TWENTY-FIFTH ANNUAL EASTERN FISH HEALTH WORKSHOP MARCH 10-13, 2000   The Incidence And Effect Of Yellow-Blotch Disease In The Southern Caribbean     Andrew W. Bruckner   NOAA/National Marine Fisheries Service, Office of Protected Resources, 1315 East West Highway, Silver Spring, MD   20910       A recent emergence of yellow-blotch disease (YBD) on reefs in Curaçao is causing widespread colony mortality to the susceptible scleractinian corals, Montastraea annularis, M. faveolata and M. franksi (star corals).  Yellow-blotch disease manifests as a pale, circular patch of translucent tissue surrounded by fully pigmented tissue, or as a narrow band of lightened tissue at the colony’s margin; no prominent area of clean, denuded skeleton is usually present. Repeat examination of tagged YBD-infected colonies demonstrates that this syndrome causes patterns of coral tissue mortality similar to that observed in other “band” diseases; however, the progression of the disease is significantly slower and the duration of individual infections may be longer. In all tagged corals, YBD progressively advanced over the coral’s surface, causing mortality at a rate of 7-15 cm per year. In addition, the disease spread from one colony to an adjacent colony or to an adjacent location on the same colony. Transects performed in June, 1997 from 12 locations around Curacao indicated that YBD was present on all reefs, regardless of depth, affecting 15-65% of all star coral colonies. Transects on four reefs were reexamined in August, 1998 and January 2000, and 7-42% of the colonies were affected. Although new colonies became infected since initial observations in 1997, and individual colonies exhibited signs of YBD throughout the 30 month study, the incidence of YBD appears to have declined. This decline is attributed to the mortality of YBD-affected colonies infected in 1997 or 1998(6% of tagged colonies), partial mortality followed by disease remission (3% of tagged colonies), and the loss of infected colonies during a recent (1999) hurricane (4%).  Limited attempts to identify a pathogen, and to transmit this disease to uninfected corals, have failed.  With the regional decline of staghorn (Acropora cervicornis) and elkhorn (A. palmata) corals, star corals are now the most abundant and important reef-building corals on Caribbean reefs. High rates of mortality in these species due to the continued spread of YBD and other emerging coral diseases may lead to reduced rates of reef accretion, and a potential restructuring of the reef community to one dominated by shorter-lived, brooding corals.   Return to 25th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page