Amphipods are good bioindicators of the impact of oil spills on soft-bottom macrobenthic communities

The Amoco Cadiz oil spill in 1978, and the Aegean Sea oil spill in 1992, affected soft-bottom communities, respectively from the Bay of Morlaix (western English Channel) and from the Ria de Ares and Betanzos in the northwestern Iberian peninsula. These infralittoral communities on muddy fine sand showed similar species composition and structure and occurred in similar hydro-climatic conditions. The effects of the spills were identical in both areas with the disappearance of the amphipods especially those from the amphipod genus Ampelisca with a very low colonization of these species during the four years after the spill. The recovery rate of the amphipods was slow but progressive, In such communities no proliferation of opportunistics was observed after the stress. In the sites, where polychaetes dominated before the spill, they remained dominant, whereas other sites showed very low total abundances during the two years after the spill due to the absence of compensation for the disappearance of these crustaceans, In fact, there was a very low impact of the spill on polychaetes, but a high one on amphipods, In the future, it is suggested to focus monitoring after a spill only on a single amphipod group proposed as a bioindicator for detecting the impact of pollution. A polychaete/amphipod ratio is proposed to reflect temporal change of soft-bottom communities analogous to the nematode/copepod previously suggested for the meiobenthos, Detailed knowledge of the qualitative and quantitative structure of a benthic community is still needed in order to identify very precisely the effect of a pollution event. (C) 2000 Elsevier Science Ltd. All rights reserved.