AbstractAn investigation of the influence of light intensity and photoadaptation on the toxicity of polychlorinated biphenyls (PCBs) to the marine diatom,Ditylum brightwellu, was undertaken Cultures were adapted to six light intensities (30, 50, 75, 100, 125 and 150 μEm2s−1) for a period of three months During this time a significant decrease in cell size occurred at the lower light intensities (The cultures grown at 30, 100 and 150 μEm2s−1were then tested for sensitivity to 10 μg/L PCB ) Rates of growth and photosynthesis (uptake of 14CHCO3/μg Chla/h) and cellular concentrations of chlorophyllaand carotenoids, as well as cell size, were measuredPCB toxicity was greatest at the higher light intensities Adapted cultures were less sensitive to PCB than unadapted cultures indicating that photoadaptation increased tolerance to PCB In the unadapted cultures growth rates and photosynthetic activity were significantly depressed by all PCB treatments In the adapted cultures growth rate at 150 μEm2s−1was the only measurement to show a significant decrease with PCB treatment Cellular concentrations of chlorophyllaand carotenoids varied with adaptation history, light intensity and PCB treatment14CPCB (Aroclor 1254) accumulation was compared in adapted and nonadapted cultures The nonadapted cultures accumulated an order of magnitude more PCB, and the greatest accumulations correlated with reduced rates of photosynthesis and growth in cultures grown at the highest l
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