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United States Department of Agriculture

Agricultural Research Service


Location: Hydrology and Remote Sensing Laboratory

Title: Pesticides in amphibian habitats of central and northern California

item Fellers, G
item Sparling, D
item Mcconnell, Laura
item Kleeman, P
item Drakeford, L

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 9/15/2013
Publication Date: 12/15/2013
Citation: Fellers, G.M., Sparling, D.W., McConnell, L.L., Kleeman, P., Drakeford, L. 2013. Pesticides in amphibian habitats of central and northern California. In: McConnell, L.L., Dachs, J., Hapeman, C.J., editors. Occurrence Fate and Impact of Atmospheric Pollutants on Environmental and Human Health. Oxford, United Kingdom: Oxford University Press. p. 123-154.

Interpretive Summary: Frogs, salamanders and other amphibians are sensitive to chemical contaminants in their habitat. Wildlife biologists who track populations of amphibians have noticed significant declines in many areas of the world. This study examines the presence of pesticide residues in water and sediment of amphibian habitats (wetlands and ponds) and in the tissues of Pacific tree frogs in four, East-West transects across the state of California. Concentrations of the 20-25 different pesticides measured were very low or below detection limits for most samples. However, locations with detections of multiple chemicals, especially endosulfan, chlorpyrifos and trifluralin were associated with sites with significant population declines. This may indicate that combinations of compounds have a greater toxicity than the individual compounds alone.

Technical Abstract: 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 Pacific 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 were found in the tissues of adult P. regilla. Seventeen contaminants were found in sediments including endosulfan sulfate, chlordanes, 1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethenyl]benzene (4,4’-DDE), and chlorpyrifos. The average (standard deviation) 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.

Last Modified: 06/22/2017
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