bluuebunny/crossref_metadata_2025 huggingface dataset:
Inquiry-based learning in civil engineering laboratory classes
Authors: Boxall Joby , Tait Simon
Published: July 2008

Laboratory classes are a fundamental part of university-level education for civil engineers, reinforcing engineering theory through practical experience. However, due to the need for universities to become ever more efficient, resources for laboratory staff and space are becoming smaller with the result that laboratory classes are often demonstrations to large groups with little or no opportunity for students to develop and explore their own lines of inquiry. This paper reports on an initiative to address this deficiency by developing inquiry-based laboratory classes for second-year undergraduates. Initial results are encouraging, with unanimously positive feedback from students and an observable improvement in module grades.
THE HUMAN FOOTPRINT IN THE WEST: A LARGE‐SCALE ANALYSIS OF ANTHROPOGENIC IMPACTS
Authors: Leu Matthias , Hanser Steven E. , Knick Steven T.
Published: July 2008

Anthropogenic features such as urbanization, roads, and power lines, are increasing in western United States landscapes in response to rapidly growing human populations. However, their spatial effects have not been evaluated. Our goal was to model the human footprint across the western United States. We first delineated the actual area occupied by anthropogenic features, the physical effect area. Next, we developed the human footprint model based on the ecological effect area, the zone influenced by features beyond their physical presence, by combining seven input models: three models quantified top‐down anthropogenic influences of synanthropic predators (avian predators, domestic dog and cat presence risk), and four models quantified bottom‐up anthropogenic influences on habitat (invasion of exotic plants, human‐caused fires, energy extraction, and anthropogenic wildland fragmentation). Using independent bird population data, we found bird abundance of four synanthropic species to correlate positively with human footprint intensity and negatively for three of the six species influenced by habitat fragmentation. We then evaluated the extent of the human footprint in relation to terrestrial (ecoregions) and aquatic systems (major rivers and lakes), regional management and conservation status, physical environment, and temporal changes in human actions. The physical effect area of anthropogenic features covered 13% of the western United States with agricultural land (9.8%) being most dominant. High‐intensity human footprint areas (class 8–10) overlapped highly productive low‐elevation private landholdings and covered 7% of the western United States compared to 48% for low‐intensity areas (class 1–3), which were confined to low‐productivity high‐elevation federal landholdings. Areas within 1 km of rivers were more affected by the human footprint compared to lakes. Percentage human population growth was higher in low‐intensity human footprint areas. The disproportional regional effects of the human footprint on landscapes in the western United States create a challenge to management of ecosystems and wildlife populations. Using footprint models, managers can plan land use actions, develop restoration scenarios, and identify areas of high conservation value at local landscapes within a regional context. Moreover, human footprint models serve as a tool to stratify landscapes for studies investigating floral and faunal response to human disturbance intensity gradients.
OPTIMIZING DISPERSAL CORRIDORS FOR THE CAPE PROTEACEAE USING NETWORK FLOW
Authors: Phillips Steven J. , Williams Paul , Midgley Guy , Archer Aaron
Published: July 2008

We introduce a new way of measuring and optimizing connectivity in conservation landscapes through time, accounting for both the biological needs of multiple species and the social and financial constraint of minimizing land area requiring additional protection. Our method is based on the concept of network flow; we demonstrate its use by optimizing protected areas in the Western Cape of South Africa to facilitate autogenic species shifts in geographic range under climate change for a family of endemic plants, the Cape Proteaceae. In 2005, P. Williams and colleagues introduced a novel framework for this protected area design task. To ensure population viability, they assumed each species should have a range size of at least 100 km2 of predicted suitable conditions contained in protected areas at all times between 2000 and 2050. The goal was to design multiple dispersal corridors for each species, connecting suitable conditions between time periods, subject to each species' limited dispersal ability, and minimizing the total area requiring additional protection. We show that both minimum range size and limited dispersal abilities can be naturally modeled using the concept of network flow. This allows us to apply well‐established tools from operations research and computer science for solving network flow problems. Using the same data and this novel modeling approach, we reduce the area requiring additional protection by a third compared to previous methods, from 4593 km2 to 3062 km2, while still achieving the same conservation planning goals. We prove that this is the best solution mathematically possible: the given planning goals cannot be achieved with a smaller area, given our modeling assumptions and data. Our method allows for flexibility and refinement of the underlying climate‐change, species‐habitat‐suitability, and dispersal models. In particular, we propose an alternate formalization of a minimum range size moving through time and use network flow to achieve the revised goals, again with the smallest possible newly protected area (2850 km2). We show how to relate total dispersal distance to probability of successful dispersal, and compute a trade‐off curve between this quantity and the total amount of extra land that must be protected.
PARTICIPATORY INDICATOR DEVELOPMENT: WHAT CAN ECOLOGISTS AND LOCAL COMMUNITIES LEARN FROM EACH OTHER
Authors: Reed Mark S. , Dougill Andrew J. , Baker Timothy R.
Published: July 2008

Given the growing popularity of indicators among policy‐makers to measure progress toward conservation and sustainability goals, there is an urgent need to develop indicators that can be used accurately by both specialists and nonspecialists, drawing from the knowledge possessed by each group. This paper uses a case study from the Kalahari, Botswana to show how participatory and ecological methods can be combined to develop robust indicators that are accessible to a range of users to monitor and enhance the sustainability of land management. First, potential environmental sustainability indicators were elicited from pastoralists in three study sites. This knowledge was then evaluated by pastoralists, before being tested empirically using ecological and soil‐based techniques. Despite the wealth of local knowledge about indicators, this knowledge was thinly spread. The knowledge was more holistic than published indicator lists for monitoring rangelands, encompassing vegetation, soil, livestock, wild animal, and socioeconomic indicators. Pastoralist preferences for vegetation and livestock indicators match recent shifts in ecological theory suggesting that livestock populations reach equilibrium with key forage resources in semiarid environments. Although most indicators suggested by pastoralists were validated through empirical work (e.g., decreased grass cover and soil organic matter content, and increased abundance of Acacia mellifera and thatching grass), they were not always sufficiently accurate or reliable for objective degradation assessment, showing that local knowledge cannot be accepted unquestioningly. We suggest that, by combining participatory and ecological approaches, it is possible to derive more accurate and relevant indicators than either approach could achieve alone.
INCORPORATING COVARIATES INTO FISHERIES STOCK ASSESSMENT MODELS WITH APPLICATION TO PACIFIC HERRING
Authors: Deriso Richard B. , Maunder Mark N. , Pearson Walter H.
Published: July 2008

We present a framework for evaluating the cause of fishery declines by integrating covariates into a fisheries stock assessment model. This allows the evaluation of fisheries' effects vs. natural and other human impacts. The analyses presented are based on integrating ecological science and statistics and form the basis for environmental decision‐making advice. Hypothesis tests are described to rank hypotheses and determine the size of a multiple covariate model. We extend recent developments in integrated analysis and use novel methods to produce effect size estimates that are relevant to policy makers and include estimates of uncertainty. Results can be directly applied to evaluate trade‐offs among alternative management decisions. The methods and results are also broadly applicable outside fisheries stock assessment. We show that multiple factors influence populations and that analysis of factors in isolation can be misleading. We illustrate the framework by applying it to Pacific herring of Prince William Sound, Alaska (USA). The Pacific herring stock that spawns in Prince William Sound is a stock that has collapsed, but there are several competing or alternative hypotheses to account for the initial collapse and subsequent lack of recovery. Factors failing the initial screening tests for statistical significance included indicators of the 1989 Exxon Valdez oil spill, coho salmon predation, sea lion predation, Pacific Decadal Oscillation, Northern Oscillation Index, and effects of containment in the herring egg‐on‐kelp pound fishery. The overall results indicate that the most statistically significant factors related to the lack of recovery of the herring stock involve competition or predation by juvenile hatchery pink salmon on herring juveniles. Secondary factors identified in the analysis were poor nutrition in the winter, ocean (Gulf of Alaska) temperature in the winter, the viral hemorrhagic septicemia virus, and the pathogenIchthyophonus hoferi. The implication of this result to fisheries management in Prince William Sound is that it may well be difficult to simultaneously increase the production of pink salmon and maintain a viable Pacific herring fishery. The impact can be extended to other commercially important fisheries, and a whole ecosystem approach may be needed to evaluate the costs and benefits of salmon hatcheries.
URBAN LAND USE PREDICTS WEST NILE VIRUS EXPOSURE IN SONGBIRDS
Authors: Bradley Catherine A. , Gibbs Samantha E. J. , Altizer Sonia
Published: July 2008

Urbanization is a widespread phenomenon that is likely to influence the prevalence and impact of wildlife pathogens, with implications for wildlife management and public health policies toward zoonotic pathogens. In this study, wild songbird populations were sampled at 14 sites along an urban–rural gradient in the greater metropolitan Atlanta (Georgia, USA) area and tested for antibodies to West Nile virus (WNV). The level of urbanization among sites was quantitatively assessed using a principal component analysis of key land use characteristics. In total, 499 individual birds were tested during the spring and summer over three years (2004–2006). Antibody prevalence of WNV increased from rural to urban sites, and this trend was stronger among adult birds relative to juveniles. Furthermore, antibody prevalence among Northern Cardinals (Cardinalis cardinalis) was significantly higher than in other songbird species along the urban gradient. Findings reported here indicate that ecological factors associated with urbanization can influence infection patterns of this vector‐borne viral disease, with likely mechanisms including changes in host species diversity and the tolerance or recovery of infected animals.
IS THE EFFECT OF FOREST STRUCTURE ON BIRD DIVERSITY MODIFIED BY FOREST PRODUCTIVITY
Authors: Verschuyl Jacob P. , Hansen Andrew J. , McWethy David B. , Sallabanks Rex , Hutto Richard L.
Published: July 2008

Currently, the most common strategy when managing forests for biodiversity at the landscape scale is to maintain structural complexity within stands and provide a variety of seral stages across landscapes. Advances in ecological theory reveal that biodiversity at continental scales is strongly influenced by available energy (i.e., climate factors relating to heat and light and primary productivity). This paper explores how available energy and forest structural complexity may interact to drive biodiversity at a regional scale.

We hypothesized that bird species richness exhibits a hump‐shaped relationship with energy at the regional scale of the northwestern United States. As a result, we hypothesized that the relationship between energy and richness within a landscape is positive in energy‐limited landscapes and flat or decreasing in energy‐rich landscapes. Additionally, we hypothesized that structural complexity explains less of the variation in species richness in energy‐limited environments and more in energy‐rich environments and that the slope of the relationship between structural complexity and richness is greatest in energy‐rich environments.

We sampled bird communities and vegetation across seral stages and biophysical settings at each of five landscapes arrayed across a productivity gradient from the Pacific Coast to the Rocky Mountains within the five northwestern states of the contiguous United States. We analyzed the response of richness to structural complexity and energy covariates at each landscape. We found that (1) richness had a hump‐shaped relationship with available energy across the northwestern United States, (2) the landscape‐scale relationships between energy and richness were positive or hump shaped in energy‐limited locations and were flat or negative in energy‐rich locations, (3) forest structural complexity explained more of the variation in bird species richness in energy‐rich landscapes, and (4) the slope of the relationship between forest structural complexity and richness was steepest in energy‐limited locations. In energy‐rich locations, forest managers will likely increase landscape‐scale bird diversity by providing a range of forest structural complexity across all seral stages. In low‐energy environments, bird diversity will likely be maximized by managing local high‐energy hotspots judiciously and adjusting harvest intensities in other locations to compensate for slower regeneration rates.
A NONINVASIVE DEMOGRAPHIC ASSESSMENT OF SEA LIONS BASED ON STAGE‐SPECIFIC ABUNDANCES
Authors: Wielgus Jeffrey , Gonzalez-Suarez Manuela , Aurioles-Gamboa David , Gerber Leah R.
Published: July 2008

A pressing need exists to develop new approaches for obtaining information on demographic rates without causing further threats to imperiled animal populations. In this paper, we illustrate and apply a data‐fitting technique based on quadratic programming that uses stage‐specific abundance data to estimate demographic rates and asymptotic population growth rates (λ). We used data from seven breeding colonies of California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Estimates of λ were similar to those from previous studies relying on a diffusion approximation using trends in total abundance. On average, predicted abundances were within 24% of the observed value for the inverse estimation method and within 29% of the observed value for the diffusion approximation. Our results suggest that three of the seven populations are declining (λ < 1), but as many as six may be at risk. Elasticity and sensitivity analyses suggest that population management in most sites should focus on the protection of adults, whose survival generally contributes the most to λ. The quadratic programming approach is a promising noninvasive technique for estimating demographic rates and assessing the viability of populations of imperiled species.
THE INFLUENCE OF SUCCESSIONAL PROCESSES AND DISTURBANCE ON THE STRUCTURE OFTSUGA CANADENSISFORESTS
Authors: D'Amato Anthony W. , Orwig David A. , Foster David R.
Published: July 2008

Old‐growth forests are valuable sources of ecological, conservation, and management information, yet these ecosystems have received little study in New England, due in large part to their regional scarcity. To increase our understanding of the structures and processes common in these rare forests, we studied the abundance of downed coarse woody debris (CWD) and snags and live‐tree size‐class distributions in 16 old‐growth hemlock forests in western Massachusetts. Old‐growth stands were compared with eight adjacent second‐growth hemlock forests to gain a better understanding of the structural differences between these two classes of forests resulting from contrasting histories. In addition, we used stand‐level dendroecological reconstructions to investigate the linkages between disturbance history and old‐growth forest structure using an information–theoretic model selection framework.

Old‐growth stands exhibit a much higher degree of structural complexity than second‐growth forests. In particular, old‐growth stands had larger overstory trees and greater volumes of downed coarse woody debris (135.2 vs. 33.2 m3/ha) and snags (21.2 vs. 10.7 m3/ha). Second‐growth stands were characterized by either skewed unimodal or reverse‐J shaped diameter distributions, while old‐growth forests contained bell‐shaped, skewed unimodal, rotated sigmoid, and reverse J‐shaped distributions. The variation in structural attributes among old‐growth stands, particularly the abundance of downed CWD, was closely related to disturbance history. In particular, old‐growth stands experiencing moderate levels of canopy disturbance during the last century (1930s and 1980s) had greater accumulations of CWD, highlighting the importance of gap‐scale disturbances in shaping the long‐term development and structural characteristics of old‐growth forests. These findings are important for the development of natural disturbance‐based silvicultural systems that may be used to restore important forest characteristics lacking in New England second‐growth stands by integrating structural legacies of disturbance (e.g., downed CWD) and resultant tree‐size distribution patterns. This silvicultural approach would emulate the often episodic nature of CWD recruitment within old‐growth forests.
NATURAL FLOW REGIMES, NONNATIVE FISHES, AND NATIVE FISH PERSISTENCE IN ARID‐LAND RIVER SYSTEMS
Authors: Propst David L. , Gido Keith B. , Stefferud Jerome A.
Published: July 2008

Escalating demands for water have led to substantial modifications of river systems in arid regions, which coupled with the widespread invasion of nonnative organisms, have increased the vulnerability of native aquatic species to extirpation. Whereas a number of studies have evaluated the role of modified flow regimes and nonnative species on native aquatic assemblages, few have been conducted where the compounding effects of modified flow regimes and established nonnatives do not confound interpretations, particularly at spatial and temporal scales that are relevant to conservation of species at a range‐wide level. By evaluating a 19‐year data set across six sites in the relatively unaltered upper Gila River basin, New Mexico, USA, we tested how natural flow regimes and presence of nonnative species affected long‐term stability of native fish assemblages. Overall, we found that native fish density was greatest during a wet period at the beginning of our study and declined during a dry period near the end of the study. Nonnative fishes, particularly predators, generally responded in opposite directions to these climatic cycles. Our data suggested that chronic presence of nonnative fishes, coupled with naturally low flows reduced abundance of individual species and compromised persistence of native fish assemblages. We also found that a natural flow regime alone was unlikely to ensure persistence of native fish assemblages. Rather, active management that maintains natural flow regimes while concurrently suppressing or excluding nonnative fishes from remaining native fish strongholds is critical to conservation of native fish assemblages in a system, such as the upper Gila River drainage, with comparatively little anthropogenic modification.
THE ADAPTIVE VALUE OF REMNANT NATIVE PLANTS IN INVADED COMMUNITIES: AN EXAMPLE FROM THE GREAT BASIN
Authors: Leger Elizabeth A.
Published: July 2008

Changes in the species composition of biotic communities may alter patterns of natural selection occurring within them. Native perennial grass species in the Intermountain West are experiencing a shift in the composition of interspecific competitors from primarily perennial species to an exotic, annual grass. Thus traits that confer an advantage to perennial grasses in the presence of novel annual competitors may evolve in invaded communities. Here I show that such traits are apparent in populations of a native perennial grass, big squirreltail (Elymus multisetus M.E. Jones), exposed to cheatgrass (Bromus tectorum L.) competitors. Dormant big squirreltail plants were collected from cheatgrass‐invaded and uninvaded sites near Bordertown, California, USA, a mid‐elevation (1600 m) sagebrush community, and transplanted into pots in a greenhouse. Individual plants were split into equal halves. One half was grown with competition from cheatgrass, and the other half was grown without competition. Plants collected from invaded sites responded more quickly to watering, growing more leaves in the first 10 days after transplanting. In addition, big squirreltail plants collected from invaded areas experienced a smaller decrease in plant size when grown with competition than did plants collected from uninvaded areas. Accordingly, while there were fewer big squirreltail individuals in the invaded sites, they were more competitive with cheatgrass than were the more abundant conspecifics in nearby uninvaded areas. It is possible that annual grasses were the selective force that caused these population differences, which may contribute to the long‐term persistence of the native populations. While it is tempting to restore degraded areas to higher densities of natives (usually done by bringing in outside seed material), such actions may impede long‐term adaptation to new conditions by arresting or reversing the direction of ongoing natural selection in the resident population. If hot spots of rapid evolutionary change can be identified within invaded systems, these areas should be managed to promote desirable change and could serve as possible sources of restoration material or reveal traits that should be prioritized during the development of restoration seed material.
THE OASIS EFFECT: RESPONSE OF BIRDS TO EXURBAN DEVELOPMENT IN A SOUTHWESTERN SAVANNA
Authors: Bock Carl E. , Jones Zach F. , Bock Jane H.
Published: July 2008

Ranches are being converted to exurban housing developments in the southwestern United States, with potentially significant but little‐studied impacts on biological diversity. We counted birds in grasslands and savannas in southeastern Arizona that were grazed by livestock, embedded in low‐density exurban housing developments, or both, or neither. Species richness and bird abundance were higher in exurban neighborhoods than in undeveloped landscapes, independent of livestock grazing. The positive response to development was particularly evident among doves, quail, hummingbirds, aerial insectivores, and some but not all ground‐foraging sparrows. Effects of livestock grazing were comparatively minor and mostly involved birds with requirements for tall ground cover or the lack of it. The average rank correlation between counts of individual species and housing density was positive across all transects. However, this relationship disappeared among the exurban transects alone, and bird species richness on the exurban transects was negatively correlated with the number of homes nearby. These results suggest that the positive influence of exurban development on avian abundance and variety was greatest at the lowest housing densities. We attribute the attraction of many birds to exurban development to an oasis effect, in which resources otherwise scarce in arid southwestern environments (shade, nectar, nest sites, and especially water) are relatively abundant around exurban home sites. This finding is consistent with the hypothesis that exurban home sites represented resource supply points inside birds' home ranges otherwise consisting mostly of natural vegetation.
Is Social Anxiety Making Us Depressed?: A Social Evolutionary Hypothesis for Why SSRIs Work
Authors: Kerr Laura K.
Published: July 2008

In the developed world, the use of selective serotonin reuptake inhibitors (SSRIs) has skyrocketed since 1988, when Prozac was first released in the United States. Biomedical psychiatry’s explanation for their success is an unsubstantiated hypothesis that claims SSRIs treat a chemical imbalance in people who suffer from low levels of the neurotransmitter serotonin. Using social evolutionary theory, this article provides an alternative hypothesis for why SSRIs work for some people. SSRIs’ success is attributed to their capacity to adapt people to the increased status anxiety occurring in developed nations grappling with the effects of unprecedented global competition. Biomedical psychiatry is depicted as adjusting patients to prevailing social norms rather than contributing to mental health.
Application of statistical experimental design and multivariate data analysis for evaluation of mixtures using cytochrome P4501A induction
Authors: Jensen Maria Helene Steinnes , Krøkje Åse
Published: July 2008

Cytochrome P4501A (CYP1A) induction was evaluated in the rat hepatoma cell line H4IIE as a biomarker of exposure to organic compounds. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide assay was performed to assess the viability of cells exposed to environmentally relevant concentrations of cadmium. Cadmium concentrations greater than approximately 0.7 μM were found to affect cell viability. Cells were exposed to environmentally relevant concentrations of 3,3′,4,4′-tetrachlorobiphenyl (PCB 77) or benzo[a]pyrene (BaP) and to combinations of PCB 77, BaP, and cadmium based on a statistical experimental design. Quantification of CYP1A proteins using Western blot analysis showed that both BaP and PCB 77 induced CYP1A in a concentration-dependent manner up to 5 μM. Response surface modeling for evaluation of the combined effect of compounds was conducted using the multivariate regression model projection to latent structures (PLS). Analysis of response surface models for the ternary mixtures indicated antagonistic interactions between BaP and PCB 77 and a possible inhibitory effect of cadmium on PCB 77-induced CYP1A. Use of CYP1A induction in the H4IIE cell line with immunodetection of CYP1A proteins, combined with the application of response surface design and PLS, is shown to be a suitable strategy for evaluating combined effects in pollutant mixtures.
Effects of methylmercury and spatial complexity on foraging behavior and foraging efficiency in juvenile white ibises (Eudocimus albus)
Authors: Adams Evan M , Frederick Peter C
Published: July 2008

Methylmercury is a globally distributed neurotoxin, endocrine disruptor, and teratogen, the effects of which on wildlife at environmentally relevant levels are largely unknown. In birds, foraging efficiency and learning may be sensitive endpoints for sublethal methylmercury toxicity, and these endpoints also may be biologically relevant at the population level. In the present study, groups of wild-caught, prefledgling white ibises (Eudocimus albus) were raised in a free-flight, open-air aviary on diets that approximated the measured range of methylmercury exposure in the Everglades ecosystem (0, 0.05, 0.1, and 0.3 mg/kg/d). The effect of methylmercury exposure on group foraging efficiency was examined by allowing birds to forage on 200 fathead minnows (Pimephales promelas) in artificial ponds for 15 min by straining the arenas' contents through a seine net and counting all remaining prey. Additionally, we varied the difficulty of foraging by these tactile feeding birds by adding multiple levels of structural complexity (e.g., increased vegetation and prey refugia) to the pond. Structural complexity affected both foraging efficiency and the rate of increase in efficiency over time (improvement). Methylmercury exposure affected foraging efficiency (p = 0.03). It did not affect foraging improvement in the face of increasingly challenging environments, however, and the dose-response relationship was nonlinear (e.g., the control and high-exposure groups were the least efficient foragers). Evidence for an effect of methylmercury on foraging efficiency therefore was inconclusive because of unpredicted results and no interaction with time or habitat complexity. These data suggest a nonlinear dose-response relationship at low levels of methylmercury exposure; future research is needed to verify this hypothesis. This appears to be the first experimental demonstration of the effects of habitat complexity on foraging efficiency in long-legged wading birds.
Direct and indirect photolysis of polycyclic aromatic hydrocarbons in nitrate-rich surface waters
Authors: Jacobs Laura E , Weavers Linda K , Chin Yu-Ping
Published: July 2008

The photolysis of three polycyclic aromatic hydrocarbons (PAHs)—pyrene, phenanthrene, and naphthalene—were studied in waters taken from creosote-contaminated sites in Gary (IN, USA) and Wilmington (NC, USA). Direct photolysis of all PAHs was observed under simulated solar radiation, with pyrene degrading at a faster rate than either phenanthrene or naphthalene. Phenanthrene degradation, when compared to its direct photolysis rate, increased in Gary water but decreased in Wilmington water. Analysis of the waters for dissolved organic carbon (DOC) and nitrate revealed higher levels of DOC in the Wilmington sample (9.29 mg/L) compared with the Gary sample (6.73 mg/L), as well as significantly less nitrate (0.046 mM vs 0.205 mM for the Gary sample). The slightly lower rate of phenanthrene degradation observed for the Wilmington sample, corrected for light attenuation effects, is statistically the same as that in the direct photolysis experiments. Therefore, we attribute the lower rate of degradation in the presence of Wilmington water to light screening by DOC, but we believe the faster reaction rate observed for the Gary water results from hydroxyl radical (OH•) chemistry generated by nitrate photolysis. Indeed, degradation of the target compound increased when nitrate (at 0.2 and 0.4 mM) was added to the Wilmington sample, further corroborating this conclusion. Overall photoreaction rates decreased for the lower-molecular-weight PAHs, because the fastest naphthalene photolytic rate was roughly two orders of magnitude slower than that of pyrene.
Clutch morphology and the timing of exposure impact the susceptibility of aquatic insect eggs to esfenvalerate
Authors: Palmquist Katherine R , Jenkins Jeffrey J , Jepson Paul C
Published: July 2008

We investigated Baetis spp. (mayfly), Hesperoperla pacifica (stonefly), and Brachycentrus americanus (caddisfly) susceptibility at the egg stage to esfenvalerate, a synthetic pyrethroid insecticide. Eggs were obtained from the field or from field-collected gravid females at sites near Corvallis (OR, USA) and the Metolius River at Camp Sherman (OR, USA) for static exposures under controlled conditions for temperature and light. Eggs were exposed to esfenvalerate for 48 h at concentrations ranging from 0.025 to 4.0 μg/L. No effect on mortality or posthatch growth was detected in H. pacifica eggs exposed to esfenvalerate concentrations up to 1.0 μg/L. Exposure to 0.07 μg/L of esfenvalerate, however, caused a significant increase in Baetis spp. egg mortality, and exposure of near-eclosion eggs to lower concentrations (0.025 and 0.05 μg/L) resulted in behavioral effects and reduced survivorship in newly hatched Baetis nymphs. Early stage B. americanus eggs were 10-fold more sensitive to esfenvalerate when removed from the gelatinous clutch before exposure, an indication that the gelatin affords protection from toxicant exposure. Exposures of near-hatch B. americanus clutches to esfenvalerate concentrations ranging between 0.035 and 0.2 μg/L, however, resulted in significant clutch death within clutches resulting from behavioral aberrations of first-instar larvae. The results of the present study suggest that aquatic insect egg clutch morphology can be a strong influence on susceptibility of embryos to esfenvalerate exposure.
Impact of aquatic insect life stage and emergence strategy on sensitivity to esfenvalerate exposure
Authors: Palmquist Katherine R , Jepson Paul C , Jenkins Jeffrey J
Published: July 2008

We investigated the impact of aquatic insect life stage and emergence strategy on sensitivity to esfenvalerate, a synthetic pyrethroid insecticide, using field-collected Brachycentrus americanus Banks (Trichoptera: Brachycentridae) and Cinygmula reticulata McDunnough (Ephemeroptera: Heptageniidae) insects. Final-instar C. reticulata emergence was observed for one week following three environmentally relevant, 48-h esfenvalerate exposures (0.005, 0.01, and 0.015 μg/L). Emergence was significantly depressed following exposure to esfenvalerate and resulted from an increase in nymph mortality during the emergence process. This experiment was duplicated for late-instar C. reticulata nymphs, which were similar in size to the final-instar nymphs but were not near emergence. Late-instar C. reticulata mayflies were approximately fivefold less sensitive to esfenvalerate exposures as gauged by one-week mortality rates. Brachycentrus americanus pupal mortality was significantly increased over that in controls following 48-h esfenvalerate exposures of 0.1 and 0.2 μg/L. These response concentrations correlated closely with those for case-abandonment rates of fourth-instar B. americanus larvae (a sublethal effect of esfenvalerate exposure). Pupal mortality rates were approximately 16-fold higher than those observed in larvae. Adult female egg weight as a percentage of total body weight was significantly decreased following pupal esfenvalerate exposures of 0.05, 0.1, and 0.2 μg/L. These findings suggest that exposure to esfenvalerate may impair hemimetabolous insect emergence behaviors and may decrease fecundity in holometabolous aquatic insects.
Effects of dietary esfenvalerate exposures on three aquatic insect species representing different functional feeding groups
Authors: Palmquist Katherine R , Jenkins Jeffrey J , Jepson Paul C
Published: July 2008

Given the chemical properties of synthetic pyrethroids, it is probable that compounds, including esfenvalerate, that enter surface waters may become incorporated into aquatic insect food sources. We examined the effect of dietary esfenvalerate uptake in aquatic insects representing different functional feeding groups. We used three field-collected aquatic insect species: A grazing scraper, Cinygmula reticulata McDunnough (Ephemeroptera: Heptageniidae); an omnivorous filter feeder, Brachycentrus americanus Banks (Trichoptera: Brachycentridae); and a predator, Hesperoperla pacifica Banks (Plecoptera: Perlidae). Laboratory-cultured algae were preexposed for 24 h to esfenvalerate concentrations of 0, 0.025, 0.05, and 0.1 μg/L and provided to two C. reticulata age classes (small and final-instar nymphs). Reduction in small nymph growth was observed following three weeks of feeding on algae exposed to 0.05 and 0.1 μg/L of esfenvalerate, and the highest dietary exposure reduced egg production in final-instar nymphs. The diet for B. americanus and H. pacifica consisted of dead third-instar Chironomus tentans larvae preexposed for 24 h to esfenvalerate concentrations ranging between 0.1 and 1.0 μg/L. Consumption of larvae exposed to 0.5 to 1.0 μg/L of esfenvalerate caused case abandonment and mortality in B. americanus caddisfly larvae. Although H. pacifica nymphs readily consumed esfenvalerate-exposed larvae, no adverse effects were observed during the present study. Furthermore, no evidence of esfenvalerate-induced feeding deterrence was found in any of the species tested, suggesting that aquatic insects may not be able to distinguish between pyrethroid-contaminated and uncontaminated food sources. These findings indicate that feeding deterrence is not a factor in regulating aquatic insect dietary exposures to synthetic pyrethroids.
Biogeochemical toxicity and phytotoxicity of nitrogenous compounds in a variety of arctic soils
Authors: Anaka Alison , Wickstrom Mark , Siciliano Steven D
Published: July 2008

Ammonium nitrate (NH4NO3) is a common water pollutant associated with many industrial and municipal activities. One solution to reduce exposure of sensitive aquatic systems to nitrogenous compounds is to atomize (atmospherically disperse in fine particles) contaminated water over the Arctic tundra, which will reduce nitrogen loading to surface water. The toxicity of ammonium nitrate to Arctic soils, however, is poorly understood. In the present study, we characterized the biogeochemical toxicity and phytotoxicity of ammonium nitrate solutions in four different Arctic soils and in a temperate soil. Soil was exposed to a range of ammonium nitrate concentrations over a 90-d period. Dose responses of carbon mineralization, nitrification, and phytotoxicity endpoints were estimated. In addition to direct toxicity, the effect of ammonium nitrate on ecosystem resilience was investigated by dosing nitrogen-impacted soils with boric acid. Ammonium nitrate had no effect on carbon mineralization activity and only affected nitrification in one soil, a polar desert soil from Cornwallis Island, Northwest Territories, Canada. In contrast, ammonium nitrate applications (43 mmol N/L soil water) significantly impaired seedling emergence, root length, and shoot length of northern wheatgrass (Elymus lanceolatus). Concentrations of ammonium nitrate in soil water that inhibited plant parameters by 20% varied between 43 and 280 mmol N/L soil water, which corresponds to 2,100 to 15,801 mg/L of ammonium nitrate in the application water. Arctic soils were more resistant to ammonium nitrate toxicity compared with the temperate soil under these study conditions. It is not clear, however, if this represents a general trend for all polar soils, and because nitrogen is an essential macronutrient, nitrogenous toxicity likely should be considered as a special case for soil toxicity.
Global expression profiling of Chlamydomonas reinhardtii exposed to trace levels of free cadmium
Authors: Simon Dana F , Descombes Patrick , Zerges William , Wilkinson Kevin J
Published: July 2008

In the natural environment, cadmium is often found as a trace contaminant. Due to the complexity of Cd speciation and the heterogeneity of natural systems and processes, it is often difficult to determine clear relationships between analytical measurements of Cd and its induced biological response. Measurements of gene induction can be used to identify molecular mechanisms underlying toxicity and to quantify sublethal responses to trace contaminants. In the present paper, genes that could be involved in the tolerance of Cd to green algae were examined using two global transcriptome profiling strategies. Microarray and differential display techniques were used for a global transcriptome analysis of Chlamydomonas reinhardtii exposed to micromolar and lower Cd2+ concentrations for a short period (2 h). Real-time quantitative polymerase chain reaction analysis confirmed that a small set of 10 genes was differentially expressed in response to trace Cd2+ exposures ranging from 7.8 nM to 9.0 μM. Since induction was only observed for a few genes, none of which are known to function in a general stress response, it was likely the result of relevant responses to Cd exposure. The identified genes are discussed with respect to their possible involvement in Cd tolerance and to their future use as biomarkers for monitoring Cd bioavailability in natural soils and waters.
Effect of storage temperature on the activity of submitochondrial particles
Authors: Doherty Francis G
Published: July 2008

The submitochondrial particle (SMP) assay employs processed mammalian mitchondria to assess the toxicity of chemical contaminants in aqueous solutions. Particles and associated reagents are commercially available to support two individual procedures, the electron transfer (ETr) and reverse electron transfer (RET) assays. The objective of the present study was to assess the effect of storage temperature on SMP activity. One RET and one ETr assay were conducted with sodium dodecylsulfate on each of two vials of particles stored at — 20 and — 80°C at periodic intervals over a six-month span. Results demonstrated that SMP could remain active in either assay through six months of storage at either temperature. However, there were isolated vials of particles stored at —20°C that exhibited unacceptable reductions in activity for both the ETr and the RET assays that were not related to storage duration. These results were used to develop guidance in assessing the acceptability of particle activity in SMP assays.
An Investigation of Recent Deconvolution Methods for Well-Test Data Analysis
Authors: Onur M. , Çinar M. , Ilk D. , Valkó P. P. , Blasingame T. A. , Hegeman P. S.
Published: July 2008

In this work, we present an investigation of recent deconvolution methods proposed by von Schroeter et al. (2002, 2004), Levitan (2005) and Levitan et al. (2006), and Ilk et al. (2006a, b). These works offer new solution methods to the long-standing deconvolution problem and make deconvolution a viable tool for well-test and production-data analysis. However, there exists no study presenting an independent assessment of all these methods, revealing and discussing specific features associated with the use of each method in a unified manner. The algorithms used in this study for evaluating the von Schroeter et al. and Levitan methods represent our independent implementations of their methods based on the material presented in their papers, not the original algorithms implemented by von Schroeter et al. and Levitan. Three synthetic cases and one field case are considered for the investigation.

Our results identify the key issues regarding the successful and practical application of each method. In addition, we show that with proper care and attention in applying these methods, deconvolution can be an important tool for the analysis and interpretation of variable rate/pressure reservoir performance data.
Operator-Based Multiscale Method for Compressible Flow
Authors: Zhou H. , Tchelepi H. A.
Published: July 2008

Multiscale methods have been developed for accurate and efficient numerical solution of flow problems in large-scale heterogeneous reservoirs. A scalable and extendible Operator-Based Multiscale Method (OBMM) is described here. OBMM is cast as a general algebraic framework. It is natural and convenient to incorporate more physics in OBMM for multiscale computation. In OBMM, two operators are constructed: prolongation and restriction. The prolongation operator is constructed by assembling the multiscale basis functions. The specific form of the restriction operator depends on the coarse-scale discretization formulation (e.g., finite-volume or finite-element). The coarse-scale pressure equation is obtained algebraically by applying the prolongation and restriction operators to the fine-scale flow equations. Solving the coarse-scale equation results in a high-quality coarse-scale pressure. The fine-scale pressure can be reconstructed by applying the prolongation operator to the coarse-scale pressure. A conservative fine-scale velocity field is then reconstructed to solve the transport (saturation) equation. We describe the OBMM approach for multiscale modeling of compressible multiphase flow. We show that extension from incompressible to compressible flows is straightforward. No special treatment for compressibility is required. The efficiency of multi-scale formulations over standard fine-scale methods is retained by OBMM. The accuracy of OBMM is demonstrated using several numerical examples including a challenging depletion problem in a strongly heterogeneous permeability field (SPE 10).
MRI Visualization of Spontaneous Methane Production From Hydrates in Sandstone Core Plugs When Exposed to CO2
Authors: Graue A. , Kvamme B. , Baldwin B. A. , Stevens J. , Howard J. , Aspenes E. , Ersland G. , Husebø J. , Zornes D.
Published: July 2008

Magnetic resonance imaging (MRI) of core samples in laboratory experiments showed that CO2 storage in gas hydrates formed in porous rock resulted in the spontaneous production of methane with no associated water production. The exposure of methane hydrate in the pores to liquid CO2 resulted in methane production from the hydrate that suggested the exchange of methane molecules with CO2 molecules within the hydrate without the addition or subtraction of significant amounts of heat. Thermodynamic simulations based on Phase Field Theory were in agreement with these results and predicted similar methane production rates that were observed in several experiments. MRI-based 3D visualizations of the formation of hydrates in the porous rock and the methane production improved the interpretation of the experiments. The sequestration of an important greenhouse gas while simultaneously producing the freed natural gas offers access to the significant amounts of energy bound in natural gas hydrates and also offers an attractive potential for CO2 storage. The potential danger associated with catastrophic dissociation of hydrate structures in nature and the corresponding collapse of geological formations is reduced because of the increased thermodynamic stability of the CO2 hydrate relative to the natural gas hydrate.
Atomic Force Microscopy Study of Wettability Alteration by Surfactants
Authors: Kumar K. , Dao E. K. , Mohanty K. K.
Published: July 2008

Waterflooding recovers little oil from fractured carbonate reservoirs, if they are oil-wet or mixed-wet. Surfactant-aided gravity drainage has the potential to achieve significant oil recovery by wettability alteration and interfacial tension (IFT) reduction. The goal of this work is to investigate the mechanisms of wettability alteration by crude oil components and surfactants. Contact angles are measured on mineral plates treated with crude oils, crude oil components, and surfactants. Mineral surfaces are also studied by atomic force microscopy (AFM). Surfactant solution imbibition into parallel plates filled with a crude oil is investigated. Wettability of the plates is studied before and after imbibition. Results show that wettability is controlled by the adsorption of asphaltenes. Anionic surfactants can remove these adsorbed components from the mineral surface and induce preferential water wettability. Anionic surfactants studied can imbibe water into initially oil-wet parallel-plate assemblies faster than the cationic surfactant studied.