Cellular fluorescence capacity as an endpoint in algal toxicity testing

The use of a cellular fluorescence capacity (CFC) index as a toxicity end point for the alga, Selenastrum capricornutum was examined. The index is calculated from algal fluorescence before (F) and after (Fd) the addition of the herbicide 3(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) and is expressed as a proportion [(Fd−F)/Fd]. CFC was compared to algal growth response in 96-hours in bioassays with copper, zinc, pentachlorophenol, a complex mixture obtained from a sewage treatment works effluent, and four sediment pore water samples. Although not always as sensitive as the 96-hour growth response, CFC was usually more sensitive than the 24-hour growth response and was able to detect the toxicity of copper to the alga species as early as 5 hours. CFC was a useful endpoint in toxicity determinations and demonstrated potential as a rapid short term screening response for toxicity.