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INTRODUCTION:

Rafe Pomerance, Deputy Assistant Secretary for Environment and Development, US Department of State, Washington, DC.

SPEAKERS:

Dr. Raymond L. Hayes, Howard University, Washington, DC.

Dr. Alan E. Strong, National Environmental Satellite, Data, and Information Service (NESDIS), National Oceanic and Atmospheric Administration, Annapolis, MD.

Coral reef bleaching is a reduction in the density of dinoflagellate algae (marine microscopic plants) that are housed in reef ecosystems. Bleaching also represents a reduction in algal pigments, rendering reef corals bleached or white in appearance. Consequently, coral reef bleaching represents an uncoupling of the mutually life-sustaining association between algae and coral. Corals do not receive their normal nutritive support from the algae, and the algae do not receive the protective nutritive environment afforded by the corals.

Coral reef bleaching was first observed in the early 1980's. Since that time reef ecosystems in all tropical regions of the globe have experienced repetitive and more frequent episodes of mass coral reef bleaching. Although elevated salinity, toxic chemicals, elevated UV radiation, reduced temperatures, and prolonged shading due to cloud cover have been demonstrated to induce coral reef bleaching locally, there is no evidence of these factors being responsible for mass coral reef bleaching episodes. Observations also indicate that mass coral reef bleaching has coincided in space and time with the warmest season and with warmer than usual sea surface temperatures (generally in excess of an approximate temperature threshold of 30° C). Thermal anomalies of 1° C or more above the maximum warm water seasonal averages are significantly correlated with the rapid onset and duration of mass coral reef bleaching episodes. As elevated sea surface temperatures gradually fall, reefs may either recover gradually or succumb entirely to the stress. If bleaching persists, there is no net reef building and the reef frame gradually erodes, which can result in habitat destruction and mortality.

Satellite data confirm that elevated sea surface temperatures have been associated with widespread coral reef bleaching in the western Caribbean and in the Gulf of Mexico. An analysis of the satellite-derived sea surface temperatures show that the summer of 1995 was the warmest since 1984 (when reliable records were first obtained) for Belizian Reefs and for the entire Caribbean Basin. Belize represents the Western Hemisphere's longest and most pristine barrier reef, and massive coral reef bleaching broke out for the first time in Belize in September, 1995.

Prolonged coral reef bleaching can alter the relative abundance of reef organisms and, in so doing, alter the biodiversity of the reef communities. The physical reef structures can also suffer gradual physical losses and/or be covered by algae, thus leading to light and oxygen starvation, and changes in pH in the surrounding water column. As reef ecosystems change in composition, a new community equilibrium may appear, while some medically important members of former reef communities may disappear. Loss of physical reef habitat for young fish may also lead to a reduction in reef fish and, in turn, a decline in economically important open ocean fish stocks.

Dr. Raymond L. Hayes is currently Assistant Dean for Medical Education, and Professor of Anatomy, at Howard University in Washington, DC. Dr. Hayes formerly served as Chair in the Department of Anatomy at Howard University and at the University of Pittsburgh. He has also held academic appointments in the Department of Anatomy at Harvard Medical School, the Department of Anatomy and Cell Biology at the University of Pittsburgh, and in the Department of Anatomy at Morehouse School of Medicine in Atlanta, Georgia. His research interests include the biology of coral reefs and reef ecosystems, reef ecosystems and climate change, and human health and climate change. Dr. Hayes has served as a member of the National Advisory Council of the National Institute of Environmental Health Sciences, and as Acting Director of the MacLean Marine Science Center at the University of the Virgin Islands in St. Thomas, and currently serves as a Corporation Member of the Marine Biological Laboratory, Woods Hole, MA. He also serves as Vice President and Executive Board Member of the Association of Marine Laboratories of the Caribbean, and as a member of the Board of Directors for the Marine Archeological and Historical Society in Washington, DC. In 1994 Dr. Hayes received the Distinguished Service Award from Howard University. He received his BS degree from Amherst College, MA, and his MS and Ph.D. degrees from the University of Michigan at Ann Arbor.

Dr. Alan E. Strong has been Research Physical Scientist at the National Oceanic and Atmospheric Administration's Environmental Satellite, Data, and Information Service (NESDIS) since 1991. Prior to that he served at NESDIS's Office of Research and Applications Oceanic Sciences Branch, using satellite data to address oceanographic problems. In 1986 Dr. Strong was assigned to serve as Chair of Remote Sensing in the Oceanography Department of the US Naval Academy in Annapolis, MD. In 1991 Dr. Strong was also appointed Project Manager of NOAA's Cooperative Project in Oceanic Remote Sensing (CPORS) with the US Naval Academy. His research interests include: satellite monitoring of sea surface temperature, wind speed, and ocean color; monitoring volcanic aerosols; using satellite data to investigate coral bleaching and sea surface temperature changes; monitoring sea surface temperature trends; using satellite data to study global change and El Nino phenomena; and the application of satellite data to study other important environmental issues. For the past three years he has also been involved in teaching global climate change at the US Naval Academy. Dr. Strong received his BA degree in mathematics at Kalamazoo College, MI, and his MS and Ph.D. degrees in Oceanography at the University of Michigan.