Citation:

ZEPP, R. G., D. J. ERICKSON III, N. D. PAUL, AND B. A. SULZBERGER. CHANGING CLIMATE AND PHOTOBIOGEOCHEMICAL CYCLES IN AQUATIC ENVIRONMENTS. Presented at 33rd American Society for Photobiology Meeting, Rio Grande, PUERTO RICO, July 08 - 12, 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:

Global biogeochemistry plays a critical role in controlling life processes, climate and their interactions, including effects on atmospheric greenhouse gas concentrations. Recent evidence indicates that the light-driven part of aquatic biogeochemical cycles is being altered by interactive global changes in solar UV irradiance, warming, precipitation, clouds and atmospheric circulation. Four specific examples are reviewed here: 1) changes in runoff from land to water; 2) changes in stratification and mixing; 3) warming-induced changes in microbial cycling of UV-absorbing colored dissolved organic matter; 4) changes in water to atmosphere fluxes of trace gases. For example, warming and precipitation change can alter the transfer of organic matter from terrestrial to aquatic ecosystems and thereby influence UV penetration into water bodies, with major consequences for aquatic biogeochemical processes. Moreover, future changes in climate may enhance stratification, reduce vertical mixing and alter the mixed layer depth of lakes and the ocean, which will alter UV effects on biogeochemistry in the surface layer. These changes in biogeochemistry include modification of carbon cycling that is linked to effects on the cycling of metals and mineral nutrients such as nitrogen. Changes in metal cycling can also affect the light-induced production of reactive oxygen species in aquatic systems, and these changes in oxidative activity affect contaminant decomposition and microbial cycling of carbon and other elements. Interactions between changing solar UV and climate change in aquatic environments are changing water-to-atmosphere exchange of trace gases, such as methyl bromide and dimethylsulfide. Methyl bromide can catalyze depletion of the ozone layer and oceanic emissions of dimethylsulfide produce particulates (i.e., sulfate aerosols) that directly and indirectly (via clouds) have a cooling effect on the marine atmosphere.

Record Details: