PRELIMINARY DATA ON THE NEAR-BOTTOM MESOZOOPLANKTONIC AND MACROZOOPLANKTONIC FAUNA FROM THE EASTERN BAY OF SEINE - FAUNISTIC COMPOSITION, VERTICAL-DISTRIBUTION AND DENSITY VARIATION

In the eastern Bay of Seine, just in front of the Seine estuary, two s eries of samples were collected in June 1992 with a new version of the Macer-GIROQ suprabenthic sledge, using 0.5 mm mesh size plankton nets . Chaetognaths, ctenophores and copepods (holoplankton), fish postlarv ae, polychaete and crustacean larvae (meroplankton) were sorted, count ed and identified. The most abundant taxa of the near-bottom meso- and macrozoo-planktonic fauna were copepods, the ctenophore Pleurobrachia pileus, larvae of crustaceans and the polychaete Lanice conchilega, p ostlarvae of clupeids, gobiids. Three patterns of density variations w ere found: (1) dominance of diurnal vertical migrations, with high abu ndances near the bottom around sunset and sunrise, e.g. clupeid postla rvae; (2) dominance of tidal advections, with maximal abundances durin g flood tide, e.g. gobiid postlarvae, or during ebb tide, e.g. Pleurob rachia pileus; and (3) a combination of tidal advections and diurnal m igrations, e.g. copepods.