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Auteur (up) Malauene, B.S.; Moloney, C.L.; Lett, C.; Roberts, M.J.; Marsac, F.; Penven, P. url  doi
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  Titre Impact of offshore eddies on shelf circulation and river plumes of the Sofala Bank, Mozambique Channel Type Article scientifique
  Année 2018 Publication Revue Abrégée Journal of Marine Systems  
  Volume 185 Numéro Pages 1-12  
  Mots-Clés Mesoscale eddies; River plume; Roms; Shelf processes; SOMs  
  Résumé A high-resolution, two-way nested Regional Ocean Modeling System, forced with monthly climatologies, has been set up for the Sofala Bank and adjacent deeper ocean of the Mozambique Channel to investigate the role of offshore mesoscale eddies on the shelf circulation, hydrographic structures and river plumes. The model is shown in comparison with available observations and published studies. Most known oceanographic features are reproduced by our model. We applied Self-Organizing Maps and showed that offshore passing eddies, depending on their strength and proximity to the shelf, modulate the shelf circulation and river plume direction and spread. The presence of a strong cyclonic eddy close to the shelf induces northward surface shelf currents. In contrast, the presence of a strong anticyclonic eddy close to the shelf induces a strong southward current over most of the shelf, except off Beira. Our analyses confirm that the plume of the Zambezi River is bi-directional. The southward-directed plume patterns, opposite to the dominant northwards, occur in response to nearby offshore anticyclonic eddies (26% of occurrence). This behavior could have an influence on water dispersal, shelf ecosystems and important fisheries. Therefore, offshore mesoscale eddies should be taken into account when studying the ocean dynamics of the Sofala Bank.  
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  ISSN 0924-7963 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2358  
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Auteur (up) Moullec, F.; Gascuel, D.; Bentorcha, K.; Guénette, S.; Robert, M. url  doi
openurl 
  Titre Trophic models: What do we learn about Celtic Sea and Bay of Biscay ecosystems? Type Article scientifique
  Année 2017 Publication 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 (up) Perry, R.I.; Cury, P.; Brander, K.; Jennings, S.; Mollmann, C.; Planque, B. url  doi
openurl 
  Titre Sensitivity of marine systems to climate and fishing: Concepts, issues and management responses Type Article scientifique
  Année 2010 Publication Revue Abrégée Journal of Marine Systems  
  Volume 79 Numéro Pages 427-435  
  Mots-Clés change; climate; Communities; ecosystems; fisheries; Fishing; management; Populations; variability  
  Résumé Modern fisheries research and management must understand and take account of the interactions between climate and fishing, rather than try to disentangle their effects and address each separately. These interactions are significant drivers of change in exploited marine systems and have ramifications for ecosystems and those who depend on the services they provide. We discuss how fishing and climate forcing interact on individual fish, marine populations, marine communities, and ecosystems to bring these levels into states that are more sensitive to (i.e. more strongly related with) climate forcing. Fishing is unlikely to alter the sensitivities of individual finfish and invertebrates to climate forcing. It will remove individuals with specific characteristics from the gene pool, thereby affecting structure and function at higher levels of organisation. Fishing leads to a loss of older age classes, spatial contraction, loss of sub-units, and alteration of life history traits in populations, making them more sensitive to climate variability at interannual to interdecadal scales. Fishing reduces the mean size of individuals and mean trophic level of communities, decreasing their turnover time leading them to track environmental variability more closely. Marine ecosystems under intense exploitation evolve towards stronger bottom-up control and greater sensitivity to climate forcing. Because climate change occurs slowly, its effects are not likely to have immediate impacts on marine systems but will be manifest as the accumulation of the interactions between fishing and climate variability – unless threshold limits are exceeded. Marine resource managers need to develop approaches which maintain the resilience of individuals, populations, communities and ecosystems to the combined and interacting effects of climate and fishing. Overall, a less-heavily fished marine system, and one which shifts the focus from individual species to functional groups and fish communities, is likely to provide more stable catches with climate variability and change than would a heavily fished system. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.  
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  Numéro d'Appel LL @ pixluser @ collection 95  
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Auteur (up) Schloss, I.R.; Nozais, C.; Mas, S.; van Hardenberg, B.; Carmack, E.; Tremblay, J.-E.; Brugel, S.; Demers, S. url  doi
openurl 
  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 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 (up) Tew-Kai, E.; Marsac, F. url  doi
openurl 
  Titre Patterns of variability of sea surface chlorophyll in the Mozambique Channel : a quantitative approach Type Article scientifique
  Année 2009 Publication Revue Abrégée Journal of Marine Systems  
  Volume 77 Numéro 1-2 Pages 77-88  
  Mots-Clés Climate forcing; Mesoscale; Mozambique Channel; Quantitative approach; Seasonal variability; Sea Surface chlorophyll  
  Résumé We analyse the coupling between sea surface chlorophyll concentration (CC) and the physical environment in the Mozambique Channel (MZC) using statistical models. Seasonal and interannual patterns are studied along with the role of mesoscale dynamics on enhancement and concentration processes for phytoplankton. We use SeaWifs data for CC and two other remotely sensed data sets, TMMI for sea surface temperature (SST) and merged altimetry products for sea level anomaly and geostrophic current. Empirical Orthogonal Functions (EOF) on SSC and SST show strong seasonality and partition the MZC into three distinct sub-areas. The chlorophyll variability is mostly driven by seasonality, but more in the North (10 degrees S-16 degrees S) and South (24 degrees S-30 degrees S), and explains respectively 64% and 82% of the CC variance. In the Central part (16 degrees S-24 degrees S), the seasonal signal has less influence (60% variance). There, complex EOFs on Sea Level Anomaly (SLA) highlight the role of mesoscale activity (i.e. eddies and filament structures) in the spatial distribution of chlorophyll. Five mesoscale descriptors (shear, stretch, vorticity, deformation and eddy kinetic energy) are derived from the altimetry data to quantify the eddies-related physical patterns in the central region of the MZC. We use generalized Additive Models to explain the effect of those features on phytoplankton enhancement. The best model fit (r(2) = 0.73) includes shear, stretch, vorticity and the latitude-longitude interaction as eddies are well structured in space. Cyclonic eddies associated with negative vorticity are conductive to phytoplankton enhancement by the effect of upwelling in the core notably during the spin-up phase. The interaction between eddies generate strong frontal mixing favourable to the production and aggregation of organic matter. The mesoscale activity is also affected by interannual variability with consequences on CC. We highlight a substantial reduction of the SLA pattern in 2000-2001 when the SOI positive phase is peaking (Nina-type pattern). The strong relationship between mesoscale eddies and SOI suggests that primary productivity in the MZC is also under the influence of distant forcing at a basin scale.  
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  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 0924-7963 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel LL @ pixluser @ collection 13  
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