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Auteur Bouvier, T.; Venail, P.; Pommier, T.; Bouvier, C.; Barbera, C.; Mouquet, N. url  doi
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  Titre Contrasted Effects of Diversity and Immigration on Ecological Insurance in Marine Bacterioplankton Communities Type Article scientifique
  Année 2012 Publication Revue Abrégée PLoS One  
  Volume 7 Numéro 6 Pages  
  Mots-Clés 16s ribosomal-rna; bacterial communities; biodiversity; dispersal; fresh-water; gradient gel-electrophoresis; metacommunities; predictability; productivity; stability  
  Résumé The ecological insurance hypothesis predicts a positive effect of species richness on ecosystem functioning in a variable environment. This effect stems from temporal and spatial complementarity among species within metacommunities coupled with optimal levels of dispersal. Despite its importance in the context of global change by human activities, empirical evidence for ecological insurance remains scarce and controversial. Here we use natural aquatic bacterial communities to explore some of the predictions of the spatial and temporal aspects of the ecological insurance hypothesis. Addressing ecological insurance with bacterioplankton is of strong relevance given their central role in fundamental ecosystem processes. Our experimental set up consisted of water and bacterioplankton communities from two contrasting coastal lagoons. In order to mimic environmental fluctuations, the bacterioplankton community from one lagoon was successively transferred between tanks containing water from each of the two lagoons. We manipulated initial bacterial diversity for experimental communities and immigration during the experiment. We found that the abundance and production of bacterioplankton communities was higher and more stable (lower temporal variance) for treatments with high initial bacterial diversity. Immigration was only marginally beneficial to bacterial communities, probably because microbial communities operate at different time scales compared to the frequency of perturbation selected in this study, and of their intrinsic high physiologic plasticity. Such local “physiological insurance” may have a strong significance for the maintenance of bacterial abundance and production in the face of environmental perturbations.  
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  ISSN 1932-6203 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 499  
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Auteur Gounand, I.; Daufresne, T.; Gravel, D.; Bouvier, C.; Bouvier, T.; Combe, M.; Gougat-Barbera, C.; Poly, F.; Torres-Barcelo, C.; Mouquet, N. doi  openurl
  Titre Size evolution in microorganisms masks trade-offs predicted by the growth rate hypothesis Type Article scientifique
  Année 2016 Publication Revue Abrégée Proc. R. Soc. B-Biol. Sci.  
  Volume 283 Numéro 1845 Pages 20162272  
  Mots-Clés Bacteria; bacterial community; biological stoichiometry; cell-size; escherichia-coli; experimental evolution; fresh-water; growth rate hypothesis; inorganic polyphosphate; intrinsic growth; mechanistic approach; Pseudomonas fluorescens; resource competition; r/K strategies; Stoichiometry; variable environment  
  Résumé Adaptation to local resource availability depends on responses in growth rate and nutrient acquisition. The growth rate hypothesis (GRH) suggests that growing fast should impair competitive abilities for phosphorus and nitrogen due to high demand for biosynthesis. However, in microorganisms, size influences both growth and uptake rates, which may mask trade-offs and instead generate a positive relationship between these traits (size hypothesis, SH). Here, we evolved a gradient of maximum growth rate (mu(max)) from a single bacterium ancestor to test the relationship among mu(max), competitive ability for nutrients and cell size, while controlling for evolutionary history. We found a strong positive correlation between mu(max) and competitive ability for phosphorus, associated with a trade-off between mu(max) and cell size: strains selected for high mu(max) were smaller and better competitors for phosphorus. Our results strongly support the SH, while the trade-offs expected under GRH were not apparent. Beyond plasticity, unicellular populations can respond rapidly to selection pressure through joint evolution of their size and maximum growth rate. Our study stresses that physiological links between these traits tightly shape the evolution of competitive strategies.  
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  ISSN 0962-8452 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2055  
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Auteur Escalas, A.; Catherine, A.; Maloufi, S.; Cellamare, M.; Hamlaoui, S.; Yepremian, C.; Louvard, C.; Troussellier, M.; Bernard, C. doi  openurl
  Titre Drivers and ecological consequences of dominance in periurban phytoplankton communities using networks approaches Type Article scientifique
  Année 2019 Publication Revue Abrégée Water Res.  
  Volume 163 Numéro Pages Unsp-114893  
  Mots-Clés blooms; climate-change; Co-occurrence network; Community cohesion; Community functioning; cooccurrence patterns; cyanobacteria dominance; diversity; Dominance; fresh-waters; lakes; light; Periurban waterbodies; Phytoplankton; resource use efficiency; species richness  
  Résumé Evaluating the causes and consequences of dominance by a limited number of taxa in phytoplankton communities is of huge importance in the current context of increasing anthropogenic pressures on natural ecosystems. This is of particular concern in densely populated urban areas where usages and impacts of human populations on water ecosystems are strongly interconnected. Microbial biodiversity is commonly used as a bioindicator of environmental quality and ecosystem functioning, but there are few studies at the regional scale that integrate the drivers of dominance in phytoplankton communities and their consequences on the structure and functioning of these communities. Here, we studied the causes and consequences of phytoplankton dominance in 50 environmentally contrasted waterbodies, sampled over four summer campaigns in the highly-populated Ile-de-France region (IDF). Phytoplankton dominance was observed in 32-52% of the communities and most cases were attributed to Chlorophyta (35.5-40.6% of cases) and Cyanobacteria (30.3-36.5%). The best predictors of dominance were identified using multinomial logistic regression and included waterbody features (surface, depth and connection to the hydrological network) and water column characteristics (total N, TN:TP ratio, water temperature and stratification). The consequences of dominance were dependent on the identity of the dominant organisms and included modifications of biological attributes (richness, cohesion) and functioning (biomass, RUE) of phytoplankton communities. We constructed co-occurrence networks using high resolution phytoplankton biomass and demonstrated that networks under dominance by Chlorophyta and Cyanobacteria exhibited significantly different structure compared with networks without dominance. Furthermore, dominance by Cyanobacteria was associated with more profound network modifications (e.g. cohesion, size, density, efficiency and proportion of negative links), suggesting a stronger disruption of the structure and functioning of phytoplankton communities in the conditions in which this group dominates. Finally, we provide a synthesis on the relationships between environmental drivers, dominance status, community attributes and network structure. (C) 2019 Elsevier Ltd. All rights reserved.  
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  ISSN 0043-1354 ISBN Médium  
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  Notes WOS:000483006400038 Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2636  
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Auteur Cormier, B.; Batel, A.; Cachot, J.; Begout, M.-L.; Braunbeck, T.; Cousin, X.; Keiter, S.H. doi  openurl
  Titre Multi-Laboratory Hazard Assessment of Contaminated Microplastic Particles by Means of Enhanced Fish Embryo Test With the Zebrafish (Danio rerio) Type Article scientifique
  Année 2019 Publication Revue Abrégée Front. Environ. Sci.  
  Volume 7 Numéro Pages 135  
  Mots-Clés aromatic-hydrocarbons pahs; benzo[a]pyrene; chronic dietary exposure; cyp1a; erod; fish embryotoxicity test (FET); fresh-water; gene-expression; hydrophobic organic-chemicals; marine-environment; oxybenzone; perfluorooctane sulfonate; plastic debris; resin pellets; risk-assessment; swimming behavior; uv-filters  
  Résumé As wide-spread pollutants in the marine environment, microplastics (MPs) have raised public concern about potential toxic effects in aquatic organisms, and, among others, MPs were suspected to act as a vector for organic pollutants to biota. The purpose of the present study was to investigate effects by three model pollutants, oxybenzone (BP3), benzo[a] pyrene (BaP), and perfluorooctane sulfonate (PFOS) adsorbed to polyethylene MPs on the basis of a standard assay, the acute fish embryo toxicity test (FET; OECD TG 236) with zebrafish (Danio rerio) supplemented by additional endpoints such as induction of ethoxyresorufin-O-deethylase (EROD) activity, modification of cyp1a gene transcription and changes in larval swimming behavior. FET assays were performed in three laboratories using slightly different husbandry and exposure conditions, which, however, were all fully compatible with the limits defined by OECD TG 236. This allowed for testing of potential changes in the FET assay due to protocol variations. The standard endpoints of the FET (acute embryotoxicity) did not reveal any acute toxicity for both virgin MPs and MPs spiked with BP3, BaP, and PFOS. With respect to sublethal endpoints, EROD activity was increased after exposure to MPs spiked with BP3 (3 h pulse) and MPs spiked with BaP (96 h continuous exposure). Cyp1a transcription was increased upon exposure to MPs spiked with BP3 or BaP. For the selected combination of MPs particles and contaminants, the basic FET proved not sensitive enough to reveal effects of (virgin and spiked) MPs. However, given that the FET can easily be supplemented by a broad variety of more subtle and sensitive endpoints, an enhanced FET protocol may provide a relevant approach with developmental stages of a vertebrate animal model, which is not protected by current EU animal welfare legislation (Directive EU 2010/63).  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2646  
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Auteur Masroor, W.; Farcy, E.; Blondeau-Bidet, E.; Venn, A.; Tambutte, E.; Lorin-Nebel, C. doi  openurl
  Titre Effect of salinity and temperature on the expression of genes involved in branchial ion transport processes in European sea bass Type Article scientifique
  Année 2019 Publication Revue Abrégée J. Therm. Biol.  
  Volume 85 Numéro Pages Unsp-102422  
  Mots-Clés cftr anion channel; chloride channel; cod gadus-morhua; Dicentrarchus labrax; dicentrarchus-labrax; fresh-water; functional classification; Gill; h+-atpase; Ion transporter; mRNA expression; na+/k+-atpase; na+/k+/2cl(-) cotransporter; Salinity; seawater-acclimated medaka; Thermal acclimation  
  Résumé The responses of European sea bass to temperature increase and salinity decrease were investigated measuring mRNA expression levels of main genes involved in ion transport. Juvenile fish were pre-acclimated to seawater (SW) at 18 degrees C (temperate) or 24 degrees C (warm) for two weeks and then transferred for two weeks to either fresh water (FW) or SW at the respective temperature. Unlike temperate conditions, there is no change in Na+/K+-ATPase ala (nka ala) and Na+/H+ exchanger 3 (nhe3) mRNA expression following FW transfer in warm conditions. This is linked to the high expression of these genes in warm SW compared to temperate SW. Na+/Cl--cotransporter (ncc2a) expression however is increased following FW transfer in temperate and warm conditions. Main transporters involved in ion excretion (Na+/K+/2Cl-1( )cotransporter, nkcc1 and cystic fibrosis transmembrane conductance regulator, cftr) as well as nitrogen excretion (Rh-glycoproteins, rhcg1 and rhbg) and acid-base regulation (V-H+-ATPase, vha-a and b) are highly expressed in SW warm conditions vs FW warm. Overall, our results suggest a higher activation of ion transport processes in warm conditions and more strikingly in SW. This is linked to a strong interplay between diverse ion transporters in order to coordinate physiological responses at the gill level.  
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  ISSN 0306-4565 ISBN Médium  
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  Notes WOS:000497246100023 Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2669  
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