68 documents.
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Marín I., S. Nunes, E.D. Sánchez-Pérez, E. Txurruka, C. Antequera, M.M. Sala, C. Marrasé, F. Peters
Frontiers in Microbiology, 8, 2215, 1-17. (BibTeX: marin.etal.2017)
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Ortega-Retuerta E., M.M. Sala, E. Borrull, M. Mestre, F.L. Aparicio, R. Gallisai, C. Antequera, C. Marrasé, F. Peters, R. Simó, J.M. Gasol
Frontiers in Microbiology, 7, 2159. DOI: 10.3389/fmicb.2016.02159 (BibTeX: ortegaretuerta.etal.2017a)
Resum: Veure
Transparent Exopolymer Particles (TEP) are relevant in particle and carbon fluxes in the ocean, and have economic impact in the desalination industry affecting reverse osmosis membrane fouling. However, general models of their occurrence and dynamics are not yet possible because of the poorly known co-variations with other physical and biological variables. Here, we describe TEP distributions in the NW Mediterranean Sea during late spring 2012, along perpendicular and parallel transects to the Catalan coast. The stations in the parallel transect were sampled at the surface, while the stations in the perpendicular transect were sampled from the surface to the bathypelagic, including the bottom nepheloid layers. We also followed the short-term TEP dynamics along a 2-day cycle in offshore waters. TEP concentrations in the area ranged from 4.9 to 122.8 and averaged 31.4 ± 12.0 μg XG eq L−1. The distribution of TEP measured in transects parallel to the Catalan Coast correlated those of chlorophyll a (Chla) in May but not in June, when higher TEP-values with respect to Chla were observed. TEP horizontal variability in epipelagic waters from the coast to the open sea also correlated to that of Chla, O2 (that we interpret as a proxy of primary production) and bacterial production (BP). In contrast, the TEP vertical distributions in epipelagic waters were uncoupled from those of Chla, as TEP maxima were located above the deep chlorophyll maxima. The vertical distribution of TEP in the epipelagic zone was correlated with O2 and BP, suggesting combined phytoplankton (through primary production) and bacterial (through carbon reprocessing) TEP sources. However, no clear temporal patterns arose during the 2-day cycle. In meso- and bathypelagic waters, where phytoplanktonic sources are minor, TEP concentrations (10.1 ± 4.3 μg XG eq l−1) were half those in the epipelagic, but we observed relative TEP increments coinciding with the presence of nepheloid layers. These TEP increases were not paralleled by increases in particulate organic carbon, indicating that TEP are likely to act as aggregating agents of the mostly inorganic particles present in these bottom nepheloid layers.
Paraules clau: Transparent exopolymer particles, chlorophyll a, bacteria, carbon, Mediterranean Sea
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Sánchez-Pérez E.D., I. Marín, S. Nunes, F.L. Aparicio, L. Fernández-González, F. Peters, M. Pujo-Pay, P. Conan, C. Marrasé
Scientia Marina, 80, 4, 437-446. DOI: 10.3989/scimar.04318.20B (BibTeX: sanchezperez.etal.2016a)
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Marín I., S. Nunes, E.D. Sánchez-Pérez, F.L. Aparicio, M. Estrada, C. Marrasé, T. Moreno, T. Wagener, X. Querol, F. Peters
Science of The Total Environment, 574, 553-568. DOI: 10.1016/j.scitotenv.2016.09.005 (BibTeX: marin.etal.2016a)
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Gallisai R., G. Volpe, F. Peters
Global Biogeochemical Cycles, 30, 1725-1737. DOI: 10.1002/2016GB005404 (BibTeX: gallisai.etal.2016a)
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Amato A., S. Fortini, R. Watteaux, M. Diano, S. Espa, S. Esposito, M.I. Ferrante, F. Peters, D. Iudicone, M. Ribera d’Alcalà
Review of Scientific Instruments, 87, 035119, DOI: 10.1063/1.4944813 (BibTeX: amato.etal.2016)
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Romero E., J. Gamier, G. Billen, F. Peters, L. Lassaletta
Science of The Total Environment, 573, 420-432. DOI: 10.1016/j.scitotenv.2016.08.007 (BibTeX: romero.etal.2016c)
Resum: Veure
Nitrogen (N) retention sensu lato refers to all processes preventing new reactive nitrogen brought into watersheds through agricultural or industrial activities to be exported by river systems to the sea. Although such processes protect marine systems from the threat of eutrophication and anoxia, they raise other environmental issues, including the acidification of soils, the emission of ammonia and greenhouse gases, and the pollution of aquifers. Despite these implications, the factors involved in N retention are still poorly controlled, particularly in arid and semi-arid systems. The present study evaluates the N fluxes of 38 catchments in the Iberian Peninsula with contrasting climatic characteristics (temperate and Mediterranean), land uses, and water management practices. This diversity allows addressing the contribution of physical and socioecological factors in N retention, and more specifically, exploring the relation between N retention and water regulation. We hypothesise that the extreme flow regulation implemented in the Mediterranean enhances the high N retention values associated with arid and semi-arid regions. The results show that reservoirs and irrigation channels account for > 50% of the variability in N retention values, and above a certain regulation threshold, N retention peaks to values > 85–90%. Future climate projections forecast a decrease in rainfall and an increase in agricultural intensification and irrigation practices in many world regions, most notably in arid and semi-arid areas. Increased water demand will likely lead to greater flow regulation, and the situation in many areas may resemble that of Iberian Mediterranean catchments. High N retention and the associated environmental risks must therefore be considered and adequately addressed
Paraules clau: N retention, water regulation, reservoirs, irrigation, Mediterranean climate, river basin
Ramon Margalef, ecólogo de la biosfera: una biografía científica (2015)
Prat N., J. Ros, F. Peters
Publicacions i Edicions de la Universitat de Barcelona. 184. ISBN: 978-84-475-3747-1 (BibTeX: prat.etal.2015)
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Romero E., F. Peters, L. Arin, J. Guillén
Journal of Sea Research, 88, 130-143. DOI: 10.1016/j.seares.2014.01.010 (BibTeX: romero.etal.2014a)
Resum: Veure
Contrary to what happens in open waters, where chlorophyll values and plankton dynamics can be predicted with a reasonable accuracy on an annual basis, biological parameters analyzed for coastal waters often show slight seasonality, and are exposed to numerous and convergent forcing factors that make it difficult to draw clear patterns. On top of this large natural variability, coastal locations subjected to urban sprawl suffer further human impact that may increase the unpredictability of plankton dynamics. Here we present the results of a multi-year time series of monthly samplings carried out in a coastal location by the city of Barcelona (NW Mediterranean) that is highly exposed to anthropogenic disturbances. Our data confirm the existence of complex patterns throughout the year. Freshwater inputs proved to be an important source of nutrients, yet the response of the planktonic organisms was vague and not systematic, contrary to the results of a previous study at a nearby coastal site less affected by human activities. The severity of anthropogenic disruptions was partially masked by the co-occurrence of natural physical phenomena, e.g., waste spills often come with downpours and large river discharge. In the NW Mediterranean, there seems to be a gradient of decreasing predictability on plankton dynamics from offshore to coastal waters with little human influence, where seasonality can be largely modified by local processes but the biological response is systematic and fairly predictable, and finally to urban coastal locations, where the seasonal background is diluted by numerous perturbations and there exists a variable pattern of biological responses. Our study underlines the importance of specific coastal processes in determining the structure and dynamics of the planktonic community, and the need to characterize coastal areas setting aside some of the assumptions valid for open ocean regions (e.g., (1) in the open ocean seasonality dominates annual nutrient fluxes, which are tightly linked to mixing and turbulence, while nutrient inputs at the coast can occur anytime throughout the year and may not be coincident with increased water-column mixing (Cloern, 1996; Cloern and Jassby, 2008); and (2) in coastal regions the concentration of nutrients during nutrient pulses can be greatly imbalanced with regard to Redfield elemental ratios (Jickells, 1998 and Justić et al., 1995 and references therein)).
Paraules clau: Plankton dynamics; Coastal areas; Anthropogenic pressure; Physical drivers; Seasonality; NW Mediterranean
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Gallisai R., F. Peters, G. Volpe, S. Basart, J.M. Baldasano
Plos One. Open acces, 9, 10, e110762. DOI: 10.1371/journal.pone.0110762 (BibTeX: gallisai.etal.2014a)
Resum: Veure
The surface waters of the Mediterranean Sea are extremely poor in the nutrients necessary for plankton growth. At the same time, the Mediterranean Sea borders with the largest and most active desert areas in the world and the atmosphere over the basin is subject to frequent injections of mineral dust particles. We describe statistical correlations between dust deposition over the Mediterranean Sea and surface chlorophyll concentrations at ecological time scales. Aerosol deposition of Saharan origin may explain 1 to 10% (average 5%) of seasonally detrended chlorophyll variability in the low nutrient-low chlorophyll Mediterranean. Most of the statistically significant correlations are positive with main effects in spring over the Eastern and Central Mediterranean, conforming to a view of dust events fueling needed nutrients to the planktonic community. Some areas show negative effects of dust deposition on chlorophyll, coinciding with regions under a large influence of aerosols from European origin. The influence of dust deposition on chlorophyll dynamics may become larger in future scenarios of increased aridity and shallowing of the mixed layer.
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Guieu C., O. Aumont, A. Paytan, L. Bopp, C.S. Law, N. Mahowald, E.P. Achterberg, E. Marañón, B. Salihoglu, A. Crise, T. Wagener, B. Herut, K. Desboeufs, M. Kanakidou, N. Olgun, F. Peters, E. Pulido-Villena, A. Tovar-Sanchez, C. Völker
Global Biogeochemical Cycles, 28, 11, 1179-1198. DOI: 10.1002/2014GB004852 (BibTeX: guieu.etal.2014b)
Resum: Veure
In the vast Low Nutrient Low-Chlorophyll (LNLC) Ocean, the vertical nutrient supply from the subsurface to the sunlit surface waters is low, and atmospheric contribution of nutrients may be one order of magnitude greater over short timescales. The short turnover time of atmospheric Fe and N supply (<1 month for nitrate) further supports deposition being an important source of nutrients in LNLC regions. Yet, the extent to which atmospheric inputs are impacting biological activity and modifying the carbon balance in oligotrophic environments has not been constrained. Here, we quantify and compare the biogeochemical impacts of atmospheric deposition in LNLC regions using both a compilation of experimental data and model outputs. A metadata-analysis of recently conducted field and laboratory bioassay experiments reveals complex responses, and the overall impact is not a simple “fertilization effect of increasing phytoplankton biomass” as observed in HNLC regions. Although phytoplankton growth may be enhanced, increases in bacterial activity and respiration result in weakening of biological carbon sequestration. The application of models using climatological or time-averaged non-synoptic deposition rates produced responses that were generally much lower than observed in the bioassay experiments. We demonstrate that experimental data and model outputs show better agreement on short timescale (days to weeks) when strong synoptic pulse of aerosols deposition, similar in magnitude to those observed in the field and introduced in bioassay experiments, is superimposed over the mean atmospheric deposition fields. These results suggest that atmospheric impacts in LNLC regions have been underestimated by models, at least at daily to weekly timescales, as they typically overlook large synoptic variations in atmospheric deposition and associated nutrient and particle inputs. Inclusion of the large synoptic variability of atmospheric input, and improved representation and parameterization of key processes that respond to atmospheric deposition, is required to better constrain impacts in ocean biogeochemical models. This is critical for understanding and prediction of current and future functioning of LNLC regions and their contribution to the global carbon cycle.
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Romero E., F. Peters, O. Guadayol
Limnology and Oceanography, 58, 3, 903-920. DOI: 10.4319/lo.2013.58.3.0903 (BibTeX: romero.etal.2013a)
Resum: Veure
Two intensive surveys were conducted in the coastal waters of Barcelona (northwest Mediterranean) to assess short-term variations of biological parameters in relation to environmental conditions. Surveys lasted 1 week, with three to four samplings per day, and were carried out in autumn and spring. Rather than exploring extreme events, we aimed to study the effects of regular low or moderate perturbations, such as meteorological fronts, on the dynamics of the system. We focused on two attributes: wave height, as a proxy for mechanical energy entering the system, and nutrient inputs, whose variability in total load and relative composition is a central characteristic of coastal areas. The effects of the temporal coupling or uncoupling of both factors were examined. Sudden nutrient fluxes uncoupled from water motion tended to favor bacteria and heterotrophic nanoflagellates, while their concurrence with some water column mixing shaped a favorable scenario for large autotrophs. Ultimately, these two distinct biological responses pointed toward two main disturbance scenarios: episodes of nutrient enrichment uncoupled from mixing, mostly related to episodic water spills from the nearby city that contributed to high relative loads of ammonium and organic compounds; and episodes of increased wind caused by passing weather fronts that promoted some water column mixing and the entrainment of nutrients from bottom sediments or from adjacent water masses.
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Gasol J.M., R. Massana, R. Simó, C. Marrasé, S.G. Acinas, C. Pedrós-Alió, C. Pelejero, M.M. Sala, E. Calvo, D. Vaqué, F. Peters
ICES Phytoplankton and Microbial Plankton Status Report 2009/2010. sp issue, 138-141. (BibTeX: gasol.etal.2012)
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Romero E., F. Peters, C. Marrasé
Marine Ecology Progress Series, 464, 69-87. DOI: 10.3354/meps09846 (BibTeX: romero.etal.2012)
Resum: Veure
We carried out 2 experimental simulations in which natural planktonic communities were subjected to a combination of turbulence and variable nutrient forcing. Nutrient addition was varied both in terms of total nutrient load and in the balance of elements. Unbalanced nutrient inputs (with regard to Redfield values) and varying nitrogen sources are frequent in coastal areas heavily exposed to human perturbations. The relative abundance of nitrate and ammonium has been related to shifts in the size distribution of the planktonic community, so we explored whether uneven inputs of ammonium and nitrate could be major factors driving plankton dynamics in coastal environments. The occasional uncoupling between turbulence and nutrient pulses is also a distinctive feature of nearshore waters compared with open ocean environments. Thus, we further tested the match–mismatch between nutrient enrichments and turbulent mixing. Both turbulence and nutrient inputs had a significant positive effect on the growth of planktonic organisms, with some synergistic effects. Shifts in community composition appeared to be mostly related to the interplay between turbulence and N partitioning. Under still conditions, ammonium-rich waters favoured small organisms and reinforced the microbial loop, whereas nitrate mostly favoured diatom growth. Turbulence added complexity to the final outcome, because mixing tended to favour large over small osmotrophs. Accordingly, the rapid growth of small autotrophs and heterotrophic bacteria in ammonium-rich waters may be partly counteracted by diatom increases if nutrient pulses are coupled with turbulent mixing; diatom bursts after nitrate enrichments may also be enhanced by concomitant turbulence.
Paraules clau: Eutrophication · Mediterranean Sea · Nitrate · Ammonium · Plankton · Experimental simulation · Coastal areas
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Kuwata A., M. Bernal, F. Peters, D. Vaqué
76, 7-7. ISSN: 0214-8358 (BibTeX: kuwata.etal.2012)
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Kuwata A., M. Bernal, F. Peters, D. Vaque
76, ISSN: 0214-8358 (BibTeX: kuwata.etal.2012a)
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Pascual M., C. Pelejero, F. Peters, D. Vaqué
76, (BibTeX: pascual.etal.2012)
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Sheldon J.E., P.C. Griffith, F. Peters, W.M. Sheldon, J.O. Blanton, J. Amft, L.R. Pomeroy
Biogeochemistry, 107, 1-3, 501-506. DOI: 10.1007/s10533-010-9552-0 (BibTeX: sheldon.etal.2012)
Resum: Veure
Respiratory rates on the U. S. southeastern continental shelf have been estimated several times by different investigators, most recently by Jiang et al. (Biogeochemistry 98:101–113, 2010) who report lower mean rates than were found in earlier work and attribute the differences to analytical error in all methods used in earlier studies. The differences are, instead, attributable to the differences in the geographical scope of the studies. The lower estimates of regional organic carbon flux of Jiang et al. (Biogeochemistry 98:101–113, 2010) are a consequence of their extrapolation of data from a small portion of the shelf to the entire South Atlantic Bight. This comment examines the methodologies used as well as the variability of respiratory rates in this region over space and time.
Paraules clau: Microbial respiration – Southeastern U. S. continental shelf – Dissolved oxygen – Bacteria
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Romero E., F. Peters, C. Marrasé, Ò. Guadayol, J.M. Gasol, M.G. Weinbauer
Estuarine, Coastal and Shelf Science, 93, 1, 27-39. DOI: 10.1016/j.ecss.2011.03.019 (BibTeX: romero.etal.2011)
Resum: Veure
An enhancement of aeolian inputs to the ocean due to a future increase in aridity in certain parts of the world is predicted from global change. We conducted an experimental simulation to assess the biological response of NW Mediterranean coastal surface waters to an episodic dust addition. On the assumption that planktonic growth was limited by phosphorus, dust effects were compared to those induced by equivalent enrichments of phosphate. The experiment analyzed the dynamics of several parameters during one week: inorganic nutrients, total and fractioned chlorophyll a, bacterial abundance, phytoplankton species composition, abundance of autotrophic and heterotrophic flagellates, particulate organic carbon and particulate organic nitrogen. The maximum addition of dust (0.5 g dust L−1) initiated an increase in bacterial abundance. After 48 h, bacterial numbers decreased due to a peak in heterotrophic flagellates and a significant growth of autotrophic organisms, mainly nanoflagellates but also diatoms, was observed. Conversely, lower inputs of dust (0.05 g dust L−1) and phosphate enrichments (0.5 μmol PO43− L−1) only produced increases in phototrophic nanoflagellates. In our experiment, dust triggered bacterial growth, changed phytoplankton dynamics and affected the ratio of autotrophic to heterotrophic biomass, adding to the variability in the sources that affect system dynamics, energy and carbon budgets and ultimately higher trophic levels of the coastal marine food web.
Paraules clau: aeolian dust; nutrient enrichment; microbial community; turbulence; NW Mediterranean; coastal area
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Editorial (2011)
Font J., F. Peters
75, 423. ISSN: 0214-8358 (BibTeX: font.peters.2011j)
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Peters F., D. Vaqué
75, 631. ISSN: 0214-8358 (BibTeX: peters.vaque.2011a)
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Lekunberri I., A. Calvo-Díaz, E. Teira, X.A.G. Morán, F. Peters, M. Nieto-Cid, O. Espinoza-González, I.G. Teixeira, J.M. Gasol
Aquatic Microbial Ecology, 59, 2, 183. DOI: 10.3354/ame01380 (BibTeX: lekunberri.etal.2010a)
Resum: Veure
We studied the effects of the Prestige oil spill on Ría de Vigo bacterial abundance, production and community structure by using mesocosms (ca. 3500 l) filled with water from the center of the Ría, to which we added a realistic concentration of polycyclic aromatic hydrocarbons (PAHs; initial concentrations of approximately 20 to 30 µg l–1 chrysene equivalents) at each of the 4 periods of the seasonal cycle: spring bloom, summer stratification, autumn upwelling and winter. We followed the changes in bacterial activity by leucine and thymidine incorporation, and the changes in bacterial assemblage structure by 16S rDNA DGGE. In addition, simultaneously with the winter mesocosm experiment, we ran microcosms with fuel additions equivalent to 0.5, 1, 2 and 4× the treatment imposed on the mesocosms in the seasonal experiments. Bacterial community structure was also analyzed by CARD-FISH. We detected significant effects of the PAHs on bacterial community structure (increased number of bands) and production only in the summer experiment. In the microcosm experiments, we found similar effects to those in the mesocosms at PAH concentrations of ca. 20 to 40 µg l–1, and clear detrimental effects on phytoplankton at concentrations of ca. 80 µg l–1, with large development of Gammaproteobacteria. Our results indicate that an oil spill of the Prestige’s magnitude will have effects on the microbial resident community only at certain times of the year, while at higher PAH concentrations the effects might be more evident. For most of the year, the resident Ría de Vigo microbial communities appear to be accustomed to PAH concentrations such as those used in these experiments.
Paraules clau: PAHs · Bacterioplankton · Production · Bacterial community structure · Mesocosms · Prestige oil
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Lekunberri I., T. Lefort, E. Romero, E. Vázquez-Domínguez, C. Romera-Castillo, C. Marrasé, F. Peters, M. Weinbauer, J.M. Gasol
Journal of Plankton Research, 32, 4, 381-396. DOI: 10.1093/plankt/fbp137 (BibTeX: lekunberri.etal.2010)
Resum: Veure
The Mediterranean coast receives large inputs of dust with a potential fertilization effect. We evaluated the effect of a wet dust deposition event on microbial abundance and activity, community structure and metabolic balance. Dust collected during a dust storm event was added to a series of microcosms. We added a realistic concentration (0.05 g L–1) based on the phosphorus concentration contained in the dust and, in addition, we included a P amended tank to distinguish the effect of dust from that of the phosphorus in the dust. We also included a higher dust concentration tank (0.5 g L–1). Dust increased the initial water–phosphorus concentration by 0.3 µM and the dissolved organic carbon (DOC) concentration by 14 µM, and increased bacterial abundance (1.8-fold) and bacterial production (5-fold). At the end of the experiment, primary production and community respiration were stimulated by dust and by P, but the net result of the addition of low amounts of dust was an initial switch towards heterotrophy, whereas the net result of the high-dust (DH) additions and the P addition was a shift towards autotrophy. Bacterial community structure changed little between P and low dust, but these were very different from the control and the DH communities.
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Pedrotti M.L., F. Peters, S. Beauvais, M. Vidal, J. Egge, A. Jacobsen, C. Marrasé
Marine Ecology Progress Series, 419, 57-69. DOI: 10.3354/meps08840 (BibTeX: pedrotti.etal.2010)
Resum: Veure
The production of transparent exopolymer particles (TEP) in response to several environmental variables was studied in 2 mesocosm experiments. The first (Expt 1) examined a gradient of 4 nutrient levels; the second (Expt 2) examined different conditions of silicate availability and zooplankton presence. Tanks were separated in 2 series, one subjected to turbulence and the other not influenced by turbulence. In tanks with nutrient addition, TEP were rapidly formed, with net apparent production rates closely linked to chl a growth rates, suggesting that phytoplankton cells were actively exuding TEP precursors. High nutrient availability increased the absolute concentration of TEP; however, the relative quantity of TEP produced was found to be lower, as TEP concentration per unit of phytoplankton biomass was inversely related to the initial nitrate dose. In Expt 1, an increase in TEP volume (3 to 48 μm equivalent spherical diameter) with nutrient dose was observed; in Expt 2, both silicate addition and turbulence enhanced TEP production and favored aggregation to larger TEP (>48 μm). The presence of zooplankton lowered TEP concentration and changed the size distribution of TEP, presumably by grazing on TEP or phytoplankton. For lower nutrient concentrations, the ratio of particulate organic carbon (POC) to particulate organic nitrogen (PON) followed the Redfield ratio. At higher nutrient conditions, when nutrients were exhausted during the post-bloom, a decoupling of carbon and nitrogen dynamics occurred and was correlated to TEP formation, with a large flow of carbon channeled toward the TEP pool in turbulent tanks. TEP accounted for an increase in POC concentration of 50% in high-nutrient and turbulent conditions. The study of TEP dynamics is crucial to understanding the biogeochemical response of the aquatic system to forcing variables such as nutrient availability and turbulence intensity.
Paraules clau: Transparent exopolymer particles · TEP production · Phytoplankton · Particulate organic carbon · POC · Turbulence · Nutrients · Mesocosms
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Iversen K.R., R. Primicerio, A. Larsen, J.K. Egge, F. Peters, Ó. Guadayol, A. Jacobse, H. Havskum, C. Marrasé
Journal of Plankton Research, 32, 2, 197-208. DOI: 10.1093/plankt/fbp113 (BibTeX: iversen.etal.2010a)
Resum: Veure
Small-scale turbulence affects the pelagic food web and energy flow in marine systems and the impact is related to nutrient conditions and the assemblage of organisms present. We generated five levels of turbulence (2*10–9 to 1*10–4 W kg–1) in land-based mesocosms (volume 2.6 m3) with and without additional nutrients (31:16:1 Si:N:P µM) to asses the effect of small-scale turbulence on the lower part of the pelagic food web under different nutrient conditions. The ecological influence of nutrients and small-scale turbulence on lower trophic levels was quantified using multivariate statistics (RDA), where nutrients accounted for 31.8% of the observed biological variation, while 7.2% of the variation was explained by small-scale turbulence and its interaction with nutrients. Chlorophyll a, primary production rates, bacterial production rates and diatom and dinoflagellate abundance were positively correlated to turbulence, regardless of nutrient conditions. Abundance of autotrophic flagellates, total phytoplankton and bacteria were positively correlated to turbulence only when nutrients were added. Impact of small-scale turbulence was related to nutrient conditions, with implications for oligotrophic and eutrophic situations. The effect on community level was also different compared to single species level. Microbial processes drive biogeochemical cycles, and nutrient-controlled effects of small-scale turbulence on such processes are relevant to foresee altered carbon flow in marine systems.
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Peters F.,
Limnology and oceanography bulletin, 19, 1, 2-15. (BibTeX: peters.2010a)
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Pedrotti M.l., S. Beauvais, M.E. Kerros, K. Iversen, F. Peters
Aquatic Microbial Ecology, 55, 3, 301-312. DOI: 10.3354/ame01308 (BibTeX: pedrotti.etal.2009)
Resum: Veure
We examined bacterial colonization of transparent exopolymeric particles (TEP) in nutrient-manipulated mesocosms subjected to different turbulence intensities. We quantified heterotrophic bacterial abundance, production and diversity using fluorescence in situ hybridization (FISH). The abundance of attached bacteria increased significantly with TEP size in all treatments. The slope values of the number of bacteria scaled with TEP size varied from 1.15 on Day 1 to 2.04 on Day 11 in still and turbulent tanks, respectively. Comparison between these slopes indicated that the number of attached bacteria for a given TEP diameter was higher under turbulence. The addition of nutrients and turbulence in mesocosms neither supported higher bacterial abundance nor resulted in a correlation between bacterial concentrations and TEP. However, in enriched turbulent tanks, the number of attached bacteria was higher and was linked to rapid TEP formation after the diatom bloom. This was accompanied by higher bacterial production (1.21 µmol C l–1 d–1 at the intermediate level of turbulence on Day 9), which was positively related to TEP. These correlations highlight the finding that higher bacterial productivity was due to a larger fraction of attached bacteria (up to 56.4%). Changes in bacterial production occurred with simultaneous changes in the community structure, i.e. the percentages of the Cytophaga-Flavobacteria-Bacteroides cluster increased significantly. By Day 9, this cluster became the dominant group of bacteria attached to TEP (85 and 90%, respectively at intermediate and high levels of turbulence). Among the marine heterotrophic bacterioplankton, this phylum is known to be common as attached bacteria. Therefore, it seems that the added nutrients and subsequent TEP production can be used by bacteria more efficiently under turbulent conditions through a shift in group-specific composition towards more attached bacteria with higher production rates.
Paraules clau: Transparent exopolymer particles · Particle colonization · Bacteria · FISH · Turbulence · Nutrients · Mesocosms
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Vaqué D., Ò. Guadayol, F. Peters, J. Felipe, A. Malits, C. Pedrós-Alió
Aquatic Microbial Ecology, 54, 1, 101-112. DOI: 10.3354/ame01259 (BibTeX: vaque.etal.2009)
Resum: Veure
Narrow annual ranges of temperature characterize polar waters. Consequently, small increases in temperature could significantly affect the metabolic processes of marine microorganisms. We investigated the response of bacterial heterotrophic production (BHP) and grazing rates to small temperature changes in 3 zones near the western Antarctic Peninsula—Bransfield and Gerlache Straits, and Bellingshausen Sea—during December 2002. We performed 8 grazing experiments with water samples collected from depths where chlorophyll a (chl a) concentration was maximum, and incubated the samples at ambient temperature and at –1, 1, 2 and 5°C. We expected that grazing would increase in parallel with BHP at increasing temperatures; however, temperature differentially affected these 2 microbial activities. Thus, grazing rates increased maximally at temperatures ≤2°C, except in 1 station in the Gerlache Strait, while BHP increased maximally at temperatures ≥2°C, except in 1 station in the Bellingshausen Sea. The percentage of grazed bacteria to BHP at the highest experimental temperatures was low (56 ± 19%) in the Gerlache Strait, high (395 ± 137%) in the Bransfield Strait and approximately balanced (97 ± 24%) in the Bellingshausen Sea. This suggests that differential microbial processes in each zone at increasing temperatures will also depend on the autochthonous community. The present study contributes to the understanding of the variability of polar biogeochemical fluxes, and may aid in predicting the response of microorganisms in future scenarios with local and seasonal changes in temperature.
Paraules clau: Bacterial heterotrophic production · Grazing rates · Temperature · Antarctic waters
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Guadayol Ò., F. Peters, C. Marrasé, J.M. Gasol, C. Roldán, E. Berdalet, R. Massana, A. Sabata
Marine Ecology Progress Series, 381, 139-155. DOI: 10.3354/meps07939 (BibTeX: guadayol.etal.2009)
Resum: Veure
In temperate coastal zones, episodic meteorological forcing can have a strong impact on the classical seasonal phytoplankton succession. Episodes of continental runoff and wind storms involve nutrient enrichment and turbulence, 2 factors that can promote primary production and alter the planktonic community species composition and size structure. We determined the joint influence of these 2 variables on the osmotrophic plankton of an oligotrophic NW Mediterranean open bay. We used an 8 yr long time series of monthly physical, chemical and biological water-column parameters, and we looked for correlations between these and several meteorological and physical high-frequency time series through cross-correlation analyses. Influence of river runoff in this particular location was found to be very important for phytoplankton dynamics, whereas no immediate response of bacterioplankton was detected. Resuspension events caused by waves had a secondary importance. Cross correlations allowed defining a sequence of responses to these types of forcing, from changes in water turbidity and salinity, to increases in phytoplankton and bacteria abundances through nutrient enrichments. The maximum response of the ecosystem in terms of chlorophyll a concentration lagged nutrient enrichment events by about 1 wk. A more detailed analysis was performed between June 2003 and June 2004, a period characterised by an intense drought in summer and by 6 strong meteorological events afterwards. The increase in the frequency of meteorological events during this period drove the system from heterotrophy to autotrophy. Our data stress the importance of episodic meteorological events in coastal planktonic communities.
Paraules clau: Episodic meteorological forcing · Coastal osmotrophic plankton · Waves · Terrestrial runoff · Sediment resuspension · Nutrients · Time series · NW Mediterranean
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Guadayol Ò., F. Peters, J.E. Stiansen, C. Marrasé, A. Lohrmann
Limnology and Oceanography : Methods, 7, 287-303. (BibTeX: guadayol.etal.2009a)
Resum: Veure
The effects of turbulent motion on planktonic organisms have mainly been studied in the laboratory with devices capable of generating controlled turbulent conditions. Owing to technical and logistical difficulties, thorough assessments of hydrodynamics in such experiments are not routinely made. In this study, we examined the suitability of two widely used systems to generate isotropic, homogeneous, and stationary turbulence in laboratory containers: oscillating grid devices with large stroke length and relatively low frequencies of oscillation and orbital shaker tables. Turbulent kinetic energy dissipation rates were estimated from velocity measurements made with acoustic Doppler velocimeters. Both systems were shown to generate isotropic conditions in a relatively broad range of dissipation rates. Grid-stirred tanks produce homogeneous turbulence in both the horizontal and vertical dimensions, as long as stroke length is comparable to the height of the container. Turbulence in orbital shakers is not completely homogeneous, as it depends on the distance to the wall and to the surface. Empirical models are derived as a tool for the calculation of dissipation rates in the two systems within the ranges and conditions examined in this study.
399.1 Kb
Guadayol Ò., C. Marrasé, F. Peters, E. Berdalet, C. Roldán, A. Sabata
Journal of Plankton Research, 31, 6, 583-600. DOI: 10.1093/plankt/fbp019 (BibTeX: guadayol.etal.2009b)
Resum: Veure
A year-long series of monthly experiments with laboratory enclosures were conducted with water from Blanes Bay (NW Mediterranean) to analyse the change in the short-time response of the osmotrophic planktonic community to simulated turbulence and nutrient input events. Both experimental factors triggered a relative increase of biomass in the enclosures, in terms of chlorophyll a, bacteria and particulate organic matter. Ratios of particulate organic nitrogen to phosphorus became lower in the water than in the sediment, although turbulence partially smoothed out this difference. Initial physico-chemical conditions significantly influenced the short-time responses to experimental forcing. The response to turbulence, in terms of chlorophyll a, was maximum in spring. The response to nutrient enrichment was found to be seasonal, and was correlated with photoperiod and temperature, and also in situ nitrate and silicate concentrations and Secchi depth, which are proxies of recent inputs of nutrients resulting from episodes of resuspension and river discharge. This study shows robust qualitative regularities in the response of the osmotrophic planktonic community to episodes of turbulence and nutrient enrichment, with quantitative variability throughout the year, depending mostly on the recent record of hydrodynamic forcing.
801.9 Kb
Masaló I., Ò. Guadayol, F. Peters, J. Oca
Aquacultural Engineering, 38, 2, 135-144. DOI: 10.1016/j.aquaeng.2008.01.004 (BibTeX: masalo.etal.2008)
Resum: Veure
Sedimentation and resuspension processes of aquaculture biosolids (non-ingested feed and faeces) are analysed using vertically oscillating grids as a source of turbulence in fluid tanks. An oscillating grid system consists of a container in which a grid is stirred vertically generating a well-known turbulent field that is function of amplitude and frequency of oscillation, distance between grid and measurement point, and mesh spacing of the grid. The grid used in this study had a mesh spacing of 1.2 cm, and was calibrated using different amplitudes (1, 1.5 and 2 cm), frequencies (from 1 to 6 Hz) and distances (2.4, 2.7 and 3 cm). After calibration, the turbulence needed to resuspend biosolids and to maintain them in the water column following different times of consolidation, and with biosolids of different origin, was analysed. It was observed that the turbulence needed to resuspend aquaculture biosolids increased with the time of consolidation. When the turbulence was decreased after a resuspension process, the next sedimentation of biosolids showed a hysteretic behaviour: turbulence needed to resuspend a fixed percent of biosolids from the tank bottom is substantially higher than that needed to maintain the same percentage suspended in the water column. Differences in resuspension behaviour of biosolids originated in different tanks were also observed. The method provides useful information that can be compared with turbulence generated by fish swimming activity, in order to determine the culture conditions, which can promote self-cleaning conditions in a particular tank.
Paraules clau: Turbulence; Fish faeces; Solid waste; Resuspension; Oscillating grid
96 Kb
Burchard H., L. Umlauf, F. Peters
Journal of Marine Systems, 70, 3-4, 215-216. DOI: 10.1016/j.jmarsys.2007.06.002 (BibTeX: burchard.etal.2008)
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Vaqué D., Ò. Guadayol, F. Peters, J. Felipe, L. Angel-Ripoll, R. Terrado, C. Lovejoy, C. Pedrós-Alió
Limnology and Oceanography, 53, 6, 2427-2438. (BibTeX: vaque.etal.2008)
Resum: Veure
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.
906.8 Kb
Thingstad T. F., H. Havskum, U.L. Zweifel, E.Berdalet, M.M. Sala, F. Peters, M. Alcaraz, R. Scharek, M. Perez, S. Jacquet, G.A.F. Flaten, J.R. Dolan, C. Marrasé, F. Rassoulzadegan, A. Hagstrøm, D. Vaulot
Journal of Marine Systems, 64, 1-4, 15-34. DOI: 10.1016/j.jmarsys.2006.02.009 (BibTeX: f.thingstad.etal.2007)
Resum: Veure
We compared an idealised mathematical model of the lower part of the pelagic food web to experimental data from a mesocosm experiment in which the supplies of mineral nutrients (nitrogen and phosphorous), bioavailable dissolved organic carbon (BDOC, as glucose), and silicate were manipulated. The central hypothesis of the experiment was that bacterial consumption of BDOC depends on whether the growth rate of heterotrophic bacteria is limited by organic-C or by mineral nutrients. In previous work, this hypothesis was examined qualitatively using a conceptual food web model. Here we explore the extent to which a “simplest possible” mathematical version of this conceptual model can reproduce the observed dynamics. The model combines algal bacterial competition for mineral nutrients (phosphorous) and accounts for alternative limitation of bacterial and diatom growth rates by organic carbon and by silicate, respectively. Due to a slower succession in the diatom copepod, compared to the flagellate ciliate link, silicate availability increases the magnitude and extends the duration of phytoplankton blooms induced by mineral nutrient addition. As a result, Si interferes negatively with bacterial consumption of BDOC consumption by increasing and prolonging algal bacterial competition for mineral nutrients. In order to reproduce the difference in primary production between Si and non-Si amended treatments, we had to assume a carbon overflow mechanism in diatom C-fixation. This model satisfactorily reproduced central features observed in the mesocosm experiment, including the dynamics of glucose consumption, algal, bacterial, and mesozooplankton biomass. While the parameter set chosen allows the model to reproduce the pattern seen in bacterial production, we were not able to find a single set of parameters that simultaneously reproduces both the level and the pattern observed for bacterial production. Profound changes in bacterial morphology and stoichiometry were reported in glucose-amended mesocosms. Our “simplest possible” model with one bacterial population with fixed stoichiometry cannot reproduce this, and we suggest that a more elaborate representation of the bacterial community is required for more accurate reproduction of bacterial production.
497.7 Kb
Bolli L., G. Llaveria, E. Garcés, O. Guadayol, K. Van Lenning, F. Peters, E. Berdalet
Biogeosciences, 4, 4, 559-567. DOI: 10.5194/bg-4-559-2007 (BibTeX: bolli.etal.2007c)
Resum: Veure
Some dinoflagellate species have shown different physiological responses to certain turbulent conditions. Here we investigate how two levels of turbulent kinetic energy dissipation rates (ε = 0.4 and 27 cm² s−3) affect the PSP toxins and ecdysal cyst dynamics of two bloom forming species, Alexandrium minutum and A. catenella. The most striking responses were observed at the high ε generated by an orbital shaker. In the cultures of the two species shaken for more than 4 days, the cellular GTX(1+4) toxin contents were significantly lower than in the still control cultures. In A. minutum this trend was also observed in the C(1+2) toxin content. For the two species, inhibition of ecdysal cyst production occurred during the period of exposure of the cultures to stirring (4 or more days) at any time during their growth curve. Recovery of cyst abundances was always observed when turbulence stopped. When shaking persisted for more than 4 days, the net growth rate significantly decreased in A. minutum (from 0.25±0.01 day−1 to 0.19±0.02 day−1) and the final cell numbers were lower (ca. 55.4%) than in the still control cultures. In A. catenella, the net growth rate was not markedly modified by turbulence although under long exposure to shaking, the cultures entered earlier in the stationary phase and the final cell numbers were significantly lower (ca. 23%) than in the control flasks. The described responses were not observed in the experiments performed at the low turbulence intensities with an orbital grid system, where the population development was favoured. In those conditions, cells appeared to escape from the zone of the influence of the grids and concentrated in calmer thin layers either at the top or at the bottom of the containers. This ecophysiological study provides new evidences about the sensitivity to high levels of small-scale turbulence by two life cycle related processes, toxin production and encystment, in dinoflagellates. This can contribute to the understanding of the dynamics of those organisms in nature.
271.4 Kb
Berdalet E., F. Peters, V. Lila Koumandou, C. Roldan, O. Guadayol, M. Estrada
Journal of Phycology, 43, 965-977. DOI: 10.1111/j.1529-8817.2007.00392.x (BibTeX: berdalet.etal.2007)
2.3 Mb
Guadayol Ò., F. Peters
Scientia Marina, 70, 1, 9-20. (BibTeX: guadayol.peters.2006)
Resum: Veure
Turbulence at different scales, from generation to dissipation, influences planktonic communities. Many experimental studies have recently been done to determine the effects of small-scale turbulence on plankton, but it is difficult to state the relevance of the findings since there is little unbiased information on turbulence variability in the sea. In this study, we use wind velocity data series from several meteorological stations located along the Catalan coast to estimate the spatial and temporal variability of small-scale turbulence in the upper ocean. Using a peaks-over-threshold approach, we develop a statistical model to assess the frequency of wind events as a function of their persistence and intensity. Finally, the wind speed data series are converted into turbulent energy dissipation rate estimates at 1 m depth to determine the general distribution of turbulence on the Catalan coast. Geographical variability is larger than seasonal variability in frequency and persistence of wind events, owing to differences in local relief. These statistical models developed for wind events combined with empirical relationships between wind and turbulence, are tools for estimating the occurrence and persistence of turbulent events at a given location and season. They serve to put into context the past, present and future studies of the effects of turbulence on coastal planktonic organisms and processes.
Paraules clau: wind events, small-scale turbulence, plankton, peaks-over-threshold approach.
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Peters F., L. Arin, C. Marrasé, E. Berdalet, M.M. Sala
Journal of Marine Systems, 61, 134-148. (BibTeX: peters.etal.2006b)
Resum: Veure
The effect of turbulence on the nutrient flux towards osmotrophic cells is predicted to be size dependent. This should translate into growth. We experimentally followed and modelled the growth of two marine diatoms of different size (Thalassiosira pseudonana, 6 mu m in diameter and Coscinodiscus sp., ca. 109 mu m in diameter) under still water and turbulent conditions, using a shaker table. Experiments were done with phosphorus-limited cultures and lasted for ca. 5 days. Turbulence enhanced the growth of Coscinodiscus sp. in agreement with theory but not the growth of T pseudonana, which was actually slightly lower under turbulence. At the end of the experiments there were about 1.7 times as many. Coscinodiscus sp. cells in the turbulent treatment than in the still treatment, while for T pseudonana almost the same cell concentration was found in both conditions. In addition, the Coscinodiscus sp. cells growing under still conditions presented a higher specific alkaline phosphatase activity than those growing in turbulence which indicates a higher need for phosphorus in the still cultures. A simple dynamic model, based on Michaelis-Menten nutrient uptake kinetics, needed nearly no optimisation other than using observed initial conditions of phosphate and cell concentrations. The model showed how an increased nutrient flux towards the cells translates non-linearly into cell growth, most likely by affecting the half-saturation constant (K-M). However, since Coscinodiscus sp. experienced significant mortality and cells partially settled to the bottom of the containers, unequivocal support for the size-dependent effect of turbulence on nutrient uptake will require further experiments and more sophisticated modelling. The mechanisms to connect an increased nutrient flux towards cells with population growth and whether this process is size dependent are important in parameterizing the effects of turbulence on marine plankton in coupled physical-biological models. (c) 2006 Elsevier B.V. All rights reserved.
Paraules clau: diatom growth, half saturation constant, maximum uptake velocity, nutrient uptake, phosphorus affinity, size, turbulence
78.1 Kb
Hannah C., F. Peters
Journal of Marine Systems, 31, 3-4, 115-117. DOI: 10.1016/j.jmarsys.2006.01.003 (BibTeX: hannah.peters.2006)
Experimental analysis of coagulation of particles under low-shear flow (2005)
Colomer J., F. Peters, C. Marrasé
Water Research, 39, 2994-3000.
322.7 Kb
Pinhassi J., M.M. Sala, H. Havskum, F. Peters, O. Guadayol, A. Malits, C. Marrasé
Applied and Environmental Microbiology, 70, 11, 6753-6766. DOI: 10.1128/AEM.70.11.6753-6766.2004 (BibTeX: pinhassi.etal.2004b)
Resum: Veure
The results of empirical studies have revealed links between phytoplankton and bacterioplankton, such as the frequent correlation between chlorophyll a and bulk bacterial abundance and production. Nevertheless, little is known about possible links at the level of specific taxonomic groups. To investigate this issue, seawater microcosm experiments were performed in the northwestern Mediterranean Sea. Turbulence was used as a noninvasive means to induce phytoplankton blooms dominated by different algae. Microcosms exposed to turbulence became dominated by diatoms, while small phytoflagellates gained importance under still conditions. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments showed that changes in phytoplankton community composition were followed by shifts in bacterioplankton community composition, both as changes in the presence or absence of distinct bacterial phylotypes and as differences in the relative abundance of ubiquitous phylotypes. Sequencing of DGGE bands showed that four Roseobacter phylotypes were present in all microcosms. The microcosms with a higher proportion of phytoflagellates were characterized by four phylotypes of the Bacteroidetes phylum: two affiliated with the family Cryomorphaceae and two with the family Flavobacteriaceae. Two other Flavobacteriaceae phylotypes were characteristic of the diatom-dominated microcosms, together with one Alphaproteobacteria phylotype (Roseobacter) and one Gammaproteobacteria phylotype (Methylophaga). Phylogenetic analyses of published Bacteroidetes 16S rRNA gene sequences confirmed that members of the Flavobacteriaceae are remarkably responsive to phytoplankton blooms, indicating these bacteria could be particularly important in the processing of organic matter during such events. Our data suggest that quantitative and qualitative differences in phytoplankton species composition may lead to pronounced differences in bacterioplankton species composition.
Turbulence increases the average settling velocity of phytoplankton cells (2004)
Ruiz J., D. Macias, F. Peters
Proceedings of the National Academy of Sciences of the United States of America, 101, 51, 17720-17724.
Helical Lévy walks: Adjusting searching statistics to resource availablity in microzooplankton (2003)
Bartumeus F., F. Peters, S. Pueyo, C. Marrasé, J. Catalan
Proceedings of the National Academy of Sciences of the United States of America, 100, 22, 12771-12775.
Interaccions entre la turbulència de petita escala i els organismes i processos planctònics en el marc de canvis globals (2003)
Peters F.,
Treballs de la Societat Catalana de Biologia, 54, 51-64.
3.1 Mb
Havskum H., T.F. Thingstad, R. Scharek, F. Peters, E. Berdalet, M.M. Sala, M. Alcaraz, J.C. Bangsholt, U.L. Zweifel, A. Hagström, M. Perez, J.R. Dolan
Limnology and Oceanography, 48, 1, 129-140. (BibTeX: havskum.etal.2003)
Resum: Veure
The effects of organic and inorganic nutrient enrichments on algal-bacterial competition were investigated using mesocosms. Interactions were followed over 10 d in 12, 3-m3 seawater mesocosms in the Isefjord, Denmark. Two sets of four mesocosms were given the same daily addition of "phytoplankton nutrients" (phosphate and nitrate) but received different amounts of glucose, and one set was kept in excess with respect to silicate. Four additional mesocosms served as controls and received either no additions, silicate alone, or glucose alone. In the mesocosm set where no silicate was added, enrichment with phytoplankton nutrients and glucose led to a replacement of diatoms, not by other algae, but by heterotrophic bacteria, mainly bacteria > 2 /,m. In the mesocosm set where silicate was kept replete, diatoms competed successfully with bacteria for the uptake of mineral nutrients. Even in mesocosms enriched with high amounts of glucose, primary production increased throughout the experimental period, while bacterial production, after an initial increase, leveled off. In addition, turnover time of glucose increased in the silicate-replete mesocosm set, consistent with the idea that bacterial consumption was hampered by diatoms competing successfully for phosphate and nitrate. The size and shape of different algal and bacterial groups in relation to nutrient uptake and grazer avoidance are discussed. Both accumulation and consumption of dissolved organic carbon could depend on the structure of the microbial food web.
232.1 Kb
Arin L., C. Marrasé, M. Maar, F. Peters, M.M. Sala, M. Alcaraz
Aquatic Microbial Ecology, 29, 51-61. DOI: 10.3354/ame029051 (BibTeX: arin.etal.2002)
Resum: Veure
The response of phytoplankton and bacteria dynamics to turbulence and nutrient availability interactions was studied in natural coastal waters enclosed in 15 l microcosms. The effect of turbulence was examined under 3 different nutrient-induced conditions: nitrogen surplus (N, with initial addition of an excess of nitrogen, N:P ratio = 160), nitrogen:phosphorus ratio balanced (NP, with initial addition of nitrogen and phosphorus as Redfield ratio, N:P ratio = 16) and control (C, no nutrient addition). Turbulence (ε = 0.055 cm2 s-3) was generated by vertically oscillating grids. The experiment lasted for 8 d and samples were generally taken daily for nutrient and plankton measurements. Turbulence increased the relative importance of phytoplankton to bacteria when nutrients were added, while in the control the effect of turbulence was negligible. Turbulence also influenced the species¹ composition and the size distribution of the phytoplankton community. The relative contribution of diatoms to total phytoplankton biomass and the average cell size were higher under turbulence, particularly in N and NP treatments. The results of these experiments indicate the importance of considering the hydrodynamic conditions in studies addressing competition for nutrients among different osmotrophic organisms in plankton communities.
Paraules clau: Small-scale turbulence, Phytoplankton:bacteria relationship, Phytoplankton size distribution, Phytoplankton composition, Microcosms
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Maar M., L. Arin, R. Simó, M.M. Sala, F. Peters, C. Marrasé
Aquatic Microbial Ecology, 29, 1, 63-72. DOI: 10.3354/ame029063 (BibTeX: maar.etal.2002)
Resum: Veure
In the oligotrophic sea, phytoplankton and bacteria compete for nutrients. Turbulence changes the outcome of this competition by means of an increase in the nutrient flux to cells by the shear fields, which is cell-size dependent. This effect is insignificant for small cells such as natural bacteria. The hypothesis is that turbulence will increase the phytoplankton competition-capability for nutrients and reduce the organic matter utilisation by bacteria. Consequently, the composition of particulate organic matter should change. To test this hypothesis, we studied the response of natural plankton communities to turbulence enclosed in 15 l microcosms. We evaluated the response in terms of the ratio of heterotrophic:total biomass and the stoichiometry of particulate organic matter. Results under turbulent and still conditions were compared in 3 nutrient-induced conditions: nitrogen surplus (N, with initial addition of an excess of nitrogen, N:P ratio = 160), nitrogen:phosphorus ratio balanced (NP, with initial addition of nitrogen and phosphorus as Redfield ratio, N:P ratio = 16) and control (C, no nutrient addition). In N and NP conditions, turbulence decreased the heterotrophic:total biomass ratio up to 2-fold, and induced changes in the stoichiometry of the particulate organic matter. We found higher values of carbon:phosphorus and nitrogen:phosphorus ratios in turbulent than in still treatments. The magnitude of these responses to turbulence depended on the induced nutrient conditions. In the control microcosms, we found the maximum differences of carbon:phosphorus ratio between turbulence and still treatments. In terms of biomass, the response to turbulence was clear in the enriched conditions and insignificant in the control microcosms.
Paraules clau: Small-scale turbulence, Phosphorus, Particulate organic matter stoichiometry, Microcosms
Effects of turbulence conditions on the balance between production and respiration in marine planktonic communities (2002)
Alcaraz M., C. Marrasé, F. Peters, L. Arin, A. Malits
Marine Ecology Progress Series, 242, 63-71.
Microcosms: applications in marine phytoplankton studies (2002)
Estrada M., F. Peters
In: Pelagic ecology methodology, Ed. D.V. Subba Rao. Balkema Publishers. 359-370. Rotterdam.
Overcoming linearisation errors in calculating bacterial growth rates (2002)
Peters F.,
Marine Ecology Progress Series, 245, 305-308.
446.6 Kb
Sala M.M., F. Peters, J.M. Gasol, C. Pedrós-Alió, C. Marrasé, D. Vaqué
Aquatic Microbial Ecology, 27, 1, 47-56. DOI: 10.3354/ame027047 (BibTeX: sala.etal.2002)
Resum: Veure
Nutrient limitation of bacterioplankton growth was studied in the western Mediterranean Sea to determine its spatial and temporal variations. Shipboard microcosm experiments were performed in June 1995, June 1996 and September 1996. Seawater was amended with carbon (C, as glucose), nitrate (N) and phosphate (P), individually or in combination. The limiting nutrient was inferred from the combination that stimulated the highest bacterial production and generated the highest bacterial biomass in the experiments. The results of the experiments carried out along a coastal-to-open sea transect, with both surface and deep chlorophyll maximum depth waters (DCM), suggest that there is a strong variability in the factors limiting bacteria. While phosphorus was most often the limiting nutrient in the surface samples, at the DCM depths nitrogen or carbon limitation was also found. The surface waters of the open sea station were also studied during the 3 cruises to provide an estimate of seasonal variation of bacterial limitation. Phosphorus limitation was found in the 3 periods: very clear phosphorus limitation in September 1996, possible phosphorus limitation in June 1995 and possible co-limitation with carbon in June 1996. Our results show that phosphorus is the main nutrient limiting bacterioplankton growth in the NW Mediterranean. However, while phosphorus was usually the limiting nutrient in the surface layers, nitrogen and carbon limitation also occurred at other depths. Thus, seasonal and spatial variability in the nutrient limiting bacterial growth should be expected.
Paraules clau: Nutrient limitation, Bacterioplankton, NW Mediterranean, Spatial variation, Temporal variation
828.3 Kb
Peters F., C. Marrasé, H. Havskum, F. Rassoulzadegan, J. Dolan, M. Alcaraz, J.M. Gasol
Journal of Plankton Research, 24, 4, 321-331. DOI: 10.1093/plankt/24.4.321 (BibTeX: peters.etal.2002)
Resum: Veure
Changes in picoplankton population abundance and growth under turbulence have been suggested to be the consequence of turbulence affecting larger trophic levels and hence the grazing pressure. We designed a laboratory set-up to assess the effects of turbulence on plankton assemblages, and tested the degree of food-web complexity needed to produce cascading effects on picoplankton and the interactions with nutrient enrichment. Grazing pressure on bacteria was relaxed under turbulence and we show that one trophic link is enough to produce effects at the picoplankton level. Nutrient enrichment increased the effect of turbulence as there was more biomass to act upon. The organisms responsible for driving the grazing pressure shifts could not be identified since they seemed to change depending on initial conditions and experimental treatment. A trend of increased heterotrophic biomass under turbulence was found in all cases, which can have important implications in community metabolism dynamics
Seawater-atmosphere O2 exchange rates in open-top laboratory microcosms: application for continuous estimates of planktonic primary production and respiration (2001)
Alcaraz M., C. Marrasé, F. Peters, L. Arin, A. Malits
Journal of Experimental Marine Biology and Ecology, 257, 1-12.
Effects of turbulence on plankton: an overview of experimental evidence and some theoretical considerations (2000)
Peters F., C. Marrasé
Marine Ecology Progress Series, 205, 291-306.
Seasonal changes in microbial processes in estuarine and continental shelf waters of the South-eastern U.S.A. (2000)
Pomeroy L.R., J.E. Sheldon, W.M. Sheldon, Jr., J.O. Blanton, J. Amft, F. Peters
Estuarine, Coastal and Shelf Science, 51, 415-428.
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Vazquez Dominguez E., F. Peters, J.M. Gasol, D. Vaqué
Aquatic Microbial Ecology, 20, 2, 119-128. DOI: 10.3354/ame020119 (BibTeX: vazquezdominguez.etal.1999a)
Resum: Veure
Fluorescently labeled tracers (FLT) are often used to estimate the loss rates of picoplankton to grazers. These tracers are commonly enumerated by epifluorescence microscopy, although flow cytometry is a viable alternative in the detection of FITC (fluorescein-5-isothiocyanate)- or DTAF (5-([4,6-dichlorotriazin-2-yl)amino]-fluorescein)-stained bacterial tracers. However, the bacterivory measured with FLT has hardly been applied to routine monitoring of oceanic waters, partly because of the time-consuming preparation of the tracers and other problems associated with the long-term incubations needed to generate detectable rates of tracer change. In addition, these long-term incubations make samples especially sensitive to the unwanted addition of nutrients carried over with the tracers. Here we present some experiments designed to ease the estimation of grazing rates on bacteria with this technique. Two bacterial strains and 2 fluorescent dyes were tested: Escherichia coli minicells (0.065 μm3) and Pseudomonas diminuta (0.064 μm3), stained with DTAF or with FITC. In addition, instead of the common use of pyrophosphate buffer during the staining protocol, the use of carbonate-bicarbonate buffer and cells scraped directly from solid media is suggested to avoid the problems associated with phosphorus enrichment of the sample that at times can occur in oligotrophic water samples. The FITC- or DTAF-stained tracers can be observed with either epifluorescence microscopy or flow cytometry. However, FITC- or DTAF-stained P. diminuta were more easily resolved with the flow cytometer than stained minicells. Flow cytometric detection of P. diminuta tracers, prepared in bicarbonate-buffer and stained with FITC, is a fast protocol for the estimation of the grazing loss rates of bacteria in oceanic environments.
Paraules clau: Bacterial grazing rates; Flagellates; Flow cytometry; Pseudomonas diminuta
233.5 Kb
Gasol J.M., U. Li Zweifel, F. Peters, J. A. Fuhrman, A. Hagström
Applied and Environmental Microbiology, 65, 10, 4475-4483. (BibTeX: gasol.etal.1999)
Resum: Veure
Total bacterial abundances estimated with different epifluorescence microscopy methods (4′,6-diamidino-2-phenylindole [DAPI], SYBR Green, and Live/Dead) and with flow cytometry (Syto13) showed good correspondence throughout two microcosm experiments with coastal Mediterranean water. In the Syto13-stained samples we could differentiate bacteria with apparent high DNA (HDNA) content and bacteria with apparent low DNA (LDNA) content. HDNA bacteria, “live” bacteria (determined as such with the Molecular Probes Live/Dead BacLight bacterial viability kit), and nucleoid-containing bacteria (NuCC) comprised similar fractions of the total bacterial community. Similarly, LDNA bacteria and “dead” bacteria (determined with the kit) comprised a similar fraction of the total bacterial community in one of the experiments. The rates of change of each type of bacteria during the microcosm experiments were also positively correlated between methods. In various experiments where predator pressure on bacteria had been reduced, we detected growth of the HDNA bacteria without concomitant growth of the LDNA bacteria, such that the percentage contribution of HDNA bacteria to total bacterial numbers (%HDNA) increased. This indicates that the HDNA bacteria are the dynamic members of the bacterial assemblage. Given how quickly and easily the numbers of HDNA and LDNA bacteria can be obtained, and given the similarity to the numbers of “live” cells and NuCC, the %HDNA is suggested as a reference value for the percentage of actively growing bacteria in marine planktonic environments.
2 Mb
Peters F., C. Marrasé, J.M. Gasol, M.M. Sala, L. Arin
Marine Ecology Progress Series, 172, 293-303. DOI: 10.3354/meps172293 (BibTeX: peters.etal.1998)
Resum: Veure
We performed laboratory experiments with natural seawater communities of the Northwestern Mediterranean to test whether turbulence could affect bacterial abundance and activity. There was no direct effect of turbulence on bacteria when they were uncoupled from the remainder of the microbial community. In the presence of the microbial community, bacteria showed higher activity and maintained high abundances for a longer time under turbulence than in still water. Thus, turbulence sufficiently altered some microbial component or process in the water samples that indirectly affected bacteria. The population dynamics of bacteria and pigmented eukaryotes suggests that, under turbulence, there is a community grazing shift from smaller to larger prey sizes. This shift can be explained in terms of the advantage to protozoan predators which are able to prey on larger and more nutritious cells when the encounter rates with these cells are increased through the shear present under turbulence. The result is a higher control on phytoplankton and a relaxation of grazing on bacteria. Hence, episodic high turbulence events in coastal systems could accelerate nutrient recycling.
Paraules clau: Bacteria, Turbulence, Bacterial activity, Phototrophic pico- and nanoplankton, Grazing, Shift of preferred prey size
Turbulence generation and measurement: application to studies on plankton (1997)
Peters F., J.M. Redondo
Scientia Marina, 61, supl. 1, 205-228.
Nutrients, primary production and microbial heterotrophy in the southeastern Chukchi Sea: Arctic summer nutrient depletion and heterotrophy (1996)
Cota G.F., L.R. Pomeroy, W.G. Harrison, E.P. Jones, F. Peters, W.M. Sheldon, Jr.T.R. Weingartne
Marine Ecology Progress Series, 135, 247-258.
Paraphysomonas imperforata Lucas (Protista, Chrysomonadida) under different turbulence levels: feeding, physiology and energetics (1996)
Peters F., J.W. Choi, T. Gross
Marine Ecology Progress Series, 134, 235-245.
11 Mb
Peters F.,
PhD thesis. Director/es: L.R. Pomeroy. (BibTeX: peters.1995a)
Limits to growth and respiration of bacterioplankton in the Gulf of Mexico. (1995)
Pomeroy L.R., J.E. Sheldon, W.M. Sheldon, F. Peters
Marine Ecology Progress Series, 117, 259-268.
Increased grazing rates of microplankton in response to samll-scale turbulence (1994)
Peters F., T. Gros
Marine Ecology Progress Series, 115, 299-307.
11 Mb
Gasol J.M., F. Peters, R. Guerrero, C. Pedrós-Alió
Archiv fur Hydrobiologie, 123, 3, 275-303. (BibTeX: gasol.etal.1992)
Effects of temperature on two psychrophilic ecotypes of a heterotrophic nanoflagellate, Paraphysomonas imperforata (1992)
Choi J.W., F. Peters
Applied and Environmental Microbiology, 58, 2, 593-599.
7.1 Mb
Gasol J.M., J. García Cantizano, R. Massana, F. Peters, R. Guerrero, C. Pedrós-Alió
Hydrobiologia, 211, 3, 227-240. DOI: 10.1007/BF00008536 (BibTeX: gasol.etal.1991c)
Resum: Veure
The microstratification of the metalimnetic community in Lake Cisó was followed through the diel cycle by means of a fine sampler with syringes spaced at 3 cm intervals. Populations were sharply stratified. The uppermost part of the metalimnion was occupied by the rotifer Anuraeopsis fissa. Next, layers of the ciliate Coleps hirtus and the flagellate Cryptomonas phaseolus were found. Finally, purple sulfur bacteria appeared at the bottom part of the metalimnion. Although in lower abundances, characteristic populations of ciliates were found at each depth: Strombidium inhabited zones with oxygen, while Plagiopyla and Metopus lived at depths with sulfide. Several members of the community moved vertically about 20 cm during the diel cycle. Cryptomonas performed larger vertical migrations of 40 cm. This organism concentrated at the upper metalimnion during the day, and dispersed through the lower metalimnion during the night. At night, Cryptomonas lived in an environment without oxygen and with sulfide concentrations up to 0.6 mM.
Paraules clau: Diel cycle; Vertical migration; Cryptomonas phaseolus; Anaerobic ciliates; Fine sampling; Stratification