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Auteur Kolasinski, J.; Kaehler, S.; Jaquemet, S.
Titre Distribution and sources of particulate organic matter in a mesoscale eddy dipole in the Mozambique Channel (south-western Indian Ocean): Insight from C and N stable isotopes Type Article scientifique
Année 2012 Publication (up) Revue Abrégée Journal of Marine Systems
Volume 96–97 Numéro Pages 122-131
Mots-Clés Channel; Mozambique
Résumé This study investigates eddy induced transport processes that affect the sources and sinks of organic matter in the Mozambique Channel (MC). Eddies generated in the MC interact with the continental shelf and have been hypothesized to act as conveyor belts that entrain coastal production offshore. A combination of natural isotope tracers, elemental composition and physico-chemical variables allowed distinguishing two sources of organic matter within the eddy dipole. Near the surface, coastal POM was entrained at the anti-cyclonic boundary and further transferred into the eddy. Anti-cyclonic surface POM containing coastal POM was downwelled into deeper layers where decomposition greatly affected its composition. In contrast, cyclonic water promoted new production, by upwelling nutrient-rich deep waters into the euphotic zone. This production circulated through the mixed layer of the cyclone and was possibly advected into the boundary. Boundary F(max) and surface waters shared characteristics with the cyclone and anti-cyclone respectively as the result of both import of primary production of cyclonic origin occurring at F(max) and entrainment of coastal biological material at the surface. In the overall low productivity environment of the MC, it is likely that the continuous migration of mesoscale eddies along the shelf plays an important ecological role both in enhancing pelagic production and transporting coastal production offshore.
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ISSN 0924-7963 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 200
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Auteur Jose, Y.S.; Penven, P.; Aumont, O.; Machu, E.; Moloney, C.L.; Shillington, F.; Maury, O.
Titre Suppressing and enhancing effects of mesoscale dynamics on biological production in the Mozambique Channel Type Article scientifique
Année 2016 Publication (up) Revue Abrégée Journal of Marine Systems
Volume 158 Numéro Pages 129-139
Mots-Clés chlorophyll; Mesoscale dynamics; Mozambique Channel; primary production
Résumé We used a coupled physical-biogeochemical model to investigate how the strong eddy activity typical of the Mozambique Channel affects biological production. A numerical experiment was carried out, in which mesoscale dynamics were suppressed by cancelling the nonlinear terms for horizontal momentum in the Naviers-Stokes equation. Mesoscale dynamics were found to be responsible for (1) increased offshore production in the Mozambique Channel as a result of net eddy-induced offshore transport of nutrient-rich coastal waters; (2) decreased shelf production along the central Mozambican and south-west Madagascar coast caused by a reduction in nutrient availability related to the net eddy-induced lateral transport of nutrients; (3) increased coastal production along the northern Mozambican coast caused by eddy-induced nutrient supply. The model results also showed an intensification and shallowing of the subsurface production, related to increased upper layer nutrient concentrations caused by eddy activity. In addition, by driving the detachment of the East Madagascar Current at the southern tip of the island, inertial processes intensify the southern Madagascar upwelling and causes offshore diffusion of the upwelled waters. These results emphasize the complex role played by eddy activity and, more generally, inertial processes on marine ecosystems in this region.
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ISSN 0924-7963 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1516
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Auteur Schloss, I.R.; Nozais, C.; Mas, S.; van Hardenberg, B.; Carmack, E.; Tremblay, J.-E.; Brugel, S.; Demers, S.
Titre Picophytoplankton and nanophytoplankton abundance and distribution in the southeastern Beaufort Sea (Mackenzie Shelf and Amundsen Gulf) during Fall 2002 Type Article scientifique
Année 2008 Publication (up) Revue Abrégée Journal of Marine Systems
Volume 74 Numéro 3-4 Pages 978-993
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 765
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Auteur Moullec, F.; Gascuel, D.; Bentorcha, K.; Guénette, S.; Robert, M.
Titre Trophic models: What do we learn about Celtic Sea and Bay of Biscay ecosystems? Type Article scientifique
Année 2017 Publication (up) Revue Abrégée Journal of Marine Systems
Volume 172 Numéro Pages 104-117
Mots-Clés Bay of Biscay; celtic sea; Ecopath with Ecosim; Ecosystem Approach to Fisheries Management (EAFM); EcoTroph; Trophic indicators
Résumé Trophic models are key tools to go beyond the single-species approaches used in stock assessments to adopt a more holistic view and implement the Ecosystem Approach to Fisheries Management (EAFM). This study aims to: (i) analyse the trophic functioning of the Celtic Sea and the Bay of Biscay, (ii) investigate ecosystem changes over the 1980–2013 period and, (iii) explore the response to management measures at the food web scale. Ecopath models were built for each ecosystem for years 1980 and 2013, and Ecosim models were fitted to time series data of biomass and catches. EcoTroph diagnosis showed that in both ecosystems, fishing pressure focuses on high trophic levels (TLs) and, to a lesser extent, on intermediate TLs. However, the interplay between local environmental conditions, species composition and ecosystem functioning could explain the different responses to fisheries management observed between these two contiguous ecosystems. Indeed, over the study period, the ecosystem's exploitation status has improved in the Bay of Biscay but not in the Celtic Sea. This improvement does not seem to be sufficient to achieve the objectives of an EAFM, as high trophic levels were still overexploited in 2013 and simulations conducted with Ecosim in the Bay of Biscay indicate that at current fishing effort the biomass will not be rebuilt by 2030. The ecosystem's response to a reduction in fishing mortality depends on which trophic levels receive protection. Reducing fishing mortality on pelagic fish, instead of on demersal fish, appears more efficient at maximising catch and total biomass and at conserving both top-predator and intermediate TLs. Such advice-oriented trophic models should be used on a regular basis to monitor the health status of marine food webs and analyse the trade-offs between multiple objectives in an ecosystem-based fisheries management context.
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ISSN 0924-7963 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2093
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Auteur Corrales, X.; Coll, M.; Tecchio, S.; Bellido, J.M.; Fernández, Á.M.; Palomera, I.
Titre Ecosystem structure and fishing impacts in the northwestern Mediterranean Sea using a food web model within a comparative approach Type Article scientifique
Année 2015 Publication (up) Revue Abrégée Journal of Marine Systems
Volume 148 Numéro Pages 183-199
Mots-Clés comparative approach; Ecopath model; ecosystem approach to fisheries; fishing impacts; Mass-balance model; Northwestern Mediterranean Sea
Résumé We developed an ecological model to characterize the structure and functioning of the marine continental shelf and slope area of the northwestern Mediterranean Sea, from Toulon to Cape La Nao (NWM model), in the early 2000s. The model included previously modeled areas in the NW Mediterranean (the Gulf of Lions and the Southern Catalan Sea) and expanded their ranges, covering 45,547 km2, with depths from 0 to 1000 m. The study area was chosen to specifically account for the connectivity between the areas and shared fish stocks and fleets. Input data were based on local scientific surveys and fishing statistics, published data on stomach content analyses, and the application of empirical equations to estimate consumption and production rates. The model was composed of 54 functional groups, from primary producers to top predators, and Spanish and French fishing fleets were considered. Results were analyzed using ecological indicators and compared with outputs from ecosystem models developed in the Mediterranean Sea and the Gulf of Cadiz prior to this study. Results showed that the main trophic flows were associated with detritus, phytoplankton, zooplankton and benthic invertebrates. Several high trophic level organisms (such as dolphins, benthopelagic cephalopods, large demersal fishes from the continental shelf, and other large pelagic fishes), and the herbivorous salema fish, were identified as keystone groups within the ecosystem. Results confirmed that fishing impact was high and widespread throughout the food web. The comparative approach highlighted that, despite productivity differences, the ecosystems shared common features in structure and functioning traits such as the important role of detritus, the dominance of the pelagic fraction in terms of flows and the importance of benthic–pelagic coupling.
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ISSN 0924-7963 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1327
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