SCIENTIA MARINA 79(1) March 2015, 125-135, Barcelona (Spain) ISSN-L: 0214-8358 doi: http://dx.doi.org/10.3989/scimar.04120.09A Composition and abundance of octocorals in the Sea of Marmara, where the Mediterranean meets the Black Sea Eda N. Topçu 1,2, Bayram Öztürk 1,2 1 Istanbul University Fisheries Faculty, Ordu cad No 200 Laleli, 34470 Istanbul, Turkey. E-mail:
[email protected] 2 Turkish Marine Research Foundation, No 10, Beykoz, 81650, Istanbul, Turkey. Summary: Species composition and abundance of octocoral assemblages were investigated in the Sea of Marmara, which forms the connection between the Mediterranean and the Black Seas, two semi-enclosed seas with peculiar oceanographic conditions. Fourteen octocoral species were collected in the saline layer of the Marmara Sea (20-40 m), with a mean coral abundance of 5.21±5.11 colonies m–2 (mean ± SD) calculated from a total of 1390 colonies counted in transects. In spite of severe anthropogenic disturbances, dense assemblages of corals/gorgonians were observed during this study. The coral- ligenous communities—one of the most valuable structures of the Mediterranean Sea—harbored either Eunicella cavolini or Paramuricea macrospina as the dominant gorgonian in the Marmara Sea. Furthermore, the gorgonian assemblages of the Marmara Sea differed from those of the Mediterranean in their high abundance of P. macrospina and Spinimuricea klavereni, two species rarely encountered in the Mediterranean Sea at the studied depth range. The factors behind the observed differ- ences are discussed in regard to the particular oceanographic conditions of the Marmara Sea. Finally, we revised the main threats to corals/gorgonians in the Marmara Sea and provided some insights on management recommendations for coral conservation in this area.