Papers by Nagore Sampedro
Nova Hedwigia, Beihefte
Water samples were collected from Tarragona port, Catalan coast, in July 2007, in order to study ... more Water samples were collected from Tarragona port, Catalan coast, in July 2007, in order to study the marine planktonic nanoflagellates. Scale-bearing chrysophytes species observed in the SEM included Paraphysomonas foraminifera Lucas, Paraphysomonas imperforata Lucas, Paraphysomonas cf. vestita (Stokes) De Saedeleer and Clathromonas butcheri (Pennick et Clarke) Scoble et Cavalier-Smith. Clathromonas butcheri has two different scales covering the cells: round, inner perforated plate scales, and crown (or basket)-scales with an open meshwork; the round, inner scales predominate over the crown scales. Cells of Paraphysomonas species are covered by one type of scale, with a circular base-plate (perforated or not perforated) and a single spine. In P. foraminifera the base-plates are finely perforated and have a mid annulus, and the spines appear straight or curved at the tips, with tips truncate. The other two species have their base-plates unperforated, but scales of P. imperforata showed a characteristic annulus. The morphological variation of the scales (sizes, presence or absence of annulus and thickened marginal rim, and lack of spines) of these species is discussed in the context of morphologic characters of taxonomic value, or the possible development of certain scales structures during the process of maturation.
Frontiers in Marine Science
During summer, when oligotrophic conditions prevail offshore in the Mediterranean Sea, enhanced p... more During summer, when oligotrophic conditions prevail offshore in the Mediterranean Sea, enhanced phytoplankton stripes are often observed in nearshore waters. In this study, we examine the cross-shore hydrographic variability and the associated microbial plankton communities in this zone. Detailed cross-shore underway sampling at 47 coastal sites spread along the Balearic and Catalan coasts revealed the widespread existence of narrow bands of warm and decreased salinity water beholding high phytoplankton biomass (up to 50-fold vs. offshore chlorophyll). Most intense physical and biological anomalies along these transects were generally constrained to the first hundred meters from the shoreline (i.e., a transition zone starting at ∼400 m). We use Principal Component Analysis (PCA) and k-means cluster analysis to categorize temperature, salinity and chlorophyll (T, S and Chl) in three main types of cross-shore trends. Prevalence of exponential-shaped Chl trends was observed particularly in areas with shoreward directed winds (B1-type). The other two trends (B2 and B3) presented variations off the coast produced by alongshore structures like river plumes, city outfalls and other features. Exponential-shaped cross-shore chlorophyll distribution (B1-type) accumulated 90% of the total transect Chl variation in the first 367 ± 190 m from the shoreline, whereas this distance was variable in the other profile types. Repeated daily sampling at one site with this transect typology revealed that wind forcing variations produced fast response on cross-shore T and S properties. Chl was less sensitive to changes at this timescale. Phytoplankton communities exhibited site-dependent responses to the nearshore environment. Pico-and nanoplankton assemblages, typically dominating coastal assemblages during summer in the Mediterranean Sea, showed lower cross-shore variation. Conversely, larger response to nearshore conditions was observed in microplankton populations. These larger cells, represented by dinoflagellates, cryptophytes and diatoms, were able Basterretxea et al. Cross-Shore Gradients in Coastal Phytoplankton to actively exploit the nearshore conditions constituting an independent and distinct assemblage from that one prevailing offshore. Our results suggest that despite the importance of local-scale processes in determining biotic structure, some common patterns emerge providing clues on the main drivers of this nearshore niche.
Investigacion Y Ciencia, 2013
The Alexandrium tamarense/catenella / fundyense species complex comprises four genetically differ... more The Alexandrium tamarense/catenella / fundyense species complex comprises four genetically different clades in which the similarity between strains is larger in geographically related species than between geographically distant strains of the same species. These clades are the North Atlantic, the Western European, the Temperate Asian and the Mediterranean clades. The morphological characters currently used to differentiate the species within this complex are the presence or absence of a ventral pore in 1’ plate, the ability to form chains, and the relation between the transdiameter and the length of the cells. In Alexandrium minutum the presence of the ventral pore is not a constant character, and in other species the ability to form longer or shorter chains is strain dependent, and the relation between the transdiameter and length of cells depends on whether or not they form chains. These characters alone are no longer valid to differentiate among species of this complex. In our op...
The Handbook of Environmental Chemistry, 2015
The Water Framework Directive (WFD) mandates the use of biological quality element (BQE) phytopla... more The Water Framework Directive (WFD) mandates the use of biological quality element (BQE) phytoplankton to assess the ecological status of coastal and transitional water bodies (WB). Here, we present (i) a critique of the general ecological assumptions of the WFD, (ii) a review of the ecological features of coastal phytoplankton dynamics, (iii) several approaches to establish a methodology to assess water-quality along the Catalan coast (NW Mediterranean Sea) based on BQE phytoplankton, and (iv) a critical examination of the use of phytoplankton as a BQE. Since 2005, we have followed several approaches aimed at assessing water-quality based on BQE phytoplankton and linking this indicator to a proxy to a costal pressure index. We have therefore studied phytoplankton communities at three different levels: as potentially harmful species, as functional or taxonomic groups, and with respect to their bloom frequency. Despite intense efforts, none of these fulfilled the WFD's management requirements, which in this context were found to contain several inherent flaws. As an alternative, we propose a methodology to assess water-quality based on the use of chlorophyll-a (Chl-a), as a proxy of phytoplankton biomass. The Chl-a concentration offers a very simple and representative measure of the phytoplankton community, and, importantly, it is used worldwide in water-quality studies, thus allowing not only regional but also crosscountry comparisons. Moreover, because Chl-a concentrations clearly respond to nutrient enrichment, we were able to establish a BQE-specific typology for water bodies based on salinity, which is linked to nutrient loads. Using a newly developed coastal pressure index (Land Use Simplified Index, LUSI) that also reflects nutrient
Marine Ecology Progress Series, 2005
Growth and mortality rates of natural single Alexandrium spp. cells were measured by the Landry-H... more Growth and mortality rates of natural single Alexandrium spp. cells were measured by the Landry-Hassett dilution technique during different phases of blooms. Taxon-specific experiments were conducted between May and October 2002 during 3 intense blooms of A. taylori and A. catenella at different locations of the Mediterranean Sea. In addition, dilution experiments using chlorophyll a as a proxy for total phytoplankton biomass were used to estimate daily rates of net growth and mortality of the total phytoplankton community. A. taylori growth rates ranged from 0.04 to 0.67 d-1 and mortality rates from-0.20 to-0.65 d-1. Growth rates of Gymnodinium sp., an accompanying dinoflagellate species during the A. taylori bloom studied, were similar to those measured for A. taylori, whereas their mortality rates (-0.58 to-0.82 d-1) were slightly higher. A. catenella growth and mortality rates were balanced (0.24 and 0.44 d-1 compared with-0.25 and-0.44 d-1 , respectively). The highest mortality rates (-0.65 d-1) were measured during the decline phase of 2 A taylori blooms. At the decline of the blooms, A. taylori and A. catenella showed considerable mortality, but microzooplankton grazing was not confirmed to be the main cause of the bloom termination. In general, growth was not limited by nutrients in the experiments. There were a few cases of a potential nutrient limitation in these areas and, in general, blooms were not conditioned by nutrients. When changes in biomass (chlorophyll a) were measured, non-linearity of data due to saturation was observed. The interpretation of these results required a split-function model. Saturated grazing (G s) was 28.9 µg chl a l-1 d-1 , during which the saturating phytoplankton population represented a chl a concentration of 16 µg l-1 (P s).
Journal of Industrial Microbiology & Biotechnology, 2012
Two different strains of microalgae, one raphidophyte and one dinoflagellate, were tested under d... more Two different strains of microalgae, one raphidophyte and one dinoflagellate, were tested under different abiotic conditions with the goal of enhancing lipid production. Whereas aeration was crucial for biomass production, nitrogen deficiency and temperature were found to be the main abiotic parameters inducing the high-level cellular accumulation of neutral lipids. Net neutral lipid production and especially triacylglycerol (TAG) per cell were higher in microalgae (>200% in Alexandrium minutum, and 30% in Heterosigma akashiwo) under treatment conditions (25°C; 330 μM NaNO3) than under control conditions (20°C; 880 μM NaNO3). For both algal species, oil production (free fatty acids plus TAG fraction) was also higher under treatment conditions (57 mg L−1 in A. minutum and 323 mg L−1 in H. akashiwo). Despite the increased production and accumulation of lipids in microalgae, the different conditions did not significantly change the fatty acids profiles of the species analyzed. These...
… y tendencias en …, 2008
Información del artículo Resultados del programa de seguimiento de fitoplancton tóxico y biotoxin... more Información del artículo Resultados del programa de seguimiento de fitoplancton tóxico y biotoxinas en las zonas de producción de bivalvos de Cataluña: años 2003-2006 y primer trimestre de 2007.
Applied and Environmental Microbiology, 2011
ABSTRACTThe frequency and intensity ofPseudo-nitzschiaspp. blooms along the coast of Catalonia ha... more ABSTRACTThe frequency and intensity ofPseudo-nitzschiaspp. blooms along the coast of Catalonia have been increasing over the past 20 years. As species from this genus that are documented as toxigenic have been found in local waters, with both toxic and nontoxic species cooccurring in the same bloom, there is a need to develop management tools for discriminating the difference. Currently, differentiation of toxic and nontoxic species requires time-consuming electron microscopy to distinguish taxonomic features that would allow identification as to species, and cryptic species can still remain misidentified. In this study, cells ofPseudo-nitzschiafrom clonal cultures isolated from seawater were characterized to their species identity using scanning electron microscopy, and subsamples of each culture were used to create an internal transcribed spacer 1 (ITS-1), 5.8S, and ITS-2 ribosomal DNA database for development of species-specific quantitative PCR (qPCR) assays. Once developed, the...
Growth and mortality rates of natural single Alexandrium spp. cells were measured by the Landry-H... more Growth and mortality rates of natural single Alexandrium spp. cells were measured by the Landry-Hassett dilution technique during different phases of blooms. Taxon-specific experiments were conducted between May and October 2002 during 3 intense blooms of A. taylori and A. catenella at different locations of the Mediterranean Sea. In addition, dilution experiments using chlorophyll a as a proxy for total phytoplankton biomass were used to estimate daily rates of net growth and mortality of the total phytoplankton community. A. taylori growth rates ranged from 0.04 to 0.67 d-1 and mortality rates from-0.20 to-0.65 d-1. Growth rates of Gymnodinium sp., an accompanying dinoflagellate species during the A. taylori bloom studied, were similar to those measured for A. taylori, whereas their mortality rates (-0.58 to-0.82 d-1) were slightly higher. A. catenella growth and mortality rates were balanced (0.24 and 0.44 d-1 compared with-0.25 and-0.44 d-1 , respectively). The highest mortality rates (-0.65 d-1) were measured during the decline phase of 2 A taylori blooms. At the decline of the blooms, A. taylori and A. catenella showed considerable mortality, but microzooplankton grazing was not confirmed to be the main cause of the bloom termination. In general, growth was not limited by nutrients in the experiments. There were a few cases of a potential nutrient limitation in these areas and, in general, blooms were not conditioned by nutrients. When changes in biomass (chlorophyll a) were measured, non-linearity of data due to saturation was observed. The interpretation of these results required a split-function model. Saturated grazing (G s) was 28.9 µg chl a l-1 d-1 , during which the saturating phytoplankton population represented a chl a concentration of 16 µg l-1 (P s).
Two different strains of microalgae, one raphidophyte and one dinoflagellate, were tested under d... more Two different strains of microalgae, one raphidophyte and one dinoflagellate, were tested under different abiotic conditions with the goal of enhancing lipid production. Whereas aeration was crucial for biomass production, nitrogen deficiency and temperature were found to be the main abiotic parameters inducing the high-level cellular accumulation of neutral lipids. Net neutral lipid production and especially triacylglycerol (TAG) per cell were higher in microalgae (>200% in Alexandrium minutum, and 30% in Heterosigma akashiwo) under treatment conditions (25°C; 330 μM NaNO3) than under control conditions (20°C; 880 μM NaNO3). For both algal species, oil production (free fatty acids plus TAG fraction) was also higher under treatment conditions (57 mg L−1 in A. minutum and 323 mg L−1 in H. akashiwo). Despite the increased production and accumulation of lipids in microalgae, the different conditions did not significantly change the fatty acids profiles of the species analyzed. These profiles consisted of saturated fatty acids (SAFA) and polyunsaturated fatty acids (PUFA) in significant proportions. However, during the stationary phase, the concentrations per cell of some PUFAs, especially arachidonic acid (C20:4n6), were higher in treated than in control algae. These results suggest that the adjustment of abiotic parameters is a suitable and one of the cheapest alternatives to obtain sufficient quantities of microalgal biomass, with high oil content and minimal changes in the fatty acid profile of the strains under consideration.
Scientia Marina, 2008
nou, s/n Km 5.5, 43540 Sant carles de la rapita, Spain.
Journal of Plankton Research, 2004
A recurrent Alexandrium minutum bloom in the Arenys de Mar harbour (Catalan coast, North Western ... more A recurrent Alexandrium minutum bloom in the Arenys de Mar harbour (Catalan coast, North Western Mediterranean) was monitored in order to establish the relationship between vegetative cells and cyst production. The bloom lasted from January 21 to February 24, 2002 and reached cell concentrations of up to 47 Â 10 6 cell L À1 . Two aspects related to the resting cysts deposition were studied: (i) production of resting cysts during the bloom period (by means of sediment traps) and (ii) distribution of resting cysts in the sediment after the bloom (May 2002). Cyst formation in Arenys clearly started in a period with high vegetative cell densities in the water column. Once production was initiated encystment fluxes remained constant for two weeks, and covering the periods of maintenance and decline of the bloom. High cyst fluxes (up to 6000 cysts cm À2 day À1 ) were quantified as a result of the high vegetative cell concentration. Moreover, encystment occurring in less than 1% of the total population indicates that most of the cells are not involved in resting cysts formation. A comparison of the resting cyst flux values obtained from the sediment traps and the resting cyst concentrations in surface sediment (628-3270 cysts cm À3 ) three months later, revealed that the number of cysts in the sediment decreased during that time. The studies of excystment showed a high germination percentage (91%) and germling viability (100%). These data, together with the resting cyst distribution in the sediment, are important in assessing the role of resting cysts in the bloom dynamics of A. minutum in confined waters.
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Papers by Nagore Sampedro