Citation:

JONES, R., R. G. ZEPP, M. J. CYTERSKI, M. MOLINA, AND E. M. WHITE. LIGHT-INDUCED PROCESSES AFFECTING ENTEROCOCCI IN AQUATIC ENVIRONMENTS. Presented at 2008 Ocean Sciences Meeting, Orlando, FL, March 02 - 07, 2008.

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:

Fecal indicator bacteria such as enterococci have been used to assess contamination of freshwater and marine environments by pathogenic microorganisms. Various past studies have shown that sunlight plays an important role in reducing concentrations of culturable enterococci and other indicator microorganisms in aquatic environments. Results presented here indicate that several pathways contribute to the light-induced mortality of enterococci in natural waters. Studies of one species of enterococci, Enterococci faecalis, showed that a key mechanism involves mortality via direct absorption of the UV component of sunlight. Chromophoric dissolved organic matter (CDOM) and suspended sediments also can play a role in indirect pathways for light-induced deactivation. CDOM photosensitizes the production of reactive oxygen species that can affect the survivability of enterococci. Enterococci are predominantly sorbed to sediments in aquatic environments and our results showed that the sorbed enterococci from sediments of local streams were rapidly inactivated by sunlight exposure. These results suggest that photoinduced damage can be initiated by substances on the sediment surface.

Record Details: