Habitat characterization, anthropogenic impacts and conservation of rhodolith beds off southeastern Malta

Abstract

Rhodolith beds, including maerl, are structurally complex perennial habitats that support a high species diversity but are threatened by numerous human activities, particularly in the Mediterranean Sea. Despite their global ecological importance, increased research efforts are needed to facilitate development of effective measures to conserve these habitats. Two areas hosting rhodolith beds are known to occur off the coast of Malta (central Mediterranean), but only one has been previously studied. Through analysis of video footage collected from 56 different stations coupled with a desk study on human activities, the present study characterized the rhodolith bed located off the southeastern coast of Malta, including its extent, rhodolith morphotype composition, associated megabiota and impacts of anthropogenic activities thereon. The bed occurred at depths of 60–95 m and covered an area of approximately 200 km2, making it the second most extensive rhodolith area reported for the Mediterranean to date. It was dominated by spherical and branched rhodoliths whose cover reached a maximum of 74% but was more often <50%, similar to other Mediterranean rhodolith beds. A total of 84 different megafaunal species were recorded, suggesting that the diversity of megafauna associated with rhodolith bed habitats has been previously underestimated. A number of human activities, including extensive vessel anchoring and officially designated areas for aquaculture, bunkering and trawling, overlap with the mapped rhodolith distribution, highlighting the risk of habitat degradation. A holistic approach to the management of all the competing activities and interests relative to the southeastern coast of Malta that gives due consideration to this newly characterized rhodolith bed and the threats it faces is therefore recommended. The legal framework and policy recommendations for better conservation of rhodolith bed habitats in the Mediterranean and European Seas are also discussed.