Citation:

ZEPP, R. G., G. C. SHANK, E. BARTELS, E. STABENAU, W. S. FISHER, AND C. FICHOT. DYNAMIC CHANGES IN COLORED DISSOLVED ORGANIC MATTER AND TOTAL SUSPENDED MATTER CONTROL UV EXPOSURE OF CORAL REEFS IN THE FLORIDA KEYS. Presented at 2006 Ocean Sciences Meeting, Honolulu, HI, February 20 - 24, 2006.

Impact/Purpose:

The overall objective of this task is to develop quantitative relationships for assessing the vulnerability of aquatic ecosystems (freshwater and coastal) and their services to global change. The task will contribute experimental and modeling tools for assessments of the interactions of global climate and UV changes with coral reefs and selected watersheds and estuaries in the U.S. and Brazil These activities are contributing to two APGs in the ecosystems focus area of the Global Change Research Multiyear Plan: the 2008 APG (APG 2) on developing information and tools that managers will use in their decision-making about how to adapt to the effects of global change on aquatic ecosystems; and the 2010 APG (APG 3) on providing information and models that will support development of biocriteria for corals. One major task objective is to assess interactions of global warming and UV exposure that are contributing to the observed coral bleaching and disease. Our lab is working with scientists at the NHEERL Gulf Ecology Lab to characterize UV exposure and effects at several coral reef sites in the Florida Keys. This collaboration will contribute to one ERD APM in 2006 and three joint NERL-NHEERL APMs in the 2008 - 2010 period. Other research is examining the effects of changing climate and UV on microbial activity in waters close to beaches in the U.S. Work is being completed on the interactions of land use and climate changes with the ecological functioning of streams in watersheds of the southeastern U.S. The task also includes two sub-tasks that are funded mainly by funds-in IAGs. One sub-task funded by NASA involves research in central Brazil that is part of the Large Scale Biosphere Atmosphere Experiment (LBA). This work involves a close collaboration between EPA and a group of scientists from the Department of Ecology, University of Brasilia, Brazil. The objectives of this project are to assess the impacts of land use and climatic changes on soil nutrient cycles and microbiota, trace gas exchange and water quality in the Brazilian cerrado. Another sub-task funded by the Office of Naval Research is examining interactions between nitrogen and organic substances in aquatic ecosystems that produce the colored dissolved organic matter (CDOM) that controls penetration of solar UV radiation into coastal waters.

Description:

Variation in ultraviolet (UV) light exposure is one important environmental factor that influences the health of coral reefs. Here we present evidence that the reef tract in the Florida Keys experiences significantly higher variability in UV exposure than other surrounding coastal waters of South Florida. The variability is attributable primarily to fluctuations in the nature and concentration of colored dissolved organic matter (CDOM) and total suspended matter (TSM) over the reefs. The dynamic changes in CDOM are related to a combination of natural and human factors. In this presentation we use a new technique based on remotely sensed ocean color to estimate UV attenuation in the Florida Keys region. Relationships between visible remote sensing reflectance, UV attenuation, and absorption by colored dissolved organic matter (CDOM) in the ocean water are applied to SeaWiFS normalized water-leaving radiances to calculate the CDOM absorption and UV attenuation for the water over the coral reefs. Using this approach we demonstrate that patch reefs in the Keys that are well protected from UV radiation by CDOM and TSM have significantly higher coral cover than the reefs that receive higher and more variable exposure.

Record Details: