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ASSESSING UV IRRADIANCE IN CARIBBEAN REEF CORAL AND DNA DAMAGE IN THEIR CORAL AND ZOOXANTHELLAE
Citation:
Anderson, S. L., R G. Zepp, J. Machula, L J. Hansen, G. Cherr, AND E. Mueller. ASSESSING UV IRRADIANCE IN CARIBBEAN REEF CORAL AND DNA DAMAGE IN THEIR CORAL AND ZOOXANTHELLAE. Presented at American Society of Limnology and Oceanography Aquatic Sciences Meeting, Albuquerque, NM, February 12-16, 2001.
Impact/Purpose:
The overall objective of this task is to develop quantitative relationships for assessing the vulnerability of aquatic resources 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. These activities are contributing primarily to two APGs in the ecosystems component of the Global Change Research Multiyear Plan: the 2006 APG (APG 3) on building the capacity to assess global change impacts on coastal aquatic ecosystems, including coral reefs and estuaries and the 2004 APG (APG 2) on building capacity to assess and respond to global change impacts on selected watersheds. 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. Other research in this task is examining the interactions between UV-induced breakdown of refractory organic matter in estuaries and coastal areas that enhance UV penetration into the water and concurrently form biologically-labile nitrogen-, phosphorus- and carbon-containing substances that stimulate productivity and microbial activity. This task also involves research in central Brazil that is part of the Large Scale Biosphere Atmosphere Experiment (LBA). 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. This work involves a close collaboration between EPA and a group of scientists from the Department of Ecology, University of Brasilia, Brazil. Other objectives of this task are to assess the interactions of land use and climate changes with the ecological functioning of streams in watersheds of the Piedmont region of the southestern U.S.
Description:
UV penetration into the water near coral reefs may be increasing as a consequence of global climate change. Calm waters associated with ENSO conditions can enhance stratification that increases the amount of photobleaching of chromophoric dissolved organic matter (CDOM) in surface waters, causing increased UV penetration. We are examining CDOM spectral and photochemical properties and UV penetration at Florida Keys reef sites and in the adjacent Hawk Channel. Initial characterization of CDOM sources and biological, chemical and physical processes affecting its distribution are underway. We have shown that CDOM at the reefs photobleaches, and that UV penetration above the thermocline is greater than below. Sources of CDOM may include seagrass beds and mangroves. Immunoblotting and immunolocalization procedures have been developed to evaluate UV-specific DNA damages (thymine dimers) in coral and zooxanthellae of Porites porites. Laboratory studies indicated a proportional response to increases in UV radiation. Diurnal variation in thymine dimers in coral collected from reef sites indicates that cyles of damage and repair vary among colonies. Damage to DNA is localized in both coral and zooxanthellae. These findings may help to determine whether UV irradiance plays a significant role in coral bleaching.