Is there a silver lining? Aggregation and photo-transformation of silver nanoparticles in environmental waters

Is the aggregation of silver nanoparticles in environmental waters a silver lining? The answer is not simple. Clearly, however, the aggregation and photo-transformation of AgNPs are complicated and could be more significant than previously thought. The difference in the water chemistry that controls the aggregation and photo-transformation of AgNPs results in the varying behavior and fate of AgNPs among different water bodies.     

Household evacuation characteristics in American Samoa during the 2009 Samoa Islands tsunami

Tsunamis represent significant threats to human life and development in coastal communities. This quantitative study examines the influence of household characteristics on evacuation actions taken by 211 respondents in American Samoa who were at their homes during the 29 September 2009 M_w 8.1 Samoa Islands earthquake and tsunami disaster. Multiple logistic regression analysis of survey data was used to examine the association between evacuation and various household factors. Findings show that increases in distance to shoreline were associated with a slightly decreased likelihood of evacuation, whereas households reporting higher income had an increased probability of evacuation. The response in American Samoa was an effective one, with only 34 fatalities in a tsunami that reached shore in as little as 15 minutes. Consequently, future research should implement more qualitative study designs to identify event and cultural specific determinants of household evacuation behaviour to local tsunamis.     

Recognizing reflexivity among conservation practitioners

When deciding how to conserve biodiversity, practitioners navigate diverse missions, sometimes conflicting approaches, and uncertain trade-offs. These choices are based not only on evidence, funders’ priorities, stakeholders’ interests, and policies, but also on practitioners’ personal experiences, backgrounds, and values. Calls for greater reflexivity—an individual or group's ability to examine themselves in relation to their actions and interactions with others—have appeared in the conservation science literature. But what role does reflexivity play in conservation practice? We explored how self-reflection can shape how individuals and groups conserve nature. To provide examples of reflexivity in conservation practice, we conducted a year-long series of workshop discussions and online exchanges. During these, we examined cases from the peer-reviewed and gray literature, our own experiences, and conversations with 10 experts. Reflexivity among practitioners spanned individual and collective levels and informal and formal settings. Reflexivity also encompassed diverse themes, including practitioners’ values, emotional struggles, social identities, training, cultural backgrounds, and experiences of success and failure. Reflexive processes also have limitations, dangers, and costs. Informal and institutionalized reflexivity requires allocation of limited time and resources, can be hard to put into practice, and alone cannot solve conservation challenges. Yet, when intentionally undertaken, reflexive processes might be integrated into adaptive management cycles at multiple points, helping conservation practitioners better reach their goals. Reflexivity could also play a more transformative role in conservation by motivating practitioners to reevaluate their goals and methods entirely. Reflexivity might help the conservation movement imagine and thus work toward a better world for wildlife, people, and the conservation sector itself.     

Prairie strips reduce fecal indicator bacteria concentrations in simulated runoff

Vegetative filter strips (VFS) have shown promising results in reducing the downstream transport of many agroecosystem contaminants. A recently developed type of VFS, prairie strips, has been shown to significantly reduce the impact of corn and soybean production systems on water quality in terms of sediment, nitrogen, and phosphorus losses. This study assessed potential additional benefits of prairie strips to include the reduction of pathogens. To assess the impact of prairie strips on manure-laden agricultural runoff, we utilized a physical model of prairie strips in a laboratory flume to conduct highly controlled overland flow experiments. Escherichia coli and Enterococcus concentration reductions of up to 45% and 65% were observed for runoff and infiltration flows, respectively, while mass load reductions of up to 65% were observed for surficial runoff flows. The degree of concentration or mass load reductions was dependent on the residence time of the flow within the strip and the partitioning of overland flow running onto the strip to infiltration and runoff flows. Based on our results and a review of the literature, we developed a design method to provide guidance on the width of prairie strip buffer needed to achieve a user-defined reduction of fecal bacteria concentration.     

Separating the effects of partial submergence and soil oxygen demand on plant physiology

In wetlands, a distinct zonation of plant species composition occurs along moisture gradients, due to differential flooding tolerance of the species involved. However, "flooding" comprises two important, distinct stressors (soil oxygen demand [SOD] and partial submergence) that affect plant survival and growth. To investigate how these two flooding stressors affect plant performance, we executed a factorial experiment (water depth x SOD) for six plant species of nutrient-rich and nutrient-poor conditions, occurring along a moisture gradient in Dutch dune slacks. Physiological, growth, and biomass responses to changed oxygen availability were quantified for all species. The responses were consistent with field zonation, but the two stressors affected species differently. Increased SOD increased root oxygen deprivation, as indicated by either raised porosity or increased alcohol dehydrogenase (ADH) activity in roots of flood-intolerant species (Calamagrostis epigejos and Carex arenaria). While SOD affected root functioning, partial submergence tended more to reduce photosynthesis (as shown both by gas exchange and 13C assimilation), leaf dark respiration, 13C partitioning from shoots to roots, and growth of these species. These processes were especially affected if the root oxygen supply was depleted by a combination of flooding and increased SOD. In contrast, the most flood-tolerant species (Juncus subnodulosus and Typha latifolia) were unaffected by any treatment and maintained high internal oxygen concentrations at the shoot : root junction and low root ADH activity in all treatments. For these species, the internal oxygen transport capacity was well in excess of what was needed to maintain aerobic metabolism across all treatments, although there was some evidence for effects of SOD on their nitrogen partitioning (as indicated by 865N values) and photosynthesis. Two species intermediate in flooding tolerance (Carex nigra and Schoenus nigricans) responded more idiosyncratically, with different parameters responding to different treatments. These results show that partial submergence and soil flooding are two very different stressors to which species respond in different ways, and that their effects on physiology, survival, and growth are interactive. Understanding species zonation with water regimes can be improved by a better appreciation of how these factors affect plant metabolism independently and interactively.     

Soil lead (Pb) in residential transects through Lubbock,Texas: a preliminary assessment

Residential lead (Pb) contamination, resulting from decades-long use of leaded gasoline and lead-based paint, is likely to be present in soils in most urban areas. A screening level sampling effort demonstrated that Lubbock, Texas, USA, like other cities of its age and size, has areas of elevated soil Pb. This effort was based on soil sampling performed on residential, commercial and thoroughfare properties. The focus of this study was to investigate that component of soil contamination due to combustion of leaded gasoline. Soils were collected from the 1–2 cm surface layer from street-side property borders, well away from buildings that might lead to soil contamination from leaded paint chips. All samples were analyzed for Pb after a 1 M HNO₃ mild extraction to determine the amount of bioavailable Pb. Two of three transects through the city demonstrated significant trends of decreasing Pb concentrations with distance from the city center, paralleling a decrease in developed property age. Peak soil Pb concentrations outside city development was 4.9 ± 0.6 mg/kg while the median concentration for the city was 35.4 mg/kg. Peak soil Pb concentrations in the city center ranged from 90.0 to 174.0 mg/kg and decreased exponentially to 6.0–9.0 mg/kg at the furthest terminus of the residential transects.     

Sensory complementation and the acquisition of predator recognition by salmonid fishes

Following disturbance, some aquatic prey species release chemicals that act as a warning cue and increase vigilance in nearby conspecifics. Such disturbance cues evoke consistent low intensity anti-predator responses. In contrast, alarm cues from injured conspecifics often evoke stronger intensity responses in prey animals. In this study, we test the sensory complement hypothesis, which suggests that multiple cues act in an additive or synergistic fashion to provide additional information for risk assessment by prey. In the first experiment, we showed that juvenile rainbow trout pre-exposed to disturbance cues respond to a given concentration of damage-released alarm cues with a higher intensity of response than the trout that were pre-exposed to cues from undisturbed conspecifics. The two cues acted in an additive fashion. In the second experiment, we demonstrated that disturbance cues alone were not enough to elicit a conditioned response to the odour of a novel predator. We also showed that while disturbance cues elicit an increase in the response of trout to alarm cues, this increase does not translate into a stronger learned response to the predator when the predator odour is paired with alarm cues. Future studies should take into account sensory complementation to avoid underestimating the responses of prey to predators.     

Direct and indirect effects of climate and habitat factors on butterfly diversity

Many factors, including climate, resource availability, and habitat diversity, have been proposed as determinants of global diversity, but the links among them have rarely been studied. Using structural equation modeling (SEM), we investigated direct and indirect effects of climate variables, host-plant richness, and habitat diversity on butterfly species richness across Britain, at 20-km grid resolution. These factors were all important determinants of butterfly diversity, but their relative contributions differed between habitat generalists and specialists, and whether the effects were direct or indirect. Climate variables had strong effects on habitat generalists, whereas host-plant richness and habitat diversity contributed relatively more for habitat specialists. Considering total effects (direct and indirect together), climate variables had the strongest link to butterfly species richness for all groups of species. The results suggest that different mechanistic hypotheses to explain species richness may be more appropriate for habitat generalists and specialists, with generalists hypothesized to show direct physiological limitations and specialists additionally being constrained by trophic interactions (climate affecting host-plant richness).     

Metal composition of arrow squid (Nototodarus sloanii [Gray 1849]) from the Chatham Rise,New Zealand: implications for human consumption

Environmental Science and Pollution Research - Cephalopods are important in the diets of humans and many other apex predators, and can play an important role in the bioaccumulation of metals. In...