EFFECTS OF INDIVIDUAL BEHAVIORS, INTERINDIVIDUAL INTERACTIONS WITH ADULT PECTINARIA-KORENI AND OWENIA-FUSIFORMIS (ANNELIDA, POLYCHAETA), AND HYDRODYNAMISM ON PECTINARIA-KORENI RECRUITMENT

The English Channel is a megatidal sea characterized by large tidal cu rrents in which the larvae of Pectinaria koreni are dispersed on a lar ge spatial scale by tidal currents. They settle abundantly on a wide e daphic spectrum, but the populations of adults are confined to bays an d estuaries. Laboratory experiments under still water and flume flows showed that post-larvae of P. koreni were able to actively select a su itable substrate i) on a macrospatial scale by resuspending themselves in the water column; ii) on a microspatial scale by crawling at the s ediment surface. Adults also influenced the post-larvae habitat select ion. When post-larvae settle on a suitable sediment in presence of adu lts, they resuspend themselves immediately. This resuspension phenomen on is a consequence of bioturbation by the adults (subsurface deposit feeders) whose vertical movement and feeding activity are mainly depen dent on hydrodynamic conditions. However, in the presence of Owenia fu siformis adults (deposit/filter feeders), resuspension rates were weak . This recruitment facilitation might be interpreted as a limitation o f post-larval resuspension abilities, tubes in a gregarious distributi on stabilizing the sediment and resembling particle traps. The feeding behavior of O. fusiformis, which exhibited high plasticity in relatio n to hydrodynamism, also influenced the post-larvae response.