Distribution, abundance and size of Lophelia pertusa coral reefs in mid-Norway in relation to seabed characteristics

Abstract

This paper presents results on the distribution, abundance, and size of Lophelia pertusa coral reefs in mid-Norway (62°30&;–65°30&;N) as compiled from own investigations, earlier scientific reports, reports from fishery surveys and fishermen. Detailed bathymetrical mapping covering an area of ∼600 km2 along the Halten gas-pipeline, and two nearby areas across the shelf revealed 70 Lophelia reefs. In general, the reefs occurred close to breaks and escarpments. High densities of up to nine reefs per km2 were found in areas with a rugged seabed topography and with a slope >0·6°. These seabed features have probably positive influence on the transport and concentration of food particles and thus control the local distribution of Lophelia. The area covered by individual reefs varied between 1230 m2 and 37,310 m2 with a mean of 5628 m2. The height of the reefs was positively correlated with the area. Reefs <10,000 m2 had a circular outline, while larger reefs were elongate, aligned parallel to the depth contours. Along the pipeline the average density of Lophelia reefs was 0·09 km−2 which indicates that the total number of reefs is ∼6300, covering ∼35 km2 within the whole study area.