Relative roles of bioerosion and typhoon-induced disturbance on the dynamics of a high latitude scleractinian coral community

Located at 22°N on the northern shore of the South China Sea, Hong Kong experiences a seasonal, monsoonal climate and its resident scleractinian corals, comprising some 50 species, live here at the limit of their ranges. Summers are hot and wet, winters cold and dry and this study was initiated to determine the effects of bioerosion and periodic episodes of strong wave action on coral death and beaching. Coral rubble washed up on Telecom Bay Beach in the Cape d'Aguilar Marine Reserve was collected every month from January 1996 until December 1997, inclusive. Quantities were greatest after typhoons and storms, with the average monthly weight of recently-living corals accounting for approximately 0.007%, by weight, of the total live coral in the bay. Seventeen species of Mollusca were recorded from within the skeletons of this rubble and included a new record for Hong Kong, Anchomasa yoshimurai (Pholadidae). Species of Lithophaga dominated, with highest mean abundances recorded from within Goniastrea aspera, the most abundant living coral in the bay and from within the heaviest fragments. The overall incidence of borers was, however, low although it appears that dead coral borers, notably the basally boring Lithophaga lima, act to weaken coral attachment resulting in dislodgement and beaching during and after storms. At this relatively unperturbated site, therefore, the significance of borers in weakening coral attachment with subsequent detachment and beaching during and after storms, respectively, is low, a situation also seen elsewhere.