UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS
Location: Water Quality and Ecology Research
Title: Influence of selected water quality characteristics on the toxicity of lambda-cyhalothrin and gamma-cyhalothrin to Hyalella azteca
Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 2007
Publication Date: August 4, 2007
Citation: Smith Jr, S., Lizotte Jr, R.E. 2007. Influence of selected water quality characteristics on the toxicity of lambda-cyhalothrin and gamma-cyhalothrin to Hyalella azteca. Bulletin of Environmental Contamination and Toxicology. 79(5):548-551. DOI:10.1007/s00128-007-9253-0.
Interpretive Summary: Insecticides, such as lambda-cyhalothrin and gamma-cyhalothrin, are used to control insect pests of agricultural crops such as cotton. We studied the influence of four selected water quality characteristics: turbidity, suspended solids, dissolved organic carbon (DOC), and chlorophyll a, measured in field samples of natural Mississippi pond and lake water on the acute aqueous toxicity of these two insecticides to the freshwater animal, Hyalella azteca. This organism is used by regulatory agencies as one indicator of overall water quality. In our study, we found turbidity, suspended sediment, DOC, and chlorophyll a concentrations can be used to determine the toxicity of both lambda-cyhalothrin and gamma-cyhalothrin to H. azteca. In addition, our study shows that together both increased DOC and algae (as chlorophyll a) decreased toxicity of both pyrethroids to H. azteca by more than 10-fold. Such results emphasize the importance of measuring these water quality characteristics when assessing pyrethroid insecticide toxicity to aquatic organisms.
This study was conducted to assess the influence of suspended solids, dissolved organic carbon, and phytoplankton (as chlorophyll a) water quality characteristics on lambda-cyhalothrin and gamma-cyhalothrin aqueous toxicity to Hyalella azteca using natural water from 12 ponds and lakes in Mississippi, USA with varying water quality characteristics. H. azteca 48-hour immobilization EC50 values ranged from 1.4 to 15.7 ng/L and 0.6 to 13.4 ng/L for lambda-cyhalothrin and gamma-cyhalothrin, respectively. For both pyrethroids, EC50 values linearly increased as turbidity, suspended solids, dissolved organic carbon and chlorophyll a concentrations increased.