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Auteur Fouilland, E.; Tolosa, I.; Bonnet, D.; Bouvier, C.; Bouvier, T.; Bouvy, M.; Got, P.; Le Floc'h, E.; Mostajir, B.; Roques, C.; Sempéré, R.; Sime-Ngando, T.; Vidussi, F.
Titre Bacterial carbon dependence on freshly produced phytoplankton exudates under different nutrient availability and grazing pressure conditions in coastal marine waters Type Article scientifique
Année 2014 Publication Revue Abrégée FEMS microbiology ecology
Volume 87 Numéro 3 Pages (down) 757-769
Mots-Clés bacteria; carbon coupling; coastal waters; interactions; phytoplankton
Résumé The effects of grazing pressure and inorganic nutrient availability on the direct carbon transfer from freshly produced phytoplankton exudates to heterotrophic bacteria biomass production were studied in Mediterranean coastal waters. The short-term incorporation of (1)(3)C (H(1)(3)CO(3)) in phytoplankton and bacterial lipid biomarkers was measured as well as the total bacterial carbon production (BP), viral lysis and the microbial community structure under three experimental conditions: (1) High inorganic Nutrient and High Grazing (HN + HG), (2) High inorganic Nutrient and Low Grazing (HN + LG) and (3) under natural in situ conditions with Low inorganic Nutrient and High Grazing (LN + HG) during spring. Under phytoplankton bloom conditions (HN + LG), the bacterial use of freshly produced phytoplankton exudates as a source of carbon, estimated from (1)(3)C enrichment of bacterial lipids, contributed more than half of the total bacterial production. However, under conditions of high grazing pressure on phytoplankton with or without the addition of inorganic nutrients (HN + HG and LN + HG), the (1)(3)C enrichment of bacterial lipids was low compared with the high total bacterial production. BP therefore seems to depend mainly on freshly produced phytoplankton exudates during the early phase of phytoplankton bloom period. However, BP seems mainly relying on recycled carbon from viral lysis and predators under high grazing pressure.
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ISSN 1574-6941 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 444
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Auteur Dueri, S.; Bopp, L.; Maury, O.
Titre Projecting the impacts of climate change on skipjack tuna abundance and spatial distribution Type Article scientifique
Année 2014 Publication Revue Abrégée Global Change Biology
Volume 20 Numéro 3 Pages (down) 742-753
Mots-Clés Apecosm-E; Atlantic Ocean; global warming; Indian Ocean; Katsuwonus pelamis; Pacific Ocean; scenario; Tropical tuna
Résumé Climate-induced changes in the physical, chemical, and biological environment are expected to increasingly stress marine ecosystems, with important consequences for fisheries exploitation. Here, we use the APECOSM-E numerical model (Apex Predator ECOSystem Model – Estimation) to evaluate the future impacts of climate change on the physiology, spatial distribution, and abundance of skipjack tuna, the worldwide most fished species of tropical tuna. The main novelties of our approach lie in the mechanistic link between environmental factors, metabolic rates, and behavioral responses and in the fully three dimensional representation of habitat and population abundance. Physical and biogeochemical fields used to force the model are provided by the last generation of the IPSL-CM5 Earth System Model run from 1990 to 2100 under a &8216;business-as-usual&8217; scenario (RCP8.5). Our simulations show significant changes in the spatial distribution of skipjack tuna suitable habitat, as well as in their population abundance. The model projects deterioration of skipjack habitat in most tropical waters and an improvement of habitat at higher latitudes. The primary driver of habitat changes is ocean warming, followed by food density changes. Our projections show an increase of global skipjack biomass between 2010 and 2050 followed by a marked decrease between 2050 and 2095. Spawning rates are consistent with population trends, showing that spawning depends primarily on the adult biomass. On the other hand, growth rates display very smooth temporal changes, suggesting that the ability of skipjack to keep high metabolic rates in the changing environment is generally effective. Uncertainties related to our model spatial resolution, to the lack or simplification of key processes and to the climate forcings are discussed.
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ISSN 1354-1013 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 327
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Auteur Albouy, C.; Velez, L.; Coll, M.; Colloca, F.; Le Loc'h, F.; Mouillot, D.; Gravel, D.
Titre From projected species distribution to food-web structure under climate change Type Article scientifique
Année 2014 Publication Revue Abrégée Global Change Biology
Volume 20 Numéro 3 Pages (down) 730-741
Mots-Clés climate change; connectance; fish body size; food-webs; generality; Mediterranean Sea; metaweb; niche model; vulnerability
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ISSN 1354-1013 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 324
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Auteur Bez, N.; Braham, C.B.
Titre Indicator variables for a robust estimation of an acoustic index of abundance Type Article scientifique
Année 2014 Publication Revue Abrégée Canadian Journal of Fisheries and Aquatic Sciences
Volume 71 Numéro 5 Pages (down) 709-718
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Résumé In North West Africa, pelagic fisheries are an essential economic sector. However, the scientific community fails to perform satisfactory assessments of key pelagic species like sardinella, owing to a lack of relevant indices of abundance to tune the model. This paper provides an alternative acoustic index based on a semiquantitative modelisation of acoustic densities. Acoustic energy is split into binomial variables coding for null, low, medium, large, and very large densities. A multivariate geostatistical approach allows (i) mapping the spatial distribution of classes of densities and (ii) computing a new acoustic index of abundance for Sardinella aurita and Sardinella maderensis. We used the surveys of RV Fridtjof Nansen (1995-2006) and RV Al-Awam (2007-2010). Our results indicated that empirical spatial structures were highly stable over time for both between areas and surveys. Co-kriging maps also showed that sardinella had stable hot spots of distribution. The indices of abundance developed in the present study were tested in an assessment procedure and outperformed all the indices used routinely by the FAO-CECAF (Fishery Committee for the Eastern Central Atlantic) assessment working group.
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Numéro d'Appel LL @ pixluser @ collection 352
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Auteur Restrepo-Ortiz, C.X.; Auguet, J.C.; Casamayor, E.O.
Titre Targeting spatiotemporal dynamics of planktonic SAGMGC-1 and segregation of ammonia-oxidizing thaumarchaeota ecotypes by newly designed primers and quantitative polymerase chain reaction Type Article scientifique
Année 2014 Publication Revue Abrégée Environmental Microbiology
Volume 16 Numéro 3 Pages (down) 689-700
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Résumé The annual dynamics of three different ammonia-oxidizing archaea (AOA) ecotypes (amoA gene) and of the SAGMGC-1 (Nitrosotalea-like aquatic Thaumarchaeota) group (16S rRNA gene) were studied by newly designed specific primers and quantitative polymerase chain reaction analysis in a deep oligotrophic high mountain lake (Lake Redon, Limnological Observatory of the Pyrenees, Spain). We observed segregated distributions of the main AOA populations, peaking separately in time and space, and under different ammonia concentrations and irradiance conditions. Strong positive correlation in gene abundances was found along the annual survey between 16S rRNA SAGMAGC-1 and one of the amoA ecotypes suggesting the potential for ammonia oxidation in the freshwater SAGMAGC-1 clade. We also observed dominance of Nitrosotalea-like ecotypes over Nitrosopumilus-like (Marine Group 1.1a) and not the same annual dynamics for the two thaumarchaeotal clades. The fine scale segregation in space and time of the different AOA ecotypes indicated the presence of phylogenetically close but ecologically segregated AOA species specifically adapted to specific environmental conditions. It remains to be elucidated what would be such environmental drivers.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1313
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