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Remote Sensing for Coral Reef Studies: Evaluation and Application of a New Compound Active/Passive Optical Sensor: Tonya D. Clayton

Project Title: Remote Sensing for Coral Reef Studies: Evaluation and Application of a New Compound Active/Passive Optical Sensor
Mendenhall Fellow: Tonya D. Clayton, (727) 803-8747, x. 3138; tclayton@usgs.gov
Duty Station: St. Petersburg, Florida
Start Date: October 1, 2001
Education: Ph.D., 2001, Oceanography, Old Dominion University
Research Advisor: John C. Brock, (727) 803-8747, x. 3088, jbrock@usgs.gov
Project Description: Coral reefs are environments of tremendous aesthetic, economic, sociological, ecological, and geological importance. In recent years, however, reefs worldwide have experienced episodes of dramatic decline due to a variety of causes. Currently, efforts to map, monitor, and manage coral reefs are limited by a general lack of quantitative data. As a result, remote-sensing techniques are rapidly being developed to address this problem. Still, technical and practical constraints to coastal remote sensing remain, including limitations implicit in instrument design and deployment, as well as problems inherent in the application of theory to an underdetermined system.

An innovative system under development at the NASA Wallops Flight Facility -- the NASA Experimental Airborne Advanced Research Lidar (EAARL) -- has the potential to make significant contributions in this realm. Its unique features include the ability to measure water depth concurrently with hyperspectral imagery and to conduct cross-environment surveys. The primary objectives of this research project are: (1) to assist in the calibration, methods development, and validation of measurements from the first deployments of EAARL; (2) to quantitatively assess the degree of improvement in reef mapping enabled by the simultaneous acquisition of hyperspectral imagery and water-depth measurements; and (3) to apply the results to reef mapping and inter-sensor comparative studies. The use of virtual-reality data visualization in the interpretation of the complex, multi-dimensional data sets acquired may also be explored.

An associated aspect of research is the use of aircraft imagery to estimate rates of reef community metabolism. Scientists at the USGS have developed a benthic incubation chamber (the SHARQ -- Submersible Habitat for Analyzing Reef Habitat) to measures rates of calcification, photosynthesis, and respiration in a variety of reef habitats. By merging these in situ rate measurements with aircraft-derived estimates of the areal extent of each habitat type, estimates of community metabolism can be obtained. These merged data are also being used to assess the likely performance of a variety of sensors in such applications, by artificially degrading the high-quality (but expensive) aircraft data to approximate data that are perhaps more accessible to members of the reef management and conservation communities.

While these aircraft missions are focussed primarily on reefs in the Florida Keys and the Caribbean Sea, complementary field and remote sensing studies are also ongoing in the Red Sea. According to recent international status reports, the coral reefs of the Red Sea are generally in good and often pristine condition. This region is, however, experiencing significant residential, recreational, agricultural, and industrial development, and a number of associated potential threats to reef well-being have been identified. Certain aspects of these development activities (for example, landscape alteration and some types of waste disposal) are amenable to identification and monitoring from space.

As part of an ongoing study of urbanization effects on these pristine reefs, a variety of satellite data (Landsat, SPOT, ASTER) are being used to generate extensive, detailed maps of coral reefs in the eastern Red Sea. These images are being used in turn to provide estimates of reef area, to map sites of significant human activity and natural features, and to site and design baseline field studies in pristine and impacted areas.

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