Search Results

Populations of Pacific lamprey Lampetra tridentata have declined in the Columbia River basin. One factor that may have contributed to this reduction in population size is an excessive use of energy by adult lampreys as they negotiate fishways at dams during spawning migrations. To gain an understanding of the performance...

The CALFED Bay-Delta Program faces a challenging assignment: to develop a collaborative state-federal management plan for the complex river system and involve multiple stakeholders (primarily municipal, agricultural, and environmental entities) whose interests frequently are in direct conflict. Although many resource-management issues involve multiple stakeholders and conflict is integral to their...

Thirty-one samples of transported Holocene Acropora cervicornis "sticks" sampled from carbonate sand tempestite accumulations at 19 sites along a 180-km-long stretch of the Florida reef tract were dated using the radiocarbon (14C) method. The "modern fossils" collected from just a few centimeters below the surface ranged in age from 0.5...

Specific UV absorbance (SUVA) is defined as the UV absorbance of a water sample at a given wavelength normalized for dissolved organic carbon (DOC) concentration. Our data indicate that SUVA, determined at 254 nm, is strongly correlated with percent aromaticity as determined by 13C NMR for 13 organic matter isolates...

Because declines within amphibian populations can seldom be attributed to a single cause, it is important to focus on multiple stressors, both natural and anthropogenic. Variables such as UV-B radiation and chemical contamination can interact with one another in ways that might not be predicted from single-factor studies. We exposed...

The northward migration of the Mendocino triple junction has resulted in a fundamental modification of the crust of coastal California. As a consequence of viscous coupling between the southern edge of the Gorda slab and the base of the North American crust beneath the Coast Ranges of central and northern...

Detachment faults on the west flank of the Black Mountains (Nevada and California) dip 29??-36?? and cut subhorizontal layers of the 0.77 Ma Bishop ash. Steeply dipping normal faults confined to the hanging walls of the detachments offset layers of the 0.64 Ma Lava Creek B tephra and the base...

Between July 2000 and August 2001 forty-three air samples were collected in the northern Caribbean: Twenty-six in the US Virgin Islands, and 17 samples aboard ship during two 1-week cruises. Samples were collected during African dust events and non-dust conditions and screened for the presence of culturable bacteria and fungi....

The Sea Turtle Stranding and Salvage Network has been monitoring turtle strandings for more than 20 years in the United States. High numbers of strandings in the early to mid-1980s prompted regulations to require turtle excluder devices (TEDs) on shrimping vessels (trawlers). Following year-round TED implementation in 1991, however, stranding...

Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing-season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55°N, including the position of the...

A predominant cause of dispersion in groundwater is advective mixing due to variability in seepage rates. Hydraulic conductivity variations have been extensively researched as a cause of this seepage variability. In this paper the effect of variations in surface recharge to a shallow surficial aquifer is investigated as an important...

Cone penetration test (CPT) soundings at historic liquefaction sites in California were used to evaluate the predictive capability of the liquefaction potential index (LPI), which was defined by Iwasaki et al. in 1978. LPI combines depth, thickness, and factor of safety of liquefiable material inferred from a CPT sounding into...

No abstract available....

The Lik deposit in northern Alaska is a largely unexposed shale-hosted Zn-Pb-Ag massive sulphide deposit that is underlain by continuous permafrost. Residual soils overlying the mineralized zone have element enrichments that are two to six times greater than baseline values. The most prominent elements are Ag, Mo, P, Se, Sr,...

We evaluated the effects of a single electroshock on injury and mortality of hatchery-reared Cape Fear shiners Notropis mekistocholas (N = 517), an endangered cyprinid. Groups of 18-22 Cape Fear shiners were exposed to DC, 120-Hz pulsed DC (PDC), or 60-Hz PDC at voltage gradients of 1.1, 1.9, or 2.7...

Two M ??? 6 well-recorded strike-slip earthquakes struck just 4 km and 48 days apart in Kagoshima prefecture, Japan, in 1997, providing an opportunity to study earthquake interaction. Aftershocks are abundant where the Coulomb stress is calculated to have been increased by the first event, and they abruptly stop where...

We present methods for improving the location of long-period (LP) events, deep and shallow, recorded below Kilauea Volcano by the permanent seismic network. LP events might be of particular interest to understanding eruptive processes as their source mechanism is assumed to directly involve fluid transport. However, it is usually difficult...

The objectives of this pyrolysis investigation were to determine changes in (1) oil composition, (2) gas composition and (3) gas carbon isotope ratios and to compare these results with hydrocarbons in reservoirs. Laboratory cracking of a saturate-rich Devonian oil by confined, dry pyrolysis was performed at T = 350-450??C, P...

Each Mars Exploration Rover carries an integrated suite of scientific instruments and tools called the Athena science payload. The primary objective of the Athena science investigation is to explore two sites on the Martian surface where water may once have been present, and to assess past environmental conditions at those...

The San Andreas Fault Observatory at Depth pilot hole is located on the southwestern side of the Parkfield San Andreas fault. This observatory includes a vertical seismic profiling (VSP) array. VSP seismograms from nearby micro-earthquakes contain signals between the P and S waves. These signals may be P and S...

A field experiment was conducted on May 7-8, 2002 using a CODAR RiverSonde UHF radar system at Vernalis, California on the San Joaquin River. The monostatic radar configuration on one bank of the river, with the antennas looking both upriver and downriver, provided very high-quality data. Estimates of both along-river...

The U.S. Geological Survey has developed a methodology for statistically relating nutrient sources and land-surface characteristics to nutrient loads of streams. The methodology is referred to as SPAtially Referenced Regressions On Watershed attributes (SPARROW), and relates measured stream nutrient loads to nutrient sources using nonlinear statistical regression models. A spatially...

From the velocity profiles across the river, estimates of total volume flow for the four methods were calculated based on a knowledge of the bottom depth vs position across the river. It was found that the flow comparisons for the American River were much closer, within 2% of each other...

A study was undertaken to measure aerobic respiration by indigenous bacteria in a sand and gravel aquifer on western Cape Cod, MA using tetrazolium salts and by direct oxygen consumption using gas chromatography (GC). In groundwater and aquifer slurries, the rate of aerobic respiration...

High-resolution seismic-reflection data collected along the length of the Caloosahatchee River in southwestern Florida have been correlated to nannofossil biostratigraphy and strontium-isotope chemostratigraphy at six continuously cored boreholes. These data are interpreted to show a major Late Miocene(?) to Early Pliocene fluvial-deltaic depositional system that prograded southward across the carbonate Florida Platform, interrupting nearly continuous carbonate deposition since early...