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Spatial Patterns of Airborne Pesticides in the Alpine Habitat of a Declining California Amphibian, The Mountain Yellow-Legged Frog
Citation:
BRADFORD, D. F. Spatial Patterns of Airborne Pesticides in the Alpine Habitat of a Declining California Amphibian, The Mountain Yellow-Legged Frog. Presented at Sierra Nevada Alliance Workshop on State of Sierra Frogs, Sacramento, CA, July 24, 2008.
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Presentation
Description:
The mountain yellow-legged frog complex (Rana muscosa complex) has disappeared from most of its historic localities in the Sierra Nevada of California, and airborne pesticides from the Central Valley have been implicated as a causal agent. To determine the distributions and concentrations of pesticides in the habitat of this species, we sampled air, sediment, and Pacific treefrog (Pseudacris regilla) tadpoles at high elevation (2754-3378 m) throughout Sequoia and Kings Canyon National Parks. Twenty-eight sites were sampled (14 dispersed areas, 2 ponds/area) twice during summer of 2005. Passive air sampling devices, which sampled air over 30-d intervals, detected only the pesticide endosulfan II frequently. In sediment and tadpoles, we found nine pesticides or their breakdown products frequently: the currently used endosulfan (I & II), endosulfan sulfate, dacthal, and chlorpyrifos, and the historically used DDE, chlordane (trans), and nonachlor (cis & trans). Concentrations were low, a few ng/g dry mass (ppb) or less for sediment and tadpoles. Pesticide concentrations did not show consistent patterns in distribution between the two sampling periods relative to distance from agricultural source areas in the San Joaquin Valley, 43-82 km away. A preliminary analysis of the distribution of pesticides relative to the distribution of remaining populations of mountain yellow-legged frogs does not show a correspondence between the two.