RP8 Ecotoxicology of Agrochemicals and Pharmaceuticals
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(LIZ-1117-834370) Toxicity assessment of Mississippi delta oxbow lake sediments using Hyalella azteca.

Lizotte, R¹, Knight, S¹, Bryant, C¹, ¹ USDA-ARS National Sedimentation Laboratory, Oxford, MS, USA

ABSTRACT- Hyalella azteca was used to assess biological impairment in sediments from nine water bodies in the Mississippi delta (i.e., lower Mississippi alluvial plain). Water bodies were categorized according to land use and implementation of agricultural best management practices (BMPs). Three reference oxbow lakes were located in the White River National Wildlife Refuge (WRNWR), Arkansas; three Mississippi lakes were treated with varying BMPs to improve water quality/ecology; and two lakes and one bayou, also located in Mississippi, were listed as impaired according to USEPA section 303d Clean Water Act (303d). Two sediment samples were collected at each of three sites within each water body from June to July 2004 and analyzed for 17 current and historic-use pesticides and metabolites. Twenty-eight day H. azteca survival and growth were measured to assess the degree of biological impairment. All lake sediments examined had detectable levels of at least 14 of 17 analytes measured. Significant (P <0.05) mortality occurred in animals exposed to sediment from a single 303d lake. Significant growth impairment was observed in sediments from all three 303d water bodies and two of three BMP oxbow lakes, whereas no impairment was observed in any WRNWR lake. Attempts to associate sediment pesticide contamination with observed H. azteca responses had limited success. Historic-use pesticides and metabolites were implicated in two of five biologically impaired water bodies (303d bayou and BMP lake)while current-use pesticides were implicated in one 303d lake. Complex contaminant mixtures often limit attempts to provide clear, definitive sources of biological impairment. In this study, even accounting for sediment characteristics such as sand-silt-clay fractions and organic carbon content did not further elucidate sources of toxicity in some water bodies. Finally, results show that implementation of BMPs can mitigate biological impairment within lake sediments.

Key words: Hyalella azteca, Sediment, Toxicity, Mississippi