Comparison of Malathion toxicity using enchytraeid reproduction test and earthworm toxicity test in different soil types

We compared toxicity of the organophosphate pesticide malathion between the Enchytraeid Reproduction Test using Enchytraeus albidus and the Earthworm Toxicity Test using Eisenia fetida. The Enchytraeid Reproduction Test has s everal advantages over the Earthworm Toxicity Test, including greater ecolo gical relevance, world-wide distribution, a short generation time of test s pecies, and greater cost-effectiveness. Toxicity of malathion was studied i n three soils with contrasting organic matter (OM) content, including stand ard artificial soil (10 % OM), O'Neill-Hall sandy loam soil (4.3 % OM) and Sassafras sandy loam soil (2.3 % OM). In the Enchytraeid Reproduction Test, reproducing adults were incubated for three weeks. Adult worms were then r emoved and counted, and soil with cocoons was incubated for an additional t hree weeks. Earthworm toxicity was determined using the standard 14-day acu te survival Lest, and a chronic 21-day cocoon production assay. Results sho wed that malathion had similar toxic effect on E. albidus adults in artific ial and Sassafras soils (LOEC of 23.15 mg kg(-1)), and greater toxicity in the O'Neill-Hall soil (LOEC of 6.64 mg kg(-1)). The Earthworm Toxicity Test LOEC values for adult E. fetida Mere 75 mg kg(-1) inartificial and O'Neill -Hall soils, and 60 mg kg(-1) in Sassafras soil. Malathion was more toxic t o E. albidus juveniles compared with adults in artificial soil (LOEC of 7.7 5 mg kg(-1) and EC50 of 9.8 mg kg(-1)). The earthworm chronic assay LOEC va lues were 18, 14 and 21 mg kg(-1) and EC50 values were 16, 37 and 20 mg kg( -1) in artificial, O'Neill-Hall and Sassafras soils, respectively. Results of this study show that the Enchytraeid Reproduction Test is a more sensiti ve toxicity test in artificial soil, and has the potential for replacing th e Earthworm Toxicity Test in future soil toxicity testing.