Response of different benthic indices to diverse human pressures

International audienceThe interest in benthic indicators for soft-bottom marine communities has dramatically increased after a rather long period of relative stagnation due to the need for new tools to assess the status of marine waters, called for by the Clean Water Act and the Water Framework Directive. Our expertise on benthic communities has permitted us to gather a vast amount of data from diverse water bodies under unpolluted and polluted conditions (e.g., accidental oil spill, sewage, long-term anthropogenic estuarine constraints) in tidal estuaries, harbours, and on the coastal shelf from Atlantic Ocean and Mediterranean Sea. We compared the results of four biotic indices on the various available datasets: Shannon-Wiener H′ diversity, AMBI and BO2A, which divide the species into Ecological Groups, and ITI, which divides the species into trophic groups, and the agreement of Best Professional Judgement (BPJ) on the assessment of ecological conditions. Benthic indicators as "sentinel species", which is a particular species that by its presence or its relative abundance warns of possible unbalances in the surrounding environment or distortions in community functions, was also tested. Indicators, BPJ and opportunist sentinel species gave similar ECoQS for the different sampling sites. We discuss the use of Biological Indicators as 'objective' or 'subjective' alternatives for assessing soft-bottom communities, and propose to employ simple methods such as BPJ and taxonomy sufficiency in such diagnostic approaches