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Auteur Heymans, J.J.; Coll, M.; Libralato, S.; Morissette, L.; Christensen, V.
Titre Global Patterns in Ecological Indicators of Marine Food Webs: A Modelling Approach Type Article scientifique
Année 2014 Publication Revue Abrégée PLoS ONE
Volume 9 Numéro 4 Pages
Mots-Clés
Résumé Background Ecological attributes estimated from food web models have the potential to be indicators of good environmental status given their capabilities to describe redundancy, food web changes, and sensitivity to fishing. They can be used as a baseline to show how they might be modified in the future with human impacts such as climate change, acidification, eutrophication, or overfishing. Methodology In this study ecological network analysis indicators of 105 marine food web models were tested for variation with traits such as ecosystem type, latitude, ocean basin, depth, size, time period, and exploitation state, whilst also considering structural properties of the models such as number of linkages, number of living functional groups or total number of functional groups as covariate factors. Principal findings Eight indicators were robust to model construction: relative ascendency; relative overhead; redundancy; total systems throughput (TST); primary production/TST; consumption/TST; export/TST; and total biomass of the community. Large-scale differences were seen in the ecosystems of the Atlantic and Pacific Oceans, with the Western Atlantic being more complex with an increased ability to mitigate impacts, while the Eastern Atlantic showed lower internal complexity. In addition, the Eastern Pacific was less organised than the Eastern Atlantic although both of these systems had increased primary production as eastern boundary current systems. Differences by ecosystem type highlighted coral reefs as having the largest energy flow and total biomass per unit of surface, while lagoons, estuaries, and bays had lower transfer efficiencies and higher recycling. These differences prevailed over time, although some traits changed with fishing intensity. Keystone groups were mainly higher trophic level species with mostly top-down effects, while structural/dominant groups were mainly lower trophic level groups (benthic primary producers such as seagrass and macroalgae, and invertebrates). Keystone groups were prevalent in estuarine or small/shallow systems, and in systems with reduced fishing pressure. Changes to the abundance of key functional groups might have significant implications for the functioning of ecosystems and should be avoided through management. Conclusion/significance Our results provide additional understanding of patterns of structural and functional indicators in different ecosystems. Ecosystem traits such as type, size, depth, and location need to be accounted for when setting reference levels as these affect absolute values of ecological indicators. Therefore, establishing absolute reference values for ecosystem indicators may not be suitable to the ecosystem-based, precautionary approach. Reference levels for ecosystem indicators should be developed for individual ecosystems or ecosystems with the same typologies (similar location, ecosystem type, etc.) and not benchmarked against all other ecosystems.
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Auteur Levin, N.; Coll, M.; Fraschetti, S.; Gal, G.; Giakoumi, S.; Gke, C.; Heymans, J.J.; Katsanevakis, S.; Mazor, T.; ztrk, B.; Rilov, G.; Gajewski, J.; Steenbeek, J.; Kark, S.
Titre REVIEW Biodiversity data requirements for systematic conservation planning in the Mediterranean Sea Type Article scientifique
Année 2014 Publication Revue Abrégée Mar Ecol Prog Ser
Volume 508 Numéro Pages 261-281
Mots-Clés
Résumé ABSTRACT: The Mediterranean Sea’s biodiversity and ecosystems face many threats due to anthropogenic pressures. Some of these include human population growth, coastal urbanization, accelerated human activities, and climate change. To enhance the formation of a science-based system of marine protected areas in the Mediterranean Sea, data on the spatial distribution of ecological features (abiotic variables, species, communities, habitats, and ecosystems) is required to inform conservation scientists and planners. However, the spatial data required is often lacking. In this review, we aimed to address the status of our knowledge for 3 major types of spatial information: bathymetry, classification of marine habitats, and species distributions. To exemplify the data gaps and approaches to bridge them, we examined case studies that systematically prioritize conservation in the Mediterranean Sea. We found that at present the data required for conservation planning is generally more readily available and of better quality for the European countries located in the Western Mediterranean Sea. Additionally, the Mediterranean Sea is lagging behind other marine regions where rigorous criteria for conservation planning has been applied in the past 20 yr. Therefore, we call upon scientists, governments, and international governmental and non-governmental organizations to harmonize current approaches in marine mapping and to develop a framework that is applicable throughout the Mediterranean region. Such coordination between stakeholders is urgently needed before more countries undertake further extensive habitat mapping, so that future conservation planning can use integrated spatial datasets.
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Numéro d'Appel LL @ pixluser @ collection 383
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Auteur Louw, G.G.; Freon, P.; Huse, G.; Lipinski, M.R.; Coetzee, J.C.
Titre Pelagic fish species assemblages in the southern Benguela Type Article scientifique
Année 2014 Publication Revue Abrégée African Journal of Marine Science
Volume 36 Numéro 1 Pages 69-84
Mots-Clés Engraulis encrasicolus (= E. capensis); Etrumeus whiteheadi; meeting; mixed shoals; oddity effect; pelagic assemblages; point hypothesis; Sardinops sagax; school trap hypothesis; Trachurus capensis
Résumé Patterns in the co-occurrence of small pelagic fish species within single shoals were investigated using data from 6 814 throws of commercial purse-seiners in South Africa. Assuming that the throw composition reflected the true composition of the assemblage, it was shown that: (1) mixed pelagic assemblages were as prevalent as pure shoals; (2) assemblages of anchovy Engraulis encrasicolus and sardine Sardinops sagax exhibited a seasonal distribution pattern; (3) there was a highly skewed species ratio in terms of abundance by mass; and (4) patterns in the size distributions of two-species shoals were complex and dependent on the L. and the relative abundance of the species concerned. We hypothesise that the observed patterns reflect the 'net gain of the subordinate', whereby fish occurring in small numbers are less conspicuous and/or less energetically attractive for potential predators if they are smaller than the dominant component of the school. If the subordinate fish grow larger than the dominant fish, this advantage persists. Potential sources of bias are alluded to but are not considered to have had a major impact on the conclusions reached, although they may form the basis for further work.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1154
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Auteur Schwerdtner Máñez, K.; Holm, P.; Blight, L.; Coll, M.; MacDiarmid, A.; Ojaveer, H.; Poulsen, B.; Tull, M.
Titre The Future of the Oceans Past: Towards a Global Marine Historical Research Initiative Type Article scientifique
Année 2014 Publication Revue Abrégée PLoS ONE
Volume 9 Numéro 7 Pages
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Résumé Historical research is playing an increasingly important role in marine sciences. Historical data are also used in policy making and marine resource management, and have helped to address the issue of shifting baselines for numerous species and ecosystems. Although many important research questions still remain unanswered, tremendous developments in conceptual and methodological approaches are expected to contribute to a comprehensive understanding of the global history of human interactions with life in the seas. Based on our experiences and knowledge from the “History of Marine Animal Populations” project, this paper identifies the emerging research topics for future historical marine research. It elaborates on concepts and tools which are expected to play a major role in answering these questions, and identifies geographical regions which deserve future attention from marine environmental historians and historical ecologists.
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Numéro d'Appel LL @ pixluser @ collection 387
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Auteur Bertrand, A.; Grados, D.; Colas, F.; Bertrand, S.; Capet, X.; Chaigneau, A.; Vargas, G.; Mousseigne, A.; Fablet, R.
Titre Broad impacts of fine-scale dynamics on seascape structure from zooplankton to seabirds Type Article scientifique
Année 2014 Publication Revue Abrégée Nat Commun
Volume 5 Numéro Pages
Mots-Clés Biological sciences; Ecology; Oceanography
Résumé In marine ecosystems, like most natural systems, patchiness is the rule. A characteristic of pelagic ecosystems is that their ‘substrate’ consists of constantly moving water masses, where ocean surface turbulence creates ephemeral oases. Identifying where and when hotspots occur and how predators manage those vagaries in their preyscape is challenging because wide-ranging observations are lacking. Here we use a unique data set, gathering high-resolution and wide-range acoustic and GPS-tracking data. We show that the upper ocean dynamics at scales less than 10 km play the foremost role in shaping the seascape from zooplankton to seabirds. Short internal waves (100 m–1 km) play a major role, while submesoscale (~1–20 km) and mesoscale (~20–100 km) turbulence have a comparatively modest effect. Predicted changes in surface stratification due to global change are expected to have an impact on the number and intensity of physical structures and thus biological interactions from plankton to top predators.
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Numéro d'Appel LL @ pixluser @ collection 389
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