Evidence for fish dispersal from spatial analysis of stream network topology
N.P. Hitt, P. L. Angermeier
2008, Journal of the North American Benthological Society (27) 304-320
Developing spatially explicit conservation strategies for stream fishes requires an understanding of the spatial structure of dispersal within stream networks. We explored spatial patterns of stream fish dispersal by evaluating how the size and proximity of connected streams (i.e., stream network topology) explained variation in fish assemblage structure and how...
Are fractal dimensions of the spatial distribution of mineral deposits meaningful?
G. L. Raines
2008, Natural Resources Research (17) 87-97
It has been proposed that the spatial distribution of mineral deposits is bifractal. An implication of this property is that the number of deposits in a permissive area is a function of the shape of the area. This is because the fractal density functions of deposits are dependent on the...
Representing general theoretical concepts in structural equation models: The role of composite variables
J.B. Grace, K.A. Bollen
2008, Environmental and Ecological Statistics (15) 191-213
Structural equation modeling (SEM) holds the promise of providing natural scientists the capacity to evaluate complex multivariate hypotheses about ecological systems. Building on its predecessors, path analysis and factor analysis, SEM allows for the incorporation of both observed and unobserved (latent) variables into theoretically-based probabilistic models. In this paper we...
Secrets in the eyes of Black Oystercatchers: A new sexing technique
Brian M. Guzzetti, Sandra L. Talbot, David F. Tessler, Verena A. Gill, Edward C. Murphy
2008, Journal of Field Ornithology (79) 215-223
Sexing oystercatchers in the field is difficult because males and females have identical plumage and are similar in size. Although Black Oystercatchers (Haematopus bachmani) are sexually dimorphic, using morphology to determine sex requires either capturing both pair members for comparison or using discriminant analyses to assign sex probabilistically based on...
Comparative study of transport processes of nitrogen, phosphorus, and herbicides to streams in five agricultural basins, USA
Joseph L. Domagalski, S. Ator, R. Coupe, K. McCarthy, D. Lampe, Mark W. Sandstrom, N. Baker
2008, Journal of Environmental Quality (37) 1158-1169
Agricultural chemical transport to surface water and the linkage to other hydrological compartments, principally ground water, was investigated at five watersheds in semiarid to humid climatic settings. Chemical transport was affected by storm water runoff, soil drainage, irrigation, and how streams were linked to shallow ground water systems. Irrigation practices...
A deep crustal fluid channel into the San Andreas Fault system near Parkfield, California
M. Becken, O. Ritter, S. K. Park, P. A. Bedrosian, U. Weckmann, M. Weber
2008, Geophysical Journal International (173) 718-732
Magnetotelluric (MT) data from 66 sites along a 45-km-long profile across the San Andreas Fault (SAF) were inverted to obtain the 2-D electrical resistivity structure of the crust near the San Andreas Fault Observatory at Depth (SAFOD). The most intriguing feature of the resistivity model is a steeply dipping upper...
Efficacy of algal metrics for assessing nutrient and organic enrichment in flowing waters
S. D. Porter, D. K. Mueller, N.E. Spahr, M.D. Munn, N. M. Dubrovsky
2008, Freshwater Biology (53) 1036-1054
1. Algal-community metrics were calculated for periphyton samples collected from 976 streams and rivers by the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Programme during 1993–2001 to evaluate national and regional relations with water chemistry and to compare whether algal-metric values differ significantly among undeveloped and developed land-use classifications. 2. Algal...
Nitrogen immobilization by wood-chip application: Protecting water quality in a northern hardwood forest
P.M. Homyak, R.D. Yanai, Douglas A. Burns, R.D. Briggs, R.H. Germain
2008, Forest Ecology and Management (255) 2589-2601
Forest harvesting disrupts the nitrogen cycle, which may affect stream water quality by increasing nitrate concentrations, reducing pH and acid neutralizing capacity, and mobilizing aluminum and base cations. We tested the application of wood chips derived from logging slash to increase immobilization of N after harvesting, which should reduce nitrate...
Tracking the Archean-Proterozoic suture zone in the northeastern Great Basin, Nevada and Utah
B. D. Rodriguez, J. M. Williams
2008, Geosphere (4) 315-328
It is important to know whether major mining districts in north-central Nevada are underlain by crust of the Archean Wyoming craton, known to contain major orogenic gold deposits or, alternatively, by accreted crust of the Paleoproterozoic Mojave province. Determining the location and orientation of the Archean-Proterozoic suture zone between these...
Density currents in the Chicago River: Characterization, effects on water quality, and potential sources
P.R. Jackson, C.M. Garcia, K. A. Oberg, K. K. Johnson, M.H. Garcia
2008, Science of the Total Environment (401) 130-143
Bidirectional flows in a river system can occur under stratified flow conditions and in addition to creating significant errors in discharge estimates, the upstream propagating currents are capable of transporting contaminants and affecting water quality. Detailed field observations of bidirectional flows were made in the Chicago River in Chicago, Illinois...
Rainfall effects on rare annual plants
J.M. Levine, A. K. McEachern, C. Cowan
2008, Journal of Ecology (96) 795-806
Variation in climate is predicted to increase over much of the planet this century. Forecasting species persistence with climate change thus requires understanding of how populations respond to climate variability, and the mechanisms underlying this response. Variable rainfall is well known to drive fluctuations in annual plant populations, yet the...
Comparison of total mercury and methylmercury cycling at five sites using the small watershed approach
J. B. Shanley, Mast M. Alisa, K. Campbell, G. R. Aiken, D. P. Krabbenhoft, R. J. Hunt, J.F. Walker, P. F. Schuster, A. Chalmers, Brent T. Aulenbach, N.E. Peters, M. Marvin-DiPasquale, D. W. Clow, M.M. Shafer
2008, Environmental Pollution (154) 143-154
The small watershed approach is well-suited but underutilized in mercury research. We applied the small watershed approach to investigate total mercury (THg) and methylmercury (MeHg) dynamics in streamwater at the five diverse forested headwater catchments of the US Geological Survey Water, Energy, and...
Effects of climate and land management change on streamflow in the driftless area of Wisconsin
P. F. Juckem, R. J. Hunt, Marilyn P. Anderson, Dale M. Robertson
2008, Journal of Hydrology (355) 123-130
Baseflow and precipitation in the Kickapoo River Watershed, located in the Driftless Area of Wisconsin, exhibit a step increase around 1970, similar to minimum and median flows in many other central and eastern USA streams. Potential effects on streamflow due to climatic and land management changes were evaluated by comparing...
Geographic patterns of ground-dwelling arthropods across an ecoregional transition in the north American Southwest
D.C. Lightfoot, S.L. Brantley, Craig D. Allen
2008, Western North American Naturalist (68) 83-102
We examined the biogeographic patterns of ground-dwelling arthropod communities across a heterogeneous semiarid region of the Southern Rio Grande Rift Valley of New Mexico. Our 3 sites included portions of 5 ecoregions, with the middle site a transition area where all ecoregions converged. We addressed the following 3 questions: (1)...
Dissolved oxygen transfer to sediments by sweep and eject motions in aquatic environments
B.L. O’Connor, Miki Hondzo
2008, Limnology and Oceanography (53) 566-578
Dissolved oxygen (DO) concentrations were quantified near the sediment-water interface to evaluate DO transfer to sediments in a laboratory recirculating flume and open channel under varying fluid-flow conditions. DO concentration fluctuations were observed within the diffusive sublayer, as defined by the time-averaged DO concentration gradient near the sediment-water interface. Evaluation...
Peri-equatorial paleolatitudes for Jurassic radiolarian cherts of Greece
I.W. Aiello, J.T. Hagstrum, G. Principi
2008, Tectonophysics (448) 33-48
Radiolarian-rich sediments dominated pelagic deposition over large portions of the Tethys Ocean during middle to late Jurassic time as shown by extensive bedded chert sequences found in both continental margin and ophiolite units of the Mediterranean region. Which paleoceanographic mechanisms and paleotectonic setting favored radiolarian deposition during the Jurassic, and...
Spatiotemporal dynamics of black-tailed prairie dog colonies affected by plague
D.J. Augustine, Marc R. Matchett, T.P. Toombs, J.F. Cully Jr., T. L. Johnson, John G. Sidle
2008, Landscape Ecology (23) 255-267
Black-tailed prairie dogs (Cynomys ludovicianus) are a key component of the disturbance regime in semi-arid grasslands of central North America. Many studies have compared community and ecosystem characteristics on prairie dog colonies to grasslands without prairie dogs, but little is known about landscape-scale patterns of disturbance that prairie dog colony...
Evaluation of a nonlethal technique for determining sex of freshwater mussels
S. Saha, J.B. Layzer
2008, Journal of the North American Benthological Society (27) 84-89
The shells of most North American freshwater mussel species are not sexually dimorphic. During the brooding period, gravid females can be identified by inspection of marsupial gills; however, it is difficult to separate nongravid females from males in species lacking sexual dimorphism. The ability to differentiate males from females throughout...
The dams come down: Unchaining U.S. Rivers
J. O'Connor, Jon J. Major, G. Grant
2008, Geotimes (53) 22-28
No abstract available....
Scientific and public responses to the ongoing volcanic crisis at Popocatépetl Volcano, Mexico: Importance of an effective hazards-warning system
Servando De la Cruz-Reyna, Robert I. Tilling
2008, Journal of Volcanology and Geothermal Research (170) 121-134
Volcanic eruptions and other potentially hazardous natural phenomena occur independently of any human actions. However, such phenomena can cause disasters when a society fails to foresee the hazardous manifestations and adopt adequate measures to reduce its vulnerability. One of the causes of such a failure is the lack of a...
Abrupt climate change and collapse of deep-sea ecosystems
Moriaki Yasuhara, T. M. Cronin, P.B. Demenocal, H. Okahashi, B.K. Linsley
2008, Proceedings of the National Academy of Sciences of the United States of America (105) 1556-1560
We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically...
Mercury contamination and effects on survival of American avocet and black-necked stilt chicks in San Francisco Bay
Joshua T. Ackerman, John Y. Takekawa, Collin A. Eagles-Smith, S. A. Iverson
2008, Conference Paper, Ecotoxicology
We evaluated whether mercury influenced survival of free-ranging American avocet (Recurvirostra americana) and black-necked stilt (Himantopus mexicanus) chicks in San Francisco Bay, California. Using radio telemetry, we radio-marked 158 avocet and 79 stilt chicks at hatching and tracked them daily until their fate was determined. We did not find strong...
Coal and cremation at the Tschudi burn, Chan Chan, Northern Peru
W. E. Brooks, Mora C. Galvez, J.C. Jackson, J. P. McGeehin, D.G. Hood
2008, Archaeometry (50) 495-515
Analyses of a 20-30 cm thick, completely combusted ash at the 25 ?? 70 m Tschudi burn at Chan Chan, northern Peru??, contain 52-55 wt% SiO2, 180-210 ppm zirconium and are consistent with coal ash. Soil geochemistry across the burn showed elevated calcium and phosphorus content, possible evidence for reported...
Application of multiple isotopic and geochemical tracers for investigation of recharge, salinization, and residence time of water in the Souss-Massa aquifer, southwest of Morocco
L. Bouchaou, J.L. Michelot, A. Vengosh, Y. Hsissou, M. Qurtobi, C.B. Gaye, T.D. Bullen, G.M. Zuppi
2008, Journal of Hydrology (352) 267-287
Groundwater and surface water in Souss-Massa basin in the west-southern part of Morocco is characterized by a large variation in salinity, up to levels of 37 g L-1. The high salinity coupled with groundwater level decline pose serious problems for current irrigation and domestic water supplies as well as future...
Ecohydrological factors affecting nitrate concentrations in a phreatic desert aquifer in northwestern China
J.B. Gates, J.K. Böhlke, W.M. Edmunds
2008, Environmental Science & Technology (42) 3531-3537
Aerobic conditions in desert aquifers commonly allow high nitrate (NO 3-) concentrations in recharge to persist for long periods of time, an important consideration for N-cycling and water quality. In this study, stable isotopes of NO3- (??15N NO3 and ??18ONO3) were used to trace NO3- cycling processes which affect concentrations...
