Publications

Estuarine food webs are highly variable and complex, making identification of their trophic pathways difficult. Energy for the food web of the San Francisco Estuary is thought to be based largely on in situ phytoplankton production, but little attention has been paid to littoral habitats, where other energy sources may be important. We analyzed the stomach contents of over 960 juvenile...

With phase inversion, one can estimate subsurface velocities using the phases of first-arriving waves, which are the frequency-domain equivalents of the traveltimes. Phase inversion is modified to make it suitable for processing traveltimes from near-surface refraction surveys. The modifications include parameterizing the model, correcting the observed phases, and selecting the complex...

No abstract available.

Dry deposition is a major component of total atmospheric nitrogen deposition and thus an important source of bioavailable nitrogen to ecosystems. However, relative to wet deposition, less is known regarding the sources and spatial variability of dry deposition. This is in part due to difficulty in measuring dry deposition and associated deposition velocities. Passive sampling techniques...

No abstract available.

Mercury speciation, controls on methylmercury (MeHg) production, and bed sediment−pore water partitioning of total Hg (THg) and MeHg were examined in bed sediment from eight geochemically diverse streams where atmospheric deposition was the predominant Hg input. Across all streams, sediment THg concentrations were best described as a combined function of sediment percent fines (%fines...

Spatial and temporal assessments and reports of polybrominated diphenyl ether (PBDE) flame retardants in birds remain sparse. In the present study, PBDEs were detected in all 120 osprey (Pandion haliaetus) eggs collected. The eggs were collected from nests along the Columbia, Willamette and Yakima rivers of Oregon (OR) and Washington (WA) and in Puget Sound (WA) between 2002 and 2007...

Seasonal trends of benthic methylmercury (methyl-Hg) production were examined in both littoral and open water sites of three lakes (Escondido, Moreno, and Morenito) in the North Andean Patagonia region of Argentina. Potentials of methyl-Hg production were measured by amending sediment samples with inorganic 197Hg(II), incubating for either 24 and 32 h at room temperature, and...

The relation of bacterial pathogen occurrence to fecal indicator bacteria (FIB) concentrations used for recreational water quality criteria (RWQC) is poorly understood. This study determined the occurrence of Shiga-toxin producing Escherichia coli (STEC) markers and their relation to FIB concentrations in Michigan and Indiana river water. Using 67 fecal coliform (FC) bacteria cultures...

Fish harvested from the Pacific Ocean are a major contributor to human methylmercury (MeHg) exposure. Limited oceanic mercury (Hg) data, particularly MeHg, has confounded our understanding of linkages between sources, methylation sites, and concentrations in marine food webs. Here we present methylated (MeHg and dimethylmercury (Me2Hg)) and total Hg concentrations from 16 hydrographic...

BBecause vadose zone research relates to diverse disciplines, applications, and modes of research, collaboration across traditional operational and topical divisions is especially likely to yield major advances in understanding. The Unsaturated Zone Interest Group (UZIG) is an informal organization sponsored by the USGS to encourage and support interdisciplinary collaboration in vadose...

Stream water samples were collected over a range of hydrologic and seasonal conditions at three forested watersheds in the northeastern USA. Samples were analyzed for dissolved total mercury (THgd), DOC concentration and DOC composition, and UV254 absorbance across the three sites over different seasons and flow conditions. Pooling data from all sites, we found a strong positive...