Using Satellite Imagery to Assess Impacts of Land-based Pollution on Nearshore Coral Reefs in the U.S. Caribbean

Rainwater runoff from coastal watersheds, especially during flood events, transports sediment and other pollutants into estuaries and nearshore marine environments that often have negative effects on plants and animals living there. We used satellite imagery, other relevant spatial data, and computer analysis to see if a method or tool could be developed to characterize and reduce the impact of runoff to the coral reef ecosystems in the U.S. Caribbean.

Why We Care
Land-based rainwater runoff carries tremendous amounts of pollution, especially sediment, into estuarine and marine ecosystems. Too much of this pollution can reduce amounts of dissolved oxygen in the water and can physically bury plants and stationary animals in these coastal habitats. Providing an analytical tool that characterizes the sources and quantities of pollution as well as the places impacted by the pollution can help resource managers institute runoff controls to reduce the impact to coastal systems.

What We Did
Our objectives were to:

1. develop an analytical method or tool that uses satellite images and other computerized GIS data to help characterize, assess, and manage land-based sources of pollution and other threats to shallow-water coral reef ecosystems;
2. provide an analytical method or tool to local resource managers to improve conservation and management of both terrestrial and marine resources; and
3. develop quantitative methods to connect changes in land use over time and how these changes affect concentrations of pollution in runoff.

We obtained a series of Landsat Thematic Mapper (TM) satellite images for Puerto Rico and the U.S. Virgin Islands from 1986–2003, as well as 1990 and 2000, and 2003 TM imagery for Jamaica and Belize. Terrain maps were derived from the satellite data, which allow users to visualize elevation (on land) and bathymetry (underwater) in one continuous layer. This map also can be used to model how sediment and other pollutants are transported by rainfall runoff downstream to the ocean and nearshore coral reefs. The amount of sediment delivered to river mouths of several watersheds was estimated for several time periods between 1985 and 2000.

There were many partners on this project, including: USVI Department of Planning and Natural Resources, NPS Buck Island Reef National Monument, U.S. Environmental Protection Agency, USDA Natural Resources Conservation Service, Puerto Rico Department of Environmental and Natural Resources, Nature Conservancy, World Resources Institute (WRI), University of South Florida Institute for Marine Remote Sensing (ImaRS), U.S. Geological Survey (USGS), ional Aeronautics and Space Administration (NASA), National Coral Reef Institute (NCRI), University of the West Indies, Mona, Jamaica (UWI) and NOAA’s Coral Reef Conservation Program (CRCP) and NOAA/NCCOS.

Outcomes of Our Work

• The quantitative methods developed provide important information about the relationship between land use practices and the amounts of sediment and other pollution washed off of the land and transported into the ocean by rainfall.
• This type of satellite monitoring project is useful in identifying the sources of negative influences from terrestrial systems, and needs to become a fundamental component of coral reef monitoring and conservation in Puerto Rico, the USVI, and the greater Caribbean.
• This study demonstrates the capabilities of Landsat imagery to produce continuous land to ocean maps, as well as detect certain changes in the shallow-water marine environment, providing a valuable tool for efficient coastal zone monitoring and effective management and conservation.

Next Steps
This project was completed in 2008, but the approach developed in this project was tested in this project: Baseline Assessment of Contaminants and Ecological Resources in Jobos Bay, Puerto Rico.