QUANTITATIVE SAMPLING OF SOFT-BOTTOM MACROEPIFAUNA FOR ASSESSING THE BENTHIC SYSTEM IN THE BAY OF BREST (FRANCE)

Macroepifauna of mixed sediments was quantitatively studied at three s tations in the Bay of Brest. Samples were collected with the quantitat ive video dredge Aquareve II. Sampling performance varied from 6.1 to 55.6 m2 according to the mesh diameter of the net (10, 40, and 70 mm) and the quality and quantity of the hard structures lying on the botto m. The efficiency of the different sampling options is tested. The eco logical analysis shows differences between epifaunal assemblages, whic h are mainly explained by the characteristics of the ruggedness in eac h station. Ruggedness is defined in terms of quality and quantity of h ard structures (pebbles, gravel, shells, coraline algae and macroalgae ) lying on the sediment surface. Hard substrates act as microhabitats to the epifauna, providing sites for settlement to many suspension fee ders and shelter to vagile predators, particularly brachyuran decapods . The contribution of quantitative epifaunal data to overall modelling of benthic trophic food webs is later discussed.