Turnover of postlarval bivalves in sediments of tidal flats in Königshafen (German Wadden sea)

Abstract

After larval settlement, juvenile bivalves may rapidly re-enter the water column and attain secondary dispersal by byssus-drifting. In order to estimate the quantitative importance of byssus-drifting, the abundance of drifters in the water column, their re-entry into the sediment, and their density in the ambient sediment were measured simultaneously over 3 months on a tidal flat in Konigshafen near the Island of Sylt in the North Sea. Turnover of juvenile clamsMacoma balthica and cocklesCerastoderma edule was more than once per week in summer, showing strong short-term variability because of semi-lunar rhythms of drifting activity. While there is currently no evidence for active habitat selection in settlingM. balthica andC. edule larvae, it is suggested that habitat selection occurs following postlarval migrations.