| The direct effects of ultraviolet (UV) radiation and the photo-induced toxicity of polycyclic aromatic hydrocarbons (PAH) to algae have been assessed. The penetration of solar UV radiation into offshore Lake Michigan was characterized. The direct effects of solar UV radiation to the primary production of natural phytoplankton assemblages in Lake Michigan was determined utilizing in situ incubations in chambers which selectively removed portions of the solar UV spectrum. A predictive hazard assessment model to estimate the impact of current and potential UV intensities on total lake productivity was developed.; The photo-induced toxicity of the linear 3-ring PAH, anthracene, to the green alga, Selenastrum capricornutum, was characterized. The dose-response relationships among anthracene concentration, UV radiation intensity, and algal growth rate, {dollar}sp{lcub}14{rcub}{dollar}C-bicarbonate incorporation, and flow cytometric endpoints were determined. The potential environmental hazard of PAH contamination to algal communities was assessed. Fluridone, a carotenoid biosynthesis inhibiting herbicide, was utilized to investigate possible sites and modes of toxic action and the protection provided by carotenoids in algal cells to the photo-induced toxicity of anthracene.; It was concluded that solar UV radiation at current UV intensities can have considerable impact on natural algal communities through the direct effects of UV radiation and indirectly due to the photo-induced toxicity of PAH. However, stratospheric ozone depletion and the concomitant increase in solar UV radiation which is currently predicted will have negligible effects on primary production of phytoplankton assemblages in the Great Lakes. |
