incidence angles at the same location on the Earth's surface. The sea surface salinity (SSS) retrieval algorithm implemented in the Level 2 Salinity Prototype Processor (L2SPP) is based on an iterative inversion method that minimizes the differences between Tb measured at different incidence angles and Tb simulated by a full forward model. The iterative method is initialized with a first-guess surface salinity that is iteratively modified until an optimal fit between the forward model and the measurements is obtained. The forward model takes into account atmospheric emission and absorption, ionospheric effects (Faraday rotation), scattering of celestial radiation by the rough ocean surface, and rough sea surface emission as approximated by one of three models. Potential degradation of the retrieval results is indicated through a flagging strategy. We present results of tests of the L2SPP involving horizontally uniform scenes with no disturbing factors (such as sun glint or land proximity) other than wind-induced surface roughness. Regardless of the roughness model used, the error on the retrieved SSS depends on the location within the swath and ranges from 0.5 psu at the center of the swath to 1.7 psu at the edge, at 35 psu and 15degC. Dual-polarization (DP) mode provides a better correction for wind-speed (WS) biases than pseudofirst Stokes mode (ST1). For a WS bias of -1 mmiddots-1, the corresponding SSS bias at the center of the swath is equal to -0.3 psu in DP mode and to -0.5 psu in ST1 mode. The inversion methodology implicitly assumes that WS errors follow a Gaussian distribution, even though these errors should follow more closely a Rayleigh distribution. For this - reason, the use of wind components, which typically exhibit Gaussian error distributions, may be preferred in the retrieval. However, the use of noisy wind components creates WS and SSS biases at low WSs (0.1 psu at 3 mmiddots-1). At a sea surface temperature (SST) of 15degC, the retrieved SSS is weakly sensitive to the SST biases, with the SSS bias always lower than 0.3 psu for SST biases ranging from -0.5degC to -2degC. In DP mode, biases in the vertical total electron content (TEC) of the atmosphere result in SSS biases smaller than 0.2 psu. The pseudofirst Stokes mode is insensitive to TEC. Failure to fully account for sea surface roughness scattering effects in the computation of sky radiation contribution leads to a maximum SSS bias of 0.2 psu in the selected configuration, i.e., a descending orbit over the Northern Pacific in February. To achieve SSS biases that are smaller than 0.2 psu, special care must be taken to correct for biases at low WS and to ensure that the bias on the mean WS (averaged over 200 km times 200 km and ten days) remains smaller than 0.5 mmiddots-1.

Since heterotrophic prokaryotes play an important biogeochemical role in aquatic ecosystems and have a high capacity to survive in extreme environments, easy-to-perform protocols that probe their physiological states and the effects of environmental variables on those states are highly desired. Some methodologies combine a general nucleic acid stain with a membrane integrity probe. We calibrated one of these, the nucleic acid double-staining (NADS) protocol (G. Grégori, S. Citterio, A. Ghiani, M. Labra, S. Sgorbati, S. Brown, and M. Denis, Appl. Environ. Microbiol. 67:4662-4670, 2001), determining the optimal stain concentrations in seawater and the response to conditions that generate prokaryote death (such as heat) and to conditions that are known to produce death in plankton, such as nutrient limitation or flagellate grazing. The protocol was validated by comparison to two methods used to detect viability: active respiration by 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and incorporation of tritiated leucine. We show that concentrations in the range of 5 to 20 µg ml–1 of propidium iodide, simultaneous to a 10x concentration of Sybr green I, are best for detecting two separated populations of \"live\" (green cells) and \"dead\" (red cells) organisms. During exposure to heat and UVC, we observed that the number of live cells declined concurrently with that of actively respiring cells (CTC positive) and with total leucine incorporation. In seawater mesocosms, the NADS protocol allowed detection of bacterioplankton starvation-related death and flagellate predation. The protocol was also tested in deep profiles in the northwest Atlantic, demonstrating its potential for routine characterization of this fraction of the physiological diversity of marine heterotrophic prokaryotic plankton.

Keywords: Suprabenthos; Hyperbenthos; Isotopes; Seasonal variations; Mediterranean; Deep water

Stable isotope (δ13C and δ15N) analyses were performed on suprabenthic fauna collected in the western Mediterranean (NW Balearic Islands), at depths ranging between 350 and 780 m. Samples were collected seasonally at bi-monthly intervals during six cruises performed between August 2003 and June 2004, using a Macer-GIROQ suprabenthic sledge (0.5 mm mesh size). Twenty-four separate species (5 mysids, 12 amphipods, 2 cumaceans, 2 isopods, 1 euphausiid, 1 decapod and 1 fish) and bulk copepods were analyzed on a seasonal basis for stable carbon and nitrogen isotopes. Stable nitrogen isotope ratios (δ15N) ranged from 2.3‰ (the amphipod Lepechinella manco in September 2003) to 13.0‰ (the amphipod Rhachotropis caeca in August 2003). δ13C values ranged from − 24.2 (the cumacean Campylaspis sulcata in June 2004) to − 16.1 (the amphipod Bruzelia typica in November 2006). Both δ13C and δ15N values suggest that there are three trophic levels within the suprabenthic community. However, considering the bathymetric range of the species, the results suggest that the deepest assemblage supported only two trophic levels. The stable isotope ratios of suprabenthic fauna displayed a continuum of values and confirmed a wide spectrum of feeding types (from filter-feeders to predators). In general, and in spite of the poor knowledge about diets available for most suprabenthic species, higher δ15N were found for carnivorous amphipods (e.g. Rhachotropis spp., Nicippe tumida) consuming copepods. Low overlap for δ13C and δ15N values was observed, though δ15N values where less variable than δ13C, which suggests high resource partitioning in this assemblage. Seasonal variations in isotopic composition for both δ13C and δ15N were low (less than 1‰ and 3‰, respectively) and variable depending on species. Low correlations between δ13C and δ15N of suprabenthic fauna were found for all periods studied, though increasing from February 2004 to June 2004 (after the main peak of primary production in surface). C:N ratio (indicator of lipid content) showed higher values in summer than in winter. This suggests that lipid content may explain the seasonal patterns of δ13C variability and, due to the increase of storage products in phytoplankton and zooplankton, it possibly indicates the peak of primary production at the surface.

Keywords: Galicia Bank; backscatter; oil tanker Prestige; sedimentary processes; oil spill

This study is focused on the potential of using the multibeam acoustic backscatter both for sea-floor characterization of the Galicia Bank and for identification of sea-bottom oil spills. An extended multibeam data set was acquired during the RG-1 and RG-2 surveys aboard RV Hespérides in 2003 for the geological and geophysical characterization of the Galicia Bank, where the oil tanker Prestige wreck is located. 3-D images have been made by integrating bathymetry and backscatter data. Multibeam data have been additionally supported by gravity core information in order to correlate sea-floor acoustic backscatter with the surficial sediments and their physical properties. The major factors that seem to control the zonation of the backscatter intensity images are (i) the type of the sedimentary processes (gravitational, turbiditic, hemipelagic), which control at the same time, the grain size distribution, and (ii) the sea-bottom morphologies, such as basement outcrops. However, there are some backscatter halos that cannot be explained by these processes. In the backscatter maps, the bow and stern of the Prestige wreck are clearly marked by a high-backscatter intensity anomaly, whose existence is discussed.

Keywords: Farallon breakup, Galapagos hotspot, magnetic anomalies, central Pacific

The Cocos-Nazca spreading center is one of the few examples of the formation of a spreading center by splitting of oceanic lithosphere. It was created when the Farallon plate broke up in the early Miocene following the collision of the Pacific-Farallon spreading center with the North American continent. Much of the ancient Farallon plate corresponding to the area of opening is lost to subduction beneath Central America and South America, but new data from the conjugate area on the Pacific plate allow the first detailed reconstruction of the break-up process. The opening began after chron 7 (25 Ma) at a location of focused crustal extension caused by overlapping spreading centers that had evolved in response to a slight reorientation of a Pacific-Farallon ridge segment. Beginning at chron 6B (22.7 Ma), eastward progressing seafloor spreading started along an axis that most likely migrated toward the region of weak lithosphere created by the Galapagos hotspot. By chron 6 (19.5 Ma), plate splitting from the spreading center to the trench was complete, allowing the fully detached Cocos and Nazca plates to move independently. This kinematic change resulted in a significant ridge jump of the newly established Pacific-Nazca spreading center, a change in plate motion direction of the Nazca plate by 20° clockwise, and a large increase in Pacific-Cocos plate velocity in the middle Miocene.

Based on hydrographic sections carried out during the last decade in the Canary region at 29° 10′N, we show that there has been a statistically significant rise in temperature and salinity on isobars between 1500 and 2300 db. The maximum increase, found at 1600 db, is occurring at a rate of 0.29°C and 0.047 per decade. Isobaric change decomposition into changes on neutral surfaces and changes due to the vertical displacement of the isoneutrals was performed. Results reveal that the lower part of North Atlantic Central Water (NACW) cooled and freshened on neutral surfaces, suggesting changes in the freshwater fluxes at the outcropping region. However, the signal in deep waters (1500–2300 db) was principally due to a downward displacement of the isoneutrals, although water mass modification is observed in the range of Mediterranean Water (MW) influence.

Keywords: Artisanal fishery, Fisheries benefits, Fisheries management, GAMs, Geostatistics, GIS, Regression kriging, Spatial modelling

We examined the spatial dynamic of artisanal fishing fleets around five European marine protected areas (MPAs) to derive general implications for the evaluation of MPAs as fisheries management tools. The coastal MPAs studied were located off France, Malta and Spain and presented a variety of spatial designs and processes of establishment. We developed a standardized methodology to define factors influencing effort allocation and to produce fishing effort maps by merging GIS with geostatistical modelling techniques. Results revealed that in most cases the factors "distance to the no-take", "water depth", and "distance to the port" had a significant influence on effort allocation by the fishing fleets. Overall, we found local concentration of fishing effort around the MPA borders. Thus, neglecting the pattern of fishing effort distribution in evaluating MPA benefits, such as spillover of biomass, could hamper sound interpretation of MPAs as fisheries management tools.

Turbulent ows are of major interest for scientists and engineers, playing an essential role in uid dynamics. Even though a precise denition of turbulence does not exist,it is generally assumed that turbulence is a ow regime characterized by instabilities at large Reynolds numbers. The Reynolds number is a measure of the ratio of inertial forces to viscous forces. In the ocean, Reynolds number are of the order of 106, and so ocean dynamics is strongly nonlinear involving a large spectra of processes across all space and time scales. However, the ocean seems to be very active at around 30-300 Km, which is known as mesoscale. A schematic diagram of the spatial and temporal scales of various oceanic phenomena is shown in Figure 1.1. Instabilities in the ocean explain the meandering nature of oceanic currents, which can isolate and shed eddies when the meanders reach large amplitudes [3]. Examples of such ows are high- and low-pressure systems that are formed in the Gulf Stream area (see Figure 1.2). These systems have been related to coherent structures, which are a combination of the geometrical and dynamical properties of the ow, i.e., regions containing most of the surviving vorticity [56, 47]. As it occurs in the ocean, a turbulent ow self-organizes into a collection of coherent structures [91, 141]. The smaller eddies are exposed to the strain-rate eld of these coherent structures [124]. In recent studies, coherent structures not only have been identied with vortices, but also their presence has been connected with non-Gaussian Probability Density Functions (PDFs) of velocity elds from the ocean [17, 40, 54, 51, 140]. In addition to this characteristic, a near Gaussian component is expected for the background ow. These statistical distributions of ocean velocity elds have similar characteristics to the ones of numerical simulations of bidimensional turbulence.