Skeletal density and calcification of corals has recently gained attention because of the potential impacts from global climate change and their unique ability to record this change over their long lifespan (often 100+ years). Historical skeletal growth rates (extension, density, and calcification) thus become useful for testing hypotheses regarding variations in growth attributable to climatic changes such as rising carbon-dioxide levels and sea-surface temperature. Coupled with the skeletal geochemistry, annual coral density banding provides a history of what climatic conditions a coral has encountered and how the coral's growth responded to those conditions. The project collaborates closely with Dr. Peter Swart of the University of Miami's Rosenstiel School of Marine and Atmospheric Science.
Project and Findings
NCRI researchers have developed methods for accurately measuring bulk-density from x-radiographed coral skeletal slabs in order to obtain annual and sub-annual data of extension, density, and calcification. To more efficiently obtain these data, NCRI researchers designed the Coral X-radiograph Densitometry System (CoralXDS+), a Windows-based program which provides a tool for obtaining these measurements rapidly, objectively, and with a high degree of accuracy.
Corals from Southeast Florida and the Florida Keys are being analyzed to assess the effects of recent climate change on coral calcification. This work is complimented by recent coral core collections throughout the Caribbean as part of a NCRI leveraged project, the Caribbean Salinity Experiment (CASE) Cruise in 2002. By increasing the sample size and expanding the sampling range, the effects of recent climate change can be better distinguished from the background of natural variability. Similarly, by analyzing the density band record in conjunction with the geochemical record, a more accurate annual chronology can be developed and the relationship between environmental conditions and coral growth can better be determined.
Implications for Management
Management of coral reefs under changing climatic conditions and anthropogenic impacts requires an understanding of known responses of corals to these changes. Historical coral growth and proxy records provide one means of identifying the in situ response of corals to past environmental changes. With enhanced understanding of how coral growth has historically responded to climate change and anthropogenic impact, managers are better equipped to make decisions about future vulnerabilities.
NCRI via NOAA CSCOR
National Science Foundation
University of Miami Rosenstiel School of Marine and Atmospheric Science
National Coral Reef Institute
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