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Auteur Elisabeth, N.H.; Caro, A.; Cesaire, T.; Mansot, J.-L.; Escalas, A.; Sylvestre, M.-N.; Jean-Louis, P.; Gros, O. url  doi
openurl 
  Titre Comparative modifications in bacterial gill-endosymbiotic populations of the two bivalves Codakia orbiculata and Lucina pensylvanica during bacterial loss and reacquisition Type Article scientifique
  Année 2014 Publication Revue Abrégée FEMS microbiology ecology  
  Volume 89 Numéro (down) 3 Pages  
  Mots-Clés Index Medicus; Lucinidae; cell size; endosymbiotic population; genomic content; starvation; sulphur content  
  Résumé Until now, the culture of sulphur-oxidizing bacterial symbionts associated with marine invertebrates remains impossible. Therefore, few studies focused on symbiont's physiology under stress conditions. In this study, we carried out a comparative experiment based on two different species of lucinid bivalves (Codakia orbiculata and Lucina pensylvanica) under comparable stress factors. The bivalves were starved for 6months in sulphide-free filtered seawater. For C.orbiculata only, starved individuals were then put back to the field, in natural sediment. We used in situ hybridization, flow cytometry and X-ray fluorescence to characterize the symbiont population hosted in the gills of both species. In L.pensylvanica, no decrease in symbiont abundance was observed throughout the starvation experiment, whereas elemental sulphur slowly decreased to zero after 3months of starvation. Conversely, in C.orbiculata, symbiont abundance within bacteriocytes decreased rapidly and sulphur from symbionts disappeared during the first weeks of the experiment. The modifications of the cellular characteristics (SSC – relative cell size and FL1 – genomic content) of the symbiotic populations along starvation were not comparable between species. Return to the sediment of starved C.orbiculata individuals led to a rapid (2-4weeks) recovery of symbiotic cellular characteristics, comparable with unstressed symbionts. These results suggest that endosymbiotic population regulation is host-species-dependent in lucinids. 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.  
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  ISSN 1574-6941 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 481  
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Auteur Wang, T.; Lefevre, S.; Iversen, N.K.; Findorf, I.; Buchanan, R.; McKenzie, D.J. url  doi
openurl 
  Titre Anaemia only causes a small reduction in the upper critical temperature of sea bass: is oxygen delivery the limiting factor for tolerance of acute warming in fishes? Type Article scientifique
  Année 2014 Publication Revue Abrégée Journal of Experimental Biology  
  Volume 217 Numéro (down) 24 Pages 4275-4278  
  Mots-Clés aerobic scope; cardiac-performance; Cardiovascular; climate-change; dicentrarchus-labrax; ecology; exp. biol. 216; fish; Haematocrit; metabolism; Oxygen transport; phenylhydrazine-induced anemia; thermal tolerance; trout  
  Résumé To address how the capacity for oxygen transport influences tolerance of acute warming in fishes, we investigated whether a reduction in haematocrit, by means of intra-peritoneal injection of the haemolytic agent phenylhydrazine, lowered the upper critical temperature of sea bass. A reduction in haematocrit from 42 +/- 2% to 20 +/- 3% (mean +/- s.e.m.) caused a significant but minor reduction in upper critical temperature, from 35.8 +/- 0.1 to 35.1 +/- 0.2 degrees C, with no correlation between individual values for haematocrit and upper thermal limit. Anaemia did not influence the rise in oxygen uptake between 25 and 33 degrees C, because the anaemic fish were able to compensate for reduced blood oxygen carrying capacity with a significant increase in cardiac output. Therefore, in sea bass the upper critical temperature, at which they lost equilibrium, was not determined by an inability of the cardio-respiratory system to meet the thermal acceleration of metabolic demands.  
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  ISSN 0022-0949 ISBN Médium  
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  Notes <p>ISI Document Delivery No.: AW7BT<br/>Times Cited: 1<br/>Cited Reference Count: 44<br/>Wang, Tobias Lefevre, Sjannie Iversen, Nina K. Findorf, Inge Buchanan, Rasmus McKenzie, David J.<br/>Centre National de la Recherche Scientifique (CNRS); Danish Research Council; Region Languedoc-Roussillon (RLR); Ambassade de France in Copenhagen; Universite Montpellier 2<br/>This research was supported by the Centre National de la Recherche Scientifique (CNRS), the Danish Research Council, The Ambassade de France in Copenhagen and Universite Montpellier 2. T.W. was supported by a fellowship from Region Languedoc-Roussillon (RLR) as a visiting professor at Universite Montpellier 2. I.F. and N.K.I. were supported by a student grant from The Ambassade de France in Copenhagen.<br/>Company of biologists ltd<br/>Cambridge</p> Approuvé pas de  
  Numéro d'Appel MARBEC @ alain.herve @ collection 1181  
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Auteur Zhao, T.; Villeger, S.; Lek, S.; Cucherousset, J. url  doi
openurl 
  Titre High intraspecific variability in the functional niche of a predator is associated with ontogenetic shift and individual specialization Type Article scientifique
  Année 2014 Publication Revue Abrégée Ecology and Evolution  
  Volume 4 Numéro (down) 24 Pages 4649-4657  
  Mots-Clés functional traits; niche; ontogeny; overlap; stable isotope analyses  
  Résumé Investigations on the functional niche of organisms have primarily focused on differences among species and tended to neglect the potential effects of intraspecific variability despite the fact that its potential ecological and evolutionary importance is now widely recognized. In this study, we measured the distribution of functional traits in an entire population of largemouth bass (Micropterus salmoides) to quantify the magnitude of intraspecific variability in functional traits and niche (size, position, and overlap) between age classes. Stable isotope analyses (δ13C and δ15N) were also used to determine the association between individual trophic ecology and intraspecific functional trait variability. We observed that functional traits were highly variable within the population (mean coefficient variation: 15.62% ± 1.78% SE) and predominantly different between age classes. In addition, functional and trophic niche overlap between age classes was extremely low. Differences in functional niche between age classes were associated with strong changes in trophic niche occurring during ontogeny while, within age classes, differences among individuals were likely driven by trophic specialization. Each age class filled only a small portion of the total functional niche of the population and age classes occupied distinct portions in the functional space, indicating the existence of ontogenetic specialists with different functional roles within the population. The high amplitude of intraspecific variability in functional traits and differences in functional niche position among individuals reported here supports the recent claims for an individual-based approach in functional ecology.  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 1183  
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Auteur Moreau, S.; Mostajir, B.; Almandoz, G.O.; Demers, S.; Hernando, M.; Lemarchand, K.; Lionard, M.; Mercier, B.; Roy, S.; Schloss, I.R.; Thyssen, M.; Ferreyra, G.A. url  doi
openurl 
  Titre Effects of enhanced temperature and ultraviolet B radiation on a natural plankton community of the Beagle Channel (southern Argentina): a mesocosm study Type Article scientifique
  Année 2014 Publication Revue Abrégée Aquatic Microbial Ecology  
  Volume 72 Numéro (down) 2 Pages 155-173  
  Mots-Clés  
  Résumé ABSTRACT: Marine planktonic communities can be affected by increased temperatures associated with global climate change, as well as by increased ultraviolet B radiation (UVBR, 280-320 nm) through stratospheric ozone layer thinning. We studied individual and combined effects of increased temperature and UVBR on the plankton community of the Beagle Channel, southern Patagonia, Argentina. Eight 2 m3 mesocosms were exposed to 4 treatments (with 2 replicates) during 10 d: (1) control (natural temperature and UVBR), (2) increased UVBR (simulating a 60% decrease in stratospheric ozone layer thickness), (3) increased temperature (+ 3°C), and (4) simultaneous increased temperature and UVBR (60% decrease in stratospheric ozone; + 3°C). Two distinct situations were observed with regard to phytoplankton biomass: bloom (Days 1-4) and post-bloom (Days 5-9). Significant decreases in micro-sized diatoms (>20 µm), bacteria, chlorophyll a, and particulate organic carbon concentrations were observed during the post-bloom in the enhanced temperature treatments relative to natural temperature, accompanied by significant increases in nanophytoplankton (10-20 µm, mainly prymnesiophytes). The decrease in micro-sized diatoms in the high temperature treatment may have been caused by a physiological effect of warming, although we do not have activity measurements to support this hypothesis. Prymnesiophytes benefited from micro-sized diatom reduction in their competition for resources. The bacterial decrease under warming may have been due to a change in the dissolved organic matter release caused by the observed change in phytoplankton composition. Overall, the rise in temperature affected the structure and total biomass of the communities, while no major effect of UVBR was observed on the plankton community.  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 555  
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Auteur Travis, J.; Coleman, F.C.; Auster, P.J.; Cury, P.; Estes, J.A.; Orensanz, J.; Peterson, C.H.; Power, M.E.; Steneck, R.S.; Wootton, J.T. url  doi
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  Titre Integrating the invisible fabric of nature into fisheries management Type Article scientifique
  Année 2014 Publication Revue Abrégée Proceedings of the National Academy of Sciences of the United States of America  
  Volume 111 Numéro (down) 2 Pages 581-584  
  Mots-Clés alternative states; ecosystem flips; fisheries collapse; ocean fisheries  
  Résumé Overfishing and environmental change have triggered many severe and unexpected consequences. As existing communities have collapsed, new ones have become established, fundamentally transforming ecosystems to those that are often less productive for fisheries, more prone to cycles of booms and busts, and thus less manageable. We contend that the failure of fisheries science and management to anticipate these transformations results from a lack of appreciation for the nature, strength, complexity, and outcome of species interactions. Ecologists have come to understand that networks of interacting species exhibit nonlinear dynamics and feedback loops that can produce sudden and unexpected shifts. We argue that fisheries science and management must follow this lead by developing a sharper focus on species interactions and how disrupting these interactions can push ecosystems in which fisheries are embedded past their tipping points.  
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  Numéro d'Appel LL @ pixluser @ collection 336  
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