Citation:

BRADFORD, D. F., E. M. HEITHMAR, K. STANLEY, L. MCCONNELL, D. SPARLING, S. SIMONICH, N. G. TALLENT-HALSELL, G. MOMPLAISIR, C. G. ROSAL, L. A. RIDDICK, AND K. E. VARNER. TEMPORAL AND SPATIAL PATTERNS OF AIRBORNE PESTICIDES IN THE ALPINE ENVIRONMENT OF A DECLINING CALIFORNIA AMPHIBIAN, THE MOUNTAIN YELLOW-LEGGED FROG. Presented at Understanding Agriculture's Effects on Amphibians and Reptiles in a Changing World, St. Louis, MO, February 06 - 08, 2007.

Impact/Purpose:

The primary objectives of this research are to:

Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;

Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;

Develop and validate multivariate models based on quantification studies;

Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;

Complete an initial draft (potentially web based) of a national landscape condition assessment.

This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.

Description:

The mountain yellow-legged frog (Rana muscosa) 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 distribution and temporal variation of pesticide levels in the habitat of this species, we sampled multiple media at high elevation (2754-3475 m) throughout Sequoia and Kings Canyon National Parks. Results to date are preliminary. To determine temporal variation, we extracted 100-L water samples from 4 lakes monthly and 1 lake weekly from mid June to mid October 2003. Eleven pesticides were detected, four of which were frequently found: endosulfan (I and II), propargite, simazine, and dacthal. Concentrations were extremely low, on the order of ¿1 ng/L (part per trillion). For the two pesticides applied in the Central Valley concurrently with our sampling, endosulfan and propargite, temporal variation in their concentrations in lake water generally corresponded with application levels in the Valley. To determine spatial distribution, we sampled 14 dispersed areas, 2 ponds/area, 2 times during summer of 2005. Media were air, sediment, and Pacific treefrog (Pseudacris regilla) tadpoles. We also determined acetyl cholinesterase activity in treefrog tadpoles, an indicator of exposure to certain pesticides. Passive air sampling devices, which sampled air over 30-d intervals, detected 4 pesticides at very low concentrations; only endosulfan II was found commonly among sites. Six pesticides were found in tadpole tissue at low concentrations (<1 ng/g wet weight), with 4 found at most sites: p¿,p-DDE, dacthal, endosulfan II, endosulfan sulfate. Cholinesterase levels differed significantly among the 14 areas, with site means (adjusted for tadpole stage) varying by over 2-fold. The distribution of pesticides and cholinesterase levels relative to the distribution of remaining populations of Rana muscosa and proximity to the Central Valley (43-82 km away) will be addressed.

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