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International audience; Caribbean's rivers have a very original functioning due to their organization built around powerful altitudinal fluxes: material flows of terrestrial origin that have been shown to support the aquatic food webs and also biological flows between rivers and sea operated through the rivermouths that are needed to complete the life cycles of diadromous species living therein...to sum up, a very strong upstream/downstream subsidiarity. To date, few studies have taken into account the impacts of hydrothermal resurgences on freshwater macrofauna (curstaceans and fish) living in the Caribbean rivers. The data obtained highlight the interactions that may exist between river chemistry variability induced by fossil hydrothermalism and the aquatic community structure within a watershed (rivière Grande Plaine, Guadeloupe). The chemistry of the river watershed was characterized using classical analytical chemistry methods, such as ion chromatography and molecular absorption spectrometry. Based on a population dynamic approach, crustacean and fish communities were quantified in terms of « resident communities », which is an innovating aspect of this work. Chemical and biological variables were then coupled with statistical analysis. The results show a strong compartmentalization of fish and crustaceans resident communities in the river catchment, mainly explained by the variations in pH and dissolved silica content. Hydrothermal resurgences seemed to be an extremely structuring element in this river at the time of sampling, and this work opens up research hypotheses, particularly concerning the composition of the main producer of autochthonous organic matter, the epilithic biofilm, in systems submitted to hydrothermal influences.