Remote Sensing for Coral Reef Studies: Testing the Waters at Biscayne National Park

At the northern end of the Florida reef tract lies Biscayne National Park: 95% submerged with 700 km2 of mangrove forest, shallow estuarine bay waters, uninhabited keys, and the country’s northernmost coral reefs. The reef tract is famous as a classic field area for Pleistocene and Holocene carbonate studies, and the park itself was the site of some of the earliest studies in airborne remote sensing. One current research project in the park seeks to further develop remote sensing methods appropriate for shallow-bottom areas. The interpretation of radiometric data from submerged, optically shallow environments remains a challenge – especially in complex environments like coral reefs – and a promising new approach is the development of airborne sensors that simultaneously measure georeferenced submerged topography, bottom reflectivity, water-column scattering profiles, and passive upwelling radiance. In support of the development and evaluation of a new airborne sensor designed with coral reef environments in mind, a cooperative field campaign was recently conducted in Biscayne National Park for the purpose of measuring relevant in-water/benthic optical properties and submerged topography simultaneously. In August 2002, high-resolution lidar mapping was undertaken in concert with boat-based acoustic mapping and optical profiling. The lidar surveys were conducted with the Experimental Advanced Airborne Research Lidar, which collected time-synchronized georectified digital camera photography and time-resolved lidar backscatter data. Additional measurements of underwater topography were provided by acoustic fathometer, while in situ water-column measurements were made of absorption, attenuation, backscatter, fluorescence, temperature, and salinity. Benthic and remote-sensing reflectances were measured as well. Additional benthic characterization was provided by acoustic surveys and diver observation. The resulting data set has relevance to other Biscayne studies of reef metabolism and geologic controls on modern reef distribution, and is being applied to current challenges in the remote sensing of submerged habitats (e.g., the “water-column correction problem”) and to fundamental National Park Service needs for high-resolution resource mapping and monitoring