FLOW CYTOMETRIC DETERMINATION OF THE PHOTOINDUCED TOXICITY OF ANTHRACENE TO THE GREEN-ALGA SELENASTRUM-CAPRICORNUTUM

Certain PAHs are photosensitizers and in the presence of solar radiation can cause toxicity to aquatic plants and animals. The photoinduced toxicity of anthracene to the green alga Selenastrum capricornutum was assessed by the use of flow cytometry to measure cell size, cellular chlorophyll concentration, and cell viability. Anthracene was slightly toxic in the absence of UV-A radiation. The detection of the direct toxicity of anthracene in this study at a concentration of 19 mug/L anthracene resulted from the use of sensitive flow cytometric measures. There was a significant interaction between anthracene and UV-A radiation, which, in combination, caused significant toxic effects on Selenastrum capricornutum. The most sensitive flow cytometric measure of toxicity was the stress index (SI), which was predictive of longer term effects on cell growth. The 28-h EC50 and EC10 for the SI for Selenastrum capricornutum were 16.1 and 8.3 mug/L anthracene, respectively, at 125 muW/cm2 UV-A. All combinations of anthracene and UV-A that inhibited algal growth also caused a significantly greater number of nonviable cells. The flow cytometric methods used in this study proved to be sensitive, predictive measures of the direct and photoinduced toxicity of anthracene and UV-A radiation to Selenastrum capricornutum.