C. Rice | USGS Science

USGS2009

Prevalence of viral erythrocytic necrosis in Pacific herring and epizootics in Skagit Bay, Puget Sound, Washington.

Epizootics of viral erythrocytic necrosis (VEN) occurred among juvenile Pacific herring Clupea pallasii in Skagit Bay, Puget Sound, Washington, during 2005-2007 and were characterized by high prevalences and intensities of cytoplasmic inclusion bodies within circulating erythrocytes. The prevalence of VEN peaked at 67% during the first epizootic in October 2005 and waned to 0% by August 2006. A second VEN epizootic occurred throughout the summer of 2007; this was characterized by disease initiation and perpetuation in the age-1, 2006 year-class, followed by involvement of the age-0, 2007 year-class shortly after the latter's metamorphosis to the juvenile stage. The disease was detected in other populations of juvenile Pacific herring throughout Puget Sound and Prince William Sound, Alaska, where the prevalences and intensities typically did not correspond to those observed in Skagit Bay. The persistence and recurrence of VEN epizootics indicate that the disease is probably common among juvenile Pacific herring throughout the eastern North Pacific Ocean, and although population-level impacts probably occur they are typically covert and not easily detected.

Journal of Aquatic Animal Health↗

USGS2003

Aqueous-phase disappearance of atrazine, metolachlor, and chlorpyrifos in laboratory aquaria and outdoor macrocosms

Dissipation processes are described for a combination of commonly used pesticides—atrazine (6-chloro-4-ethylamino-6-isopropylamino- s -triazine), metolachlor (2-chloro- N -[2-ethyl-6-methyl-phenyl]- N -[2-methoxy-1-methylethyl] acetamide), and chlorpyrifos ( O-O diethyl O -[3,5,6-trichloro-2-pyridinyl] phosphorothioate)—in a laboratory and outdoor pond systems. Dosing rates and timing were designed to duplicate those common in the mid-Atlantic Coastal Plain, USA. Treatments ranged from 2 and 2.5 mg/L to 0.2 and 0.25 mg/L respectively for atrazine and metolachlor, and chlorpyrifos was added at 1.0 and 0.1 mg/L in the aquaria and at 0.1 mg/L in the outdoor macrocosms. Chlorpyrifos disappearance was rapid in all of the systems and followed a two-phase sequence. Initial half-lives varied from 0.16 day to 0.38 day and showed similar rates in the aquaria and the outdoor systems. The second phase of the chlorpyrifis loss pattern was slower (18–20 days) in all the treatments except for the low herbicide treatment in the outdoor test, where it was 3.4 days. Compared to the outdoor system, herbicide losses were much slower in the aquaria, e.g., 150 days for atrazine and 55 days for metolachlor, and no appreciable loss of herbicide was apparent in the high-treated aquaria. In the outdoor systems, the half-lives for the low herbicide treatment were 27 days and 12 days, respectively, for atrazine and metolachlor, and 48 and 20 days, respectively for the high herbicide-treated pond. Very low levels of CIAT (6-amino-2-chloro-4-iso-propylamino- s -triazine) and CEAT (2-chloro-4-ethylamino-6-ethylamino- s -triazine), degradation products of atrazine, were observed in the outdoor studies.

Archives of Environmental Contamination and Toxico↗

USGS2003

Synergistic effects of a combined exposure to herbicides and an insecticide in Hyla versicolor

Combinations of the herbicides atrazine and metolachlor and the insecticide chlorpyrifos were tested under both laboratory and field conditions to determine their individual and combined effects on amphibian populations. In the lab Hyla versicolor tadpoles experienced 100% mortality when exposed to a high combination of the pesticides (2.0 mg/L atrazine, 2.54 mg/L metolachlor, 1.0 mg/L chlorpyrifos) whereas low concentrations of the pesticides (0.2 mg/L atrazine, 0.25 mg/L metolachlor, 0.1 mg/L chlorpyrifos) or high concentrations of either herbicides or insecticide alone caused lethargy, reduced growth and delayed metamorphosis but no significant mortality. In the field high herbicide, low insecticide and low herbicide, low insecticide mixtures significantly reduced amphibian populations compared to controls but in the low herbicide, low insecticide wetlands amphibian populations were able to recover through recruitment by the end of the season.

Book chapter↗

USGS2003

Synergistic effects of a combined exposure to herbicides and an insecticide in Hyla versicolor

Combinations of the herbicides atrazine and metolachlor and the insecticide chlorpyrifos were tested under both laboratory and field conditions to determine their individual and combined effects on amphibian populations. In the lab Hyla versicolor tadpoles experienced 100% mortality when exposed to a high combination of the pesticides (2.0 mg/L atrazine, 2.54 mg/L metolachlor, 1.0 mg/L chlorpyrifos) whereas low concentrations of the pesticides (0.2 mg/L atrazine, 0.25 mg/L metolachlor, 0.1 mg/L chlorpyrifos) or high concentrations of either herbicides or insecticide alone caused lethargy, reduced growth and delayed metamorphosis but no significant mortality. In the field high herbicide, low insecticide and low herbicide, low insecticide mixtures significantly reduced amphibian populations compared to controls but in the low herbicide, low insecticide wetlands amphibian populations were able to recover through recruitment by the end of the season.

Conference Paper↗