Considerations on the ecological role of wrack accumulations on sandy beaches in the Maltese Islands and recommendations for their conservation management

Abstract

Beaches in the Maltese Islands, as in others along the Mediterranean coast, receive copious annual inputs of Posidonia oceanica wrack. A seasonal survey of macrofaunal communities colonising the wrack beached on three groomed and three ungroomed Maltese beaches was made with the principal aim of identifying any significant community differences between the two types of beaches and, consequently, to make recommendations for the conservation management of the wrack resource. Beaches were sampled during the winter and summer of 2002 and 2003 using pitfall traps and coring. The macrofauna collected by coring belonged to fourteen main taxa; Gastropoda and Isopoda were the most represented in terms of individual abundance, and Coleoptera (mainly the families Staphylinidae and Histeridae) were the most species-diverse. Some taxa, such as Staphylinidae, as well as some species, such as the gastropod Truncatella subcylindrica, were only recorded from the wrack on the ungroomed beaches. NMDS ordination and analysis of dominance patterns showed that macrofaunal communities in aged wrack on ungroomed beaches were distinct from those in ‘young’ wrack accumulations on the regularly groomed beaches, with differences being attributed mainly to the conduction of grooming activities or otherwise, rather than to differences in substratum type.