Uranium sequestration in sediment at an iron-rich contaminated site at Oak Ridge, Tennessee via. bioreduction followed by reoxidation

This study evaluated uranium sequestration performance in iron-rich(30 g/kg) sediment via bioreduction followed by reoxidation. Field tests(1383 days) at Oak Ridge, Tennessee demonstrated that uranium contents in sediments increased after bioreduced sediments were re-exposed to nitrate and oxygen in contaminated groundwater. Bioreduction of contaminated sediments(1200 mg/kg U) with ethanol in microcosm reduced aqueous U from 0.37 to 0.023 mg/L. Aliquots of the bioreduced sediment were reoxidized with O_2, H_2O_2,and NaNO_3, respectively, over 285 days, resulting in aqueous U of 0.024, 1.58 and 14.4 mg/L at pH 6.30, 6.63 and 7.62, respectively. The source-and the three reoxidized sediments showed different desorption and adsorption behaviors of U, but all fit a Freundlich model.The adsorption capacities increased sharply at pH 4.5 to 5.5, plateaued at pH 5.5 to 7.0, then decreased sharply as pH increased from 7.0 to 8.0. The O_2-reoxidized sediment retained a lower desorption efficiency at pH over 6.0. The NO_3~--reoxidized sediment exhibited higher adsorption capacity at pH 5.5 to 6.0. The pH-dependent adsorption onto Fe(Ⅲ) oxides and formation of U coated particles and precipitates resulted in U sequestration, and bioreduction followed by reoxidation can enhance the U sequestration in sediment.     

Estimation of spatiotemporal trends in bat abundance from mortality data collected at wind turbines

Renewable energy sources, such as wind energy, are essential tools for reducing the causes of climate change, but wind turbines can pose a collision risk for bats. To date, the population-level effects of wind-related mortality have been estimated for only 1 bat species. To estimate temporal trends in bat abundance, we considered wind turbines as opportunistic sampling tools for flying bats (analogous to fishing nets), where catch per unit effort (carcass abundance per monitored turbine) is a proxy for aerial abundance of bats, after accounting for seasonal variation in activity. We used a large, standardized data set of records of bat carcasses from 594 turbines in southern Ontario, Canada, and corrected these data to account for surveyor efficiency and scavenger removal. We used Bayesian hierarchical models to estimate temporal trends in aerial abundance of bats and to explore the effect of spatial factors, including landscape features associated with bat habitat (e.g., wetlands, croplands, and forested lands), on the number of mortalities for each species. The models showed a rapid decline in the abundance of 4 species in our study area; declines in capture of carcasses over 7 years ranged from 65% (big brown bat [Eptesicus fuscus]) to 91% (silver-haired bat [Lasionycteris noctivagans]). Estimated declines were independent of the effects of mitigation (increasing wind speed at which turbines begin to generate electricity from 3.5 to 5.5 m/s), which significantly reduced but did not eliminate bat mortality. Late-summer mortality of hoary (Lasiurus cinereus), eastern red (Lasiurus borealis), and silver-haired bats was predicted by woodlot cover, and mortality of big brown bats decreased with increasing elevation. These landscape predictors of bat mortality can inform the siting of future wind energy operations. Our most important result is the apparent decline in abundance of four common species of bat in the airspace, which requires further investigation.     

Targeted gene flow for conservation

Anthropogenic threats often impose strong selection on affected populations, causing rapid evolutionary responses. Unfortunately, these adaptive responses are rarely harnessed for conservation. We suggest that conservation managers pay close attention to adaptive processes and geographic variation, with an eye to using them for conservation goals. Translocating pre‐adapted individuals into recipient populations is currently considered a potentially important management tool in the face of climate change. Targeted gene flow, which involves moving individuals with favorable traits to areas where these traits would have a conservation benefit, could have a much broader application in conservation. Across a species’ range there may be long‐standing geographic variation in traits or variation may have rapidly developed in response to a threatening process. Targeted gene flow could be used to promote natural resistance to threats to increase species resilience. We suggest that targeted gene flow is a currently underappreciated strategy in conservation that has applications ranging from the management of invasive species and their impacts to controlling the impact and virulence of pathogens.     

Polychlorinated -dibenzo-p-dioxins/furans and -dioxin-like biphenyls in eggs of common terns from lime island,St. Mary's river,Michigan, USA

Population collapse of common tern (Sterna hirundo) from Lime Island in the St. Mary's River, Michigan, USA were related to the 2,3,7,8-chlorine substituted dioxins, furans, dioxin-like PCBs, and other possible factors using unhatch egg target contaminant analysis. The most toxic congeners, 2,3,7,8-TCDD/DF was found in all samples at noticeable concentrations. Magnitude of sum 2,3,7,8-PCDD/DFs were within the range of 39–93?pg/g wet wt. Dioxin-like PCBs were within the range of 360–1230?ng/g wet wt. Great Toxic Equivalent Quantity (TEQ) contributions by 2,3,7,8-TCDF, 2,3,4,7,8-PeCDF, 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, and dioxin-like PCBs such as CB-77, CB-126 and CB-105 are considered greatly due to their influence of poor embryo development and consequent damage of embryos of common terns in egg injection studies. However, other organochlorines, heavy metals, and/or synergistic effects also taken in to account. On the whole, TEQs in the tern eggs were greater than the Lowest-Observable-Adverse Effect Level (LOAEL) for bald eagle (Haliaeetus leucocephalus) embryos observed in British Columbia, Canada. Concentrations of dioxin-like PCBs, dioxins, furans in the St. Mary's River food chain are at levels for concern for nesting colonial waterbirds. Eventually, the possible movements of analyzed chemicals downstream from a man-made flood event are discussed.     

Effects of time since fire on birds: how informative are generalized fire response curves for conservation management?

Fire is both a widespread natural disturbance that affects the distribution of species and a tool that can be used to manage habitats for species. Knowledge of temporal changes in the occurrence of species after fire is essential for conservation management in fire-prone environments. Two key issues are: whether postfire responses of species are idiosyncratic or if multiple species show a limited number of similar responses; and whether such responses to time since fire can predict the occurrence of species across broad spatial scales. We examined the response of bird species to time since fire in semiarid shrubland in southeastern Australia using data from surveys at 499 sites representing a 100-year chronosequence. We used nonlinear regression to model the probability of occurrence of 30 species with time since fire in two vegetation types, and compared species' responses with generalized response shapes from the literature. The occurrence of 16 species was significantly influenced by time since fire: they displayed six main responses consistent with generalized response shapes. Of these 16 species, 15 occurred more frequently in mid- or later-successional vegetation (> 20 years since fire), and only one species occurred more often in early succession (< 5 years since fire). The models had reasonable predictive ability for eight species, some predictive ability for seven species, and were little better than random for one species. Bird species displayed a limited range of responses to time since fire; thus a small set of fire ages should allow the provision of habitat for most species. Postfire successional changes extend for decades and management of the age class distribution of vegetation will need to reflect this timescale. Response curves revealed important seral stages for species and highlighted the importance of mid- to late-successional vegetation (> 20 years). Although time since fire clearly influences the distribution of numerous bird species, predictive models of the spatial distribution of species in fire-prone landscapes need to incorporate other factors in addition to time since fire.     

Habitat Assessment of Non-Wadeable Rivers in Michigan

Habitat evaluation of wadeable streams based on accepted protocols provides a rapid and widely used adjunct to biological assessment. However, little effort has been devoted to habitat evaluation in non-wadeable rivers, where it is likely that protocols will differ and field logistics will be more challenging. We developed and tested a non-wadeable habitat index (NWHI) for rivers of Michigan, where non-wadeable rivers were defined as those of order ≥5, drainage area ≥1600 km², mainstem lengths ≥100 km, and mean annual discharge ≥15 m³/s. This identified 22 candidate rivers that ranged in length from 103 to 825 km and in drainage area from 1620 to 16,860 km². We measured 171 individual habitat variables over 2-km reaches at 35 locations on 14 rivers during 2000–2002, where mean wetted width was found to range from 32 to 185 m and mean thalweg depth from 0.8 to 8.3 m. We used correlation and principal components analysis to reduce the number of variables, and examined the spatial pattern of retained variables to exclude any that appeared to reflect spatial location rather than reach condition, resulting in 12 variables to be considered in the habitat index. The proposed NWHI included seven variables: riparian width, large woody debris, aquatic vegetation, bottom deposition, bank stability, thalweg substrate, and off-channel habitat. These variables were included because of their statistical association with independently derived measures of human disturbance in the riparian zone and the catchment, and because they are considered important in other habitat protocols or to the ecology of large rivers. Five variables were excluded because they were primarily related to river size rather than anthropogenic disturbance. This index correlated strongly with indices of disturbance based on the riparian (adjusted R² = 0.62) and the catchment (adjusted R² = 0.50), and distinguished the 35 river reaches into the categories of poor (2), fair (19), good (13), and excellent (1). Habitat variables retained in the NWHI differ from several used in wadeable streams, and place greater emphasis on known characteristic features of larger rivers.     

Evaluation of Optically Acquired Zooplankton Size-Spectrum Data as a Potential Tool for Assessment of Condition in the Great Lakes

An optical plankton counter (OPC) potentially provides an assessment tool for zooplankton condition in ecosystems that is rapid, economical, and spatially extensive. We collected zooplankton data with an OPC in 20 near-shore regions of 4 of the Laurentian Great Lakes. The zooplankton size information was used to compute mean size, biomass density, and size-spectra parameters for each location. The resulting metrics were analyzed for their ability to discriminate among the Great Lakes. Biomass density provided discrimination among lakes, as did several parameters describing spectra shape and distribution. A proposed zooplankton indicator, mean size (determined with OPC measurements in this study), was found to provide discrimination among lakes. Size-spectra-related parameters added increased ability to discriminate in conjunction with the biomass density (or mean size) metric. A discriminant function analysis of the multiple metrics (mean size, biomass density, and distribution parameters) suggests that a multi metric size-based approach might be used to classify communities among lakes improving a mean-size metric. The feasibility OPCs and size-based metrics for zooplankton assessment was found to have potential for further development as assessment tools for the biological condition of zooplankton communities in the Great Lakes.