Agricultural uses, continental inputs and temporal dynamics of eukaryotic taxa in a marine critical transition zone of the Petit Cul-de-Sac Marin (Guadeloupe) ; Usages agricoles, apports continentaux et dynamique temporelle des taxons eucaryotes dans une zone de transition critique marine du Petit Cul-de-Sac Marin (Guadeloupe)

International audience ; A first study by Pierre Sabatier and colleagues (co-funded by the OHM Littoral Caraïbe, APR 2018 and 2019) analyzed core sediments from both Guadeloupe and Martinique (French West Indies), and showed that the widespread use of a non-specific systemic herbicide (glyphosate) at the end of the years 1990 has induced an unprecedented rise in soil erosion and a major release of persistent chlordecone pesticides that were trapped in banana field soils. We have now studied the implications of these agricultural usages and environmental consequences on the dynamics of the eukaryotic biodiversity using a metabarcoding approach. We show that both the OTU richness and the diversity were significantly higher in samples corresponding to the period 2001-2017 which is characterized by a fast sedimentation rate (FSR), compared to the period 1950-2000 which is characterized by a slow sedimentation rate (SSR). Temporal analyses demonstrated that during the FSR period the relative read abundances of several classes were significant increasing over time while over were decreasing. On the contrary the same classes demonstrated a relative stability over the second half of the 20th century. Combined to temporal analyses of the alpha and beta diversity we could capture the ongoing temporal changes in eukaryotic community composition in a way that probably reflects the ecological processes and the ecosystem functions that are involved. Overall, our results show a correlation between concentration of pollutants from agricultural usages, modifications of the land erosion processes and compositional reorganizations over the two last decades in a critical transition zone located close to the most anthropized area of Guadeloupe ; Des premières études de Pierre Sabatier et ses collègues (cofinancées par l'OHM Littoral Caraïbe, APR 2018 et 2019) qui ont analysé des carottes de sédiments à la fois en Guadeloupe et en Martinique (Antilles Françaises), ont montré que l'utilisation généralisée d'un herbicide systémique non ...