PARENT SESSION
PT1 - Aquatic Toxicology
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P485) Traditional and Two Pulse Dose Daphnia magna Toxicity Tests Used in the Pesticide Risk Assessment Process.
Hall, A. Tilghman*,1, Kern, Matt1, Brenneke, Chris1, Banman, Chris1, Hancock, Gregg1, 1 Bayer Corporation, Stilwell, KS, USA
ABSTRACT- Daphnia magna have traditionally been used as a representative invertebrate species for acute and chronic toxicity testing in the pesticide and chemical registration process. The acute test is a 48-hour test with mortality and sublethal endpoints. The traditional chronic test lasts for 21 days and includes reproductive, growth and other sublethal endpoints. In order for the tests to be comparable across many compounds, the concentration of the test material must be maintained at a constant level. However, this condition may not mimic the fate of the compound in a natural environment. Two pulse dose Daphnia magna chronic studies have been conducted for a new pesticide currently in the registration process. Exposure to the compound was introduced as two pulses at a seven-day interval, the shortest application interval on the pesticide label. The test compound has a high binding affinity to organic carbon and therefore exposure in the aquatic environment will be driven by potential drift. The first new test mimicked a traditional 21-day test (included the same endpoints) with the exception of a static exposure system and the addition of natural sediment. The second test was a population study initiated with a mixed age group of Daphnia and was also a static test with sediment present. The primary endpoints were population estimates of neonate, juvenile and adult Daphnids. The sediment used in both tests was from a lake in California, and had high sand and silt content with low organic carbon. The combination of these studies provided insight into the potential toxicity of the compound to aquatic invertebrates under more realistic exposure scenarios than is present in the traditional test.
Key words: Daphnia magna, Pesticide, Pulse , Toxicity