Before-After analysis of the trophic network of an experimental dumping site in the eastern part of the Bay of Seine (English Channel)

International audienceAn experimental study was conducted to assess the physical and biological impacts of muddy fine sand 3 dredged material dumped on a medium sand site MACHU offshore the Seine Estuary. Complementary 4 trophic web modelling tools were applied to the MACHU ecosystem to analyse the effects of dumping 5 operations. Results show that, after the dumping operations, the biomass of fish increased while 6 invertebrate biomass remained relatively stable through time. Nevertheless, the biomasses of benthic 7 invertebrates, omnivores/scavengers and predators showed some increases, while non-selective 8 deposit feeders and filter feeders decreased. At the ecosystem level, results show that the total 9 ecosystem activity, the ascendency and the overall omnivorous character of the food-web structure 10 increased after dumping operations, whereas recycling subsequently decreased. Finally, the fine and 11 medium sand habitat offshore from the Seine estuary, which undergoes regular natural physical 12 perturbations, shows a high resilience after a short dumping phase. 1