PARENT SESSION
Oral Session #27: Aquatic Ecology: Lake structure and function. Presiding: L.A. Hansson.
Tuesday, August 7, 2001. 8:00 AM to 11:30 AM. Hall of Ideas I.

Ultraviolet radiation and benthic algae and invertebrate communities in montane lakes of Jasper, Canada.

Tank, Suzanne¹, Schindler, David¹, ¹

ABSTRACT- The increased flux of ultraviolet-B radiation to the earth's surface has been well documented. In aquatic systems, increases in water clarity caused by acidification and climate change may further elevate the penetration of all wavelengths of solar radiation, causing aquatic organisms to face increased ultraviolet (UV) exposure. Although several studies suggest that exposure to UV should cause algae to be less nutritious for their consumers, this prediction has been poorly tested in the field. This study was conducted in four montane lakes in Jasper National Park, Alberta, where epilithon (algae growing on hard substrates) was colonized under three different UV regimes, and measured for changes in biomass and food quality. UV-exposed and unexposed epilithon was also fed to benthic invertebrates, whose growth rates were measured under both treatments. Benthic invertebrates preferentially colonized substrates shielded from UV. Results suggest that UV does decrease epilithic biomass (measured by chlorophyll a and particulate carbon), while preliminary food quality data show no UV effect. Accordingly, invertebrates fed UV exposed epilithon exhibit no growth response in the above feeding experiment.

KEY WORDS: ultraviolet radiation, epilithon, invertebrates, food quality