Bionomie benthique subtidale en Baie de Douarnenez

Following a preliminary mapping survey using a combination of acoustic techniques, spatial patterns of sedimentologic and biological characteristics of the Bay of Douarnenez were studied in 2001 from a series of grab samples and underwater video recording aiming at calibrate the acoustic facies of the bottom and at characterized them from a biological point of view. Results obtained from community structure analysis showed that four principal ecological groups dominate : The coarse sands community with Branchiostoma lanceolatum, Glycymeris glycymeris and Glycera lapidum, the fine to medium sand community with Nephtys cirrosa, Ophelia borealis and Gastrosaccus spinifer, the mixed muddy sand and gravel community with Amphiura filiformis, Edwardsia sp. and Lumbrinereis gracilis and finally, the fine to very fine sand community with Tellina fabula, Paradoneis armata and Chamelea striatula. In addition, video recording transects, revealed a high diversity and abundance of vagile echinodermata: starfishes, urchins, sea cucumber and very frequently, very dense aggregates of ophiura (Ophiocomina nigra) on hard bottom substrates or in maerl beds, but in a way more dispersed in the neighborhoods.