Pesticide Fate Research Group

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FIELD STUDIES: Pesticides in Amphibian Habitats (2009-2011)

Pond in the Sierra Nevada Mountains


Amphibian populations are in decline worldwide. Most notably, studies in the Sierra Nevada Mountains of California have documented a significant decline in native amphibian populations over the last several decades. Habitat loss, predation, disease (particularly the introduction of the fungus, Batrachochytrium dendrobatidis), and pollution, including pesticides, are factors thought to be involved in this decadal decline of amphibians. Agricultural chemicals acting singly or in combination with other stressors are receiving increasing attention as a potential cause of amphibian population declines. The primary objective of this study was to investigate the potential roles of environmental contaminants, particularly pesticides, as stressors contributing to the amphibian population decline.

Water and bed-sediment samples were collected in 2009 and 2010 from 11 sites within California and 18 sites total in Colorado, Georgia, Idaho, Louisiana, Maine, and Oregon from perennial or seasonal ponds located in amphibian habitats. Water and sediment samples were collected once in 2009 during amphibian breeding seasons. In 2010, water samples were collected twice. The first sampling event coincided with the beginning of the frog breeding season for the species of interest, and the second event occurred 10–12 weeks later when pesticides were being applied to the surrounding areas.

A total of 24 pesticides were detected in one or more of the 54 water samples, including 7 fungicides, 10 herbicides, 4 insecticides, 1 synergist, and 2 pesticide degradates. On a national scale, aminomethylphosphonic acid (AMPA), the primary degradate of the herbicide glyphosate, which is the active ingredient in Roundup®, was the most frequently detected pesticide in water (16 of 54 samples) followed by glyphosate (8 of 54 samples). The maximum number of pesticides observed at a single site was nine compounds in a water sample from a site in Louisiana. The maximum concentration of a pesticide or degradate observed in water was 2,880 nanograms per liter of clomazone (a herbicide) at a site in Louisiana. In California, a total of eight pesticides were detected among all of the low and high elevation sites; AMPA was the most frequently detected pesticide, but glyphosate was detected at the highest concentrations (1.1 micrograms per liter).

In bed sediment, 22 pesticides were detected in one or more of the samples, including 9 fungicides, 3 pyrethroid insecticides, p,p’-dichlorodiphenyltrichloroethane (p,p’-DDT) and its major degradates, as well as several herbicides. Pyraclostrobin, a strobilurin fungicide, and bifenthrin, a pyrethroid insecticide, were detected most frequently. Maximum pesticide concentrations ranged from less than their respective method detection limits to 1,380 micrograms per kilogram (tebuconazole in California). The number of pesticides detected in samples from each site ranged from zero to six compounds. The sites with the greatest number of pesticides were in Maine and Oregon with six pesticides detected in one sample from each state, followed by Georgia with four pesticides in one sample. For California, a total of 10 pesticides were detected among all sites, and 4 pesticides were detected at both low and high elevation sites; tebuconazole and pyraclostrobin were the two most frequently detected pesticides in California. For the other six selected states, the most frequently detected pesticides in bed sediment were pyraclostrobin (detected in 17 of 42 samples), bifenthrin (detected in 14 of 42 samples), and tebuconazole (detected in 10 of 42 samples).

Project was in collaboration with the USGS Amphibian Research and Monitoring Initiative and the USGS Toxic Substances Hydrology Program.

Project News Release: Pesticide Accumulation in Sierra Nevada Frogs

Smalling, K.L., Fellers, G.M, Kleeman, P.M, Kuivila, K.M, Accumulation of pesticides in Pacific Chorus frogs (Pseudacris regilla) from California’s Sierra Nevada Mountains, USA, Environmental Toxicology and Chemistry.

Smalling, K.L., Orlando, J.L., Calhoun, Daniel, Battaglin, W.A., and Kuivila, K.M., 2012, Occurrence of pesticides in water and sediment collected from amphibian habitats located throughout the United States, 2009–10: U.S. Geological Survey Data Series 707, 36 p.

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