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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 (down) 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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Auteur Grenie, M.; Mouillot, D.; Villeger, S.; Denelle, P.; Tucker, C.M.; Munoz, F.; Violle, C. doi  openurl
  Titre Functional rarity of coral reef fishes at the global scale: Hotspots and challenges for conservation Type Article scientifique
  Année (down) 2018 Publication Revue Abrégée Biol. Conserv.  
  Volume 226 Numéro Pages 288-299  
  Mots-Clés biodiversity; Biodiversity facet; Coral triangle; diversity; ecology; ecosystem processes; Evolutionary distinctiveness; Functional distinctiveness; Funrar; marine-protected areas; ocean acidification; redundancy; species richness; trait; vulnerability  
  Résumé Characterizing functional diversity has become central in ecological research and for biodiversity assessment. Understanding the role of species with rare traits, i.e. functionally rare species, in community assembly, ecosystem dynamics and functioning has recently gained momentum. However, functional rarity is still ignored in conservation strategies. Here, we quantified global functional and evolutionary rarity for 2073 species of coral reef fishes and compared the rarity values to IUCN Red List status. Most species were functionally common but geographically rare. However, we found very weak correlation between functional rarity and evolutionary rarity. Functional rarity was highest for species classified as not evaluated or threatened by the IUCN Red List. The location of functional rarity hotspots (Tropical Eastern Pacific) did not match hotspots of species richness and evolutionary distinctiveness (Indo-Australian Archipelago), nor the currently protected areas. We argue that functional rarity should be acknowledged for both species and site prioritization in conservation strategies.  
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  ISSN 0006-3207 ISBN Médium  
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Auteur Krichen, E.; Harmand, T.; Torrijos, M.; Godon, J.J.; Bernet, N.; Rapaport, A. doi  openurl
  Titre High biomass density promotes density-dependent microbial growth rate Type Article scientifique
  Année (down) 2018 Publication Revue Abrégée Biochem. Eng. J.  
  Volume 130 Numéro Pages 66-75  
  Mots-Clés culture; ecology; model; systems; Density-dependent growth rate; Flocculation; influent substrate concentration; kinetics; Mass balance models; Microbial ecosystem; Microbial ecosystem structure  
  Résumé Describing the interactions between a population and its resources is a research topic in both microbiology and population ecology. When there are fewer resources for the individuals in a large population, the overcrowding can lead to a density-dependent effect which is reflected by a negative feedback of the organism density on the consumption process. In this paper, we investigate the growth rate of an aerobic microbial ecosystem by two series of experiments performed in continuous agitated cultures. Using a constant dilution rate, but different input substrate concentrations in each experiment, the biomass and substrate concentration were measured at steady state to confront their values with those obtained theoretically from the well-known mathematical model of the chemostat using either resource or density-dependent kinetics. The structures of both flocs and microbial communities were monitored in order to interpret the results. The experiments confirm that density-dependent growth-rate can result either from a high concentration of biomass or from the structuration of this biomass into flocs and we have shown that a new parametrized family of growth functions, that we proposed in this paper, suits better the experimental data than Monod or Contois growth functions. (C) 2017 Elsevier B.V. All rights reserved.  
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  ISSN 1369-703x ISBN Médium  
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Auteur Reygondeau, G.; Guidi, L.; Beaugrand, G.; Henson, S.A.; Koubbi, P.; MacKenzie, B.R.; Sutton, T.T.; Fioroni, M.; Maury, O. doi  openurl
  Titre Global biogeochemical provinces of the mesopelagic zone Type Article scientifique
  Année (down) 2018 Publication Revue Abrégée J. Biogeogr.  
  Volume 45 Numéro 2 Pages 500-514  
  Mots-Clés community; classification; ecology; ocean; macroecology; biogeography; north-atlantic; export; biogeochemical provinces; environmental division; mesopelagic; objective methodology; Ocean; particle-size; Twilight zone; world  
  Résumé Aim: Following the biogeographical approach implemented by Longhurst for the epipelagic layer, we propose here to identify a biogeochemical 3-D partition for the mesopelagic layer. The resulting partition characterizes the main deep environmental biotopes and their vertical boundaries on a global scale, which can be used as a geographical and ecological framework for conservation biology, ecosystem-based management and for the design of oceanographic investigations. Location: The global ocean. Methods: Based on the most comprehensive environmental climatology available to date, which is both spatially and vertically resolved (seven environmental parameters), we applied a combination of clustering algorithms (c-means, k-means, partition around medoids and agglomerative with Ward's linkage) associated with a nonparametric environmental model to identify the vertical and spatial delineation of the mesopelagic layer. Results: First, we show via numerical interpretation that the vertical division of the pelagic zone varies and, hence, is not constant throughout the global ocean. Indeed, a latitudinal gradient is found between the epipelagic-mesopelagic and mesopelagic-bathypelagic vertical limits. Second, the mesopelagic layer is shown here to be composed of 13 distinguishable Biogeochemical Provinces. Each province shows a distinct range of environmental conditions and characteristic 3-D distributions. Main conclusions: The historical definition of the mesopelagic zone is here revisited to define a 3-D geographical framework and characterize all the deep environmental biotopes of the deep global ocean. According to the numerical interpretation of mesopelagic boundaries, we reveal that the vertical division of the zone is not constant over the global ocean (200-1,000 m) but varies between ocean basin and with latitude. We also provide evidence of biogeochemical division of the mesopelagic zone that is spatially structured in a similar way than the epipelagic in the shallow waters but varies in the deep owing to a change of the environmental driving factors.  
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  ISSN 0305-0270 ISBN Médium  
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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 (down) 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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  ISSN 0079-6611 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2292  
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