Balancing the edge effects budget: bay scallop settlement and loss along a seagrass edge

Edge effects are a dominant subject in landscape ecology literature, yet they are highly variable and poorly understood. Often, the literature suggests simple models for edge effects-positive (enhancement at the edge), negative (enhancement at the interior), or no effect (neutral)--on a variety of metrics, including abundance, diversity, and mortality. In the marine realm, much of this work has focused on fragmented seagrass habitats due to their importance for a variety of commercially important species. In this study, the settlement, recruitment, and survival of bay scallops was investigated across a variety of seagrass patch treatments. By simultaneously collecting settlers (those viable larvae available to settle and metamorphose) and recruits (those settlers that survive some period of time, in this case, 6 weeks) on the same collectors, we were able to demonstrate a "balance" between positive and negative edge effects, resulting in a net neutral effect. Scallop settlement was significantly enhanced along seagrass edges, regardless of patch type while survival was elevated within patch interiors. However, recruitment (the net result of settlement and post-settlement loss) did not vary significantly from edge to center, representing a neutral effect. Further, results suggest that post-settlement loss, most likely due to predation, appears to be the dominant mechanism structuring scallop abundance, not patterns in settlement. These data illustrate the complexity of edge effects, and suggest that the metric used to investigate the effect (be it abundance, survival, or other metrics) can often influence the magnitude and direction of the perceived effect. Traditionally, high predation along a habitat edge would have indicated an "ecological trap" for the species in question; however, this study demonstrates that, at the population level, an ecological trap may not exist.     

Remaking the world in our own image: vulnerability,resilience and adaptation as historical discourses

A warming climate and less predictable weather patterns, as well as an expanding urban infrastructure susceptible to geophysical hazards, make the world an increasingly dangerous place, even for those living in high‐income countries. It is an opportune moment, therefore, from the vantage point of the second decade of the twenty‐first century, to review the terms and concepts that have been employed regularly over the past 50 years to assess risk and to measure people's exposure to such events in the light of the wider geopolitical context. In particular, it is useful to examine ‘vulnerability’, ‘resilience’, and ‘adaptation’, the principal theoretical concepts that, from an historical perspective, have dominated disaster studies since the end of the Second World War. In addition, it is valuable to enquire as to the extent to which such discourses were ideological products of their time, which sought to explain societies and their environments from the stance of competing conceptual frameworks.     

Behavioral consequences of exotic host plant adoption and the differing roles of male harassment on female movement in two checkerspot butterflies

Herbivorous insects may evolve convergent behaviors when independent adoption of a shared novel host plant places populations in environmental conditions that diverge from the ancestral state. We investigated the behavioral consequences of adopting Plantago lanceolata, an exotic species to North America, in populations of Euphydryas p. phaeton and Euphydryas editha taylori, on the east and west coasts of North America. Activity budgets and short-term movements suggested that innate species tendencies exert a greater impact on behavior than adoption of the same exotic host plant. However, female E. phaeton from a Plantago-dependent population spent more time inspecting host plants than females from a population dependent on the native host plant, Chelone glabra. Both checkerspot species had similar diffusion coefficients (D) regardless of host plant association. But, E. e. taylori step-lengths appeared bimodal and power law distributed while E. phaeton step-lengths were unimodal and best fit by an exponential distribution. We attribute this bimodal step-length distribution to the persistent harassment of courting males which induces a “long-distance” evasive flight in otherwise sedentary E. e. taylori females. In contrast, the longer distance step-lengths of E. phaeton were associated with the inspection of oviposition plants. These two checkerspot species appear to move greater distances across the reproductive landscape with contrasting motivational states that could lead to either intimate mapping (E. phaeton) or coarse mapping (E. e. taylori) of host resources.     

Chromium accumulation,transport and toxicity in plants∗

The predominant pathway for human exposure to chromium in non‐occupationally exposed individuals is via food with a daily intake of around 30–100 μgd^–1, with vegetables providing a major contribution. Unlike reports of chromium essentiality to man and animals, plants appear not to require chromium in spite of some early reports of a stimulatory growth effect.

Most reports on chromium in plants have been concerned with their growth on soils amended with sewage sludge, pF‐ash, tannery waste, or on ultra basic soils, which contain extreme concentrations of the element. Experimental studies with plants grown in hydroponic solution have often been undertaken at unrealistically high concentrations to examine the uptake of chromium in various forms, either as CrIII or CrVI at different pHs. In most cases, reports on chromium in plants deal with element concentrations and plant/soil relationships rather than detailed biochemical and physiological processes.

In general, chromium is largely retained in the roots of plants, although the oxidation state of chromium, pH, presence of humates and fulvates and plant species, affect plant uptake and transport. Leaves usually contain higher concentrations than grains. The uptake of CrIII is largely a passive process, whereas CrVI uptake is a metabolically mediated process via the sulphate pathway and is thus readily transported around the plant. The presence of a compound similar to trioxalate CrIII has been recorded while little chromium has been reported to be associated with cell organelles or soluble proteins.     

Comparison of recidivism rates for a teenage trauma prevention program after the addition of high-fidelity patient simulation

Objectives: We evaluated the benefits of adding high-fidelity simulation to a teenage trauma prevention program to decrease recidivism rates and encourage teens to discuss actionable steps toward safe driving.

Methods: A simulated pediatric trauma scenario was integrated into an established trauma prevention program. Participants were recruited because they were court-ordered to attend this program after misdemeanor convictions for moving violations. The teenage participants viewed this simulation from the emergency medical services (EMS) handoff to complete trauma care. Participants completed a postsimulation knowledge assessment and care evaluation, which included narrative data about the experience. Qualitative analysis of color-coded responses identified common themes and experiences in participants' answers. Court records were reviewed 6 years after course completion to determine short- and long-term recidivism rates, which were then compared to our program's historical rate.

Results: One hundred twenty-four students aged 16–20 years participated over a 2-year study period. Narrative responses included general reflection, impressions, and thoughts about what they might change as a result of the course. Participants reported that they would decrease speed (30%), wear seat belts (15%), decrease cell phone use (11%), and increase caution (28%). The recidivism rate was 55% within 6 years. At 6 months it was 8.4%, at 1 year it was 20%, and it increased approximately 5–8% per year after the first year. Compared with our programs, for historical 6-month and 2-year recidivism rates, no significant difference was seen with or without simulation.

Conclusions: Adding simulation is well received by participants and leads to positive reflections regarding changes in risk-taking behaviors but resulted in no changes to the high recidivism rates This may be due to the often ineffectiveness of fear appeals.     

Mapping trees outside forests using high-resolution aerial imagery: a comparison of pixel- and object-based classification approaches

Discrete trees and small groups of trees in nonforest settings are considered an essential resource around the world and are collectively referred to as trees outside forests (ToF). ToF provide important functions across the landscape, such as protecting soil and water resources, providing wildlife habitat, and improving farmstead energy efficiency and aesthetics. Despite the significance of ToF, forest and other natural resource inventory programs and geospatial land cover datasets that are available at a national scale do not include comprehensive information regarding ToF in the United States. Additional ground-based data collection and acquisition of specialized imagery to inventory these resources are expensive alternatives. As a potential solution, we identified two remote sensing-based approaches that use free high-resolution aerial imagery from the National Agriculture Imagery Program (NAIP) to map all tree cover in an agriculturally dominant landscape. We compared the results obtained using an unsupervised per-pixel classifier (independent component analysis—[ICA]) and an object-based image analysis (OBIA) procedure in Steele County, Minnesota, USA. Three types of accuracy assessments were used to evaluate how each method performed in terms of: (1) producing a county-level estimate of total tree-covered area, (2) correctly locating tree cover on the ground, and (3) how tree cover patch metrics computed from the classified outputs compared to those delineated by a human photo interpreter. Both approaches were found to be viable for mapping tree cover over a broad spatial extent and could serve to supplement ground-based inventory data. The ICA approach produced an estimate of total tree cover more similar to the photo-interpreted result, but the output from the OBIA method was more realistic in terms of describing the actual observed spatial pattern of tree cover.     

Fecal indicator bacteria (FIB) levels during dry weather from Southern California reference streams

High levels of fecal indicator bacteria (FIB) in surface waters is a common problem in urban areas that often leads to impairment of beneficial uses such as swimming. Once impaired, common management and regulatory solutions include development of total maximum daily loads (TMDLs) and other water quality management plans. A critical element of these plans is establishment of a "reference" level of exceedances against which to assess management goals and TMDL compliance. The goal of this study was to provide information on indicator bacteria contributions from natural streams in undeveloped catchments throughout southern California during dry weather, non-storm conditions. To help establish a regional reference data set, bacteria levels [i.e. Escherichia coli (E. coli), enterococci and total coliforms] were measured from 15 unimpaired streams in 11 southern California watersheds weekly for one full year. Concentrations measured from reference areas were typically between one to two orders of magnitude lower than levels found in developed watersheds. Nearly 82% of the time, samples did not exceed daily and monthly bacterial indicator thresholds. E. coli had the lowest daily percent exceedance (1.5%). A total of 13.7% of enterococci exceeded daily thresholds. Indicator bacteria levels fluctuated seasonally with an average of 79% of both enterococci and total coliforms exceedances occurring during summer months (June to August). Temperature, at all sites, explained about one-half the variation in total coliforms density suggesting that stream temperatures regulated bacterial populations. Accounting for natural background levels will allow for management targets that are more reflective of the contributions from natural sources.     

Distribution of sulfamethazine, chlortetracycline and tylosin in manure and soil of Canadian feedlots after subtherapeutic use in cattle

Feedlots are potential point sources for the flow of antibiotics into the environment due to common use of antibiotics such as sulfamethazine, chlortetracycline and tylosin. Hence soils and manures originating from a grassland control, an experimental and a commercial feedlot were analyzed and mass balances were calculated for these antibiotics. Up to 9990 μg kg⁻¹ sulfamethazine and 401 μg kg⁻¹ chlortetracycline on a dry matter basis were determined in feedlot manure. Soil concentrations were two orders of magnitude smaller. This corresponds to 7-40% of the calculated residual amount. In the commercial feedlot chlortetracycline was found down to soil depths of −40 cm; sulfamethazine was still detectable 1 year after medication. Sulfamethazine and chlortetracycline were additionally determined in manure of a control treatment in the experimental feedlot where cattle never received antibiotics. This was attributed to runoff from upslope pens. Consequently, antibiotics partially persist within feedlots and may be dislocated into the surrounding environment by vertical transport and runoff.     

Human Influences on Water Quality in Great Lakes Coastal Wetlands

A better understanding of relationships between human activities and water chemistry is needed to identify and manage sources of anthropogenic stress in Great Lakes coastal wetlands. The objective of the study described in this article was to characterize relationships between water chemistry and multiple classes of human activity (agriculture, population and development, point source pollution, and atmospheric deposition). We also evaluated the influence of geomorphology and biogeographic factors on stressor-water quality relationships. We collected water chemistry data from 98 coastal wetlands distributed along the United States shoreline of the Laurentian Great Lakes and GIS-based stressor data from the associated drainage basin to examine stressor-water quality relationships. The sampling captured broad ranges (1.5–2 orders of magnitude) in total phosphorus (TP), total nitrogen (TN), dissolved inorganic nitrogen (DIN), total suspended solids (TSS), chlorophyll a (Chl a), and chloride; concentrations were strongly correlated with stressor metrics. Hierarchical partitioning and all-subsets regression analyses were used to evaluate the independent influence of different stressor classes on water quality and to identify best predictive models. Results showed that all categories of stress influenced water quality and that the relative influence of different classes of disturbance varied among water quality parameters. Chloride exhibited the strongest relationships with stressors followed in order by TN, Chl a, TP, TSS, and DIN. In general, coarse scale classification of wetlands by morphology (three wetland classes: riverine, protected, open coastal) and biogeography (two ecoprovinces: Eastern Broadleaf Forest [EBF] and Laurentian Mixed Forest [LMF]) did not improve predictive models. This study provides strong evidence of the link between water chemistry and human stress in Great Lakes coastal wetlands and can be used to inform management efforts to improve water quality in Great Lakes coastal ecosystems.