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Indirect effects of ultraviolet-B radiation on amphibians: using mesocosm experiments to examine UV-B effects on trophic level interactions.
Scheessele, Erin *,1, Garcia, Tiffany1, Blaustein, Andrew1, 1 Oregon State University, Corvallis, Oregon
ABSTRACT- While most of the existing information on the role of ultraviolet-B (UV-B) radiation in aquatic ecosystems is at the organismal or suborganismal level, it is essential to investigate the community and ecosystem level responses to UV-B. Previous studies have found counterintuitive increases in productivity under elevated UV-B due to differential sensitivity between algae and their consumers. We used a three-trophic level mesocosm experiment to explore community level responses to ambient UV-B. We hypothesized UV-B exposure would differentially affect adjacent trophic levels of a simple food web with potential effects on the life history characteristics of amphibian larvae. For the three-trophic level food web, we used a natural algae assemblage as the primary producer, a natural zooplankton community as the primary consumer and long-toed salamander larvae (Ambystoma macrodactylum) as the top predator. When exposed to ambient UV-B, we predicted the algal community would experience a change in species composition and would tend to increase in biomass. We predicted the density of the primary consumer (zooplankton) would be correlated with UV-B exposure. The top predator, long-toed salamander larvae, would most likely be negatively affected by a combination of direct and indirect UV-B effects. We manipulated levels of UV-B exposure and trophic complexity, having either two or three trophic levels. At regular intervals we measured species composition and biomass of the primary producer trophic level, abundance and size and age distribution of the primary consumer trophic level, and mortality and growth rates of the top level consumers. The results of this experiment will be discussed.
Key words: Ambystoma macrodactylum, mesocosm, ultraviolet-B radiation, food webs