M2 AM Aquatic Ecotoxicology (Part 1)
Monday, 14 November 2005: 8:00 AM - 11:40 AM in Ballroom 2

(ROB-1118-064820) PAH-mediated photoinduced toxicity in Sierra Nevada alpine lakes.

Roberts, A¹, Oris, J¹, ¹ Miami University, Oxford, OH, USA

ABSTRACT- Polycyclic aromatic hydrocarbons (PAHs) are a ubiquitous environmental contaminant and occur as a result of releases from both natural and anthropogenic sources. Their presence has been documented in a wide variety of aquatic habitats contaminated from oil spills, industrial processes, and boating activity. PAHs are able to absorb photon energy from solar ultraviolet radiation, particularly that in the UV-A range, and increase levels of oxidative damage in tissues. This phenomenon, photoinduced toxicity, has been shown to be one mechanism for acute toxicity of PAHs to aquatic biota. The purpose of these experiments was to determine the potential for photoinduced toxicity at sites on three oligotrophic, high-use, alpine lakes in the Sierra Nevada mountains. Because these lakes contain low amounts of organic material, we hypothesized that PAHs would be highly bioavailable and that UV would be able to penetrate deep into the water column, thus increasing the potential for photoinduced toxicity. Potential for photoinduced toxicity was assessed using in-situ daphnia bioassays, in-situ caged fish biomarker response, and water chemistry and biliary metabolite analyses. Daphnia bioassays were carried out in both UV-transparent exposure chambers as well as UV-opaque chambers to distinguish between toxicity and photoinduced toxicity. Water chemistry, biliary metabolites, and CYPIA1 mRNA biomarker response indicated that PAHs were present and bioavailable in all lakes. Mortality was observed in the daphnia bioassays, both in UV-opaque and UV-transparent treatments, and was highly correlated with water column PAH concentrations (r2 = 76%, p<0.001). No differences between UV-treatments were observed with the exception of one site on Lake Tahoe where the UV-transparent treatment resulted in a 50% increase in daphnia mortality, indicating phototoxic potential. These results indicate that bioavailable PAHs are found in the waters of these lakes and that these waters were somewhat toxic to daphnia with and without the presence of UV radiation. Significant photoinduced toxicity was observed in Lake Tahoe and was likely related to the ultraoligotrophic characteristics of the lake water.

Key words: phototoxicity, PAH, Lake Tahoe