Publications

Phytoplankton cells reside in a turbulent medium partitioned into an upper photic zone that sustains photosynthesis, and a lower aphotic zone that does not. In estuaries, vertical mixing rates between these 2 zones can be rapid ( 1 generation time) because of tidal stirring and because the mixing depth is generally shallow. Moreover, the photic depth is characteristically shallow in...

Soils from three agricultural fields in the Panoche Creek alluvial fan area in the western San Joaquin Valley, California, were analyzed for soluble, adsorbed, and total concentrations of selenium (Se) to assess the distribution and forms of Se in relation to the leaching of Se from soils. This assessment is needed to evaluate the importance of soil Se in affecting ground water...

Samples of shallow groundwater that underlies much of the irrigated area in the western San Joaquin Valley, CA, were analyzed for various major ions and trace elements, including selenium. Concentrations of the major ions generally were similar for groundwater collected in the two primary geologic zones - the alluvial fan and basin trough. Selenium concentrations are significantly (α = 0...

Concentrations of total selenium were high in 1983 in water, sediment, organic detritus, aquatic plants and invertebrates, and mosquitofish (Gambusia affinis) from Kesterson Reservoir (San Joaquin Valley, California) and the San Luis Drain. Selenium concentrations in biota from the Reservoir and Drain (referred to here collectively as “Kesterson”) exceeded 300 (μg/g dry weight in some...

In a recent study at Kesterson Reservoir in California, selenium was shown to cause mortality and deformities in embryos of aquatic birds. The present study was conducted to determine if selenium or other contaminants in agricultural drainwater used for marsh management were likely to cause similar adverse effects in the nearby Grasslands area. Selenium concentrations were elevated...

A portable apparatus was used to filter large quantities of water from streams in California's Sierra Nevada. Samples were processed and examined for Giardia spp. Cysts of Giardia were detected in 22 of 49 (44.9 percent) samples collected at sites downstream from areas of high recreational use and in 5 of 29 (17.2 percent) samples collected at sites downstream from areas of low...

Phytoplankton biomass (as carbon) was estimated from chlorophyll a concentrations (Chla) and a mean value for the ratio of phytoplankton carbon to chlorophyll a in San Francisco Bay. The ratio was determined as the slope of a Model II regression of POC' against (Chla), where POC' is total particulate organic carbon minus sediment-associated non-phytoplankton carbon. Samples from 30 fixed...

In the summer of 1985, the U.S. Geological Survey conducted a reconnaissance geochemical survey of the Skedaddle (CA-020-612) and Dry Valley Rim (CA-020-615) Wilderness Study Areas in Lassen County, California, and Washoe County, Nevada. Skedaddle and Dry Valley Rim are contiguous wilderness study areas (WSA) located in the eastern part of the Modoc Plateau in Lassen County, northeastern...

Acid mine drainage has acidified large volumes of water and added high concentrations of dissolved heavy metals to West Squaw Creek, a California stream draining igneous rocks of low acid-neutralizing capacity. During mixing of the acid sulfate stream waters in the South Fork of West Squaw Creek with an almost equal volume of dilute uncontaminated water, Cu, Zn, Mn, and Al remained in...

Samples of bluegills (Lepomis macrochirus) and common carp (Cyprinus carpio) collected from the San Joaquin River and two tributaries (Merced River and Salt Slough) in California were analyzed for 21 organochlorine chemical residues by gas chromatography to determine if pesticide contamination was confined to downstream sites exposed to irrigated agriculture, or if nonirrigated upstream...

A study was performed to assess the accuracy of a daily solar radiation model for horizontal or sloping sites in terrain where surrounding ridges and tall trees block both direct beam and diffuse sky short wave radiation. To simulate adequately the major effects of these environments on radiation, the model incorporated (1) standard treatment of solar geometry (after Harris, 1983); (2)...

The chemical and isotopic composition of rainfall and stream water was monitored during a storm in the Mattole River basin of northwestern California. About 250 mm of rain fell during 6 days (∼80% within a 42 h period) in late January, 1972, following 24 days of little or no precipitation. River discharge near Petrolia increased from 22 m3 s−1 to a maximum of 1300 m3s−1 while chloride...