Toxicity Evaluation of a Conservation Effects Assessment Program Watershed, Beasley Lake, in the Mississippi Delta, USA

Beasley Lake was assessed monthly in 2005 for biological impairment from 17 historic and current-use pesticides in water and leaf litter using Hyalella azteca (Saussure). Sixteen pesticides were detected in both water and leaf litter with peak detections in spring and summer. Detections ranged from 1–125 ng L −1 in water and 1–539 ng g −1 OC in leaf litter. Ten-day H. azteca survival and growth (mg dw) bioassay results indicated no adverse effects on survival or growth in H. azteca exposed to water or leaf litter. Rather, enhanced growth occurred in both lake water and leaf litter exposures for 8 and 6 months, respectively.