Wild cyprids metamorphosing in vitro reveal the presence of Balanus amphitrite Darwin, 1854 in the German Bight basin

Balanus amphitrite has not been recorded in the German Bight until now. However, harbour water from the East Frisian Island Norderney contained cyprids identified as B. amphitrite. Following these observations in summer 2002 the search for adult individuals in the German Bight, especially in the harbour of Norderney was enhanced with regular inspections until 2007. The consistent absence of adult individuals indicates that the cyprids are unable to settle under the environmental conditions in the German Bight. In contrast, wild cyprids settled and metamorphosed spontaneously within one day after transfer into the laboratory, where the temperature of the untreated seawater was raised from 18 to 27[degree]C. The findings suggest that there is a threshold temperature critical for the successful recruitment of settling stages in the German Bight with the local water temperatures being currently too low.