Monitoring the coral disease, plague type two, on coral reefs in St. John, U.S. Virgin Islands

Miller, J.; Rogers, C.; Waara, R.; National Park Service; US Geologic Survey

In July 1997, conspicuous white patches of necrotic tissue began to appear on scleractinian corals in several bays around St. John, US Virgin Islands. Analysis of diseased coral tissue from five different species confirmed the presence of Sphingomonas, the pathogen for plague type II. To date, 14 species of hard corals have been affected by plague type II around St. John. This disease was monitored at Haulover and Tektite Reefs at depths ranging from 7-12 meters. The study site at Tektite Reef is a nearly monospecific stand of Montastraea annularis with percent cover by hard coral of >50%. Monthly surveys at Tektite Reef from December 1997 to May 2001 documented new incidence of disease (bare white patches of skeleton) every month with associated loss of living coral. The frequency of disease within transects ranged from 3 to 58%, and the area of disease patches ranged from 0.25 to 9000 cm2. The average percent cover by the disease ranged from 0.01% (± 0.04 SD) to 1.74% (± 9.08 SD). Photo-monitoring of 28 diseased corals of 9 species (begun in September 1997) at Haulover Reef (estimated hard coral cover 20%) revealed no recovery of diseased portions with all necrotic tissue being overgrown rapidly, usually within less than one month, by turf algae. Most coral colonies suffered partial mortality yet some colonies greater than 1.5 m in diameter were completely consumed in less than six months. Some limited recruitment (e.g., Agaricia spp., Favia spp. and sponges) has been noted on the diseased areas.

Monitoring the coral disease, plague type two, on coral reefs in St. John, U.S. Virgin Islands

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