ASSESSMENT OF BENTHIC STRUCTURE IN THE BA Y OF BREST

Shallow-water macrofaunal assemblages were studied over several years in the Bay of Brest. Sampling stations were located on extremely shall ow (< 5 m) mud banks. Some of the stations were chosen in order to stu dy the impact of the main sources of urban, industrial perturbations. Others were located remote from such sources. The analytic method used to assess the ecological health of different benthic structures is ba sed on the recognition of ecological groups of different sensitivity t o pollution. Their relative abundances allow seven stages of perturbat ion to be identified. Heavily polluted areas are easily identified, bu t our method also allows the first signs of imbalance to be discerned, essentially related to eutrophication. With respect to the latter, qu ite different situations were shown for the northern and southern basi ns.