Rapana venosa as an indicator species for TBT exposure over decadal and seasonal scales

Imposex and decline in reproductive output in marine gastropods have been linked to tributyltin (TBT) exposure. This study describes Chesapeake Bay, USA, veined rapa whelk Rapana venosa imposex incidence and sex ratios from 1998 to 2009. Tissue TBT concentrations (ng g^?1) were examined with respect to whelk sex, size, and water temperature at the time of collection, and also to egg case size, hatching success, and veliger diameter. Imposex incidence declined and population sex ratios moved closer to parity from 1998 to 2009. Observed TBT concentrations (ng g^?1) were higher in James River than in Ocean View whelks with higher TBT concentrations observed in males than in females. Exponential declines in TBT concentrations from female-specific first to last clutches within a reproductive season were observed, indicating that whelks depurate TBT through egg case deposition. Egg capsule hatching success and veliger size were similar for female and imposex whelks. The R. venosa imposex levels observed in Chesapeake Bay apparently do not affect the production, release, or viability of larvae.     

Flooding,resettlement, and change in livelihoods: evidence from rural Mozambique

Post‐disaster development policies, such as resettlement, can have major impacts on communities. This paper examines how and why people's livelihoods change as a result of resettlement, and relocated people's views of such changes, in the context of natural disasters. It presents two historically‐grounded, comparative case studies of post‐flood resettlement in rural Mozambique. The studies demonstrate a movement away from rain‐fed subsistence agriculture towards commercial agriculture and non‐agricultural activities. The ability to secure a viable livelihood was a key determinant of whether resettlers remained in their new locations or returned to the river valleys despite the risks posed by floods. The findings suggest that more research is required to understand i) why resettlers choose to stay in or abandon designated resettlement areas, ii) what is meant by ‘voluntary’ and ‘involuntary’ resettlement in the realm of post‐disaster reconstruction, and iii) the policy drivers of resettlement in developing countries.     

An ecosystem model for estimating potential shellfish culture production in sheltered coastal waters

A generic ecosystem model has been developed for estimating the potential production of shellfish culture and the effect of that cultivation on the pelagic ecosystem in sheltered coastal waters. The model describes the dynamics of a simple food web, nutrient cycling and growth of shellfish. The design of the model is closely tied to the temporal and spatial scales that are important in determining the sustainable production level for a particular embayment. The pelagic ecosystem, mussel energetics, population dynamics and hydrodynamics are coupled to allow fully dynamic predictions of the effect of the shellfish density. When applied to Beatrix Bay, an intensive culture embayment in the Pelorus Sound of New Zealand, the model successfully captured main features of the observed system behaviour. The hydrodynamic regime of the bay controls mussel growth and production. Although high fluxes of water into the bay suppress nutrient and carbon cycling signals in the system, the model simulations demonstrated that the mussel cultivation can have considerable effects on the ecosystem of the bay including food depletion and nutrient cycling. One of the most obvious effects is nutrient enhancement through mussel excretion at low cultivation densities, which promotes primary production particularly during the N-limitation period in summer. The sensitivity analysis identified uncertainty in some parameters and indicated areas for which experimental studies could lead to model improvement. The modelling exercise has established a primary predictive tool for managing mussel aquaculture of a coastal embayment to estimate relationships between the stock level and the growth rate of mussels, and the potentially achievable harvest and stocking density.     

What happens when you trust your supervisor? Mediators of individual performance in trust relationships

To understand how trust in supervisor translates into individual job performance, we hypothesize that trust in supervisor facilitates positive psychological conditions of meaningfulness, safety, and availability, which in turn predict individual job performance. We assert that each of the three mediating paths in our model represents a distinct mechanism by which trust in supervisor contributes to individual job performance. We test our hypotheses with 206 supervisor–subordinate dyads and find that trust in supervisor contributes to job performance through psychological availability and psychological safety but not psychological meaningfulness. By examining three different psychological mechanisms within the same frame, we provide a test that compares and contrasts the uniqueness of the three pathways. Our findings suggest practical ways for managers to build trust with subordinates and guidance for the design of productive work conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Establishing the green neighbourhood: approaches to neighbourhood-scale sustainability certification in Portland,Oregon

ABSTRACT

While local governance is widely acknowledged as an important element in the pursuit of sustainability, local action alone is insufficient to produce lasting change. One recent solution to this quandary has been the production of certification frameworks that encourage sustainable development at the neighbourhood scale by providing local actors with standardised definitions of sustainable practices. While these frameworks facilitate the spread of sustainable development strategies between local communities, there are significant contrasts between their approaches to encouraging local sustainable development that simultaneously fulfils global objectives. This article explores these contrasts through two neighbourhood-scale sustainability certification frameworks: LEED for Neighborhood Development (LEED-ND) and the EcoDistricts Protocol. Analysis of these frameworks in the context of two centrally-located neighbourhoods in Portland, Oregon, reveals substantial contrasts between the two frameworks in terms of the relative flexibility of their sustainability metrics, the time frame over which decisions regarding sustainable development are made, and community involvement in the process of pursuing specific objectives. Furthermore, it suggests that greater flexibility in the application of standards, continuous governance, and greater community involvement lead to more dynamic and holistic forms of sustainability that evolve as both local community needs and broader understandings of sustainability change over time.     

Incorporating low-resolution historic species location data decreases performance of distribution models

Developing robust species distribution models is important as model outputs are increasingly being incorporated into conservation policy and management decisions. A largely overlooked component of model assessment and refinement is whether to include historic species occurrence data in distribution models to increase the data sample size. Data of different temporal provenance often differ in spatial accuracy and precision. We test the effect of inclusion of historic coarse-resolution occurrence data on distribution model outputs for 187 species of birds in Australian tropical savannas. Models using only recent (after 1990), fine-resolution data had significantly higher model performance scores measured with area under the receiver operating characteristic curve (AUC) than models incorporating both fine- and coarse-resolution data. The drop in AUC score is positively correlated with the total area predicted to be suitable for the species (R² = 0.163-0.187, depending on the environmental predictors in the model), as coarser data generally leads to greater predicted areas. The remaining unexplained variation is likely to be due to the covariate errors resulting from resolution mismatch between species records and environmental predictors. We conclude that decisions regarding data use in species distribution models must be conscious of the variation in predictions that mixed-scale datasets might cause.     

Darwin’s “tug-of-war” vs. starlings’ “horse-racing”: how adaptations for sequential encounters drive simultaneous choice

Charles Darwin aided his private decision making by an explicit deliberation, famously deciding whether or not to marry by creating a list of points in a table with two columns: “Marry” and “Not Marry”. One hundred seventy-two years after Darwin’s wedding, we reconsider whether this process of choice, under which individuals assign values to their options and compare their relative merits at the time of choosing (the tug-of-war model), applies to our experimental animal, the European Starling, Sturnus vulgaris. We contrast this with the sequential choice model that postulates that decision-makers make no comparison between options at the time of choice. According to the latter, behaviour in simultaneous choices reflects adaptations to contexts with sequential encounters, in which the choice is whether to take an opportunity or let it pass. We postulate that, in sequential encounters, the decision-maker assigns (by learning) a subjective value to each option, reflecting its payoff relative to background opportunities. This value is expressed as latency and/or probability to accept each opportunity as opposed to keep searching. In simultaneous encounters, choice occurs through each option being processed independently, by a race between the mechanisms that generate option-specific latencies. We describe these alternative models and review data supporting the predictions of the sequential choice model.     

A landscape-scale framework to identify refugia from multiple stressors

From a conservation perspective, quantifying potential refugial capacity has been predominantly focused on climate refugia, which is critical for maintaining the persistence of species and ecosystems. However, protection from other stressors, such as human-induced changes in fire and hydrology, that cause habitat loss, degradation, and fragmentation is also necessary to ensure that conservation efforts focused on climate are not undermined by other threats. Thus, conceptual and methodological advances for quantifying potential refugia from multiple anthropogenic stressors are important to support conservation efforts. We devised a new conceptual approach, the domains of refugia, for assessing refugial capacity that identifies areas where exposure to multiple stressors is low. In our framework, patterns of environmental variability (e.g., increased frequency of warm summers), thresholds of resilience, and extent and intensity of stressors are used to identify areas of potential refugia from a suite of ongoing anthropogenic stressors (e.g., changes in fire regime). To demonstrate its utility, we applied the framework to a Southern California landscape. Sites with high refugial capacity (super-refugia sites) had on average 30% fewer extremely warm summers, 20% fewer fire events, 10% less exposure to altered river channels and riparian areas, and 50% fewer recreational trails than the surrounding landscape. Our results suggest that super-refugia sites (∼8200 km²) for some natural communities are underrepresented in the existing protected area network, a finding that can inform efforts to expand protected areas. Our case study highlights how considering exposure to multiple stressors can inform planning and practice to conserve biodiversity in a changing world.     

Towards the development of a multidisciplinary understanding of the effects of toxic chemical mixtures on health

Mixtures can be divided into simple (chemicals with comparable properties—health risk assessments on the chemicals) and complex, which can be further subdivided into defined (a reasonably distinct composition, created at a specific time and place despite dissimilar components—risk assessments on the common source) and coincidental (chemicals without similar properties or constant composition in time or space—risk assessments on the receptor). Interactions recognized are: independent action, dose addition (additivity), and potentiation (synergy and antagonism). Unpredicted outcomes need recognition. New approaches in higher education and multidisciplinary investigations are essential. The community of the Society for Environmental Geochemistry and Health should help clarify points such as when transformations in mixtures may become important enough to alter the classification and the risk assessment. The multidisciplinary community is also well placed to support the integration of nonchemical influences into mixture analysis and to contribute to the investigation of cumulative and multiple exposures.