Résumé
A challenge for the sustainable development of marine aquaculture is to determine the appropriate level of production that respects the ecological carrying capacity (ECC) of the receptor ecosystems. Most environmental thresholds have only been defined for temperate ecosystems, and very few studies have quantified impact thresholds in tropical environments. This presentation exposes results of a sampling campaign conducted in 2022 in Martinique. To quantify discharges from a fish farm (S. ocellatus), sediment traps were deployed at 0, 25, 50 and 150 m from the cages, along two transects (T1 and T2). Hydrodynamics and zootechnical data were also collected to model the environmental footprint of the farm with the NewDEPOMOD model. Grab samples were taken to analyze the structure and diversity of benthic communities, supplemented by sediment cores to analyze sediment physico-chemical parameters. Isotopic signatures of each compartment (fish feed, sediment trap materials and sediment) were also carried out to trace fish farming waste dispersion in the environment. Initial results of this study show that sedimentation rates are significantly higher at 0 m sites compared to other stations. Conversely, OM content in sediments was not significantly different between stations and transects. Isotopic signatures of OM from sediment trap samples ranged from -22.45 ± 0.57 to -18.77 ± 0.17 ‰ (δ13C ) and 3.18 ± 0.02 to 4.89 ± 0.29 ‰ (δ15N). Samples follow a clear gradient along both transects, with a depletion in δ13C and an enrichment in δ15N at 0 m. A similar but less marked pattern was also observed for δ13C and δ15N values of OM from the grab samples in the main current direction. Ongoing analyses (benthic communities structure, farm waste modelling) are in progress to explain and precise these observations.