Articles

32 documents.
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Rigual-Hernández A.S., J.A. Flores, F.J. Sierro, M.A. Fuertes, L. Cros, T.W. Trull
Biogeosciences, 15, 1843-1862. DOI: 10.5194/bg-15-1843-2018 (BibTeX: rigualhernandez.etal.2018)
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Young J.R., P.R. Bown, L. Cros, K. Hagino, R.W. Jordan
Journal of Nannoplankton Research, 38, (BibTeX: young.etal.2018)
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Sala M.M., F. Aparicio, V. Balagué, J.A. Boras, E. Borrull, C. Cardelús, L. Cros, A. Gomes, A. López-Sanz, A. Malits, R.A. Martínez, M. Mestre, J.M. Movilla, H. Sarmento, E. Vázquez-Domínguez, D. Vaqué, J. Pinhassi, A. Calbet, E. Calvo, J.M. Gasol, C. Pelejero, C. Marrasé
ICES Journal of Marine Science, 73, 3, 670-679. DOI: 10.1093/icesjms/fsv130 (BibTeX: sala.etal.2016a)
Resum: Veure
We investigated the effects of an increase in dissolved CO2 on the microbial communities of the Mediterranean Sea during two mesocosm experiments in two contrasting seasons: winter, at the peak of the annual phytoplankton bloom, and summer, under low nutrient conditions. The experiments included treatments with acidification and nutrient addition, and combinations of the two. We followed the effects of ocean acidification (OA) on the abundance of the main groups of microorganisms (diatoms, dinoflagellates, nanoeukaryotes, picoeukaryotes, cyanobacteria, and heterotrophic bacteria) and on bacterial activity, leucine incorporation, and extracellular enzyme activity. Our results showed a clear stimulation effect of OA on the abundance of small phytoplankton (pico- and nanoeukaryotes), independently of the season and nutrient availability. A large number of the measured variables showed significant positive effects of acidification in summer compared with winter, when the effects were sometimes negative. Effects of OA were more conspicuous when nutrient concentrations were low. Our results therefore suggest that microbial communities in oligotrophic waters are considerably affected by OA, whereas microbes in more productive waters are less affected. The overall enhancing effect of acidification on eukaryotic pico- and nanophytoplankton, in comparison with the non-significant or even negative response to nutrient-rich conditions of larger groups and autotrophic prokaryotes, suggests a shift towards medium-sized producers in a future acidified ocean.
Paraules clau: Acidification, eutrophication, Mediterranean sea, mesocosm, microorganisms
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Thomsen H.A., L. Cros, E. Malinverno, J.B. Østergaard, M.Y. Cortés, M. Geisen, J.R. Young
Journal of Micropalaeontology, 35, 125-135. DOI: 10.1144/jmpaleo2015-013 (BibTeX: thomsen.etal.2016)
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Jewson D., A. Kuwata, Ll. Cros, J.-M. Fortuño, M. Estrada
Scientia Marina, 80, S1, 89-96. DOI: 10.3989/scimar.04331.06C (BibTeX: jewson.etal.2016a)
Resum: Veure
Minidiscus comicus is a marine centric diatom that has cells with diameters as small as 1.9 μm, which brings it close to the lower limit of diatom cell size and also near to the lower limit of photosynthetic eukaryote cells. One of the questions that this raises is whether the cycle of size decline and size restoration used by most diatoms to time their life cycle can operate in such small cells. In samples collected from the western Mediterranean during 2009, M. comicus cells were found with diameters ranging from 1.9 to 6.0 μm. The larger cells were initial cells after size restoration, and these still had the valves of their parent cells attached, making it possible to determine the diameter of the threshold below which size restoration could be induced (3.1 μm). During size decline, M. comicus cell shape changed from discoid to spherical. This adaptation helped to reduce and even halt the rate of cell volume decrease, allowing cells to continue to use diameter decline as a clocking mechanism. The results show how adaptable the diatom cell wall can be, in spite of its rigid appearance.
Paraules clau: Marine diatom, Minidiscus comicus, size change, size limit, size restoration, diatomea marina, cambio de tamaño, tamaño límite, tamaño de restauración
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Narciso A., Valente Gallo F., Cachão A., Cros M., Azevedo L., Barcelos e Ramos E.B.
Continental Shelf Research, 117, 43-65. DOI: 10.1016/j.csr.2016.01.019 (BibTeX: narciso.etal.2016)
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Solé J., E. Berdalet, L. Arin, Ll. Cros, M. Delgado, A. Kuwata, C. Llebot, C. Marrasé
Scientia Marina, 80, S1, 33-38. DOI: 10.3989/scimar.04520.06D (BibTeX: sole.etal.2016e)
Resum: Veure
Plankton ecology has been the object of intense research and progress in the last few decades. This has been partly due to technological advances that have facilitated the multidisciplinary and high-resolution sampling of ecosystems and improved experimentation and analytical methodologies, and to sophisticated modelling. In addition, exceptional researchers have had the vision to integrate all these innovative tools to form a solid theoretical background in ecology. Here we provide an overview of the outstanding research work conducted by Professor Marta Estrada and her pioneering contribution to different areas of research in the last four decades. Her research in biological oceanography has mainly focussed on phytoplankton ecology, taxonomy and physiology, the functional structure of plankton communities, and physical and biological interactions in marine ecosystems. She has combined a variety of field and laboratory approaches and methodologies, from microscopy to satellite observations, including in-depth statistical data analysis and modelling. She has been a reference for scientists all over the world. Here, her contributions to plankton ecology are summarized by some of her students and closest collaborators, who had the privilege to share their science and everyday experiences with her.
Paraules clau: Phytoplankton ecology, taxonomy, functional structure of plankton communities, physical-biological interactions, ecología del fitoplancton, taxonomía, estructura funcional de las comunidades plantónicas, interacciones física-biología
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Thomsen H.A., J.B. Østergaard, L. Cros
Acta Protozoologica, 54, 4, 275-281. DOI: 10.4467/16890027AP.15.022.3536 (BibTeX: thomsen.etal.2015a)
Resum: Veure
It has been known for some time that the distinctive polar weakly calcified coccolithophores are also present in samples from lower latitudes. While polar species may actually have a geographic range that vastly extends beyond the polar realms, it is often the case that the warm water regions contribute species that can be allocated to genera previously described based on polar material. We are currently in the process of formally dealing with the warm water species diversity affiliated with the family Papposphaeraceae. In this paper we describe a new genus and species Ventimolina stellata based on material from the Andaman Sea (type locality) and the NW Mediterranean
Paraules clau: Ventimolina, V. stellata, Papposphaeraceae, Andaman Sea, NW Mediterranean, electron microscopy
Cros Ll., Lluïsa, P.B. McGrane
Journal of Nannoplankton Research, 34, 23-25. (BibTeX: cros.etal.2014a)
Resum: Veure
The holococcolithophore Anthosphaera origami sp. nov., which has very characteristic dimorphic coccospheres, is described on the basis of Scanning Electronic Microscopy (SEM) observations. The body coccoliths are calyptroliths with distal structures that resemble origami paper boats and, in apical position, there are fragarioliths which present delicate fanciful ornamentation
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Guerreiro C., C. Sá, H. De Stigter, A. Oliveira, M. Cachao, L. Cros, C. Borges, L. Quaresma, A.I. Santos, J.M. Fortuño, A. Rodrigues
Deep-Sea Research Part II: Topical Studies in Oceanography, 104, 335-358. DOI: 10.1016/j.dsr2.2013.09.011 (BibTeX: guerreiro.etal.2014)
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Cros L., J.-M. Fortuño, M. Estrada
Scientia Marina, 77, ss1, 63-67. DOI: 10.3989/scimar.03727.27E (BibTeX: cros.etal.2013)
Resum: Veure
Coccolithophores produce calcium carbonate platelets, the coccoliths, and play a significant role in the C and Ca cycles. Coccoliths are important components of marine biogenic carbonate sediments and their chemical analysis can provide tools for paleoceanographic investigation. In particular, the Mg/Ca ratio of coccoliths has been proposed as a paleotemperature proxy. The present study uses X-ray microanalysis to evaluate the Ca and Mg composition of heterococcoliths and holococcoliths of different coccolithophore species. Our measurements indicate that the Mg values in heterococcoliths do not exceed a low threshold and do not show any consistent relationship with the Ca content, while the Mg content of holococcoliths spans a wider range, can reach much higher values and shows a linear relationship with the Ca content. Several heterococcolithophore species tend to form separate clusters according to their Mg and Ca values. Within each cluster, there were no consistent differences in the Mg/Ca ratios of specimens sampled at different temperatures or seasons, suggesting that using the Mg/Ca ratio as a paleothermometer may be problematic. Our findings could have implications for the interpretation of the fossil record because Mg-rich calcite dissolves more easily.
Paraules clau: coccolithophores, X-ray microanalysis, calcium, magnesium, holococcoliths, heterococcoliths
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Cros L., M. Estrada
Marine Ecology Progress Series, 492, 57-68. DOI: 10.3354/meps10473 (BibTeX: cros.estrada.2013)
Resum: Veure
Many coccolithophores have complex life cycles with haploid and diploid stages bearing structurally different coccolith types (holococcoliths and heterococcoliths, respectively). Laboratory studies suggest that holo- and heterococcolithophores may occupy distinct ecological niches, but the potential ecological implications of the existence of haploid and diploid stages are poorly known. We present here a study of holo- and heterococcolithophore distributions in the Catalano-Balearic Sea, during 2 cruises (MESO-96, from 18 June to 3 July, and FRONTS-96, from 16 to 21 September) that covered 2 intervals of the stratification period of 1996. We define a holococcolithophore prevalence index (HOLP index), calculated for each coccolithophore-containing sample, as the percent ratio between the number of holococcolithophores and the total number of holo- and heterococcolithophores belonging to families with alternation of holo- and heterococcolithophore life stages (coccolithophores having HOL-HET life cycles; Total_HHLC). In both cruises, the distribution of holo- and heterococcolithophores and the HOLP index indicated a preference of the holococcolithophores for shallower waters and of the heteroccolithophores for deeper layers. This segregation may be linked to a differentiation of ecological niches, with the haploid holococcolithophores occupying the more oligotrophic upper layers and the diploid heterococcolithophores inhabiting relatively rich deeper waters.
Paraules clau: Holococcolithophore prevalence index · Haploid-diploid life cycles · Coccolithophores · NW Mediterranean
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Guerreiro C., A. Oliveira, H. de Stigter, M. Cachão, C. Sá, C. Borges, L. Cros, A. Santos, J.-M. Fortuño, A. Rodrigues
Continental Shelf Research, 59, 65-83. DOI: 10.1016/j.csr.2013.04.016 (BibTeX: guerreiro.etal.2013)
Resum: Veure
Coccolithophore communities collected during late winter (9–19 March of 2010) over the central Portuguese margin showed a major change in species abundance and composition within a few days\' time, closely related to the highly transient meteorological and oceanographic conditions. Particularly favourable conditions for coccolithophore growth resulted from late winter continental runoff combined with northerly winds prevailing over the shelf, under clear sky conditions. A nutrient-rich Buoyant Plume (BP) resulting from intense river water runoff prior to and during the start of the cruise, was observed to spread out over the denser winter mixed layer water beneath, and extend equatorwards and offshore under influence of Ekman superficial dynamics. Stabilization of buoyancy, settling of suspended sediment from the BP and the prevailing clear sky conditions in the transition to the 2nd leg of the cruise resulted in optimum conditions for coccolithophores to develop, at the expense of nutrient availability in the superficial sunlit layer. Within a few days, coccolithophore cell densities and associated phytoplankton biomass more than tripled, reaching maximum values of 145,000 cells/l and ~13 µg/l Chl-a, respectively. Often considered as a uniform functional group of calcifying phytoplankton thriving in low-turbulence, low-nutrients and high-light environments, results presented in this study clearly show that coccolithophore life strategies are much more diverse than expected. The increase of cell densities was mainly due to the bloom of Emiliania huxleyi and Gephyrocapsa oceanica in the coastal region west off Cape Carvoeiro, together with other opportunistic phytoplankton genera (Chaetoceros s.l., Thalassiosira s.l and Skeletonema s.l.). This confirms their role as early succession r-selected taxa, capable of rapid growth within nutrient-rich environments. On the contrary, Syracosphaera spp. and Ophiaster spp. displayed the characteristics of K-selected species, being consistently more abundant in more oceanic and less eutrophic waters, away from the influence of the BP, during both low- and high-productive periods. A general description of coccolithophore communities as well as the environmental conditions during this period is presented in this study (i.e. hydrography and nutrient availability). Multivariate analysis was used to investigate the impact of short-term environmental changes on the productivity and ecology of this group. In view of the observed dominance of coccolithophores off Portugal during winter, this transitional period appears particularly favourable for coccolithophores to develop. The results highlight the importance of taking short-term hydrographic and meteorological variability into account when interpreting the ecological preferences of coccolithophores from coastal-neritic-oceanic transitional settings.
Paraules clau: Coccolithophore ecology; River runoff; Ekman circulation; Haline-stratification; Portuguese margin
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Álvarez M.C., F. Ornella-Amore, L. Cros, B. Alonso, J. Alcántara-Carrió
Revista Española de Micropaleontología, 42, 3, 359-371. (BibTeX: alvarez.etal.2010)
Resum: Veure
en este trabajo se estudió la distribución de cocolitos en muestras de sedimentos superficiales del margen ibérico mediterráneo. Se calculó la abundancia total y se representó en un mapa de distribución. La mayor abundancia de cocolitos se registró en tres muestras situadas en los alrededores de las islas Baleares y se relacionó con los aportes de las aguas atlánticas modificadas más modernas (Modified Atlantic Water, MAW). La menor abundancia total se registró cerca de la costa, en el área de acción de la corriente del Norte (NC) y del frente Catalán y se ha relaiconado principalmente con los aportes terrígenos del río Ebro. Las abundancias relativas muestran que los pequeños placolitos (Emiliania huxleyi, Gephyrocapsa ericsonii) son las formas dominantes de la asociación de cocolitos en el Mediterráneo occidental, disminuyendo su abundancia con la distancia a la costa y relacionándolas con concentraciones de nutrientes. La distribución de Gephyrocapsa oceanica y Gephyrocapsa muellerae parece estar relacionada con la MAW de las proximidades del estrecho de Gibraltar y con alguno de los remolinos costeros generados por la corriente de Argelia (AC), respectivamente. Syracosphaera spp. y Helicosphaera spp. también alcanzan una abundancia significativa mostrando una distribución concéntrica en el mar Catalano-Balear. La distribución de Florisphaera profund, que mostró algunos valores más altos al sur del delta del Ebro, también puede ser de interés biogeográfico
Paraules clau: Cocolitóforos, sedimentos superficiales, biogeografía, Mediterráneo occidental, margen ibérico mediterráneo
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Aymerich I.F., J. Piera, A. Soria-Frisch, L. Cros
Applied Spectroscopy, 63, 6, 716-726. (BibTeX: aymerich.etal.2009)
Resum: Veure
Fluorescence spectroscopy has been demonstrated to be a powerful tool for characterizing phytoplankton communities in marine environments. Using different fluorescence spectra techniques, it is now possible to discriminate the major phytoplankton groups. However, most of the current techniques are based on fluorescence excitation measurements, which require stimulation at different wavelengths and thus considerable time to obtain the complete spectral profile. This requirement may be an important constraint for several mobile oceanographic platforms, such as vertical profilers or autonomous underwater vehicles, which require rapid-acquisition instruments. This paper presents a novel technique for classifying fluorescence spectra based on self-organizing maps (SOMs), one of the most popular artificial neural network (ANN) methods. The method is able to achieve phytoplankton discrimination using only fluorescence emission spectra (single wavelength excitation), thus reducing the acquisition time. The discrimination capabilities of SOM using excitation and emission spectra are compared. The analysis shows that the SOM has a good performance using excitation spectra, whereas data preprocessing is required in order to obtain similar discrimination capabilities using emission spectra. The final results obtained using emission spectra indicate that the discrimination is properly achieved even between algal groups, such as diatoms and dinoflagellates, which cannot be discriminated with previous methods. We finally point out that although techniques based on excitation spectra can achieve a better taxonomic accuracy, there are some applications that require faster acquisition processes. Acquiring emission spectra is almost instantaneous, and techniques such as SOM can achieve good classification performance using appropriately preprocessed data.
Paraules clau: Self-organizing maps; SOMs; Phytoplankton discrimination; Classification; Fluorescence spectra; Derivative analysis.
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Quintero-Torres R., J.L. Aragón, M. Torres, M. Estrada, L. Cros
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics, 74, 3, 032901-1/4. DOI: 10.1103/PhysRevE.74.032901 (BibTeX: quinterotorres.etal.2006)
Resum: Veure
By considering the structure of holococcoliths (calcite plates that cover holococcolithophores, a haploid phase of the coccolithophore life cycle) as a photonic structure, we apply a discrete dipolar approximation to study the light backscattering properties of these algae. We show that some holococcolith structures have the ability to scatter the ultraviolet radiation. This property may represent an advantage for holococcolithophores possessing it, by allowing them to live higher in the water column than other coccolithophores.
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Jordan R.W., L. Cros, J.R. Young
Micropaleontology, 50, Suppl. 1, 55-79. (BibTeX: jordan.etal.2004)
Resum: Veure
A comprehensive classification of extant haptophytes is presented, with full citations of all taxa from species to class level within the division Haptophyta. Almost 100 notes discuss aspects of classification and nomenclature, with particular attention being paid to problems related to recognition of life-cycle associations. One new genus Holococcolithophora is described and six species are recombined in it. Appendices list conserved and rejected names, the type species of genera, and basionyms of recombined species.
Picarola margalefii, gen. Et sp. Nov., a new planktonic coccolithophore from NW Mediterrranean waters (2004)
Cros L., M. Estrada
Scientia Marina, 68, Suppl. 1, 243-248.
Species level variation in coccolithophores (2004)
Geisen M., J. R. Young, I. Probert, A. G. Sáez, K.-H. Baumann, C. Sprengel, J. Bollmann, L. Cros, C. de Vargas, L. K. Medlin
In: Coccolithophores - From molecular processes to global impact, Ed. Thierstein, H.R. and Young, J.R.. Springer. 327-366. Berlin. ISBN: 3-540-21928-5
A guide to extant coccolithophore taxonomy (2003)
Young J., M. Geisen, L. Cros, A. Kleijne, C. Sprengel, I. Probert, J. Ostergaard
Journal of Nannoplankton Research, Sp. Iss. 1, 1-121.
Concentrations of plutonium and americium in plankton from the western Mediterranean Sea (2003)
Sánchez-Cabeza J.-A., J. Merino, P. Masqué, P.I. Mitchell, L. León Vintró, W.R. Schell, Ll. Cros, A. Calbet
The Science of the Total Environment, 311, 233-245.
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Fortuño L. Cros J.M.,
Scientia Marina, 66, sup. 1, 7-182. (BibTeX: crosj.m.fortuno.2002)
Resum: Veure
The present Atlas contains a detailed study, based in scanning electron microscopy (SEM) observations, of living coccolithophores from NW Mediterranean waters. The study contains 103 figures with 411 micrographs, which correspond to 168 coccolithophores (including different taxonomic and morphotypic entities). The figured specimens were collected during different cruises carried out from 1995 to 1999. Classification of the organisms follows modern taxonomy of living calcareous nannoplankton. Measures of the specimens and notes on their taxonomy are given in addition to abridged descriptions of the studied taxa. The atlas contains a large number of previously undescribed forms, specially in the genera Syracosphaera, Papposphaera, Polycrater, Anthosphaera, Corisphaera and Sphaerocalyptra. Several species never illustrated in the literature are presented here for the first time. Coccospheres having coccoliths of different recognized species are presented. These combination coccospheres are nowadays considered as transitional steps between different phases in the cellular life-cycle. An introduction with a brief overview of the actual coccolithophore knowledge and an abridged glossary with figures of the basic terminology are included.
Paraules clau: coccolithophores, calcareous nannoplankton, living, Haptophyta, Prymnesiophyceae, NW Mediterranean Sea, SEM photomicrographs.
Five new species of the coccolithophorid genus Alisphaera (Haptophyta), with notes on their distribuition, coccolith structure and taxonomy (2002)
Kleijne A., R.W. Jordan, B.R. Heimdal, C. Samtleben, A.H.L. Chamberlain, L. Cros
Phycologia, 40, 6, 583-601.
Life-cycle associations involving pairs of holococcolithophorid species: intraspecific variation or cryptic speciation? (2002)
Geisen M., C. Billard, A.T.C. Broerse, L. Cros, I. Probert, J.R. Young
European Journal of Phycology, 37, 4, 531-550.
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Cros i Miguel M.Ll.,
PhD thesis. Director/es: R. Margalef i López. Barcelona. (BibTeX: crosimiguel.2001b)
Resum: Veure
Este trabajo estudia las algas haptófitas que de una manera continuada, o en algún momento de su ciclo de vida, producen y llevan cocolitos. Los cocolitos son delicadas y muy bellas plaquitas de carbonato cálcico, que no se sabe bien para qué les sirven, pero que tienen un papel muy importante en la translocación del carbonato cálcico y otros elementos, desde la columna de agua hacia los sedimentos. [...]
New examples of holococcolith-heterococcolith combination coccospheres and their implications for coccolithophorid biology (2000)
Cros L., A. Kleijne, A. Zeltner, C. Billard, J. R. Young
Marine Micropaleontology, 39, 1-4, 1-34.
Variety of exothecal coccoliths of Syracosphaera (2000)
Cros L.,
Journal of Nannoplankton Research, 22, 1, 41-51.
Notes on nannoplankton systematics and life-cycles - Ceratolithus cristatus, Neosphaera coccolithomorpha and Umbilicosphaera sibogae (1998)
Young J.R., R.W. Jordan, L. Cros
Journal of Nannoplankton Research, 20, 2, 89-99.
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Cros Ll.,
, Ed. F.J. Sierro, J.A. Flores. 47-59. ISBN: 84-600-9305-0 (BibTeX: cros.1995b)
Resum: Veure
The calcareous nannoplankton in 15 surficial sediments from the NW Mediterranean have been studied. The siliceous skeletal remains appeared to ha ve been dissolved, but the carbonate remains were well conserved in the sampIes. Emiliania huIxleyi was the most abundant species, followed by species of the genus Gephyrocapsa, especially G. mueIlerae. The gradients in the distribution of calcareous nannoplankton in the Catalano-Balearic Sea sediments can be related to the hydrography of the area.
Paraules clau: Coccoliths, nannoplankton, sediments, NW Mediterranean
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Cros Ll., J. Serra
In: The dynamics and environmental contexts of aeolian sedimentary systems edited by K. Pye., Geological Society Special Publication. Vol. 72. Ed. K. Pye. Geological Society of London. 191-199. DOI: 10.1144/GSL.SP.1993.072.01.16 ISBN: 0-903317-88-5 (BibTeX: cros.serra.1993a)
Resum: Veure
The dune system of Baix Empordà, Catalonia, Spain is composed of sediments supplied by the Ter and Daró rivers, transported by the effective north-northwesterly local wind called the Tramuntana. Dune formation is mostly related to the vegetation on the plains area and to topographic obstacles in the Begur Massif zone. Morphologically, these dunes are mainly parabolics and blowouts. Climbing, falling and 'passadis' dunes are present in the mountainous zone, the latter being a newly proposed name for a type of lee dune. The sands are differentiated into distinct groups according to their sedimentological features and marine faunal content. Their evolution and age have been determined by mapping, and by geological and historical information, respectively.
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Cros Miguel Ll.,
PhD thesis. Director/es: J. Serra i Raventós. Barcelona. (BibTeX: crosmiguel.1987b)
Resum: Veure
Aquest treball és un estudi de les dunes de Begur "conegudes ab lo nom de sorres de Begur, que lo vent porta de la platja de Pals y mou d'una banda a l'altre" (BOTET i SISO, CARRERAS CANDI s.d.), però que un cop encetat i per enmarcar-les dins el seu context ens hem sentit obligats a extendre'l a totes les formacions eòliques del Baix Empordà. [...]