palmata bleached for the first time on 

record in the USVI (fig. 6). About 

50 percent of the A. palmata colonies 

being monitored at the time bleached, 

with 15 percent of these colonies dying 

entirely and 35 percent showing partial 

mortality. Although all coral species 

suffered some losses, some were more 

vulnerable to disease than others. 

Disease caused more mortality than 

bleaching on all species, except 

Agaricia agaricites. 

Declines in Coral Cover

Coral cover at the five sites 

continued to decline through the end 

of 2007, even during periods of cooler 

water temperature. The mean coral 

cover dropped from 21.4 percent to 

8.3 percent over the two years, a decrease 

of 61 percent. During the peak of the 

disease outbreak, the mean number of 

lesions increased 51-fold and the mean 

area killed by disease increased 13-fold 

when compared to disease levels before 

bleaching. No other studies have shown 

such dramatic declines in coral cover 

from disease over such an extensive area.

Correlation between Seawater 

Temperature and Disease

In a three-year study of A. palmata

in Hawksnest Bay, St. John, within 

Virgin Islands National Park, Muller 

and others (2008) showed a correlation 

between temperature and disease, but 

only in 2005 when corals were bleached. 

The size of lesions from white pox and 

other undescribed white syndromes 

increased as temperature increased but 

only for bleached colonies. 

disease, primarily white plague, were 

recorded along permanent, randomly 

selected long-term transects maintained 

by the NPS South Florida/Caribbean 

Inventory and Monitoring Network 

(fig. 4). The number and size of disease 

lesions on each coral colony within one 

meter on either side of each transect were 

quantified (fig. 5). Effects of bleaching 

and disease on A. palmata colonies were 

followed at shallower reefs monitored 

by USGS.

Effects on Major Frameworkbuilding Coral Species

This bleaching/disease event caused 

losses of the two coral species that 

contribute most to the architecture and 

framework of USVI reefs, A. palmata 

and Montastraea annularis. Montastraea 

annularis, which initially made up 

55.6 percent of the coral cover at the five 

sites, remained the most abundant species 

but was especially susceptible to disease, 

declining in relative abundance to 

40.9 percent by 2007. Acropora 

Severe Bleaching in 2005

Record-high seawater temperatures 

and calm seas in the summer of 2005 

led to the most severe coral bleaching 

(greater than 90 percent bleached coral 

cover) ever observed in the U.S. Virgin 

Islands (USVI) (figs. 1 and 2). All but a 

few coral species bleached, including the 

threatened species, Acropora palmata. 

Bleaching was seen from the surface to

depths over 20 meters.

Disease Outbreak

With cooler temperatures in 

October, some corals began to regain 

their color. However, many corals then 

died partially or totally in a regional disease outbreak (Miller and others, 2006). 

U.S. Geological Survey (USGS) and 

National Park Service (NPS) 

scientists collaborated to increase the 

frequency of monitoring at five reefs, 

four of them within Marine Protected 

Areas, Virgin Islands National Park 

and Buck Island Reef National 

Monument (fig. 3). The effects of 

Coral diseases following massive bleaching in 2005 

cause 60 percent decline in coral cover and mortality 

of the threatened species, Acropora palmata, on reefs 

in the U.S. Virgin Islands

Fact Sheet 2008-3058

June 2008 Printed on recycled paper

Figure 1. Extensive coral bleaching on 

a reef off St. John, U.S. Virgin Islands. 

(Photograph courtesy of C. Rogers, USGS)

U.S. Department of the Interior

U.S. Geological Survey
St. Thomas

St. Croix

CARIBBEAN SEA

ATLANTIC OCEAN

20

0 10 20 30 KILOMETERS

0 10 30 MILES

18°00 ́

18°30 ́

67°00 ́ 30 ́ 66°00 ́ 30 ́ 65°00 ́ 64°30 ́

Puerto Rico

St. John

For additional information, 

please contact: 

Caroline S. Rogers

USGS Caribbean Field Station

1300 Cruz Bay Creek

St. John, USVI 00830

phone: 340-693-8950 x 221

fax: 340-693-9500

caroline_rogers@usgs.gov

Jeff Miller

National Park Service

South Florida/Caribbean Inventory 

and Monitoring Network

1300 Cruz Bay Creek

St. John, USVI 00830

william_j_miller@nps.gov

Erinn M. Muller

Florida Institute of Technology 

150 W University Blvd. 

Melbourne, FL 32901

emuller@fit.edu

Greater Coral Mortality than from 

any other Previous Stressors

The effects of bleaching and disease 

on coral reefs in the USVI have been 

profound, and no other stressors have 

caused greater or more rapid coral cover 

declines on these reefs (Rogers and 

others, 2008). These and other studies 

show that losses were similar for reefs 

inside and outside marine protected areas, 

including marine reserves. The anticipated benefits (for example, replenishment of fish and corals) from marine 

reserves (Virgin Islands Coral Reef 

National Monument and Buck Island 

Reef National Monument) established in 

the USVI in 2001 could be undermined 

by these significant declines in coral 

cover (Rogers and others, 2007). 

No measurable recovery has been 

documented to date. The recovery of 

USVI coral reefs will depend on the 

severity and frequency of expected future 

bleaching and disease events. It will also 

depend on their connectivity with sources 

of larvae for coral, fish, and other 

organisms. 

Effective management of human 

activities that contribute to reef degradation could be significant in enabling 

coral reefs in the USVI to persist and 

grow, in the face of regional and global 

stressors such as bleaching, disease, and 

ocean acidification. Further research on 

coral diseases, and the synergy between 

bleaching and diseases is an urgent 

priority. 

References

Miller, J., Waara, R., Muller, E., and 

Rogers, C., 2006, Coral bleaching 

and disease combine to cause extensive mortality on reefs in U.S. Virgin 

Islands: Coral Reefs 25:418.

Muller, E.M., Rogers, C.S., Spitzack, 

A.S., and van Woesik, R., 2008, 

Bleaching increases likelihood of 

disease on Acropora palmata 

(Lamarck) in Hawksnest Bay, 

St. John, U.S. Virgin Islands: Coral 

Reefs 27:191-195.

Rogers, C.S., Davis, G., and McCreedy, 

C., 2007, National Parks and Caribbean Marine Reserves Research and 

Monitoring Workshop: National Park 

Service Water Resources Division 

Technical Report, NPS/NRWRD/

NRTR-2007/362. 

Rogers, C.S., Miller, J., Muller, E.M., 

and others, 2008, Ecology of Coral 

Reefs in the U.S. Virgin Islands, in 

Riegl, B., and Dodge, R.E., eds., Coral 

Reefs of the USA: Springer, 

p. 303-374.

Figure 3. The frequency of monitoring 

of long-term transects on U.S. Virgin 

Islands coral reefs was increased to every 

2-4 months in response to widespread 

bleaching and disease. (Photograph 

courtesy of C. Rogers, USGS)

Figure 2. Location map showing the U.S. Virgin Islands and 

Puerto Rico.

Figure 4. White plague on Montastraea 

annularis colonies. (Photograph courtesy 

of C. Rogers, USGS)

Figure 5. USGS employees record coral 

diseases along permanent transects. 

(Photograph courtesy of C. Rogers, USGS)

Figure 6. Bleaching 

of the threatened 

species Acropora 

palmata had not been 

reported in the U.S. 

Virgin Islands before 

2005. (Photograph 

courtesy of E. Muller, 

Florida Institute of 

Technology)