The deep-sea macrobenthos on the continental slope of the northwestern Mediterranean Sea: a quantitative approach

As part of the ECOMARGE operation (J.G.O.F.S. France), macrobenthic assemblages in the Toulon Canyon were described and quantified on the basis of sampling carried out between 250 and 2000 m depth on the Mediterranean continental slope. Results show that Mediterranean bathyal assemblages are made up mainly of continental shelf eurybathic species. The qualitative and quantitative composition of populations varies with depth on the slope and also varies with station position at equivalent depth, whether on the flanks or in the canyon channel. Various analyses have provided evidence on the factors responsible for this population distribution pattern. No single factor emerges as predominant, but rather a group of factors, which are related to the nature and origin of sediments and more particularly their grain size distribution, geochemical composition and mode of transportation and sedimentation (benthic nepheloid or originating from the water column), act in conjunction to determine the pattern. Comparison with ocean continental slopes shows that in the Mediterranean Sea the absence of tidal current modifies the trophic structure of the macrobenthic assemblages, which are characterized by a dominance of surface and subsurface deposit feeders as compared to a dominance of suspension feeders and carnivores in the upper and median part of the slope in the ocean. Surface dumping of dredge spoil at the canyon head and channelling of waste induces an increase of organic matter and pollutant concentrations in sediment from the upper part of the canyon channel but does not give rise to any marked population degradation

Analyse statistique de processus physiques et chimiques en océanologie c^otière à l'aide d'une méthode de régression et de classification par arbre décisionnel (Application à l'étude d'un milieu fortement perturbé : l'Etang de Berre)

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocAIX-MARSEILLE2-Stat.Mar. Endoume (130552206) / SudocSudocFranceF

Analyse multi-composantes de la diversité spécifique (applications aux peuplements marins)

Depuis de nombreuses années, la biodiversité suscite l intérêt croissant de la communauté civile et scientifique afin de l évaluer et de la préserver. Inscrit dans ce contexte, ce travail de thèse propose une approche méthodologique qui prend directement en compte le caractère multi-composantes de la diversité, dans la perspective d améliorer sa description et de favoriser sa gestion. Cette approche permet de retenir uniquement les indices de diversité qui s'avèrent complémentaires pour décrire différentes facettes de la diversité étudiée. Nos résultats constituent une information importante pour le suivi de la diversité spécifique de peuplements car elle peut contribuer à fournir une première liste réduite d indices et ainsi faciliter la description de ces systèmes. De façon générale, cette approche pourrait permettre une meilleure évaluation de la capacité des différents descripteurs utilisés dans une étude à servir d indicateurs du suivi des peuplements et des écosystèmes.For many years, biodiversity has been of growing interest, in both the lay and the scientific community, with regard to its assessment and preservation. In this context, the present study proposes a methodological framework which explicitly takes into account the multi-component character of diversity with the aim of improving diversity assessment and management. This approach allows to choose only complementary diversity indices that can serve to describe the various facets of the species diversity studied. Our results are important for monitoring the diversity of assemblages as it can serve as a basis for drawing up a preliminary shortlist of indices and thus facilitate the description of these systems. Finally, this approach could allow better assessment of the relative suitability of the various descriptors studied as indicators for monitoring settlements and ecosystems.AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocPARIS-Museum-Bib. d'ichtyologie (751052306) / SudocSudocFranceF

Coarse Vector Response Regression for long-term monitoring of ecosystems: revealing the causes of regime shifts in a brackish lagoon

Cover is the most frequently used measure for vegetation surveys. Generally, it is coded with the Abundance/ Dominance Braun-Blanquet's integer code, giving rise to data which are generally considered as ordinal. Since each one of these integers is associated with a whole interval of values, we argue that these codes actually convey more information than that of a simple order, and develop this point of view, considering them as imprecise data. To our knowledge, there is no ready-made method to investigate relation-ships between a vector of such responses and several explanatory variables. Consequently, we propose a three-step method for this purpose. These steps are: (1) randomly recover (through a probability associated with the assessor's subjectivity) possible "original numerical responses"; (2) cluster these numerical response vectors according to an appropriate metric, into an appropriate num-ber of groups; (3) average every variable conditionally to the classifier associated with step two, giving rise to "per group regression functions". This method is applied to explain with hydrological variables the abundance variations of Pota-mogeton pectinatus in a brackish lagoon (the Berre lagoon, Provence, France). We reveal the main relationships between P. pectinatus cover and fresh water inputs, salinity and nutrient abundance (nitrate and phosphate); the obtained results are compared to those from Canonical Correspondence Analysis. The proposed method is also tested on artificial data, similar to the original cover data

Identifying spatial relationships at multiple scales: principal coordinates of neighbour matrices (PCNM) and geostatiscal approaches

International audienc

Effects of geomorphological zones, reefs and seasons on coral reef fish communities of Reunion Island, Mascarene Archipelago, SW Indian Ocean

International audienc