Coral disease outbreak in the Florida Keys: Plague Type II

A coral disease characterized by a novel pattern of rapid tissue destructio n first appeared on reefs of the middle Florida Keys in June 1995. Between June and October 1995 the disease infected 17 species of scleractinian cora ls and the hydrocoral Millepora alcicornis. Localized populations of Dichoc oenia stokesi, the species most affected, revealed up to 38% mortality. Man y colonies exhibited complete tissue loss within days as the disease moved across colonies at rates of up to 2 cm per 24 hr. Typically tissue loss was initiated at the base of the colony and moved upward. At times disease pro gression halted and colonies retained partial tissue resembling a cap on th e top of an otherwise denuded colony. Laboratory cultures of samples from t he disease line revealed a dominant bacterium that, when isolated and chara cterized using genetic and metabolic techniques,most closely matched the ge nus Sphingomonas. Pure laboratory cultures of the bacterium produced diseas e in freshly collected coral colonies incubated in laboratory aquaria. The disease that we call plague type II appeared on different reefs of south Fl orida and the Florida Keys in 1996 and 1997. While coral mortality associat ed with each of the three outbreaks was regionally confined and did not rec ur in subsequent years on the same reefs, the high mortality rates distingu ish this disease as one of the most serious yet documented.