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Registros recuperados: 12
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Hyperspectral and Lidar: Complementary Tools to Identify Benthic Features and Assess the Ecological Status of Sabellaria alveolata Reefs ArchiMer
Bajjouk, Touria; Jauzein, Cecile; Drumetz, Lucas; Dalla Mura, Mauro; Duval, Audrey; Dubois, Stanislas.
Sabellaria alveolata is a sedentary gregarious tube-building species widely distributed from southwest Scotland to Morocco. This species builds what are currently considered the largest European biogenic reefs in the bay of Mont-Saint-Michel (France). As an ecosystem engineer, S. alveolata generates small to large scale topographic complexity, creating numerous spatial and trophic niches for other species to colonize. Sabellaria reefs are also under anthropogenic pressures, leading locally to massive degradation. However, stakeholders lack spatially explicit measures of reef ecological status, at adapted spatial resolution to provide key management information for this protected habitat. Traditional field surveys are extremely time-consuming and rely on...
Tipo: Text Palavras-chave: Benthic habitats; Biogenic reefs; Ecological status; Hyperspectral; Intertidal; Lidar; Mapping.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00654/76574/77710.pdf
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Oligotrophication and emergence of picocyanobacteria and a toxic dinoflagellate in Thau lagoon, southern France ArchiMer
Collos, Yves; Bec, Beatrice; Jauzein, Cecile; Abadie, Eric; Laugier, Thierry; Lautier, Jacques; Pastoureaud, Annie; Souchu, Philippe; Vaquer, Andre.
Time series data have been examined in Thau lagoon (Southern France) from 1972 to 2006 for water temperature, salinity, nutrients and from 1987 to 2006 for phytoplankton. A first main trend identified is an increase in mean annual water temperature (1.5 degrees C over 33 years or 0.045 degrees C/year) that was not evenly distributed among seasons. The highest rate of increase was in the spring (+ 3.0 degrees C over 33 years), followed by summer (+ 2.0 degrees C and fall (+ 1.7 degrees C. In winter, no significant increase over the 33 year period could be found. A second clear trend is a large decrease in soluble reactive phosphorus (SRP) concentration over the same 33 year period (summer values decreased from 10 mu M to 1 mu M. while winter values...
Tipo: Text Palavras-chave: Skeletonema costatum; Alexandrium catenella; Picocyanobacteria; Oligotrophication; Long term variability; Thau lagoon.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6420.pdf
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Comparing diatom and Alexandrium catenella/tamarense blooms in Thau lagoon: Importance of dissolved organic nitrogen in seasonally N-limited systems ArchiMer
Collos, Yves; Jauzein, Cecile; Ratmaya, Widya; Souchu, Philippe; Abadie, Eric; Vaquer, André.
Diatom blooms in Thau lagoon are always related to rain events leading to inputs of inorganic nutrients such as phosphate, ammonium and nitrate through the watershed with time lags of about 1 week. In contrast, blooms of Alexandrium catenella/tamarense can occur following periods of 3 weeks without precipitation and no significant input of conventional nutrients such as nitrate and phosphate. Field results also indicate a significant drop (from 22–25 to 15–16 μM over 3 days) in dissolved organic nitrogen (DON) at the bloom peak, as well as a significant inverse relationship between A. catenella/tamarense cell density and DON concentrations that is not apparent for diatom blooms. Such dinoflagellate blooms are also associated with elevated (6–9 μM) ammonium...
Tipo: Text Palavras-chave: Alexandrium catenella/tamarense; Non classical blooms; Organic nitrogen; Ammonium; Growth rate.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00194/30488/29758.pdf
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Variable inter and intraspecies alkaline phosphatase activity within single cells of revived dinoflagellates ArchiMer
Girault, Mathias; Siano, Raffaele; Labry, Claire; Latimier, Marie; Jauzein, Cecile; Beneyton, Thomas; Buisson, Lionel; Del Amo, Yolanda; Baret, Jean-christophe.
Adaptation of cell populations to environmental changes is mediated by phenotypic variability at the single-cell level. Enzyme activity is a key factor in cell phenotype and the expression of the alkaline phosphatase activity (APA) is a fundamental phytoplankton strategy for maintaining growth under phosphate-limited conditions. Our aim was to compare the APA among cells and species revived from sediments of the Bay of Brest (Brittany, France), corresponding to a pre-eutrophication period (1940’s) and a beginning of a post-eutrophication period (1990’s) during which phosphate concentrations have undergone substantial variations. Both toxic marine dinoflagellate Alexandrium minutum and the non-toxic dinoflagellate Scrippsiella acuminata were revived from...
Tipo: Text Palavras-chave: Climate-change ecology; Microbial ecology.
Ano: 2021 URL: https://archimer.ifremer.fr/doc/00679/79097/81568.pdf
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Paramétrisation de la nutrition azotée et phosphorée d'Alexandrium catenella, microalgue toxique responsable d'efflorescences dans la lagune de Thau ArchiMer
Jauzein, Cecile.
In the Thau lagoon, blooms of the toxic microalgae Alexandrium catenella have induced regular losses of shellfish production since 1998 due to bioaccumulation of toxins in oysters and mussels. This thesis was conducted to enhance knowledge of toxic bloom development regulation by environmental factors, focusing on nitrogen and phosphorus nutrients influence on A. catenella growth. These works highlighted a large variety of potential nutritive sources for this species and a major part of these nutrients appeared to be potentially regenerated in the water column. Different organic sources may contribute to the growth of A. catenella from diverse nutrition processes: direct absorption through the cell membrane (for urea), enzymatic degradation in the...
Tipo: Text Palavras-chave: Alkaline phosphatases; Mixotrophy; Phosphate; Urea; Ammonium; Uptake kinetics; Alexandrium catenella; Phosphatases alcalines; Mixotrophie; Phosphate; Urée; Ammonium; Cinétiques d'absorption; Alexandrium catenella.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/these-6511.pdf
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Optimization of sampling, cell collection and counting for the monitoring of benthic harmful algal blooms: Application to Ostreopsis spp. blooms in the Mediterranean Sea ArchiMer
Jauzein, Cecile; Acaf, Laury; Accoroni, Stefano; Asnaghi, Valentina; Fricke, Anna; Hachani, Mohamed Amine; Saab, Marie Abboud-abi; Chiantore, Mariachiara; Mangialajo, Luisa; Totti, Cecilia; Zaghmouri, Imen; Lemee, Rodolphe.
Toxic blooms of Ostreopsis spp. are greatly challenging to monitor due to the complexity and variability of cell repartition among benthic and pelagic compartments. This results in marked differences in employed methodologies for the survey of their dynamics and hampers the definition of the associated toxic risk. The present study aims at testing and improving common methodologies used for sampling, processing and counting of field samples. It contributes to the identification of the most suitable strategies for the monitoring and mitigation of Ostreopsis blooms in coastal waters. For a sampling based on the collection of macrophytes, the role of the fixative addition and of agitation steps in the efficiency of epiphytic cell collection was defined. For...
Tipo: Text Palavras-chave: Patchiness; Macrophyte substrate; Artificial substrate; Recommendations for monitoring.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00436/54714/56188.pdf
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Short-term temporal variability of ammonium and urea uptake by Alexandrium catenella (Dinophyta) in cultures ArchiMer
Jauzein, Cecile; Collos, Yves; Garces, E; Vila, M; Maso, M.
In batch cultures of four Mediterranean strains (from France, Italy, and Spain) of Alexandrium catenella (Whedon et Kof.) Balech growing on a daily light cycle, ammonium and urea uptake were estimated by the N-15 tracer technique. Ammonium uptake could be described by Michaelis-Menten kinetics along a substrate gradient of 0.1-10 mu gat N.L-1 for the four strains, while two different patterns were observed for urea uptake with Michaelis-Menten kinetics for one strain and linear kinetics for the others. In all cases, an increase in uptake rates with time was noted over the daylight period. This trend led to a net increase in the maximum uptake rate (V-max; for saturable kinetics) and in the initial slope alpha. For ammonium, V-max increased by a factor of...
Tipo: Text Palavras-chave: Urea; Uptake kinetics; Temporal variability; Ammonium release; Ammonium; Alexandrium catenella.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-6416.pdf
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Dark metabolism and carbon-nitrogen uncoupling in the toxic dinoflagellate Alexandrium catenella (Dinophyceae) ArchiMer
Jauzein, Cecile; Collos, Yves; Laabir, Mohamed; Vaquer, Andre.
Uptake rates of three potential N-sources (ammonium, nitrate and N-urea) and two potential C-sources (HCO(3)(-) and C-urea) were estimated during growth of Alexandrium catenella in both light and dark phases. According to the variations observed in (13)C-isotopic ratio, A. catenella cells were not able to use C-urea. Furthermore, decreases in (13)C cell content during darkness revealed a probably high involvement of C recently fixed in dark respiration. Dark N-uptake capacities of A. catenella were characterized by dark/light uptake ratio of 27%, 43% and 65% for NO(3)(-), NH(4)(+) and N-urea, respectively. An accumulation of C-rich compounds during the light period was highlighted through strong diel variations in C:N ratio and would provide C and energy...
Tipo: Text Palavras-chave: Diel cycle; Dark uptake; Nitrogen; Carbon; Uncoupling; Alexandrium catenella.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00056/16699/14199.pdf
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Uptake of dissolved inorganic and organic nitrogen by the benthic toxic dinoflagellate Ostreopsis cf. ovata ArchiMer
Jauzein, Cecile; Couet, Douglas; Blasco, Thierry; Lemee, Rodolphe.
Environmental factors that shape dynamics of benthic toxic blooms are largely unknown. In particular, for the toxic dinoflagellate Ostreopsis cf. ovata, the importance of the availability of nutrients and the contribution of the inorganic and organic pools to growth need to be quantified in marine coastal environments. The present study aimed at characterizing N-uptake of dissolved inorganic and organic sources by O. cf. ovata cells, using the 15N-labelling technique. Experiments were conducted taking into account potential interactions between nutrient uptake systems as well as variations with the diel cycle. Uptake abilities of O. cf. ovata were parameterized for ammonium (NH4+), nitrate (NO3−) and N-urea, from the estimation of kinetic and inhibition...
Tipo: Text Palavras-chave: Uptake; Nitrogen; Dinoflagellate; Ostreopsis; Kinetics; Interactions.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00382/49368/49840.pdf
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Growth and phosphorus uptake by the toxic dinoflagellate Alexandrium catenella (dinophyceae) in response to phosphate limitation ArchiMer
Jauzein, Cecile; Labry, Claire; Youenou, Agnes; Quere, Julien; Delmas, Daniel; Collos, Yves.
Alexandrium catenella (Whedon et Kof.) Balech has exhibited seasonal recurrent blooms in the Thau lagoon (South of France) since first reported in 1995. Its appearance followed a strong decrease (90%) in phosphate (PO(4)3-) concentrations in this environment over the 1970-1995 period. To determine if this dinoflagellate species has a competitive advantage in PO(4)3--limited conditions in terms of nutrient acquisition, semicontinuous cultures were carried out to characterize phosphorus (P) uptake by A. catenella cells along a P-limitation gradient using different dilution rates (DRs). Use of both inorganic and organic P was investigated from measurements of 33PO(4)3- uptake and alkaline phosphatase activity (APA), respectively. P status was estimated from...
Tipo: Text Palavras-chave: Alexandrium catenella; Alkaline phosphatase; Limitation; Phosphorus; Semicontinuous cultures.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00015/12641/9570.pdf
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Interactions between ammonium and urea uptake by five strains of Alexandrium catenella (Dinophyceae) in culture ArchiMer
Jauzein, Cecile; Loureiro, Sofia; Garces, Esther; Collos, Yves.
Short-term experiments were carried out to investigate whether interactions between ammonium (NH4+) and urea uptake regulate the total nitrogen assimilation of the toxic dinoflagellate Alexandrium catenella. To test for strain variability, 5 strains of A. catenella from the NW Mediterranean were used: 3 strains from the Thau lagoon (southern France) and 2 strains from the Catalonia basin (Spain). For each strain, the uptake rate of 1 nutrient (NH4+ or urea) at a reference concentration (10 mu gatN l(-1)) was measured as a function of the increasing concentration of the other nutrient (0 to 10 mu gatN l(-1)). Simultaneous N uptake rates of the distinct nitrogen sources were obtained from N-15-NH4+ and N-15-urea incorporation measurements. A strong...
Tipo: Text Palavras-chave: Strain variability; Interactions; Urea; Ammonium; Alexandrium catenella.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-6432.pdf
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The significance of organic nutrients in the nutrition of Pseudo-nitzschia delicatissima (Bacillariophyceae) ArchiMer
Loureiro, Sofia; Jauzein, Cecile; Garces, Esther; Collos, Yves; Camp, Jordi; Vaque, Dolors.
The influence of organic nutrients on the evolution of Pseudo-nitzschia delicatissima cultures was investigated in an enrichment experiment with high-molecular-weight dissolved organic matter (HMWDOM) and in an uptake assay with N-15-ammonium and N-15-urea. HMWDOM was extracted from seawater collected at a nearby shore station during the decline of a diatom bloom. Four incubations were prepared: L1/5+DOM (P. delicatissima grown in L1 growth medium with 1/5 of the nitrate concentration of standard L1), (L1-N)+DOM (L1 without nitrate, i.e. nitrogen-deficient treatment), L1-DOM (control culture without added DOM) and BV+DOM (bacterial and viral control, free of microalgae). Incubations were carried out for 10 days. Chlorophyll a concentrations differed after...
Tipo: Text Palavras-chave: Harmful Algal Blooms (HABs); Nitrogen Uptake; Urea; Dissolved Organic Matter (DOM).
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6438.pdf
Registros recuperados: 12
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