North Atlantic rhodolith beds

Beds of coralline algal sediment form ecologically and economically important habitats in the North Atlantic. These habitats can occur from the intertidal down to 60 m depth, and they are locally abundant in several countries. Thirteen species of coralline algae form rhodoliths or maerl in this region; Lithothamnion corallioides, L. glaciale, L. tophiforme and Phymatolithon calcareum are the most widely recorded. The structure and biodiversity of these habitats is destroyed by dredging and can be degraded by towed demersal fishing gear and by mussel and salmon farming. Legislation has been passed in the European Union (EU) to protect P. calcareum and L. corallioides which should be extended to include the other maerl species from the region. Outside the EU there is a lack of baseline information concerning the importance of these habitats: a fuller understanding of their role may lead to protection in Scandinavia, Iceland and the Atlantic coasts of Canada and the United States. The design of such protected areas would need to consider the ongoing effects of invasive species, ocean warming and acidification.