Population turnover in the soft coral genera Sinularia and Sarcophyton on the Great Barrier Reef

Aspects of the life history of 2 common soft coral genera, Sinularia and Sarcophyton were investigated on 360 tagged colonies over 3.5 years. Measurements were carried out at 18 sites on 6 mid- (Centipede, Grub, Yankee) and outer-shelf reefs (Bowl, Coil, Dip) of the Great Barrier Reef and included rates of growth, colony fission, mortality, sublethal predation and algae infection. Photographic monitoring was carried out on [approximately] an additional 500 colonies from 16 genera.High numbers of the crown-of-thorns starfish, Acanthaster planci, had removed most of the hard coral cover on Grub, Yankee and Dip Reefs 5-8 years prior to the study, relieving soft corals from space competition with hard corals. The other 3 reefs in the study were little affected by Acanthaster planci and had high hard coral cover. Three sites were established on the windward sides of each reef at 10m depth, and percent hard and soft coral cover, current and wave exposure and slope angle were recorded. Turnover rates over the 40 month period were recorded as the proportion of colonies which: remained (R), disappeared (D), or appeared new (A). (The term, 'Colony Groups', was used for clusters of colonies in which the fate of individual colonies could not be followed due to high colony density or movement).
To investigate life history characteristics which might allow the 2 genera to achieve such prominence, and to assess the role of space competition with hard corals in population dynamics.
Soft coral species:Family Alcyoniidae (Cladiella, Lobophytum, Sarcophyton, Sinularia); Family Asterospiculariidae (Asterospicularia); Family Briareidae (Briareum); Family Clavulariidae (Clavularia); Family Isididae (Isis); Family Nephtheidae (Capnella, Dendronephthya, Lemnalia, Nephthya, Paralemnalia, Stereonephthya); Family Tubiporidae (Tubipora); Family Xeniidae (Efflatournaria, Xenia).