Temporal and spatial variation of atmospherically deposited organic contaminants at high elevation in Yosemite National Park, California, USA.

Contaminants used at low elevation, such as pesticides on crops, can be transported tens of kilometers and deposited in adjacent mountains in many parts of the world. Atmospherically deposited organic contaminants in the Sierra Nevada Mountains of California, USA, have exceeded some thresholds of concern, but the spatial and temporal distributions of contaminants in the mountains are not well known. The authors sampled shallow-water sediment and tadpoles (Pseudacris sierra) for pesticides, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls in four high-elevation sites in Yosemite National Park in the central Sierra Nevada twice during the summers of 2006, 2007, and 2008.

Contaminant residues and declines of the Cascades frog (Rana cascadae) in the California Cascades, USA.

Populations of Cascades frogs (Rana cascadae) have declined precipitously in the Mount Lassen area, but remain abundant in the other half of their California range in the Klamath Mountains. To evaluate the role of contaminants in Cascade frog declines, we sampled sediment and frog tadpole tissue at 31 sites where Cascades frogs had disappeared and sites where Cascades frogs are still present across the Lassen and Klamath regions. Pacific chorus frogs (Pseudacris regilla) were tested and used as surrogates for residue concentrations in Cascades frogs.

Complex modulation of androgen responsive gene expression by methoxyacetic acid.

Background: Optimal androgen signaling is critical for testicular development and spermatogenesis. Methoxyacetic acid (MAA), the primary active metabolite of the industrial chemical ethylene glycol monomethyl ether, disrupts spermatogenesis and causes testicular atrophy. Transcriptional trans-activation studies have indicated that MAA can enhance androgen receptor activity, however, whether MAA actually impacts the expression of androgen-responsive genes in vivo, and which genes might be affected is not known.

Pesticide distributions and population declines of California, USA, alpine frogs, Rana muscosa and Rana sierrae.

Atmospherically deposited pesticides from the intensively cultivated Central Valley of California, USA, have been implicated as a cause for population declines of several amphibian species, with the strongest evidence for the frogs Rana muscosa and Rana sierrae at high elevation in the Sierra Nevada mountains. Previous studies on these species have relied on correlations between frog population status and either a metric for amount of upwind pesticide use or limited measurements of pesticide concentrations in the field. The present study tested the hypothesis that pesticide concentrations are negatively correlated with frog population status (i.

Spatial patterns of atmospherically deposited organic contaminants at high elevation in the southern Sierra Nevada mountains, California, USA.

Atmospherically deposited contaminants in the Sierra Nevada mountains of California, USA have been implicated as adversely affecting amphibians and fish, yet little is known about the distributions of contaminants within the mountains, particularly at high elevation. The hypothesis that contaminant concentrations in a high-elevation portion of the Sierra Nevada decrease with distance from the adjacent San Joaquin Valley was tested. Air, sediment, and tadpoles were sampled twice at 28 water bodies in 14 dispersed areas in Sequoia and Kings Canyon National Parks (2,785-3,375 m elevation; 43-82 km from Valley edge).

Endosulfan I and endosulfan sulfate disrupts zebrafish embryonic development.

Fish in agricultural and remote areas may be exposed to endosulfan and its degradation products as a result of direct runoff, atmospheric transport and deposition. The following study used the zebrafish developmental model to investigate the responses to endosulfan I and endosulfan sulfate, the major degradation product of endosulfan I and II. Embryos were dechorionated and waterborne exposed to the endosulfan I or endosulfan sulfate from 6 to 120h post-fertilization (hpf).

Comparison of pressurized liquid extraction and matrix solid-phase dispersion for the measurement of semivolatile organic compound accumulation in tadpoles.

Analytical methods capable of trace measurement of semivolatile organic compounds (SOCs) are necessary to assess the exposure of tadpoles to contaminants as a result of long-range and regional atmospheric transport and deposition. The present study compares the results of two analytical methods, one using pressurized liquid extraction (PLE) and the other using matrix solid-phase dispersion (MSPD), for the trace measurement of more than 70 SOCs in tadpole tissue, including current-use pesticides. The MSPD method resulted in improved SOC recoveries and precision compared to the PLE method.