An in vitro oxidative stress test for determining pollutant tolerance in algae.

An in vitro oxidative stress test has been developed to assess pollutant tolerance in freshwater algae using Euglena gracilis as the test organism and FeSO4 and NaC1 as the pollutants. The test evaluates free radical-mediated oxidative stress through the concomitant application of three biochemical assays: (1) the non-invasive, gas chromatographic-volatile headspace analysis of hydroxyl radicals ((OH)-O-center dot) using dimethyl-sulphoxide as a radical trap; (2) the spectroscopic determination of total antioxidant activity; (3) a fluorescent microscopy viability test. In vitro pollutant testing was devised to simulate contaminant loadings that impact urban retention ponds. E. gracilis was found to be tolerant to FeSO4 (2-10% (w/v)) and NaCl (10-5000 ppm) as indicated by high positive viabilities (ca. 100%) and low, or no (OH)-O-center dot production, as compared to controls. Total antioxidant activity increased with increasing pollutant loading suggesting that the organism has the capacity to enhance antioxidant defence in response to pollutant stress. This in vitro test provides a new approach to monitor the effects of water quality on the biological components of urban and/or polluted aquatic ecosystems. It also has a potential application in the identification of putative algal phytoremediators. (c) 2005 Elsevier Ltd. All fights reserved.