Deep-water coral occurrences in the Strait of Gibraltar.

This study reports for the first time on the occurrences of deep-water coral species in the Spanish territorial waters of the Strait of Gibraltar. Based on an extensive dataset of 334 grab samples, 16 species of calcareous corals have been identified in water depths between 13–443 m. Scleractinian corals form the dominant benthic community between 140–330 m water depth. The corals appear on the seabed both as solitary individuals and as patches on small biological topographic build-ups. The most common coral species Lophelia pertusa and Madrepora oculata are associated with coarse-grained calcareous sediments and mound structures. In the shallowest part of the study area (<150 m) algae and bryozoans are dominant and only a few coral species are observed. This zonation and the occurrence of the azooxanthellate corals in the Strait of Gibraltar relates to light availability and perhaps also to the complex interaction between the outflow of Mediterranean water and surficial inflow of Atlantic water into the Mediterranean Sea. [ABSTRACT FROM AUTHOR]