Miami ecologists: UV radiation has detrimental and beneficial effects on freshwater ecosystems

Recent research has shed light on the beneficial, as well as detrimental, effects of ultraviolet radiation (UV) on individual organisms, and thus on natural ecosystems, according to Miami University ecologists.

Craig Williamson, professor of zoology and Ohio Eminent Scholar of Ecosystem Ecology, and Kevin Rose, doctoral student in zoology, provide highlights of recent research on the effects of UV on freshwater ecosystems in “When UV Meets Fresh Water”(PDF) a Perspectives article published in the Aug. 6 issue of Science magazine.

The contrasting effects of UV, combined with a changing UV environment, have important implications for the freshwater ecosystems on which humans depend, say Williamson and Rose.

Exposure to UV can damage DNA and impair an organism’s ability to reproduce, sense its environment and resist disease. However, a wide variety of fish, birds, spiders, insects, zooplankton and other organisms use UV in orientation, communication, navigation, foraging and mate selection.

Williamson and Rose highlight growing evidence of the beneficial effects of UV on individual organisms and ecosystems including:

• UV allows some fish to attract mates but not predators, because some predatory fish cannot see UV;
• Levels of UV radiation found in natural sunlight have been shown to kill water-borne human pathogens such as Cryptosporidium under environmentally realistic conditions;
• Maintenance of high levels of UV transparency in clear, cold-water lakes such as Lake Tahoe may be the key to reducing invasion of warm-water fish, such as bluegill, that threaten the native fish species in the lake. (This study was led by Andrew Tucker, doctoral student in zoology at Miami, with scientists and colleagues of Williamson’s Global Change Limnology Laboratory and published in the March issue of the journal Ecology.)

Williamson, a member of the Environmental Effects Assessment Panel of the United Nations Environment Program, says the panel is monitoring how stratospheric ozone, which shields organisms from the most damaging wavelengths of UV, and the beneficial and damaging effects of UV are changing over time. 

Rose was part of an expedition in 2008 funded by the NASA Astrobiology Institute in Chile and Bolivia to document the impact of rapid climate change on high altitude lakes in the Central Andes, considered “hot spots” of global warming and its effects. He is also involved with the Global Lake Ecological Observatory Network (GLEON), recently as chair of the GLEON Student Association. 

Williamson’s research focuses on understanding the role of UV radiation in aquatic systems and the effects of climate change on lakes. 
His work is centered on alpine and subalpine lakes in the Beartooth Mountains of Montana and Wyoming; the Canadian Rocky Mountains; Lake Tahoe in California; and lower elevation lakes in Pennsylvania and reservoirs in Ohio. 
For more information about Williamson’s Global Change Limnology Laboratory, including photos and video, go to www.users.muohio.edu/willia85/index.html. 

He is a member of Miami’s Center for Aquatic and Watershed Studies (CAWS), a proposed Center of Excellence of the University System of Ohio.