Soft corals (Octocorallia, Alcyonacea) of the southern Red Sea

The species composition of soft corals of the families Tubiporidae, Alcyoniidae, Nephtheidae, and Xeniidae is presented for the Dahlak Archipelago (15-16degreesS) in the southern Red Sea in Eritrean waters. A comprehensive collection was made during several field trips (1993-2002) to various sites in this archipelago. Some unexamined specimens obtained during the Israeli South Red Sea expeditions (1962 and 1965) to the region were also included in the study. A systematic list of soft corals is presented, comprising 28 species based on the material and previous literature. The list includes five genera (Rhytisma, Sinularia, Paralemnalia, Scleronephthya, and Heteroxenia) and sixteen species recorded for the first time in the southern Red Sea. Seven of these species belong to the genus Sinularia and three to Ovabunda. All the species found belong to the Indo-Pacific faunistic province and have been previously recorded elsewhere in the Red Sea. A distinct north to south latitudinal diversity attenuation of soft corals at both the species and generic levels is evident in the Red Sea. This pattern can be at least partially attributed to differences in environmental conditions between the two extremities of the Red Sea, such as surface temperature, salinity, nutrient concentrations, and turbidity. The biogeographic setting of the southern Red Sea reefs, the gateway to the Indian Ocean, makes them a stimulating target for future research on soft corals. Such studies will contribute to our knowledge on the status of the reefs in this region and will include,a temporal scale to provide feedback on reef health for conservation purposes.