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Auteur Grüss, A.; Schirripa, M.J.; Chagaris, D.; Drexler, M.; Simons, J.; Verley, P.; Shin, Y.-J.; Karnauskas, M.; Oliveros-Ramos, R.; Ainsworth, C.H. url  doi
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  Titre Evaluation of the trophic structure of the West Florida Shelf in the 2000s using the ecosystem model OSMOSE Type Article scientifique
  Année 2015 Publication Revue Abrégée Journal of Marine Systems  
  Volume (down) 144 Numéro Pages 30-47  
  Mots-Clés Gag grouper; Marine ecosystem modeling; Natural mortality; resource management; trophic structure; West Florida Shelf  
  Résumé We applied the individual-based, multi-species OSMOSE modeling approach to the West Florida Shelf, with the intent to inform ecosystem-based management (EBM) in this region. Our model, referred to as ‘OSMOSE-WFS’, explicitly considers both pelagic-demersal and benthic high trophic level (HTL) groups of fish and invertebrate species, and is forced by the biomass of low trophic level groups of species (plankton and benthos). We present a steady-state version of the OSMOSE-WFS model describing trophic interactions in the West Florida Shelf in the 2000s. OSMOSE-WFS was calibrated using a recently developed evolutionary algorithm that allowed simulated biomasses of HTL groups to match observed biomasses over the period 2005–2009. The validity of OSMOSE-WFS was then evaluated by comparing simulated diets to observed ones, and the simulated trophic levels to those in an Ecopath model of the West Florida Shelf (WFS Reef fish Ecopath). Finally, OSMOSE-WFS was used to explore the trophic structure of the West Florida Shelf in the 2000s and estimate size-specific natural mortality rates for a socio-economically important species, gag grouper (Mycteroperca microlepis). OSMOSE-WFS outputs were in full agreement with observations as to the body size and ecological niche of prey of the different HTL groups, and to a lesser extent in agreement with the observed species composition of the diet of HTL groups. OSMOSE-WFS and WFS Reef fish Ecopath concurred on the magnitude of the instantaneous natural mortality of the different life stages of gag grouper over the period 2005–2009, but not always on the main causes of natural mortality. The model evaluations conducted here provides a strong basis for ongoing work exploring fishing and environmental scenarios so as to inform EBM. From simple size-based predation rules, we were indeed able to capture the complexity of trophic interactions in the West Florida Shelf, and to identify the predators, prey and competitors of socio-economically important species as well as pivotal prey species of the ecosystem.  
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  Volume de collection Numéro de collection Edition  
  ISSN 0924-7963 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1253  
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Auteur Alegre, A.; Bertrand, A.; Espino, M.; Espinoza, P.; Dioses, T.; Ñiquen, M.; Navarro, I.; Simier, M.; Ménard, F. url  doi
openurl 
  Titre Diet diversity of jack and chub mackerels and ecosystem changes in the northern Humboldt Current system: A long-term study Type Article scientifique
  Année 2015 Publication Revue Abrégée Progress in Oceanography  
  Volume (down) 137, Part A Numéro Pages 299-313  
  Mots-Clés  
  Résumé Jack mackerel Trachurus murphyi (JM) and chub mackerel Scomber japonicus (CM) are medium size pelagic fish predators and highly exploited resources. Here we investigated the spatiotemporal patterns of JM and CM diet composition using a large dataset of stomach samples collected from 1973 to 2013 along the Peruvian coast. In total 47,535 stomachs (18,377 CM and 29,158 JM) were analysed, of which 23,570 (12,476 CM and 11,094 JM) were non-empty. Results show that both species are opportunistic and present a trophic overlap. However, despite their smaller maximal size, CM consumed more fish than JM. Both diets presented high spatiotemporal variability. Spatially, the shelf break appears as a strong biogeographical barrier affecting prey species distribution and thus CM and JM diet. Opportunistic foragers are often considered as actual indicators of ecosystem changes; we show here that diet composition of CM and JM reveal ecosystem changes but is not always a good indicator of changes in prey biomass as prey accessibility and energy content can also play an important role. In addition we found that El Niño events have a surprisingly weak effect on stomach fullness and diet. Finally our results show that the classic paradigm of positive correlation between diversity and temperature is unlikely to occur in the Humboldt Current system where productivity seems to be the main driver. We show how energy content of forage species and the strength of the oxygen minimum zone most likely play an important role prey diversity and accessibility, and thus in fish foraging behaviour.  
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  ISSN 0079-6611 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1319  
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Auteur Reygondeau, G.; Molinero, J.C.; Coombs, S.; MacKenzie, B.R.; Bonnet, D. doi  openurl
  Titre Progressive changes in the Western English Channel foster a reorganization in the plankton food web Type Article scientifique
  Année 2015 Publication Revue Abrégée Prog. Oceanogr.  
  Volume (down) 137 Numéro Pages 524-532  
  Mots-Clés abundance; climate-change; dynamics; ecosystems; global ocean; north-sea; regime shifts; sardine sardina-pilchardus; station l4  
  Résumé Growing evidence has shown a profound modification of plankton communities of the North East Atlantic and adjacent seas over the past decades. This drastic change has been attributed to a modification of the environmental conditions that regulate the dynamics and the spatial distribution of ectothermic species in the ocean. Recently, several studies have highlighted modifications of the regional climate station L4 (50 degrees 15.00'N, 4 degrees 13.02'W) in the Western English Channel. We here focus on the modification of the plankton community by studying the long-term, annual and seasonal changes of five zooplankton groups and eight copepod genera. We detail the main composition and the phenology of the plankton communities during four climatic periods identified at the L4 station: 1988-1994, 1995-2000, 2001-2007 and 2008-2012. Our results show that long-term environmental changes underlined by Molinero et al. (2013) drive a profound restructuration of the plankton community modifying the phenology and the dominance of key planktonic groups including fish larvae. Consequently, the slow but deep modifications detected in the plankton community highlight a climate driven ecosystem shift in the Western English Channel. Crown Copyright (C) 2015 Published by Elsevier Ltd. All rights reserved.  
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  Langue English Langue du Résumé Titre Original  
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  ISSN 0079-6611 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 1479  
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Auteur Pringault, O.; Aube, J.; Bouchez, O.; Klopp, C.; Mariette, J.; Escudie, F.; Senin, P.; Goni-Urriza, M. url  doi
openurl 
  Titre Contrasted effects of natural complex mixtures of PAHs and metals on oxygen cycle in a microbial mat Type Article scientifique
  Année 2015 Publication Revue Abrégée Chemosphere  
  Volume (down) 135 Numéro Pages 189-201  
  Mots-Clés Biofilm; Carbon cycle; Maturation; Microelectrodes; Production; Respiration  
  Résumé The contamination of polluted environments is often due to a complex mixture of pollutants sometimes at trace levels which nevertheless may have significant effects on the diversity and functioning of organisms. The aim of this study was to assess the functional responses of a microbial mat exposed to a natural complex mixture of PAHs and metals as a function of the maturation stage of the biofilm. Microbial mats sampled in a slightly polluted environment were exposed to contaminated water of a retention basin of an oil refinery. The responses of the microbial mats differed according to season. In spring 2012, strong inhibition of both oxygen production and respiration was observed relative to the control, with rates representing less than 5% of the control after 72 h of incubation. A decrease of microbial activities was followed by a decrease of the coupling between autotrophs and heterotrophs. In contrast, in autumn 2012, no significant changes for oxygen production and respiration were observed and the coupling between autotrophs and heterotrophs was not altered. The differences observed between the spring and autumn mats might be explained by the maturity of the microbial mat with dominance of heterotrophic bacteria in spring, and diatoms and cyanobacteria in autumn, as well as by the differences in the chemical composition of the complex mixture of PAHs and metals.  
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  Volume de collection Numéro de collection Edition  
  ISSN 0045-6535 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1333  
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Auteur Tecchio, S.; Coll, M.; Sardà, F. url  doi
openurl 
  Titre Structure, functioning, and cumulative stressors of Mediterranean deep-sea ecosystems Type Article scientifique
  Année 2015 Publication Revue Abrégée Progress in Oceanography  
  Volume (down) 135 Numéro Pages 156-167  
  Mots-Clés  
  Résumé Environmental stressors, such as climate fluctuations, and anthropogenic stressors, such as fishing, are of major concern for the management of deep-sea ecosystems. Deep-water habitats are limited by primary productivity and are mainly dependent on the vertical input of organic matter from the surface. Global change over the latest decades is imparting variations in primary productivity levels across oceans, and thus it has an impact on the amount of organic matter landing on the deep seafloor. In addition, anthropogenic impacts are now reaching the deep ocean. The Mediterranean Sea, the largest enclosed basin on the planet, is not an exception. However, ecosystem-level studies of response to varying food input and anthropogenic stressors on deep-sea ecosystems are still scant. We present here a comparative ecological network analysis of three food webs of the deep Mediterranean Sea, with contrasting trophic structure. After modelling the flows of these food webs with the Ecopath with Ecosim approach, we compared indicators of network structure and functioning. We then developed temporal dynamic simulations varying the organic matter input to evaluate its potential effect. Results show that, following the west-to-east gradient in the Mediterranean Sea of marine snow input, organic matter recycling increases, net production decreases to negative values and trophic organisation is overall reduced. The levels of food-web activity followed the gradient of organic matter availability at the seafloor, confirming that deep-water ecosystems directly depend on marine snow and are therefore influenced by variations of energy input, such as climate-driven changes. In addition, simulations of varying marine snow arrival at the seafloor, combined with the hypothesis of a possible fishery expansion on the lower continental slope in the western basin, evidence that the trawling fishery may pose an impact which could be an order of magnitude stronger than a climate-driven reduction of marine snow.  
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  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 0079-6611 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1337  
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