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Auteur 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 (up) 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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  ISSN 0924-7963 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 13  
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Auteur Thebaud, O.; Innes, J.; Doyen, L.; Lample, M.; Macher, C.; Mahevas, S.; Mullon, C.; Planque, B.; Quaas, M.; Smith, T.; Vermard, Y. url  doi
openurl 
  Titre Building ecological-economic models and scenarios of marine resource systems : workshop report Type Article scientifique
  Année 2013 Publication (up) Revue Abrégée Marine Policy  
  Volume 43 Numéro Pages 382-386  
  Mots-Clés Ecological-Economic Modelling; ecosystem approach; Integrated Assessment; Marine Resources  
  Résumé As part of the ecosystem approach to managing fisheries and other uses of marine ecosystems, there has been a growing call for the development of integrated assessment tools to support the provision of both tactical and strategic management advice. Of particular importance in this domain is the development of models that capture the dynamic interactions between social and economic systems, and marine ecosystems. In February 2013, a workshop jointly organised by the ICES working group on Integrative, Physical biological and Ecosystem Modelling and researchers attending the “Mathematics of Bio-economics” initiative, a contribution to the international event “Mathematics of Planet Earth 2013”, brought together experts to discuss recent advances and key methodological challenges posed by this field of research. The manuscript provides a brief report of the key points discussed during the workshop, including identification of the research which may help progress both the development of these modelling approaches and their application to actual management decision problems.  
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  ISSN 0308-597x ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 277  
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Auteur Travers, M.; Shin, Y.-J.; Jennings, S.; Machu, E.; Huggett, J.A.; Field, J.G.; Cury, P. url  doi
openurl 
  Titre Two-way coupling versus one-way forcing of plankton and fish models to predict ecosystem changes in the Benguela Type Article scientifique
  Année 2009 Publication (up) Revue Abrégée Ecological Modelling  
  Volume 220 Numéro 21 Pages 3089-3099  
  Mots-Clés Benguela upwelling; Ecem 07; End-to-end approach; food web; marine; Marine ecosystem model coupling; Predation  
  Résumé 'End-to-end' models have been adopted in an attempt to capture more of the processes that influence the ecology of marine ecosystems and to make system wide predictions of the effects of fishing and climate change. Here, we develop an end-to-end model by coupling existing models that describe the dynamics of low (ROMS-N(2)P(2)Z(2)D(2)) and high trophic levels(OSMOSE). ROMS-N(2)P(2)Z(2)D(2) is a biogeochemical model representing phytoplankton and zooplankton seasonal dynamics forced by hydrodynamics in the Benguela upwelling ecosystem. OSMOSE is an individual-based model representing the dynamics of several species of fish, linked through opportunistic and size-based trophic interactions. The models are coupled through a two-way size-based predation process. Plankton provides prey for fish, and the effects of predation by fish on the plankton are described by a plankton mortality term that is variable in space and time. Using the end-to-end model, we compare the effects of two-way coupling versus one-way forcing of the fish model with the plankton biomass field. The fish-induced mortality on plankton is temporally variable, in part explained by seasonal changes in fish biomass. Inclusion of two-way feedback affects the seasonal dynamics of plankton groups and usually reduces the amplitude of variation in abundance (top-down effect). Forcing and coupling lead to different predicted food web structures owing to changes in the dominant food chain which is supported by plankton (bottom-up effect). Our comparisons of one-way forcing and two-way coupling show how feedbacks may affect abundance, food web structure and food web function and emphasise the need to critically examine the consequences of different model architectures when seeking to predict the effects of fishing and climate change.  
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  ISSN 0304-3800 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 29  
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Auteur Duval, C.; Thomazeau, S.; Drelin, Y.; Yepremian, C.; Bouvy, M.; Couloux, A.; Troussellier, M.; Rousseau, F.; Bernard, C. doi  openurl
  Titre Phylogeny and salt-tolerance of freshwater Nostocales strains: Contribution to their systematics and evolution Type Article scientifique
  Année 2018 Publication (up) Revue Abrégée Harmful Algae  
  Volume 73 Numéro Pages 58-71  
  Mots-Clés baltic sea; bloom; comb. nova; Cyanobacteria; dolichospermum; genera anabaena; genetics analysis; great oxidation event; hetR; Morphology; nijH; Nostocaceae; Phylogeny; Physiology; planktonic cyanobacteria; polyphasic approach; Polyphasic approach; Salt-tolerance; toxin production  
  Résumé Phylogenetic relationships among heterocytous genera (the Nostocales order) have been profoundly modified since the use of polyphasic approaches that include molecular data. There is nonetheless still ample scope for improving phylogenetic delineations of genera with broad ecological distributions, particularly by integrating specimens from specific or up-to-now poorly sampled habitats. In this context, we studied 36 new isolates belonging to Chrysosporum, Dolichospermum, Anabaena, Anabaenopsis, and Cylindrospermopsis from freshwater ecosystems of Burkina-Faso, Senegal, and Mayotte Island. Studying strains from these habitats is of particular interest as we suspected different range of salt variations during underwent periods of drought in small ponds and lakes. Such salt variation may cause different adaptation to salinity. We then undertook a polyphasic approach, combining molecular phylogenies, morphological analyses, and physiological measurements of tolerance to salinity. Molecular phylogenies of 117 Nostocales sequences showed that the 36 studied strains were distributed in seven lineages: Dolichospermum, Chrysosporum, Cylindrospermopsis Raphidiopsis, Anabaenopsis, Anabaena sphaerica var tenuis/Sphaerospermopsis, and two independent Anabaena sphaerica lineages. Physiological data were congruent with molecular results supporting the separation into seven lineages. In an evolutionary context, salinity tolerance can be used as an integrative marker to reinforce the delineation of some cyanobacterial lineages. The history of this physiological trait contributes to a better understanding of processes leading to the divergence of cyanobacteria. In this study, most of the cyanobacterial strains isolated from freshwater environments were salt-tolerant, thus suggesting this trait constituted an ancestral trait of the heterocytous cyanobacteria and that it was probably lost two times secondarily and independently in the ancestor of Dolichospermum and of Cylindrospermopsis. (C) 2018 Elsevier B.V. All rights reserved.  
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  Langue English Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 1568-9883 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2341  
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Auteur Bundy, A.; Shannon, L.J.; Rochet, M.J.; Neira, S.; Shin, Y.-J.; Hill, L.; Aydin, K. url  doi
openurl 
  Titre The good(ish), the bad, and the ugly : a tripartite classification of ecosystem trends Type Article scientifique
  Année 2010 Publication (up) Revue Abrégée Ices Journal of Marine Science  
  Volume 67 Numéro Pages 745-768  
  Mots-Clés approach; classification; comparative; decision; ecosystem; ecosystems; exploited; indicator; marine; tree  
  Résumé Marine ecosystems have been exploited for a long time, growing increasingly vulnerable to collapse and irreversible change. How do we know when an ecosystem may be in danger? A measure of the status of individual stocks is only a partial gauge of its status, and does not include changes at the broader ecosystem level, to non-commercial species or to its structure or functioning. Six ecosystem indicators measuring trends over time were collated for 19 ecosystems, corresponding to four ecological attributes: resource potential, ecosystem structure and functioning, conservation of functional biodiversity, and ecosystem stability and resistance to perturbations. We explored the use of a decision-tree approach, a definition of initial ecosystem state (impacted or non-impacted), and the trends in the ecosystem indicators to classify the ecosystems into improving, stationary, and deteriorating. Ecosystem experts classified all ecosystems as impacted at the time of their initial state. Of these, 15 were diagnosed as “ugly”, because they had deteriorated from an already impacted state. Several also exhibited specific combinations of trends indicating “fishing down the foodweb”, reduction in size structure, reduction in diversity and stability, and changed productivity. The classification provides an initial evaluation for scientists, resource managers, stakeholders, and the general public of the concerning status of ecosystems globally.  
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  Langue Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 1054-3139 ISBN Médium  
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  Notes Approuvé pas de  
  Numéro d'Appel LL @ pixluser @ collection 60  
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