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Biophysical Interactions Control the Size and Abundance of Large Phytoplankton Chains at the Ushant Tidal Front
article scientifique - 2014-02
Landeira, JosÃ© M., et al.
Titre Biophysical Interactions Control the Size and Abundance of Large Phytoplankton Chains at the Ushant Tidal Front Type d'Ã©tude article scientifique Auteurs personnes Landeira JosÃ© M. Auteur Ferron Bruno Auteur Lunven Michel Auteur Morin Pascal Auteur MariÃ© Louis Auteur Sourisseau Marc Auteur Date de publication 2014-02 Editeur(s) [S.l.] : Public Library of Science Revue scientifique PLOS ONE RÃ©sumÃ© Phytoplankton blooms are usually dominated by chain-forming diatom species that can alter food pathways from primary producers to predators by reducing the interactions between intermediate trophic levels. The food-web modifications are determined by the length of the chains; however, the estimation is biased because traditional sampling strategies damage the chains and, therefore, change the phytoplankton size structure. Sedimentological studies around oceanic fronts have shown high concentrations of giant diatom mats (>1 cm in length), suggesting that the size of diatom chains is underestimated in the pelagic realm. Here, we investigate the variability in size and abundance of phytoplankton chains at the Ushant tidal front (NW France) using the Video Fluorescence Analyzer (VFA), a novel and non-invasive system. CTD and Scanfish profiling characterized a strong temperature and chlorophyll front, separating mixed coastal waters from the oceanic-stratified domain. In order to elucidate spring-neap variations in the front, vertical microstructure profiler was used to estimate the turbulence and vertical nitrate flux. Key findings were: (1) the VFA system recorded large diatom chains up to 10.7 mm in length; (2) chains were mainly distributed in the frontal region, with maximum values above the pycnocline in coincidence with the maximum chlorophyll; (3) the diapycnal fluxes of nitrate enabled the maintenance of the bloom in the frontal area throughout the spring-neap tidal cycle; (4) from spring to neap tide the chains length was significantly reduced; (5) during neap tide, the less intense vertical diffusion of nutrients, as well as the lower turbulence around the chains, intensified nutrient-depleted conditions and, thus, very large chains became disadvantageous. To explain this pattern, we suggest that size plasticity is an important ecological trait driving phytoplankton species competition. Although this plasticity behavior is well known from experiments in the laboratory, it has never been reported from observations in the field. CatÃ©gories thÃ©matiques plancton Echelle de territoire communes Commune(s) Ouessant Langue(s) Anglais Document en ligne http://dx.doi.org/10.1371/journal.pone.0090507 NÂ° d'Ã©dition (ISBN, DOI,...) 10.1371/journal.pone.0090507 Permalink http://etudes.bretagne-environnement.org/index.php?lvl=notice_display&id=19285Response of insect relative growth rate to temperature and host-plant phenology: estimation and validation from field data.
article dans des revues - 2014
Ciss, Mamadou, et al.
Titre Response of insect relative growth rate to temperature and host-plant phenology: estimation and validation from field data. Type d'Ã©tude article dans des revues Auteurs personnes Ciss, Mamadou Auteur Parisey, Nicolas Auteur Fournier, GwenaÃ«lle Auteur Taupin, Pierre Auteur Dedryver, Charles-Antoine Auteur Pierre, Jean-SÃ©bastien Auteur Date de publication 2014 Editeur(s) [S.l.] : Public Library of Science PLOS ONE RÃ©sumÃ© International audienceBetween 1975 to 2011, aphid Relative Growth Rates (RGR) were modelled as a function of mean outdoor temperature and host plant phenology. The model was applied to the grain aphid Sitobion avenae using data on aphid counts in winter wheat at two different climate regions in France (oceanic climate, Rennes (western France); continental climate, Paris). Mean observed aphid RGR was higher in Paris compared to the Rennes region. RGR increased with mean temperature, which is explained by aphid reproduction, growth and development being dependent on ambient temperature. From the stem extension to the heading stage in wheat, there was either a plateau in RGR values (Rennes) or an increase with a maximum at heading (Paris) due to high intrinsic rates of increase in aphids and also to aphid immigration. From the wheat flowering to the ripening stage, RGR decreased in both regions due to the low intrinsic rate of increase in aphids and high emigration rate linked to reduced nutrient quality in maturing wheat. The model validation process showed that the fitted models have more predictive power in the Paris region than in the Rennes region. CatÃ©gories thÃ©matiques insecteagriculture Mots-clÃ©s libres [SDE.BE] Environmental Sciences/Biodiversity and Ecology Echelle de territoire communes Document en ligne https://hal-univ-rennes1.archives-ouvertes.fr/hal-00976113 Permalink http://etudes.bretagne-environnement.org/index.php?lvl=notice_display&id=147843Influence of Green Tides in Coastal Nursery Grounds on the Habitat Selection and Individual Performance of Juvenile Fish
article dans des revues - 2017-01-26
Luherne, Emilie Le, et al.
Titre Influence of Green Tides in Coastal Nursery Grounds on the Habitat Selection and Individual Performance of Juvenile Fish Type d'Ã©tude article dans des revues Auteurs personnes Luherne Emilie Le Auteur Pape Olivier Le Auteur Murillo Laurence Auteur Randon Marine Auteur Lebot ClÃ©ment Auteur RÃ©veillac Elodie Auteur Ã‰cologie et santÃ© des Ã©cosystÃ¨mes (ESE) ; Institut National de la Recherche Agronomique (INRA) - Agrocampus Ouest CollectivitÃ© Ã©ditrice Date de publication 2017-01-26 Editeur(s) [S.l.] : Public Library of Science
[S.l.] : HAL CCSD
PLOS ONE vol.12 nÂ°1 RÃ©sumÃ© Coastal ecosystems, which provide numerous essential ecological functions for fish, are threatened by the proliferation of green macroalgae that significantly modify habitat conditions in intertidal areas. Understanding the influence of green tides on the nursery function of these ecosystems is essential to determine their potential effects on fish recruitment success. In this study, the influence of green tides on juvenile fish was examined in an intertidal sandy beach area, the Bay of Saint-Brieuc (Northwestern France), during two annual cycles of green tides with varying levels of intensity. The responses of three nursery-dependent fish species, the pelagic Sprattus sprattus (L.), the demersal Dicentrarchus labrax (L.) and the benthic Pleuronectes platessa L., were analysed to determine the effects of green tides according to species-specific habitat niche and behaviour. The responses to this perturbation were investigated based on habitat selection and a comparison of individual performance between a control and an impacted site. Several indices on different integrative scales were examined to evaluate these responses (antioxidant defence capacity, muscle total lipid, morphometric condition and growth). Based on these analyses, green tides affect juvenile fish differently according to macroalgal density and species-specific tolerance, which is linked to their capacity to move and to their distribution in the water column. A decreasing gradient of sensitivity was observed from benthic to demersal and pelagic fish species. At low densities of green macroalgae, the three species stayed at the impacted site and the growth of plaice was reduced. At medium macroalgal densities, plaice disappeared from the impacted site and the growth of sea bass and the muscle total lipid content of sprat were reduced. Finally, when high macroalgal densities were reached, none of the studied species were captured at the impacted site. Hence, sites affected by green tides are less favourable nursery grounds for all the studied species, with species-specific effects related to macroalgal density. CatÃ©gories thÃ©matiques alguemarÃ©e vertezone cÃ´tiÃ¨rezone intertidalelittoral Mots-clÃ©s libres algue verte/Antioxidants/Ã©cosystÃ¨me du littoral/Fish physiology/Habitats/Lipids/macroalgue/macroalgues/Marine fish/Morphometry/Otolith/Tides Echelle de territoire baies et rades Note DOI = 10.1371/journal.pone.0170110.
Article dans la revue "PLoS ONE" Ã©ditÃ©e par la Public Library of Science (ISSN : 1932-6203) en 2017 volume 12 nÂ°1, doi = 10.1371/journal.pone.0170110.
Langue(s) Anglais Document en ligne https://hal.archives-ouvertes.fr/hal-01449302 Localisation du document AccÃ¨s au texte intÃ©gral disponible en ligne sur le site de la revue =http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0170110 NÂ° d'Ã©dition (ISBN, DOI,...) 10.1371/journal.pone.0170110 Permalink http://etudes.bretagne-environnement.org/index.php?lvl=notice_display&id=159812