In 2005, high sea temperatures caused coral bleaching in the Caribbean. The goals of this this project were to characterize the spatial extent of coral bleaching and recovery and to monitor the effects of bleaching on coral reef ecosystems in four managed areas of the Caribbean.
Why We Care
Coral reefs are diverse, sensitive ecosystems that provide us recreational resources and critical habitats for important commercial fish and invertebrates. They are under increasing stress from elevated temperatures, pollution, fishing, hurricanes, and disease. In October 2005, we observed widespread bleaching of corals in U.S. Caribbean ecosystems with our collaborators from the South Florida Caribbean Network. The event, which was part of a larger bleaching event occurring throughout the tropical western Atlantic Ocean, created a need to study the extent of the damage and recovery and to determine the effects of bleaching in the area.
Coral bleaching events may alter the abundance of functional groups and their component species and have profound effects on the ability of local communities within the ecosystem to resist and recover from future disturbances. A better understanding of these indicators will help managers identify, design, and manage protected areas to promote reef ecosystem survival. Understanding reef degradation (i.e., coral bleaching) at various scales and the potential for recovery is a priority for science-based conservation and management plans.
What We Did
To determine the effects of this bleaching event, we assessed the extent of bleaching, recovery, and mortality of corals in four selected areas of the U.S. Caribbean. Our specific objectives of this project were to:
- Map the extent of coral bleaching that occurred during the bleaching event of September and October 2005 in four selected managed areas—Buck Island Reef National Monument (BUIS), the East End Marine Park (EEMP) of St. Croix, Virgin Islands Coral Reef National Monument (VICR), and the Virgin Islands National Park (VIIS) of St. John.
- Determine the spatial extent of recovery or mortality of the bleached corals.
- Characterize any effects of coral bleaching on coral reef ecosystems.
- Improve the knowledge base needed by local park managers for assessing the effectiveness of marine-protected area regulations.
- Assist the NASA Ames Research Center (ARC), with the collection of spectroradiometer measurements and calibration data for hyperspectral imagery.
What We Found
- Severe coral mortality occurred in the U.S. Virgin Islands (USVI) between July and November, 2005 because of bleaching and disease; the average decline in hard coral cover was 51.5 percent.
- Sea surface temperatures exceeded the 29.5oC coral bleaching threshold for 12 weeks in 2005; maximum temperatures exceeded 30oC.
- The reefs suffered more thermal stress during this period than during the previous 20 years combined.
- Coral bleaching was observed between July and November, 2005; on average it affected more than 90 percent of the coral cover.
- Bleaching occurred in 22 coral species over a wide range of depths.
The greatest bleaching-related mortality occurred in the genus Agaricia; bleaching also severely affected Montastraea, Colpophyllia, Diploria and Porites, but mortality in these species was usually the result of subsequent infection by white plague or white syndrome. Coral losses in late summer 2005 were more severe than any time in the last 40 years. Refer to the complete report (see link below) for more detailed results of our study.
Our project is complete, but monitoring continues in these areas.