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Auteur Annasawmy, P.; Ternon, J.F.; Marsac, F.; Cherel, Y.; Behagle, N.; Roudaut, G.; Lebourges-Dhaussy, A.; Demarcq, H.; Moloney, C.L.; Jaquemet, S.; Menard, F. doi  openurl
  Titre Micronekton diel migration, community composition and trophic position within two biogeochemical provinces of the South West Indian Ocean: Insight from acoustics and stable isotopes Type Article scientifique
  Année 2018 Publication Revue Abrégée Deep-Sea Res. Part I-Oceanogr. Res. Pap.  
  Volume 138 Numéro Pages 85-97  
  Mots-Clés Diel vertical migration; East African Coastal province; equatorial atlantic; feeding ecology; Indian South Subtropical Gyre; large pelagic fishes; mesopelagic fishes; mesoscale features; Micronekton; mozambique channel; myctophid fishes; north-atlantic ocean; respiratory carbon; Trophic level; vertical-distribution  
  Résumé Spatial distribution, community composition and trophic roles of micronekton (crustaceans, fishes and squids) were investigated in the Indian South Subtropical Gyre (ISSG) province and the East African Coastal province (EAFR), by combining acoustic surveys, mid-water trawls and stable isotope analyses from scientific cruises conducted in 2009 and 2010. Mesopelagic micronekton performed diel vertical migrations in both provinces, from deep (400-740 m) to surface (0-200 m) layers at dusk and in the opposite direction at dawn, with some species migrating below 740 m. The EAFR province was more dynamic than the oligotrophic ISSG province, with enhanced eddy activity and enhanced yearly productivity. The active enrichment mechanisms in the EAFR, in terms of available primary production, led to high micronekton acoustic density (as a proxy of micronekton abundance) and large micronekton weight and abundance estimates from trawl data. Particulate organic matter in the EAFR exhibited greater enrichment in C-13 and N-15 compared to the ISSG and, consequently, tissues of selected micronekton organisms in the EAFR were more enriched in N-15 (higher delta N-15 values). In both provinces, micronekton encompassed a wide range of isotopic niches, with large overlaps between species. Micronekton and swordfish in the EAFR had an overlapping range of delta N-15 values, contrasting with the ISSG province where swordfish were two trophic levels higher than the sampled micronekton. Our results provide some evidence that the combined action of riverine input and the dynamics of eddies might influence productivity in the EAFR, and hence the abundance of micronekton and the enrichment of tissues in N-15, compared to the oligotrophic ISSG province.  
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  ISSN 0967-0637 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2431  
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Auteur Brochier, T.; Ecoutin, J.M.; de Morais, L.T.; Kaplan, D.M.; Lae, R. doi  openurl
  Titre A multi-agent ecosystem model for studying changes in a tropical estuarine fish assemblage within a marine protected area Type Article scientifique
  Année 2013 Publication Revue Abrégée Aquatic Living Resources  
  Volume 26 Numéro 02 Pages 147-158  
  Mots-Clés ecosystem model; Life history; marine protected area; Spill-over; trophic level; Tropical estuarine fish assemblage; West Africa  
  Résumé As marine protected areas (MPAs) are increasingly being utilised as a tool for fishery management, their impact on the food web needs to be fully understood. However, little is known about the effect of MPAs on fish assemblages, especially in the presence of different life history and ecological traits. Modelling the observed changes in fish population structures may provide a mechanistic understanding of fish assemblage dynamics. In addition, modelling allows a quantitative estimate of MPA spill-over. To achieve this purpose, we adapted an existing ecosystem model, OSMOSE (Object-oriented simulator of marine biodiversity exploitation), to the specific case of the presence of fish with multiple life histories. The adapted model can manage 4 main categories of life history identified in an estuary MPA: fish that (1) spend their entire life cycle locally, (2) are present only as juveniles, (3) enter the area as juveniles and stay permanently except during reproduction periods, which occur outside the estuary, and (4) are present occasionally and for a short time for foraging purposes. To take into account these specific life-history traits, the OSMOSE code was modified. This modelling approach was developed in the context of the Bamboung Bolong MPA, located in a mangrove area in the Sine-Saloum Delta, Senegal. This was the ideal case to develop our approach as there has been scientific monitoring of the fish population structure inside the MPA before fishery closure, providing a reference state, and continuous monitoring since the closure. Ecologically similar species were pooled by trophic traits into 15 groups that represented 97% of the total biomass. Lower trophic levels (LTL) were represented by 6 compartments. The biomass of the model species was calibrated to reproduce the reference situation before fishery closure. Model predictions of fish assemblage changes after fishery closure corresponding to the Bamboung MPA creation scenario were compared to field observations; in most cases the model reproduces observed changes in biomass (at least in direction). We suggest the existence of a “sanctuary effect”, that was not taken into account in the model, this could explain the observed increase in biomass of top predators not reproduced by the model. Finally, the annual MPA fish spill-over was estimated at 11 tons (~33% of the fish biomass) from the model output, mainly due to diffusive effects.  
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  Numéro d'Appel LL @ pixluser @ collection 298  
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Auteur Celeste Lopez-Abbate, M.; Molinero, J.-C.; Perillo, G.M.E.; Barria de Cao, M.S.; Pettigrosso, R.E.; Guinder, V.A.; Uibrig, R.; Berasategui, A.A.; Vitale, A.; Marcovecchio, J.E.; Hoffmeyer, M.S. doi  openurl
  Titre Long-term changes on estuarine ciliates linked with modifications on wind patterns and water turbidity Type Article scientifique
  Année 2019 Publication Revue Abrégée Mar. Environ. Res.  
  Volume 144 Numéro Pages 46-55  
  Mots-Clés Acartia tonsa; bahia-blanca estuary; biogenic carbon; community structure; diversity; driven; Estuaries; ocean acidification; Oligotrichs; sea-level; shallow; suspended clay; Tintinnids; Turbidity; variability; Wind  
  Résumé Planktonic ciliates constitute a fundamental component among microzooplankton and play a prominent role in carbon transport at the base of marine food webs. How these organisms respond to shifting environmental regimes is unclear and constitutes a current challenge under global ocean changes. Here we examine a multi-annual field survey covering 25 years in the Bahfa Blanca Estuary (Argentina), a shallow, flood-plain system dominated by wind and tidal energy. We found that the estuary experienced marked changes in wind dominant regimes and an increase in water turbidity driven from the joint effect of persistent long-fetch winds and the indirect effect of the Southern Annular Mode. Along with these changes, we found that zooplankton components, i.e. ciliates and the dominant estuarine copepod Acartia tonsa, showed a negative trend during the period 1986-2011. We showed that the combined effects of wind and turbidity with other environmental variables (chlorophyll, salinity and nutrients) consistently explained the variability of observed shifts. Tintinnids were more vulnerable to wind patterns and turbidity while showed a loss of synchrony with primary productivity. Water turbidity produced a dome-like pattern on tintinnids, oligotrichs and A. tonsa, implying that the highest abundance of organisms occurred under moderate values (similar to 50 NTU) of turbidity. In contrast, the response to wind patterns was not generalizable probably owing to species-specific traits. Observed trends denote that wind induced processes in shallow ecosystems with internal sources of suspended sediments, are essential on ciliate dynamics and that such effects can propagate trough the interannual variability of copepods.  
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  ISSN 0141-1136 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2546  
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Auteur Chassot, E.; Rouyer, T.; Trenkel, V.M.; Gascuel, D. url  doi
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  Titre Investigating trophic-level variability in Celtic Sea fish predators Type Article scientifique
  Année 2008 Publication Revue Abrégée Journal of Fish Biology  
  Volume 73 Numéro 4 Pages 763-781  
  Mots-Clés food web; Gam; Indicator; omnivory; Predation; Trophic level  
  Résumé The trophic level (TL) mean and variance, and the degree of omnivory for five Celtic Sea fish predators were estimated using a database of stomach content records characterized by a high level of taxonomic resolution. The predators occupied a high position in the food web, i.e. 4·75 for Atlantic cod Gadus morhua, 4·44 for haddock Melanogrammus aeglefinus, 4·88 for European hake Merluccius merluccius, 5·00 for megrim Lepidorhombus whiffiagonis and 5·27 for whiting Merlangius merlangus. The level of taxonomic resolution of the prey did not greatly affect mean TL predator values; an effect on variance was evident, low resolution masking intra-population variability in TL. Generalized additive models (GAM) were used to explain the variability of predator TL caused by environmental variables (International Council for the Exploration of the Sea, ICES, division and season) and predator characteristics (total length, LT). Significant year, location season and interaction effects were found for some species and with LT at the scale of ICES subdivision. The species-specific variability of TL could be due to spatio-temporal variations in prey availability and in predator selectivity following ontogenetic changes. Omnivorous fish TL was less affected by spatio-temporal variations. In addition, results showed that the omnivory index and TL variability provide dissimilar information on predator feeding strategy. Combining information on TL variability and omnivory allowed between within-individual and between-individual components contributing to trophic niche width to be separated and the type of generalization of fish predators to be identified.  
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  ISSN 1095-8649 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1674  
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Auteur Descombes, P.; Leprieur, F.; Albouy, C.; Heine, C.; Pellissier, L. doi  openurl
  Titre Spatial imprints of plate tectonics on extant richness of terrestrial vertebrates Type Article scientifique
  Année 2017 Publication Revue Abrégée J. Biogeogr.  
  Volume 44 Numéro 5 Pages 1185-1197  
  Mots-Clés american biotic interchange; amphibian; andean uplift; bird; climate-change; continental drift; diversification rates; diversity; global patterns; indo-pacific; large-scale patterns; madagascar; mammal; plate tectonics; sea-level; Southeast Asia; species richness; Wallace line; wallaces line  
  Résumé AimIn interaction with past climate changes, it is likely that plate tectonics contributed to the shaping of current global species diversity, but so far this has not been statistically quantified at the global level. Here, we tested whether plate tectonics since the breakup of Gondwana left an imprint on current patterns of species richness of amphibians, birds and mammals. LocationGlobal. MethodsWe reconstructed the absolute positions of continental plates since the Early Cretaceous and used this information to derive variables of latitudinal shifts and potential exchanges among landmasses that could have modulated species richness. Using a multi-model inference approach combining both contemporary and historical variables, we quantified the relative importance of variables related to plate tectonics in explaining the spatial variation of the richness of amphibians, birds and mammals. Next, we employed a moving window approach to test whether plate tectonics left a more marked imprint in specific regions. ResultsPlatetectonics left an imprint on current patterns of vertebrate species richness in geologically singular regions, especially in the Indo-Australian Archipelago and the region comprising eastern Africa and Madagascar. For birds and mammals, but not amphibians, we found a marked contrast in species richness across Australia and Southeast Asia and eastern Africa and Madagascar associated with plate tectonics. Moreover, the relationship between species richness and plate tectonics varied across taxonomic orders for birds and mammals. Main conclusionsWhile no general imprint of plate tectonics was detected at the global scale, our regional analysis highlighted a substantial role of geodynamics in shaping current patterns of vertebrate species richness in Southeast Asia and Madagascar. Future studies should integrate the full range of processes associated with plate tectonics, including orogeny, not considered here.  
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  ISSN 0305-0270 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2129  
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