Exotic Cirripedia (Balanomorpha) from Buoys off the Belgian Coast

Abstract

Between November 1997 and November 1999, 52 buoys from the Belgian coastal waters were inspected for sessile fouling macrofauna. The position of the buoys varied between 0 km and 25 km offshore. The period these buoys had been out at sea varied between 4 and 24 months. Upon 'landing' of each of these buoys, the sessile macrofauna was examined for the presence of non-indigenous cirriped species (Thoracica, Balanomorpha). A total of eleven species was found, nine of which are exotic for the region. Six of these, Balanus reticulatus, B. variegatus, B. trigonus, B. perforatus, Megabalanus coccopoma and M. tintinnabulum are new for the Belgian fauna. With the exception of B. perforatus and M. tintinnabulum these are also new autochthonous records for the Southern Bight of the North Sea. Other exotics include the species B. improvisus, B. amphitrite and Elminius modestus, which were introduced earlier and now form an integral part of the regional fauna. B. amphitrite used to occur only in artificially warmed waters and in harbours. Our records show that this species is currently capable of surviving in open coastal waters. The observation of gravid and 2-year old individuals of B. variegatus and M. coccopoma indicate that at least these two new exotic species might establish self-sustaining populations in the area. Except for B. perforatus, which is probably a southern vagrant, all these cirripeds were most likely introduced with ballast water or originated from larvae released from the fouling community on ships. Recent climate changes and the beneficial habitat of the buoys favour the introduction of exotic cirripeds.