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Communication at the NABS Annual meeting, Keystone, 2000
(260) LABORATORY AND FIELD VALIDATION OF AN IN SITU BIOASSAY BASED ON POST-EXPOSURE FEEDING RATE.
R.A. McWilliam and D.J. Baird. Institute of Aquaculture, University of Stirling, Stirling, Scotland, UK, FK9 4LA
Daphnia magna demonstrates feeding inhibition under contaminant exposure. This ecologically relevant endpoint affects life-history performance and could be used to assess ecotoxicity in situ. Since feeding is difficult to measure in the field, feeding during recovery from exposure was used to measure toxic effect. A bioassay was developed where 4-5d old D. magna were exposed to contaminants for 24hrs and transferred to clean media and allowed to feed post-exposure for 4hrs. This method was first verified under laboratory conditions by demonstrating delayed recovery after exposure of D. magna to a range of contaminants with varying modes of action. The influence of environmental factors such as flow rate, suspended solids, organic matter, temperature and hardness on post-exposure feeding rates under clean conditions was also studied. Suspended organic matter was the only environmental factor which significantly affected bioassay performance. Field testing was carried out at 4 contaminated river sites and also in laboratory and field mesocosms. When feeding rates of animals at contaminated and reference sites were compared, rates were depressed and response variability increased under contaminant exposure. Results show potential for this method to be used for in situ toxicity testing purposes.
Presented at 10:15 AM on Thursday, June 1, 2000 in Ecotoxicology
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