Zoological Studies

Soft Coral (Cnidaria: Alcyonacea) Distribution Patterns in Thai Waters

Thanongsak Chanmethakul, Hansa Chansang, and Supareok Watanasit (2010) The aim of this study was to conduct a biodiversity survey of soft corals in Thai waters by focusing on genera richness, distribution, and ecological aspects.  The locations of the study were in 2 geographic regions: the Andaman Sea coast of Thailand and the Gulf of Thailand.  All of the study sites were surveyed in June 2004 - May 2006.  Soft corals of 4 families comprising 19 genera were found: Alcyoniidae: Sinularia, Dampia, Cladiella, Klyxum, Sarcophyton, Lobophytum, and Eleutherobia; Nephtheidae: Nephthea, Stereonepthya, Scleronephthya, Dendronephthya, and Umbellulifera; Nidaliidae: Nidalia, Siphonogorgia, Chironephthya, and Nepthyigorgia; and Xeniidae: Xenia, Heteroxenia, and Sansibia.  The Alcyoniidae was the dominant family in the Gulf of Thailand, whereas the Nephtheidae was the dominant family along the Andaman Sea coast of Thailand.  The 3 dominant genera were Sinularia, Dendronephthya, and Sarcophyton, while Nidalia, Nephthyigorgia and Heteroxenia were rare genera in this study.  This study suggests that different genera of soft corals show different habitat preferences.  Members of the Nephtheidae are widely distributed on rocky habitats rather than on true reefs, whereas members of the Alcyoniidae have a higher distribution on true reefs rather than on rocky habitats.  Soft corals are strongly site specific and are often found on reef slopes and lower zones.  The angle of the substrate has an influence on the distribution of soft corals as well, with the Alcyoniidae found on substrates with varying angles ranging from horizontal to ~90°.  In this study, azooxanthellate genera of the Neptheidae and Nidaliidae were found attached to substrates oriented at all angles.