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Rancho Cordova, CA, United States

Hasenbein M.,University of California at Davis | Hasenbein M.,TU Munich | Werner I.,Ecole Polytechnique Federale de Lausanne | Deanovic L.A.,University of California at Davis | And 6 more authors.
Science of the Total Environment | Year: 2013

Contaminant exposure is one possible contributor to population declines of endangered fish species in the Sacramento-San Joaquin Estuary, California, including the endangered delta smelt (Hypomesus transpacificus). Herein we investigated transcriptional responses in larval delta smelt resulting from exposure to water samples collected at the Department of Water Resources Field Station at Hood, a site of concern, situated upstream of known delta smelt habitat and spawning sites and downstream of the Sacramento Regional Wastewater Treatment Plant (SRWTP). Microarray assessments indicate impacts on energy metabolism, DNA repair mechanisms and RNA processing, the immune system, development and muscle function. Transcription responses of fish exposed to water samples from Hood were compared with exposures to 9% effluent samples from SRWTP, water from the Sacramento River at Garcia Bend (SRGB), upstream of the effluent discharge, and SRGB water spiked with 2. mg/L total ammonium (9% effluent equivalent). Results indicate that transcriptomic profiles from Hood are similar to 9% SRWTP effluent and ammonium spiked SRGB water, but significantly different from SRGB. SRGB samples however were also significantly different from laboratory controls, suggesting that SRWTP effluent is not solely responsible for the responses determined at Hood, that ammonium exposure likely enhances the effect of multiple-contaminant exposures, and that the observed mortality at Hood is due to the combination of both effluent discharge and contaminants arising from upstream of the tested sites. © 2013. Source


Anderson B.S.,University of California at Davis | Phillips B.M.,University of California at Davis | Voorhees J.P.,University of California at Davis | Petersen M.A.,University of California at Davis | And 4 more authors.
Integrated Environmental Assessment and Management | Year: 2015

Many watersheds in the Central Valley region of California are listed as impaired due to pyrethroid-associated sediment toxicity. The Central Valley Regional Water Quality Control Board is developing numeric sediment quality criteria for pyrethroids, beginning with bifenthrin. Criteria are being developed using existing data, along with data from 10 d and 28 d toxicity tests with Hyalella azteca conducted as part of the current study. A single range-finder and 2 definitive tests wereconducted for each test duration. Median lethal concentrations (LC50s), as well as LC20s and inhibition concentrations (IC20s) were calculated based on measured whole sediment bifenthrin concentrations and interstitial water concentrations. Sediment LC50s were also corrected for organic C content. Average LC50s were not significantly different in 10 d versus 28 d tests with H. azteca: 9.1 and 9.6 ng/g bifenthrin for 10 d and 28 d tests, respectively. Average LC20 values were also similar with concentrations at 7.1 and 7.0 for 10 d and 28 d tests, respectively. Bifenthrin inhibition concentrations (IC20s) based on amphipod growth were variable, particularly in the 28 d tests, where a clear dose-response relationship was observed in only 1 of the definitive experiments. Average amphipod growth IC20s were 3.9 and 9.0 ng/g for 10 d and 28 d tests, respectively. Amphipod growth calculated as biomass resulted in IC20s of 4.1 and 6.3 ng/g for the 10 d and 28 d tests, respectively. Lack of a clear growth effect in the longer term test may be related to the lack of food adjustment to account for amphipod mortality in whole sediment exposures. The average C-corrected LC50s were 1.03 and 1.09 μg/g OC for the 10 d and 28 d tests, respectively. Interstitial water LC50s were determined as the measured dissolved concentration of bifenthrin relative to interstitial water dissolved organic carbon. The average LC50s for dissolved interstitial water bifenthrin were 4.23 and 4.28 ng/L for the 10 d and 28 d tests, respectively. In addition, a set of 10 d and 28 d tests were conducted at 15 °C to assess the relative toxicity of bifenthrin at a lower temperature than the standard 23 °C test temperature. These results showed that bifenthrin was more toxic at the lower temperature, with LC50s of 5.1 and 3.4 ng/g bifenthrin in 10 d and 28 d tests, respectively. Amphipod growth at 15 °C after a 28 d exposure resulted in the lowest effect concentration of all experiments conducted (IC20=0.61 ng/g). This article discusses how bifenthrin dose-response data from 10 d and 28 d exposures inform development of sediment quality criteria for this pesticide for California Central Valley watersheds. © 2015 SETAC. Source


Deanovic L.A.,University of California at Davis | Markiewicz D.,University of California at Davis | Stillway M.,University of California at Davis | Fong S.,Central Valley Regional Water Quality Control Board | Werner I.,University of California at Davis
Environmental Toxicology and Chemistry | Year: 2013

Standard U.S. Environmental Protection Agency laboratory tests are used to monitor water column toxicity in U.S. surface waters. The water flea Ceriodaphnia dubia is among the most sensitive test species for detecting insecticide toxicity in freshwater environments.Its usefulness is limited, however, when water conductivity exceeds 2,000μS/cm (approximately 1 ppt salinity) and test effectiveness is insufficient. Water column toxicity tests using the euryhaline amphipod Hyalella azteca could complement C. dubia tests; however, standard chronic protocols do not exist. The present study compares the effectiveness of two water column toxicity tests in detecting the toxicity of two organophosphate (OP) and two pyrethroid insecticides: the short-term chronic C. dubia test, which measures mortality and fecundity, and a 10-d H. azteca test, which measures mortality and growth. Sensitivity was evaluated by comparing effect data, and end point variability was evaluated by comparing minimum significant differences. Tests were performed in synthetic water and filtered ambient water to quantify the influence of water matrix on effect concentrations. The H. azteca test detected pyrethroid toxicity far more effectively, while the C. dubia test was more sensitive to OPs. Among endpoints, H. azteca mortality was most robust. The results demonstrate that the H. azteca test is preferable when conductivity of water samples is 2,000 to 10,000μS/cm or if contaminants of concern include pyrethroid insecticides. Environ. Toxicol. Chem. 2013;32:707-712. © 2012 SETAC. Source


TenBrook P.L.,University of California at Davis | TenBrook P.L.,U.S. Environmental Protection Agency | Palumbo A.J.,University of California at Davis | Fojut T.L.,University of California at Davis | And 3 more authors.
Reviews of Environmental Contamination and Toxicology | Year: 2010

A national water quality criteria methodology was established in the United States (US) in 1985 (US Environmental Protection Agency; USEPA 1985). 1 Since then, several other methods for establishing water quality criteria have been developed around the world, incorporating recent advances in the field of aquatic toxicology using a variety of different approaches. The authors of a recent review compared existing methodologies and summarized the differences between them (see tables 4 and 5 in TenBrook et al. 2009). TenBrook et al. (2009) observed that although methods from the USEPA provided a good basis for calculating criteria, many newer methodologies added valuable procedures that could improve criteria generation. Of particular concern were cases having small data sets, for which the USEPA (1985) methodology does not allow criteria calculation and provides little guidance. In this review, we elaborate on the review of methodologies by TenBrook et al. (2009) and we propose a new methodology that combines features derived from the existing methodologies that have been determined to generate the most flexible and robust criteria. This new methodology also incorporates results from recent research in aquatic ecotoxicology and environmental risk assessment and is hereafter referred to as the University of California-Davis Methodology (UCDM). © 2010 Springer Science+Business Media, LLC. Source

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