Differential recruitment of bivalve species in the northern Wadden Sea after the severe winter of 1995/96 and of subsequent milder winters
Enhanced recruitment of the bivalves Cerastoderma edule, Mytilus edulis, Macoma balthica and Mya arenaria after severe winters is an often reported phenomenon in the Wadden Sea. After the severe winter of 1995/96 Cerastoderma and Mytilus followed this pattern in the Sylt-Rømø Bigth. However, repeated sampling of Cerastoderma, Macoma and Mya following a severe (1995/96), a moderate (1996/97), and a mild winter (1997/98) revealed that recruitment started earlier and was initially highest after the mild winter. In Cerastoderma the eventual high reproductive success at the end of summer 1996 was caused by reduced benthic mortality. Low recruitment of Macoma and Mya after the severe winter may have been caused by a higher susceptibility to epibenthic predation and/or a higher susceptibility to passive re-suspension than in Cerastoderma and Mytilus. In all cases, post settlement processes were decisive for reproductive success.