Toxicity of Hydrogen Sulfide to Goldfish (Carassius auratus) as Influenced by Temperature, Oxygen, and Bioassay Techniques

Bioassays were conducted to test the effect of temperature and oxygen on H2S toxicity to goldfish (Carassius auratus L.) and to investigate some factors that influence bioassay results. Relation of H2S toxicity to temperature is negatively logarithmic over the range of 6.5–25 C. The mean 96-hr TL50 at 6 C was 530 μg/liter and at 25 C was 4 μg/liter. At temperatures of 14, 20, and 26 C, most acute mortality from H2S ended by 11 days and the 11-day TL50's at these temperatures were significantly different. In bioassays with and without prior oxygen acclimation, decreasing oxygen concentrations increased H2S toxicity. In the former, mean TL50's were 62 and 48 μg/liter H2S at oxygen concentrations of 6 and 1.5 mg/liter, respectively, and in the latter, 71 and 53 μg/liter H2S at the same oxygen concentrations. Variability in bioassay results was not affected by test temperatures of 14, 20, and 26 C, and in most cases 1 week of temperature acclimation was adequate. Stocks of fish responded differently after 11 days of bioassay, although differences were not detected after 4 days of bioassay.