Mass Mortality of a Coral Community in Ishigaki Island, Okinawa, Japan, Caused by the Discharge of Terrigenous Fine Particles

A mass mortality of coral communities dominated by Porites spp. was observed in the reef flats off the east coast of Ishigaki Island, Okinawa, Japan. Mortality was concentrated around the mouth of the Todoroki River, from which a large amount of terrigenous fine particles had been discharged during a heavy rain. Mortality was observed over an area of ca. 30 ha in early June 2001. Damaged corals included massive Porites and Favia, branching Montipora, and the blue coral Heliopora coerulea. The most conspicuous damage was evident in large colonies of Porites because of the abundance of this species in the area. Fine particles 0.5%) just after the mass-mortality event and decreased over time. This mass mortality was apparently caused by several simultaneously occurring factors, including low tide, unusually strong north winds, and heavy precipitation that caused extensive sediment runoff.