Pesticides in Amphibian Habitats of Central and Northern California

Abstract/Summary

Amphibians in California are facing serious population declines. Contaminants, especially pesticides, have been linked to these declines. This study reports on a survey of central and northern California wetlands sampled along four transects associated with Lassen National Park, Lake Tahoe, Yosemite National Park and Sequoia National Park; each transect was sampled from the coast to the Sierra Nevada mountains. Pacific treefrogs (Pseudacris regilla), water, and sediment were collected from 49 wetlands in 2001 and frogs and sediments were collected from 55 wetlands in 2002. Twenty-three pesticides were found in frog, water, or sediment samples. Eleven contaminants including trifluralin, endosulfan I, chlordanes, trans-nonachlor and polybrominated diphenyl ethers (PBDEs) were found in the tissues of adult P. regilla. Seventeen contaminants were found in sediments including endosulfan sulfate, chlordanes, DDE, and chlorpyrifos. The average (SD) number of chemicals detected per pond in sediments was 2.4 (2.5). In water 17 chemicals were detected with endosulfan II being present in almost all samples. Trifluralin, chlordanes, and chlorpyrifos were the next most common. The mean number of chemicals in water per pond was 7.8 (2.9). With the possible exception of chlorpyrifos oxon in sediments and total endosulfans, none of the contaminants by themselves exceeded known lethal or sublethal concentrations. Principal Components Analysis showed that the concentrations of endosulfans, chlorpyrifos, and trifluralin were associated with historic and present day population status of amphibians.