The U.S. Geological Survey is the Nation's primary provider of water, earth, and biological science information related to the environment, natural hazards, and mineral, energy, water, and biological resources. The agency provides world-class research and monitoring programs for volcanoes and earthquakes, monitors the status and trends of the Nation's biological resources, and is the Nation's principal civilian topographic mapping agency. With research centers and field stations in south Florida, the U.S. Virgin Islands, Hawaii, and elsewhere across the Nation, USGS is providing resource managers with information critical to the understanding of the ecology, health, structure, function, and management of coral reefs. USGS scientists are increasing our understanding of the structure and function of reef communities through their studies of the mechanisms governing reef health and disease, geologic growth and development, sediment and ground-water transport, and the effects of fishing and no-take zones on coral reef resources.
Coral Loss and Recovery: Elkhorn coral at Buck Island Reef National Monument before (top) and after (middle) Hurricane Hugo (1989). A major reef-building species in the Caribbean, elkhorn coral has suffered dramatic declines since the 1970s due to hurricanes and White Band Disease. USGS and NPS scientists have developed novel protocols for assessing recovery taking place in a few locations, such as that in Hawksnest Bay, Virgin Island National Park (bottom).
Programs and Recent Accomplishments Related to Coral Reefs:
Innovative Techniques for Determining Reef Health: Over the past decade, USGS scientists have been developing innovative techniques for monitoring coral reefs in the Virgin Islands National Park, Buck Island Reef National Monument, and Dry Tortugas National Park. A new technique developed by USGS and the NPS, combining a SONAR-based underwater positioning system with digital imaging, is the most scientifically rigorous reef-monitoring protocol in the world. These methods are being used by USGS scientists to develop indicators of reef health, such as the amount of live coral versus algae on the reef and the abundance of juvenile and adult reef fish. Results indicate that the health of coral reefs in a number of areas over the past decade has declined. New protocols are also being used to map and assess the condition of elkhorn coral. Once a dominant reef-building species in the Caribbean, elkhorn coral has suffered dramatic declines since the 1970s from White Band Disease and storm damage. USGS scientists are tracking recovery of elkhorn coral occurring in some areas and its relationship to reef community structure. USGS scientists have also developed a chamber for measuring metabolic rates (productivity) of benthic communities, such as coral reefs, seagrass beds, and other hard and sand bottom communities. The Submersible Habitat for Analyzing Reef Quality (SHARQ) is being tested to determine the potential for using benthic community metabolism as an indication of ecosystem health. By examining ecosystem health in terms of system processes or function, scientists can compare ecosystems in different geographic locations that might be characterized by different species of organisms. Monitoring efforts have begun in Biscayne National Park, Hawaii, Florida Bay, and Tampa Bay.
Hawaiian Reef Fish and Habitat: USGS studies of the relationships between Hawaiian reef fish assemblages and their coral reef habitats are providing better information to help improve management of reef areas and design of marine reserves.
Mapping in the Pacific: State-of-the-art multibeam mapping techniques are being used to map key areas around Hawaii; high-resolution bathymetric and backscatter data are being used to address questions related to environmental quality, hazards, and resources. Maps generated by USGS in 1998 are being used to characterize the condition of reef resources in the Humpback Whale National Marine Sanctuary. USGS scientists are mapping patch reefs in Hawaii and Indonesia, using satellite and aerial photography to obtain information on the location of reefs and the active sedimentary processes that affect reef conditions.
Innovative Research Tools. The Submersible Habitat for Analyzing Reef Quality (SHARQ) is a large-scale underwater incubation chamber designed by USGS scientists to isolate a mass of water over the ocean bottom. This enables scientists to measure changes in water chemistry that result from benthic community metabolism and to calculate metabolic rates associated with different types of benthic habitats.
Oblique views of the Humpback Whale National Marine Sanctuary. Mapped by USGS scientists in 1998, the image on the left shows drowned coral reef platforms and pinnacles west of Maui, Hawaii. Water depths range from more than 300 m (blue) to about 50 m (dark brown). Image on the right is an enlargement of the upper right quadrant of the left image. The drowning of the reefs occurred through a combination of global sea level rise and island subsidence.
Mapping in South Florida: USGS scientists are mapping the surface and subsurface reef structures throughout the Florida Keys to establish the relationship between reef distribution and the underlying geology, and to evaluate factors controlling reef health within the Florida Keys National Marine Sanctuary and Biscayne National Park. USGS is also developing sediment composition data for the Florida Keys showing reef area and health, on the basis of a Sanctuary-wide assessment of the Florida Keys National Marine Sanctuary. These studies have documented changes in both sediment composition and coral reef development over the past few thousand years. Descriptive and interpretive maps of the Sanctuary will be produced through the use of seismic, sidescan, and core data. Such information is useful for future coral reef management.
Florida Bay bottom types mapped by USGS scientists in 1997 from surveys conducted in 1996-1997
Water Quality Studies: To address concerns about recent algal blooms in Florida Bay and coral diseases on the reef tract, USGS scientists are working with the State Department of Environmental Protection, the U.S. Environmental Protection Agency, and university scientists to carry out routine water-quality assessments. A network of submarine monitoring wells has documented the flow of contaminated ground water in the extremely porous limestone that underlies the area. The limestone receives the effluent of approximately 30,000 septic tanks, 10,000 cesspools, and 1,000 shallow disposal wells. USGS scientists are also reconstructing the history of water quality in the bay during the past 100-150 years, using stable isotopes and trace elements in fossils and corals from well-dated cores.
Atmospheric Dust Studies: USGS geologists and coral biologists, along with researchers from the University of Miami Rosensteil School for Marine and Atmospheric Science, the University of South Florida Marine Center in St. Petersburg, and Duke University, are collaborating to determine the relationship among global warming, deposition of dust, and Caribbean-wide outbreaks of coral diseases. Results indicate that during strong "African dust events," the numbers of microorganisms can be two to three times that found during "clear atmospheric conditions." These events may be linked to outbreaks of disease in Caribbean corals, toxic algal blooms such as the red tides along Florida's coasts, and asthma in humans. Increased quantities of atmospheric dust began blowing westward in the early 1970s (1 billion tons now cross the Atlantic each year) with desertification and expanding agriculture in northern Africa.
African Dust. A giant dust storm off the northwest coast of Africa is captured in this satellite image taken on October 30, 2001 (top). Sediments are lifted by storm activity and carried thousands of miles across the Atlantic by the prevailing winds (bottom). Such dust storms appear to carry infectious microbes and toxic chemicals and are now believed to pose a hazard to the ecosystems in the Caribbean. Droughts and agricultural practices in many regions have increased the size of the arid lands and so aggravated the problem in recent decades.
Coral Skeletons as Climate Records:
Images of coral skeletons, like these of a core from Biscayne Bay National Park, allow USGS scientists to establish the age and climate history of coral colonies. An x-radiograph of the core (A), reveals annual growth bands, resembling tree rings, of the coral colony; the colony was found to be more than 350 years old. Variations in the growth bands reflect climate changes. For example, thick, dark bands correlate with very cold winter temperatures. Bright bands appear in the same core exposed to fluorescent light (B), recording years of heavy rainfall and hurricanes. For example, the bright band in 1928 records a hurricane that killed more than 2,000 people in south Florida.