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UV RADIATION EFFECTS ON MICROBES AND MICROBIAL PROCESSES
Citation:
Moran, M. A. AND R G. Zepp. UV RADIATION EFFECTS ON MICROBES AND MICROBIAL PROCESSES. Chapter 7, D.L. Kirchman (ed.), Microbial Ecology of the Oceans. John Wiley & Sons Incorporated, New York, NY, , 201-228, (2000).
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:
The ultraviolet (UV) region of solar radiation is defined as wavelengths in the range of 200 to 400 nm. In contrast to visible radiation (400 - 800 nm), which has a well-defined role as the energy source for most of the Earth's primary production, the effects of UV radiation on biological processes in the ocean include an assortment of both positive and negative aspects, the balance of which is not readily understood. Recent increases in components of UV radiation reaching the ocean surface due to stratospheric ozone depletion makes comprehending, and ultimately predicting, the effects of UV radiation on the ocean ecosystem an especially important task. Understanding the ecological effects of UV radiation in the ocean requires sufficient knowledge of a least three factors. First, information on the number of photons of light reaching the surface of the ocean for each individual wavelength in the UV range is required. Since photons at 310 nm are likely to inflict microbial damage whereas photons at 380 nm can stimulate repair of such damage, the spectrum of UV radiation reaching the seawater surface is an important determinant of its effect on marine microbes. Second, information on the penetration of UV radiation into seawater at each individual wavelength is required. UV wavelengths are differentially absorbed by seawater constituents and therefore penetrate (and have the potential to affect biological processes) to different depths within the water column. Third, information on the effectiveness of each photon surviving to a given depth to bring about photobiological or photochemical changes is required. Molecules in both living cells and non-living organic matter are susceptible to modification by UV light, and the outcome is highly dependent on wavelength. This chapter is organized as a step-wise progression through each of these important factors.