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Standardization of a short-term chronic method using Daphnia magna (SETAC EU)
Citation:
Lazorchak, J., S. Kadlec, A. Kascak, D. Mount, C. Jenson, W. Backe, S. Goodrich, L. Glimsdal, J. Hockett, A. Johnson, AND T. Norberg-King. Standardization of a short-term chronic method using Daphnia magna (SETAC EU). SETAC Europe, NA, Dublin, IRELAND, April 30 - May 04, 2023.
Impact/Purpose:
The abstract is for a poster to be presented at the SETAC Europe meeting in Dublin. It will present our latest results of standardizing a new WET method for a short-term chronic Daphnia magna method.
Description:
In 2009, U.S. EPA published development and validation of a Daphnia magna four-day survival and growth test method in ET&C. This method is being standardized so that it can potentially be used as another short-term chronic test in the National Discharge Elimination System (NPDES) permitting process for whole effluent toxicity testing and other regulatory assessments. Two ORD laboratories (Duluth, MN; Cincinnati, OH) have conducted additional testing to optimize method performance, followed by 4-d standardization studies to evaluate method variability and reproducibility using reference toxicants. The standardization studies consisted of triplicate tests conducted in parallel by both laboratories, with each of three toxicants: ammonia, zinc, and diazinon. Each toxicant was also tested using a 7-d chronic Ceriodaphnia dubia test for comparison. For ammonia, intra-laboratory variation in IC25 values for D. magna weight was relatively low (CV = 17%, 27%), but there was an apparent difference in toxicant sensitivity between laboratories, with IC25 values of 24 to 33 mg/L as N for Duluth, and from 49 to 84 mg/L as N for Cincinnati. For diazinon, CVs were also low, 25% and 7%. The IC25 values were higher for Duluth(0.63-1.01 µg/L) than Cincinnati(0.38-0.43 µg/L). C. dubia results for diazinon were similar for both labs (0.20 and 0.17 µg/L). For zinc, Duluth’s IC25s ranged from 78.8 – 114 µg/L while Cincinnati’s 2 tests conducted at this time were 110 & 143 µg/L. C. dubia results for zinc were 38 µg/L for Duluth and 103 µg/L for Cincinnati. Reasons for the differences between the labs in apparent sensitivity are under investigation, and include differences in test solution pH, potential differences in culture and algal food preparation procedures. A post hoc power analysis was done to quantify the relationship between number of replicates and statistical power to detect differences between experimental treatments. Future method standardization work will include evaluation of whole effluents with both species.
