Species and community distribution modeling is commonly used in ecology, biogeography and can constitute seminal conservation planning tools. However, available data, often compiled from ancient different campaigns, are restricted. This is a common case in low-access and little-investigated areas such as the Southern Ocean. Spatial (areas, strategies, sampling tools) and temporal heterogeneities (environmental changes over the sampling period) are present and influence the performance of modeling tools. Our work aims at testing the performance of widely used procedures (MaxEnt, BRT) to model the current distribution of four echinoid species with contrasted ecological niches over the Kerguelen plateau. Presence-only data were used. They were compiled from different campaigns (1872-2015) and might show significant heterogeneities. Model performance was first tested while comparing subsets with different occurrence numbers and spatial clustering. The influence of known environmental changes and projection quality were compared for the two algorithms. Accounting for these results, potential shifts in species distributions were modeled in accordance with the IPCC A1B scenarii (Intergovernmental Panel on Climate Change) for 2100 and 2200 and were compared to the magnitude of past changes (1955-2012).

Natural environments are increasingly affected by human activities since the early twentieth century. Both Polar Regions are particularly affected by those climate changes. The Southern Ocean plays a key role in global ocean circulation and global climate. It participated in the thermohaline circulation, which regulates the global climate. 

Marine environments in Kerguelen Islands were relatively little affected by human activities. The isotopic signatures δ13C δ15N of three species of sea urchins harvested in different environments, were analyzed to characterize their food strategies. A mapping of the trophic niche each species was performed by using the SIBER mixing model. This aim to study the trophic plasticity of these organisations and the possible interactions between them. The results show that there is no interaction between species due to their very different diets. However inter-area and inter-species differences have been identified. The isotopic values δ13C and δ15N will be sensitive to the physico-chemical conditions of the environment. A second mixture model is used, SIAR, to characterize the diet of S.diadema at Port Matha (-2m), but also C.nutrix and S.diadema of Ilot des Trois Bergers (-20m). The C.nutrix will favor sponges, S.diadema feed from different sources (sponges, algae, sediment). 

Few studies have been interested on environmental changes in Austral Ocean. The Kerguelen Islands important for marine currents are interesting for assessing these impacts on marine biodiversity. Ctenocidaris nutrix is an urchin providing micro-habitats for some organisms from his environment. Two populations of urchins were sampled at two different sites, Ile Haute and Ile Suhm, with the aim of analyzing if the two populations belong to the same species. Stable isotopic ratios (δ13C, δ15N) provide a representation of trophic niche of the two populations of C.nutrix. The isotopic mixing model (SIAR) characterizes the plasticity, position of organisms within the trophic network and their diet. The two populations have distinct trophic niches, supported by morphological and isotopic divergences and varied diets. Gut contents were analyzed and supports variations in urchin diet. Genetic analyzes are planned to confirm phenotypic and trophic differences between the two populations and it would permit to conclude whether the two populations belong to the same species.