Characterizing dissolved Cu and Cd uptake in terms of the biotic ligand and biodynamics using enriched stable isotopes
Marie Noele Croteau, Samuel N. Luoma
2007, Environmental Science & Technology (41) 3140-3145
The biotic ligand model considers the biological and geochemical complexities that affect metal exposure. It relates toxicity to the fraction of physiological active sites impacted by reactive metal species. The biodynamic model is a complementary construct that predicts bioaccumulation and assumes that toxicity occurs when influx...
The rate and pattern of bed incision and bank adjustment on the Colorado River in Glen Canyon downstream from Glen Canyon Dam, 1956-2000
P.E. Grams, J. C. Schmidt, D.J. Topping
2007, Geological Society of America Bulletin (119) 556-575
Closure of Glen Canyon Dam in 1963 transformed the Colorado River by reducing the magnitude and duration of spring floods, increasing the magnitude of base flows, and trapping fine sediment delivered from the upper watershed. These changes caused the channel downstream in Glen Canyon to incise, armor, and narrow. This...
Structure-specific scalar intensity measures for near-source and ordinary earthquake ground motions
N. Luco, C.A. Cornell
2007, Earthquake Spectra (23) 357-392
Introduced in this paper are several alternative ground-motion intensity measures (IMs) that are intended for use in assessing the seismic performance of a structure at a site susceptible to near-source and/or ordinary ground motions. A comparison of such IMs is facilitated by defining the "efficiency" and "sufficiency" of an IM,...
Tracking environmental dynamics and agricultural intensification in southern Mali
G. Gray Tappan, M. McGahuey
2007, Agricultural Systems (94) 38-51
The Office de la Haute Vallée du Fleuve Niger (OHVN) zone in southern Mali is a small but important agricultural production region. Against a background of environmental degradation including decades of declining rainfall, soil erosion, and human pressure on forest resources, numerous farming communities stand out through the use of...
Effects of prolonged exposure to perchlorate on thyroid and reproductive function in zebrafish
S. Mukhi, R. Patino
2007, Toxicological Sciences (96) 246-254
The objectives of this study were to determine the effects of prolonged exposure to perchlorate on (1) thyroid status and reproductive performance of adult zebrafish (Danio rerio) and (2) F1 embryo survival and early larval development. Using a static-renewal procedure, mixed sex populations of adult zebrafish were exposed to 0,...
Biomarkers of contaminant exposure in northern pike (Esox lucius) from the Yukon River Basin, Alaska
J.E. Hinck, V. S. Blazer, N. D. Denslow, M.S. Myers, T. S. Gross, D. E. Tillitt
2007, Archives of Environmental Contamination and Toxicology (52) 549-562
As part of a larger investigation, northern pike (n = 158; Esox lucius) were collected from ten sites in the Yukon River Basin (YRB), Alaska, to document biomarkers and their correlations with organochlorine pesticide (total p,p'-DDT, total chlordane, dieldrin, and toxaphene), total polychlorinated biphenyls (PCBs), and elemental contaminant (arsenic, cadmium,...
Invasive species and coal bed methane development in the Powder River Basin, Wyoming
E. Bergquist, P. Evangelista, T.J. Stohlgren, N. Alley
2007, Environmental Monitoring and Assessment (128) 381-394
One of the fastest growing areas of natural gas production is coal bed methane (CBM) due to the large monetary returns and increased demand for energy from consumers. The Powder River Basin, Wyoming is one of the most rapidly expanding areas of CBM development with projections of the establishment of...
Functional groups in a single pteridosperm species: Variability and circumscription (Pennsylvanian, Nova Scotia, Canada)
E.L. Zodrow, Maria Mastalerz
2007, International Journal of Coal Geology (70) 313-324
Multiple foliar specimens of the Late Pennsylvanian fossil pteridosperm [gymnosperm] Alethopteris zeilleri (Ragot) Wagner were collected from one restricted stratigraphical horizon in the Canadian Sydney Coalfield. Variability of functional-group distribution using FTIR technique was studied in compressions, adaxial versus abaxial cuticles, and in unseparated cuticles as a function of maceration...
Long-term changes in abundance and diversity of macrophyte and waterfowl populations in an estuary with exotic macrophytes and improving water quality
N. B. Rybicki, J.M. Landwehr
2007, Limnology and Oceanography (52) 1195-1207
We assessed species-specific coverage (km2) of a submerged aquatic vegetation (SAV) community in the fresh and upper oligohaline Potomac Estuary from 1985 to 2001 using a method combining field observations of species-proportional coverage data with congruent remotely sensed coverage and density (percent canopy cover) data. Biomass (estimated by density-weighted coverage)...
Using geochemistry as a tool for correlating proximal andesitic tephra: Case studies from Mt Rainier (USA) and Mt Ruapehu (New Zealand)
S.L. Donoghue, J. Vallance, I.E.M. Smith, R.B. Stewart
2007, Journal of Quaternary Science (22) 395-410
Volcanic hazards assessments at andesite stratovolcanoes rely on the assessment of frequency and magnitude of past events. The identification and correlation of proximal and distal andesitic tephra, which record the explosive eruptive history, are integral to such assessments. These tephra are potentially valuable stratigraphic marker beds useful to the temporal...
Soft-sediment deformation produced by tides in a meizoseismic area, Turnagain Arm, Alaska
S.F. Greb, A.W. Archer
2007, Geology (35) 435-438
Turnagain Arm is a semidiurnal hypertidal estuary in southeastern Alaska with a recorded tidal range of 9 m. Contorted bedding and flow rolls preserved in tidal sediments within the estuary have previously been interpreted as resulting from the Mw 9.2 Great Alaskan earthquake of 1964. Horizons of flow rolls between...
An age-structured population model for horseshoe crabs in the Delaware Bay area to assess harvest and egg availability for shorebirds
J. A. Sweka, D. R. Smith, M. J. Millard
2007, Estuaries and Coasts (30) 277-286
The objective of this simulation study was to create an age-structured population model for horseshoe crabs (Limulus polyphenols) in the Delaware Bay region using best available estimates of age-specific mortality and recent harvest levels. Density dependence was incorporated using a spatial model relating egg mortality with abundance of spawning females....
Field-derived relationships for flow velocity and resistance in high-gradient streams
F. Comiti, L. Mao, A. Wilcox, E.E. Wohl, M.A. Lenzi
2007, Journal of Hydrology (340) 48-62
We measured velocity and channel geometry in 10 reaches (bed gradient = 0.08-0.21) of a predominantly step-pool channel, the Rio Cordon, Italy, over a range of discharges (3-80% of the bankfull discharge). The resulting data were used to compute flow resistance. At-a-station hydraulic geometry relations indicate that in most reaches,...
On using surface-source downhole-receiver logging to determine seismic slownesses
D.M. Boore, E.M. Thompson
2007, Soil Dynamics and Earthquake Engineering (27) 971-985
We present a method to solve for slowness models from surface-source downhole-receiver seismic travel-times. The method estimates the slownesses in a single inversion of the travel-times from all receiver depths and accounts for refractions at layer boundaries. The number and location of layer interfaces in the model can be selected...
Rapid sea level rise and ice sheet response to 8,200-year climate event
T. M. Cronin, P.R. Vogt, Debra A. Willard, R. Thunell, J. Halka, M. Berke, J. Pohlman
2007, Geophysical Research Letters (34)
The largest abrupt climatic reversal of the Holocene interglacial, the cooling event 8.6–8.2 thousand years ago (ka), was probably caused by catastrophic release of glacial Lake Agassiz-Ojibway, which slowed Atlantic meridional overturning circulation (AMOC) and cooled global climate. Geophysical surveys and sediment cores from Chesapeake Bay reveal the pattern of...
Beyond SaGMRotI: Conversion to SaArb, SaSN, and SaMaxRot
J. A. Watson-Lamprey, D.M. Boore
2007, Bulletin of the Seismological Society of America (97) 1511-1524
In the seismic design of structures, estimates of design forces are usually provided to the engineer in the form of elastic response spectra. Predictive equations for elastic response spectra are derived from empirical recordings of ground motion. The geometric mean of the two orthogonal horizontal components of motion is often...
Formation of tellurium nanocrystals during anaerobic growth of bacteria that use Te oxyanions as respiratory electron acceptors
Shaun M. Baesman, Thomas D. Bullen, J. Dewald, Donghui Zhang, S. Curran, F.S. Islam, T.J. Beveridge, Ronald S. Oremland
2007, Applied and Environmental Microbiology (73) 2135-2143
Certain toxic elements support the metabolism of diverse prokaryotes by serving as respiratory electron acceptors for growth. Here, we demonstrate that two anaerobes previously shown to be capable of respiring oxyanions of selenium also achieve growth by reduction of either tellurate [Te(VI)] or tellurite [Te(IV)] to elemental...
Quantifying tolerance indicator values for common stream fish species of the United States
M. R. Meador, D.M. Carlisle
2007, Ecological Indicators (7) 329-338
The classification of fish species tolerance to environmental disturbance is often used as a means to assess ecosystem conditions. Its use, however, may be problematic because the approach to tolerance classification is based on subjective judgment. We analyzed fish and physicochemical data from 773 stream sites collected as part of...
Response of the St. Joseph River to lake level changes during the last 12,000 years in the Lake Michigan basin
K.A. Kincare
2007, Journal of Paleolimnology (37) 383-394
The water level of the Lake Michigan basin is currently 177 m above sea level. Around 9,800 14C years B.P., the lake level in the Lake Michigan basin had dropped to its lowest level in prehistory, about 70 m above sea level. This low level (Lake Chippewa) had profound effects...
Large-scale causes of variation in the serpentine vegetation of California
J.B. Grace, H.D. Safford, S. Harrison
2007, Conference Paper, Plant and Soil
Serpentine vegetation in California ranges from forest to shrubland and grassland, harbors many rare and endemic species, and is only moderately altered by invasive exotic species at the present time. To better understand the factors regulating the distribution of common/representative species, endemic/rare species, and the threat of exotics in this...
Testing a Mahalanobis distance model of black bear habitat use in the Ouachita Mountains of Oklahoma
E. C. Hellgren, S.L. Bales, M.S. Gregory, David M. Leslie Jr., J. D. Clark
2007, Journal of Wildlife Management (71) 924-928
Regional wildlife–habitat models are commonly developed but rarely tested with truly independent data. We tested a published habitat model for black bears (Ursus americanus) with new data collected in a different site in the same ecological region (i.e., Ouachita Mountains of Arkansas and Oklahoma, USA). We used a Mahalanobis distance...
A simulation of groundwater discharge and nitrate delivery to chesapeake bay from the lowermost delmarva peninsula, USA
W. E. Sanford, J.P. Pope
2007, Conference Paper, IAHS-AISH Publication
A groundwater model has been developed for the lowermost Delmarva Peninsula, USA, that simulates saltwater intrusion into local confined aquifers and nitrate delivery to the Chesapeake Bay from the surficial aquifer. A flow path and groundwater-age analysis was performed using the model to estimate the timing of nitrate delivery to...
A comparison of shoreline seines with fyke nets for sampling littoral fish communities in floodplain lakes
S.J. Clark, J.R. Jackson, S.E. Lochmann
2007, North American Journal of Fisheries Management (27) 676-680
We compared shoreline seines with fyke nets in terms of their ability to sample fish species in the littoral zone of 22 floodplain lakes of the White River, Arkansas. Lakes ranged in size from less than 0.5 to 51.0 ha. Most contained large amounts of coarse woody debris within the...
Spatial patterns of large natural fires in Sierra Nevada wilderness areas
B.M. Collins, M. Kelly, J. W. van Wagtendonk, S.L. Stephens
2007, Landscape Ecology (22) 545-557
The effects of fire on vegetation vary based on the properties and amount of existing biomass (or fuel) in a forest stand, weather conditions, and topography. Identifying controls over the spatial patterning of fire-induced vegetation change, or fire severity, is critical in understanding fire as a landscape scale process. We...
Self-gravity wake structures in Saturn's a ring revealed by Cassini vims
M.M. Hedman, P. D. Nicholson, H. Salo, B.D. Wallis, B. J. Buratti, K. H. Baines, R. H. Brown, R. N. Clark
2007, Astronomical Journal (133) 2624-2629
During the summer of 2005, the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft observed a series of occultations of the star o Ceti (Mira) by Saturn's rings. These observations revealed pronounced variations in the optical depth of the A ring with longitude, which can be attributed to oriented...
