Citation:

BRADFORD, D. F., E. M. HEITHMAR, N. G. TALLENT-HALSELL, G. MOMPLAISIR, C. G. ROSAL, L. A. RIDDICK, AND K. E. VARNER. TEMPORAL PATTERNS OF AIRBORNE PESTICIDES IN THE HABITATE OF THE MOUNTAIN YELLOW-LEGGED FROG IN THE SOUTHERN SIERRA NEVADA. Presented at Annual Meeting of California-Nevada Amphibian Populations Task Force, Las Vegas, NV, January 18 - 20, 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:

Airborne agricultural pesticides from the Central Valley of California have been implicated as a possible cause for recent, dramatic population declines of several amphibian species in remote mountain locations. To determine the temporal variation of pesticide levels in the habitat of one of these species, the mountain yellow-legged frog (Rana muscosa), we sampled water from four lakes at high elevation (2754-3475 m) in the southern Sierra Nevada. The lakes ranged between 45 and 85 km from the San Joaquin Valley (i.e., southern end of Central Valley). Lakes were

sampled weekly or monthly from mid June to mid October, 2003. Nine of 45 target analytes were detected at least once among the four lakes. Four pesticides were found sufficiently frequently to evaluate for temporal patterns: two insecticide/acaricides (endosulfan I and propargite) and two herbicides (dacthal [DCPA] and simazine). Concentrations of these pesticides were extremely low, on the order of 1 ng/L (parts per trillion) or less. For endosulfan and propargite, temporal variation in their concentrations corresponded closely with application

rates in the San Joaquin Valley, with a lag time of 1-2 weeks. In contrast, application of dacthal and simazine was practically nil in the Valley during the sampling period. Linear distance from the San Joaquin Valley alone did not appear to be an adequate predictor of contaminant levels in lake water. Mountain yellow-legged frog populations have largely disappeared from the vicinities of lakes with both the higher and lower pesticide concentrations observed in the study.

Record Details: