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Auteur Araújo Abrantes de Figueiredo, G.G.; Schwamborn, R.; Bertrand, A.; Munaron, J.-M.; Le Loc'h, F. doi  openurl
  Titre Body size and stable isotope composition of zooplankton in the western tropical Atlantic Type Article scientifique
  Année 2020 Publication Revue Abrégée J. Mar. Syst.  
  Volume 212 Numéro Pages 103449  
  Mots-Clés carbon; delta C-13; delta N-15; fatty-acid; fractionated zooplankton; mesozooplankton; nitrogen isotope; north pacific; particulate organic-matter; patterns; pelagic food-web; Plankton; Predator/prey mass ratio; shelf-slope; Size classes; Trophic level  
  Résumé Size-based approaches are paramount tools for the study of marine food webs. Here, we investigated the relationship between zooplankton body size, stable isotope composition and trophic level (TL) along a large-scale onshore-offshore gradient in the western tropical Atlantic. Samples were obtained on the Brazilian continental shelf, slope and in oceanic waters (off Fernando de Noronha archipelago and Rocas Atoll) in September and October 2015. Zooplankton was sieved into five size fractions. Zooplankton was dominated by copepods, except for the largest (> 2000 mu m) size fraction, that showed a high biovolume of chaetognaths, decapods, and fish larvae. Maximum zooplankton abundance and biovolume was found at the continental slope. POM showed consistently lower delta C-13 than zooplankton, indicating a selective use of C-13-rich primary food sources by zooplankton. Particulate organic matter (POM) was more C-13-enriched in shelf areas (average: -22.8, -23.6 and -24.3% at the shelf, slope and oceanic islands, respectively), probably due to the higher abundance of diatoms nearshore. POM had delta N-15 values between 2.5 and 6.9% (average: 4.0, 4.9 and 4.2% at the shelf, slope and oceanic islands, respectively). Zooplankton delta N-15 and TL increased with body size. The delta N-15 of the 200-500 mu m size fraction was used as baseline for TL estimation. Oceanic areas (average baseline delta N-15 = 5.8% +/- 0.52, n = 14) showed a higher baseline delta N-15 than the shelf (average = 3.9% +/- 0.69, n = 9) and the slope areas (average = 3.1% +/- 0.93, n = 9). In spite of differing baselines, the delta N-15 data produced a consistent pattern of log-linear increase in TL with increasing size, in all areas. The choice of input trophic enrichment factor (TEF) values only slightly changed the log10 (body size) vs TL slopes, but this choice had a considerable effect on the estimates of predator/prey size ratio (PPSR) and predator/prey mass ratio (PPMR). Using a TEF above 2.3 leads to unrealistic PPSR and PPMR estimates. Overall average slope was 0.59 +/- 0.08 TL mu m(-1) with TEF = 2.3 and 0.42 +/- 0.07 TL mu m(-1) with TEF = 3.2.  
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  ISSN 0924-7963 ISBN Médium (up)  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2884  
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Auteur Planque, B.; Mullon, C. doi  openurl
  Titre Modelling chance and necessity in natural systems Type Article scientifique
  Année 2020 Publication Revue Abrégée ICES J. Mar. Sci.  
  Volume 77 Numéro 4 Pages 1573-1588  
  Mots-Clés chaos; chaos theory; comanagement; community management; complexity; constraints; fisheries management; food-web dynamics; marine ecosystems; nonlinear systems; parametric management; participatory modelling; recruitment; time; uncertainty; viability theory  
  Résumé Nearly 30 years ago, emerged the concept of deterministic chaos. With it came sensitivity to initial conditions, nonlinearities, and strange attractors. This constituted a paradigm shift that profoundly altered how numerical modellers approached dynamic systems. It also provided an opportunity to resolve a situation of mutual misunderstanding between scientists and non-scientists about uncertainties and predictability in natural systems. Our proposition is that this issue can be addressed in an original way which involves modelling based on the principles of chance and necessity (CaN). We outline the conceptual and mathematical principles of CaN models and present an application of the model to the Barents Sea food-web. Because CaN models rely on concepts easily grasped by all actors, because they are explicit about knowns and unknowns and because the interpretation of their results is simple without being prescriptive, they can be used in a context of participatory management. We propose that, three decades after the emergence of chaos theories, CaN can be a practical step to reconcile scientists and non-scientists around the modelling of structurally and dynamically complex natural systems, and significantly contribute to ecosystem-based fisheries management.  
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  ISSN 1054-3139 ISBN Médium (up)  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2888  
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Auteur Valls, A.; Coll, M.; Christensen, V. url  doi
openurl 
  Titre Keystone species : toward an operational concept for marine biodiversity conservation Type Article scientifique
  Année 2015 Publication Ecological Monographs Revue Abrégée  
  Volume 85 Numéro 1 Pages 29-47  
  Mots-Clés classification tree; Ecopath model; food-web structure; index of keystoneness; keystone species; marine ecosystems; Meta-analysis; mixed-trophic impact; rank correlation tests; scoring method  
  Résumé Various definitions and indices have been proposed in the literature to identify keystone species. In this study, we intended to make the concept of keystone species operational for marine biodiversity conservation. We used an exclusive definition of keystone species, based on the original concept of keystone predator, and derived a new functional index of keystoneness (KS) from an ecosystem-modeling approach. First, several KS indices were formulated, by combining measures of the mixed-trophic impact (MTI) and biomass of species. Then, a meta-analysis was performed, based on 101 published Ecopath food-web models, selected with a scoring method, and representative of the variety of marine ecosystems worldwide. The indices were applied to the models, and two statistical methods were compared to select the most promising KS index. Rank correlation tests were performed to assess the balance between the contribution of the impact and biomass components to the different KS indices. In addition, a classification tree was implemented, based on ecosystem-specific thresholds applied to the latter species traits, and used to confirm the identified keystone species. The selected index obtained the highest number of models with positive results from both the rank correlation tests and the classification tree. We also demonstrated the limitations of existing KS indices previously applied in the literature. Species were ranked according to their estimates of keystoneness with the selected KS index, so that potential keystone species were quantitatively identified in the 101 modeled food webs. The standardized modeling approach allowed for a comparison of the identified keystone species across models: cartilaginous fishes and toothed whales obtained the highest occurrences. Finally, the selected KS index was applied to the well-known case study of Prince William Sound (Alaska, USA). Potentially significant anthropogenic (fishing) impacts on keystone species were also considered and discussed. The operational methodology presented is directly applicable to marine food webs, and may be adapted to other (freshwater or terrestrial) systems.  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1114  
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Auteur Danovaro, R.; Fanelli, E.; Canals, M.; Ciuffardi, T.; Fabri, M.-C.; Taviani, M.; Argyrou, M.; Azzurro, E.; Bianchelli, S.; Cantafaro, A.; Carugati, L.; Corinaldesi, C.; de Haan, W.P.; Dell'Anno, A.; Evans, J.; Foglini, F.; Galil, B.; Gianni, M.; Goren, M.; Greco, S.; Grimalt, J.; Guell-Bujons, Q.; Jadaud, A.; Knittweis, L.; Lopez, J.L.; Sanchez-Vidal, A.; Schembri, P.J.; Snelgrove, P.; Vaz, S. doi  openurl
  Titre Towards a marine strategy for the deep Mediterranean Sea: Analysis of current ecological status Type Article scientifique
  Année 2020 Publication Revue Abrégée Mar. Pol.  
  Volume 112 Numéro Pages 103781  
  Mots-Clés atmospheric deposition; Deep-sea ecosystems; downward particle fluxes; food-web structure; Marine strategy framework directive; Mediterranean basin; mercury bioaccumulation; particulate matter; polycyclic aromatic-hydrocarbons; seismic surveys; stable-isotopes; submarine canyons; trophic ecology  
  Résumé The Marine Strategy Framework Directive (MSFD), introduced in June 2008, was adopted to achieve a Good Environmental Status (GES) in the Ell's marine waters and to protect resources of socio-economic interest. The MSFD exerts to the marine area over which a Member State exercises jurisdictional rights in accordance with the United Nations Convention on the Law of the Sea (UNCLOS), including the deep-sea waters, seafloor and subseafloor of the Exclusive Economic Zones (EEZ). However, currently the MSFD focuses on coastal habitats and the shallow-water seafloor to the detriment of the deeper habitats. Despite the huge dimension of the deep sea (below 200 m of depth) covering more than 65% of the Earth's surface and including >95% of the global biosphere, the relevance of the dark portion of the seas and oceans is still almost completely neglected. Given the important bi-directional links between shallow and deep ecosystems, there is a clear need for extending the implementation of the MSFD into the deep sea, to define a sound ecosystem-based approach for the management and protection of deep-sea ecosystems and attain GES. We assembled data on drivers, anthropogenic pressures and impacts concerning the MSFD descriptors pertaining to the Mediterranean deep sea. We list deep-sea monitoring activities and the main sources providing benchmark conditions, and discuss knowledge and geographic coverage gaps. MSFD descriptors apply to the deep sea as to coastal waters, and ought to be monitored contemporaneously. We provide recommendations for guidelines for future deep-sea monitoring in the Mediterranean Sea.  
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  ISSN 0308-597x ISBN Médium (up)  
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  Notes WOS:000515208000012 Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2749  
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Auteur Meddeb, M.; Grami, B.; Chaalali, A.; Haraldsson, M.; Niquil, N.; Pringault, O.; Sakka Hlaili, A. url  doi
openurl 
  Titre Plankton food-web functioning in anthropogenically impacted coastal waters (SW Mediterranean Sea): an ecological network analysis Type Article scientifique
  Année 2018 Publication Revue Abrégée Progress in Oceanography  
  Volume Numéro Pages  
  Mots-Clés Ecological Network Analysis; Food-web modelling; Mediterranean coastal waters; plankton ecology  
  Résumé The study is the first attempt to (i) model spring food webs in three SW Mediterranean ecosystems which are under different anthropogenic pressures and (ii) to project the consequence of this stress on their function. Linear inverse models were built using the Monte Carlo method coupled with Markov Chains to characterize the food-web status of the Lagoon, the Channel (inshore waters under high eutrophication and chemical contamination) and the Bay of Bizerte (offshore waters under less anthropogenic pressure). Ecological network analysis was used for the description of structural and functional properties of each food web and for inter-ecosystem comparisons. Our results showed that more carbon was produced by phytoplankton in the inshore waters (966–1234 mg C m-2 d-1) compared to the Bay (727 mg C m-2 d-1). The total ecosystem carbon inputs into the three food webs was supported by high primary production, which was mainly due to >10µm algae. However, the three carbon pathways were characterized by low detritivory and a high herbivory which was mainly assigned to protozooplankton. This latter was efficient in channelling biogenic carbon. In the Lagoon and the Channel, foods webs acted almost as a multivorous structure with a tendency towards herbivorous one, whereas in the Bay the herbivorous pathway was more dominant. Ecological indices revealed that the Lagoon and the Channel food webs/systems had high total system throughput and thus were more active than the Bay. The Bay food web, which had a high relative ascendency value, was more organized and specialized. This inter–ecosystem difference could be due to the varying levels of anthropogenic impact among sites. Indeed, the low value of Finn’s cycling index indicated that the three systems are disturbed, but the Lagoon and the Channel, with low average path lengths, appeared to be more stressed, as both sites have undergone higher chemical pollution and nutrient loading. This study shows that ecosystem models combined with ecological indices provide a powerful approach to detect change in environmental status and anthropogenic impacts.  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2292  
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