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Auteur Tsiola, A.; Pitta, P.; Fodelianakis, S.; Pete, R.; Magiopoulos, I.; Mara, P.; Psarra, S.; Tanaka, T.; Mostajir, B. url  doi
openurl 
  Titre Nutrient Limitation in Surface Waters of the Oligotrophic Eastern Mediterranean Sea: an Enrichment Microcosm Experiment Type Article scientifique
  Année 2016 Publication (up) Revue Abrégée Microb Ecol  
  Volume 71 Numéro 3 Pages 575-588  
  Mots-Clés Ecology; Eukaryotic phytoplankton; Geoecology/Natural Processes; Heterotrophic prokaryotes; Microbial ecology; Microbiology; Nature Conservation; Prochlorococcus; Synechococcus; Viruses; Water Quality/Water Pollution  
  Résumé The growth rates of planktonic microbes in the pelagic zone of the Eastern Mediterranean Sea are nutrient limited, but the type of limitation is still uncertain. During this study, we investigated the occurrence of N and P limitation among different groups of the prokaryotic and eukaryotic (pico-, nano-, and micro-) plankton using a microcosm experiment during stratified water column conditions in the Cretan Sea (Eastern Mediterranean). Microcosms were enriched with N and P (either solely or simultaneously), and the PO4 turnover time, prokaryotic heterotrophic activity, primary production, and the abundance of the different microbial components were measured. Flow cytometric and molecular fingerprint analyses showed that different heterotrophic prokaryotic groups were limited by different nutrients; total heterotrophic prokaryotic growth was limited by P, but only when both N and P were added, changes in community structure and cell size were detected. Phytoplankton were N and P co-limited, with autotrophic pico-eukaryotes being the exception as they increased even when only P was added after a 2-day time lag. The populations of Synechococcus and Prochlorococcus were highly competitive with each other; Prochlorococcus abundance increased during the first 2 days of P addition but kept increasing only when both N and P were added, whereas Synechococcus exhibited higher pigment content and increased in abundance 3 days after simultaneous N and P additions. Dinoflagellates also showed opportunistic behavior at simultaneous N and P additions, in contrast to diatoms and coccolithophores, which diminished in all incubations. High DNA content viruses, selective grazing, and the exhaustion of N sources probably controlled the populations of diatoms and coccolithophores.  
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  ISSN 0095-3628, 1432-184x ISBN Médium  
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Auteur Fouilland, E.; Mostajir, B.; Levasseur, M.; Roy, S.; Vidussi, F.; de Mora, S.; Demers, S. url  openurl
  Titre Effect of mixing on the structure of a natural plankton community: a mesocosm study Type Article scientifique
  Année 2016 Publication (up) Revue Abrégée Vie et Milieu  
  Volume 66 Numéro 3-4 Pages 251-259  
  Mots-Clés Accumulation; Composition; nitrogen; Phytoplankton Biomass; Phytoplankton Species; Structure Of The Pelagic Food Web; Transport Rates; turbulence; Vertical Mixing  
  Résumé A plankton community (< 202 μm) from the St. Lawrence Estuary was isolated

in four outdoor mesocosms with SLOW and fast mixing regimes. Variations in the concentrations

of nutrients, chlorophyll a (Chl a), nitrogen transport rates and plankton species composition

were monitored over a 10 day period. The vertical mixing times (Tm) for the slow and

fast mixing regimes were 180 and 60 min, corresponding to a vertical eddy diffusivity (Kv) of

2.34 and 7.03 cm2 s–1, respectively. The different mixing regimes had a strong effect on the

physiology of the phytoplankton and the specific structure of the plankton assemblage. The

Slow mixing regime stimulated the development of a mixed community of flagellates, small

diatoms and proto-metazooplankton while the fast mixing regime triggered the development

of a large diatom-dominated community with lower abundances of proto-metazooplankton. At

the end of the 10 day experiment, the Chl a concentrations were 50 % higher in the mesocosms

with the fast mixing regime than in those with the slow mixing regime. These results indicate

that, under low nutrient conditions, higher turbulence gives a competitive advantage to diatoms

and decreases the zooplankton grazing pressure, resulting in net positive growth. Extrapolation

of these results to natural systems suggests that a wind-driven mixing event may increase

the net phytoplankton biomass production of a stratified water column, even if there is no external

input of nutrients.
 
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Auteur Cecchi, P.; Garrido, M.; Collos, Y.; Pasqualini, V. url  doi
openurl 
  Titre Water flux management and phytoplankton communities in a Mediterranean coastal lagoon. Part II: Mixotrophy of dinoflagellates as an adaptive strategy? Type Article scientifique
  Année 2016 Publication (up) Revue Abrégée Marine Pollution Bulletin  
  Volume 108 Numéro 1–2 Pages 120-133  
  Mots-Clés Biguglia; Mediterranean coastal lagoon; Mixotrophy; Phyto-PAM; Phytoplankton; Prorocentrum minimum  
  Résumé Dinoflagellate proliferation is common in coastal waters, and trophic strategies are often advanced to explain the success of these organisms. The Biguglia lagoon is a Mediterranean brackish ecosystem where eutrophication has long been an issue, and where dominance of dinoflagellates has persisted for several years. Monthly monitoring of fluorescence-based properties of phytoplankton communities carried out in 2010 suggested that photosynthesis alone could not support the observed situation all year round. Contrasting food webs developed depending on the hydrological season, with a gradual shift from autotrophy to heterotrophy. Progressively, microphytoplankton assemblages became unequivocally dominated by a Prorocentrum minimum bloom, which exhibited very weak effective photosynthetic performance, whereas paradoxically its theoretical capacities remained fully operational. Different environmental hypotheses explaining this discrepancy were examined, but rejected. We conclude that P. minimum bloom persistence is sustained by mixotrophic strategies, with complex compromises between phototrophy and phagotrophy, as evidenced by fluorescence-based observations.  
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  ISSN 0025-326x ISBN Médium  
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Auteur Cocquempot, L.; Delacourt, C.; Paillet, J.; Riou, P.; Aucan, J.; Castelle, B.; Charria, G.; Claudet, J.; Conan, P.; Coppola, L.; Hocdé, R.; Planes, S.; Raimbault, P.; Savoye, N.; Testut, L.; Vuillemin, R. doi  openurl
  Titre Coastal Ocean and Nearshore Observation: A French Case Study Type Article scientifique
  Année 2019 Publication (up) Revue Abrégée Front. Mar. Sci.  
  Volume 6 Numéro Pages Unsp-324  
  Mots-Clés 2013/2014 winter; atlantic coast; coastal ocean; coastline; diversity; ecosystem; increases; interdisciplinary; national structuration; nutrient ratios; observation infrastructure; phytoplankton community; temperature; variability; wave activity  
  Résumé To understand and predict the physical, chemical, and biological processes at play in coastal and nearshore marine areas requires an integrated, interdisciplinary approach. The case study of the French structuration of coastal ocean and nearshore observing systems provides an original overview on a federative research infrastructure named ILICO. It is a notable example of national structuration and pan-institution efforts to investigate the forefront of knowledge on the processes at work within the critical coastal zone. ILICO comprises, in a pluridisciplinary approach, eight distributed network-systems of observation and data analysis that are accredited and financially supported by French research institutions and the French Ministry for Higher Education, Research, and Innovation. ILICO observation points are implemented along metropolitan and overseas French coasts, where coastline dynamics, sea level evolution, physical and biogeochemical water properties, coastal water dynamics, phytoplankton composition, and health of coral reefs are monitored in order to address a wide range of scientific questions. To give an overview of the diversity and potential of the observations carried out, this paper offers a detailed presentation of three constituting networks: Service Observation en Milieu LITtoral (SOMLIT), with homogeneous sampling strategies, DYNALIT, with heterogeneous sampling strategies adapted to different environments, and Mediterranean Ocean Observing System for the Environment (MOOSE), an integrated, pluri-disciplinary coasta/offshore regional observatory in the north-western Mediterranean Sea. ILICO was conceived using a European framework. It addresses the great challenges of the next decade in terms of sustainability, cost-efficiency, interoperability, and innovation. This paper emphasizes the added-value of federating these systems, and highlights some recommendations for the future.  
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Auteur De Wit, R.; Rey-Valette, H.; Balavoine, J.; Ouisse, V.; Lifran, R. url  doi
openurl 
  Titre Restoration ecology of coastal lagoons: new methods for the prediction of ecological trajectories and economic valuation Type Article scientifique
  Année 2017 Publication (up) Revue Abrégée Aquatic Conserv: Mar. Freshw. Ecosyst.  
  Volume 27 Numéro 1 Pages 137-157  
  Mots-Clés coastal lagoon; ecosystem services; ecosystem trajectory' nutrient enrichment; marine and brackish Magnoliophyta; oligotrophication; Phytoplankton; seagrass meadow; sediment N and P contents; Water Framework Directive; willingness to pay (WTP)  
  Résumé * Conservation of the seven lagoons of the Palavas complex (southern France) has been severely impaired by nutrient over-enrichment during at least four decades. The effluents of the Montpellier wastewater treatment plant (WWTP) represented the main nutrient input. To improve the water quality of these lagoons, this WWTP was renovated and upgraded and, since the end of 2005, its effluents have been discharged 11 km offshore into the Mediterranean (total investment €150 M). * Possibilities of ecosystem restoration as part of a conservation programme were explored by a focus group of experts. Their tasks were: (i) to evaluate the impact of the reduction of the nutrient input; (ii) if necessary, to design additional measures for an active restoration programme; and (iii) to predict ecosystem trajectories for the different cases. Extension of Magnoliophyta meadows can be taken as a proxy for ecosystem restoration as they favour the increase of several fish (seahorse) and bird (ducks, swans, herons) species, albeit they represent a trade-off for greater flamingos. Additional measures for active ecosystem restoration were only recommended for the most impaired lagoon Méjean, while the least impaired lagoon Ingril is already on a trajectory of spontaneous recovery. * A multiple contingent valuation considering four different management options for the Méjean lagoon was used in a pilot study based on face-to-face interviews with 159 respondents. Three levels of ecosystem restoration were expressed in terms of recovery of Magnoliophyta meadows, including their impact on emblematic fish and avifauna. These were combined with different options for access (status quo, increasing access, increasing access with measures to reduce disturbance). The results show a willingness of local populations to pay per year about €25 for the highest level of ecological restoration, while they were only willing to allocate about €5 for additional footpaths and hides.

Copyright © 2015 John Wiley & Sons, Ltd.
 
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