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Auteur Bonilla-Findji, O.; Rochelle-Newall, E.; Weinbauer, M.G.; Pizay, M.D.; Kerros, M.E.; Gattuso, J.P.
Titre (up) Effect of seawater-freshwater cross-transplantations on viral dynamics and bacterial diversity and production Type Article scientifique
Année 2009 Publication Revue Abrégée Aquat. Microb. Ecol.
Volume 54 Numéro 1 Pages 1-11
Mots-Clés aquatic systems; Bacterial production; Bacterial richness; bacterioplankton; batch cultures; chesapeake bay; Communities; community composition; dissolved organic-matter; estuarine salinity gradient; growth efficiency; marine; microbial; population-dynamics; Transplantation; Virus
Résumé Dilution experiments were carried out to investigate the community composition and the metabolic response of seawater and freshwater bacteria to cross-transplantation, and the effects of nor.-indigenous bacterial hosts on viral dynamics. Changes in viral and bacterial abundance and production, as Well as bacterial respiration, carbon demand and diversity were regularly monitored over a 6 d period. Bacterial production in the transplanted seawater (SB-t) and freshwater (FB-t) bacteria treatments was stimulated up to 256 and 221 %, respectively, compared to controls. The stimulation of bacterial production and carbon demand was accompanied by a decrease in bacterial richness. Net viral production was stimulated by 81% in SB-t and repressed by 75% in FB-t. Transplantation increased the virus-induced mortality of marine bacteria, but decreased it for freshwater bacteria. These results suggest that (1) marine bacteria can readily oxidize freshwater dissolved organic matter, and (2) freshwater viruses might be able to infect marine hosts, thus highlighting their potential role in fueling bacterial growth under resource stress or nutrient-depleted conditions.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0948-3055 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 546
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Auteur Garrido, M.; Cecchi, P.; Vaquer, A.; Pasqualini, V.
Titre (up) Effects of sample conservation on assessments of the photosynthetic efficiency of phytoplankton using PAM fluorometry Type Article scientifique
Année 2013 Publication Revue Abrégée Deep-Sea Res. Part I-Oceanogr. Res. Pap.
Volume 71 Numéro Pages 38-48
Mots-Clés diatom, quantum yield, temperature, parameters; PAM fluorescence, Phytoplankton, Temperature Biguglia lagoon; physiological-responses, marine-phytoplankton, oxygen evolution, benthic; rapid light curves, chlorophyll-a fluorescence, in-vivo,
Résumé Pulse Amplitude Modulated (PAM) fluorometry is now a widely used method for the assessment of phytoplankton fitness, with an increasing popularity in field assessments. It is usually recommended to carry out measurements swiftly after collection, but the number of samples and analytical procedures needed to obtain valuable datasets sometimes makes immediate analysis impracticable, forcing delays between fluorescence measurements. Conservation conditions of samples before analysis may potentially affect their photosynthetic performances but no formal study documenting such impacts appears available in the literature. The aim of this study was to investigate the effects of storage conditions (temperature, duration) on photosynthetic parameters in different phytoplankton communities (characterized in situ by a BBE fluoroprobe) sampled during summer in different environmental locations in a Mediterranean lagoon (Biguglia lagoon, Corsica, France). PAM-fluorescence parameters were measured after three different conservation durations (2-4 h, 6-8 h and 10-12 h after collection) on samples stored at three different temperatures (15 degrees C, 25 degrees C and 35 degrees C). Results showed that storage at the highest temperature severely impacted photosynthetic parameters, with cumulative effects as storage duration increased. For phytoplankton samples collected in warm or tropical environments, storage at “room temperature” (25 degrees C) only appeared a valid option if measurements have to be carried out strictly within a very short delay. Inversely, cooling the samples (i.e. conservation at 15 degrees C) did not induce significant effects, independently of storage duration. Cooling appeared the best solution when sampling-to-analysis delay goes over a few hours. Long-term storage ( > 8 h) should definitively be avoided. (C) 2012 Elsevier Ltd. All rights reserved.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0967-0637 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 552
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Auteur Machu, E.; Ettahiri, O.; Kifani, S.; Benazzouz, A.; Makaoui, A.; Demarcq, H.
Titre (up) Environmental control of the recruitment of sardines (Sardina pilchardus) over the western Saharan shelf between 1995 and 2002 : a coupled physical/biogeochemical modelling experiment Type Article scientifique
Année 2009 Publication Revue Abrégée Fisheries Oceanography
Volume 18 Numéro 5 Pages 287-300
Mots-Clés biomass; Canary upwelling; hydrodynamic and biogeochemical modelling; plankton; potential spawning habitat; recruitment; Sardina pilchardus
Résumé Fisheries constitute an important economic sector for Morocco, where the species Sardina pilchardus represents the main landings. In acoustic evaluations conducted along the Moroccan coast since 1995, the absence of juveniles in 1996 and 1998 and the collapse of the sardine stock between 1996 and 1997 represent the main events until 2002. Sardines are known to be microphageous planktivores and thus are sensitive to environmental variability. A biogeochemical model coupled to a hydrodynamic model (ROMS) was run over the Canary Current System (1991-2002) to investigate the environmental factors that could have played a role in the variability of the sardine spawning. A grid refinement (1/12 degrees) centred on the Saharan Bank (SB) region was built to study the main spawning ground of sardines off northwest Africa. The volume of the potential spawning habitat (PSH) of sardines was defined as a function of depth, temperature and salinity, which are included in the ranges 0-200 m, 15-21 degrees C and 35.8-36.8, respectively. Our modelling frame was able to reproduce the seasonal cycle of temperature, phytoplankton concentration and PSH over the SB. It also captured the warming associated with the negative index of the North Atlantic Oscillation of 1995-1997 and allowed a description of the inter-annual variability of the PSH. Our experiment shows that the volume of PSH was much reduced in 1996 compared to the other years. The results suggest that the delay between high abundance of plankton and favourable spawning conditions is a good proxy for determining the recruitment failure of sardine in this oceanic region.
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Volume de collection Numéro de collection Edition
ISSN 1054-6006 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 43
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Auteur Maloufi, S.; Catherine, A.; Mouillot, D.; Louvard, C.; Couté, A.; Bernard, C.; Troussellier, M.
Titre (up) Environmental heterogeneity among lakes promotes hyper β-diversity across phytoplankton communities Type Article scientifique
Année 2016 Publication Revue Abrégée Freshw Biol
Volume 61 Numéro 5 Pages 633-645
Mots-Clés environmental heterogeneity; meta-community ecology; Phytoplankton; species sorting; turnover
Résumé * The extent to which stochastic and deterministic processes influence variations in species communities across space and time remains a central question in theoretical and applied ecology. Despite their high dispersal ability, the composition of phytoplankton communities displays striking spatial variations among lakes even at small spatial scale. * To investigate the mechanisms underlying the distribution of phytoplankton species, we evaluate the contribution of stochastic, spatial and environmental processes in determining β-diversity patterns of phytoplankton at a regional scale. Phytoplankton communities were surveyed in 50 different lakes from north-central France, a region characterised by strong environmental heterogeneity. * The regional species pool was characterised by extremely high β-diversity levels, which were mainly explained by species replacement (i.e. turnover) rather than by differences in species richness (i.e. nestedness). Null models of random species distribution and spatial processes failed to explain observed β-diversity patterns. At the opposite, local environmental conditions strongly influenced the degree of uniqueness of local phytoplankton communities, with the most contrasted environments, including human-dominated areas, promoting highly distinct phytoplankton communities. * Our results suggest that species-sorting mechanisms that arise from variations in local environmental conditions drive high species turnover at the region scale. Thus, in a landscape strongly impacted by cultural eutrophication, further anthropogenic impacts on aquatic ecosystems would likely induce regional homogenisation of phytoplankton communities. Overall, our study supports the fact that the management of lakes and reservoirs in anthropic landscapes should aim at maintaining environmental heterogeneity while preventing further eutrophication in order to favour the maintenance of high phytoplankton β- and γ-diversity.
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Volume de collection Numéro de collection Edition
ISSN 1365-2427 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1569
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Auteur Garrido, M.; Cecchi, P.; Malet, N.; Bec, B.; Torre, F.; Pasqualini, V.
Titre (up) Evaluation of FluoroProbe® performance for the phytoplankton-based assessment of the ecological status of Mediterranean coastal lagoons Type Article scientifique
Année 2019 Publication Revue Abrégée Environ Monit Assess
Volume 191 Numéro 4 Pages 204
Mots-Clés FluoroProbe®; Hplc; Mediterranean coastal lagoons; Monitoring; Phytoplankton
Résumé The European Water Framework Directive and several other legislations worldwide have selected phytoplankton for monitoring the ecological status of surface waters. This assessment is a complicated task in coastal lagoons due to their intrinsic variability, prompting moves to use real-time measurements. Here, we tested the ability of the submersible spectrofluorometer FluoroProbe® to accurately estimate the phytoplankton biomass and to efficiently discriminate spectral groups in Mediterranean coastal lagoons, by using sub-surface water samples (n = 107) collected at Biguglia lagoon (Corsica) in different environmental situations (salinity and trophic state) from March 2012 to December 2014. We compared the estimates of biomass and phytoplankton group composition obtained with the FluoroProbe® (in situ and lab measurements) with the spectrofluorimetrically measured biomass and HPLC-derived quantifications of pigment concentrations. FluoroProbe® provided good estimates of the total phytoplankton biomass (particularly, the lab measurements). The FluoroProbe® data were significantly correlated with the HPLC results, except for the in situ measurements of very weak concentrations of blue-green and red algae. Our findings indicate that factory-calibrated FluoroProbe® is an efficient and easy-to-use real-time phytoplankton monitoring tool in coastal lagoons, especially as an early warning system for the detection of potentially harmful algal blooms. Practical instructions dedicated to non-specialist field operators are provided. A simple and efficient method for discarding in situ measurement outliers is also proposed.
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Volume de collection Numéro de collection Edition
ISSN 1573-2959 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2527
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