New perspectives in ecotoxicology

The task of regulating potentially harmful chemicals in the environment is presently hindered by the lack of appropriate concepts and methods for evaluating the effects of anthropogenic chemicals on ecosystems. Toxicity tests at the molecular and physiological levels have been used successfully as indicators of adverse effects on test organisms and have been extrapolated to humans to establish a basis for risk assessment. However, laboratory measurements of effects upon individuals do not translate readily into potential effects upon natural populations, in part because natural populations interact with other populations and with the physical environment. Even more difficult to assess are the deleterious impacts of anthropogenic chemicals on ecosystems, because of effects on species interactions, diversity, nutrient cycling, productivity, climatic changes, and other processes.Effects on ecosystems resulting from chemical stresses are outside the realm of classical toxicology, and an ecosystem-level perspective is essential for the consideration of such effects; but the science that deals with ecosystem-level effects,ecotoxicology, is still developing. This article synthesizes the topics discussed at a workshop on ecotoxicology held by the Ecosystems Research Center at Cornell University. Topics covered include: the regulatory framework in which ecotoxicological research must be applied; ecosystem modification of toxicant fate and transport; how ecosystem composition, structure, and function are influenced by chemicals; methods currently available for predicting the effects of chemicals at the ecosystem level; and recommendations on research needs to enhance the state of the science of ecotoxicology.     

Integument coloration signals reproductive success,heterozygosity, and antioxidant levels in chick-rearing black-legged kittiwakes

Carotenoid pigments are important for immunity and as antioxidants, and carotenoid-based colors are believed to provide honest signals of individual quality. Other colorless but more efficient antioxidants such as vitamins A and E may protect carotenoids from bleaching. Carotenoid-based colors have thus recently been suggested to reflect the concentration of such colorless antioxidants, but this has rarely been tested. Furthermore, although evidence is accruing for multiple genetic criteria for mate choice, carotenoid-based colors have rarely been shown to reflect both phenotypic and genetic quality. In this study, we investigated whether gape, tongue, eye-ring, and bill coloration of chick-rearing black-legged kittiwakes Rissa tridactyla reflected circulating levels of carotenoids and vitamins A and E. We further investigated whether integument coloration reflected phenotypic (body condition and fledging success) and genetic quality (heterozygosity). We found that the coloration of fleshy integuments was correlated with carotenoid and vitamin A levels and fledging success but only in males. Furthermore, the coloration of tongue and eye-ring was correlated with heterozygosity in both males and females. Integument colors might therefore be reliable signals of individual quality used by birds to adjust their parental care during the chick-rearing period.     

Individual difference factors in risky driving among older adults

INTRODUCTION: Motor-vehicle crashes kill roughly 4,500 American adults over the age of 75 annually. Among younger adults, one behavioral factor consistently linked to risky driving is personality, but this predictor has been overshadowed by research on cognitive, perceptual, and motor processes among older drivers. METHOD: In this study, a sample of 101 licensed drivers, all age 75 and over, were recruited to complete self-report measures on personality, temperament, and driving history. Participants also completed a virtual environment (VE) course designed to assess risk-taking driving behavior. State records of motor-vehicle crashes were collected. RESULTS: Results suggest both a sensation-seeking personality and an undercontrolled temperament are related to risky driving among older adults. Sensation-seeking was particularly related to history of violations and tickets, while temperamental control was more broadly related to a number of risky driving measures. Methodological and crash prevention issues are discussed.     

Targeting Ecosystem Features for Conservation: Standing Crops in the Florida Everglades

Abstract: The Everglades in southern Florida, U.S.A., is a major focus of conservation activities. The freshwater wetlands of the Everglades do not have high species richness, and no species of threatened aquatic animals or plants live there. We have, however, identified a distinctive ecological feature of the Everglades that is threatened by canal construction, draining, and nutrient enrichment from agricultural runoff. Compared to values reported from other freshwater systems, standing stocks of periphyton in relatively undisturbed areas of the Everglades were unusually high, and standing stocks of invertebrates and fish were unusually low. Averaging data gathered from nine sites and five sampling periods spanning 1 year, we found that periphyton standing crop was 88.2 g/m² (ash-free dry mass), invertebrate standing stock was 0.64 g/m² (dry mass), and fish standing stock was 1.2 g/m² (dry mass of large and small species combined). We found that fish standing stocks were much higher in phosphorus-enriched sites than in nearby reference sites but that invertebrate standing stocks were similar in enriched and reference sites. Our results support the notion that oligotrophy is at least partially responsible for the low standing stocks of fish, but they also suggest that species interactions and a paucity of deep-water refugia are important. Anthropogenic eutrophication in Everglades marshes will lead to the loss of distinctive ecosystem features. A focus on species richness and "hot spots" of threatened species provides no basis for conservation of ecosystems like the Everglades. If oligotrophic ecosystems often have low species richness, they will be underrepresented in preservation networks based on some common criteria for establishing conservation priorities.     

Work stress and problem alcohol behavior: a test of the spillover model

Although previous research has found weak support for the model of stressful work ‘spilling over’ to negative coping responses during nonwork hours, we argue that a variety of conceptual and methodological problems may partially explain the weak and inconsistent findings. Two important shortcomings are inadequately specified models and a failure to consider nonescapist responses to job-related stress. We therefore propose that there may be escapist (i.e. increased drinking, working through job dissatisfaction for those who believe that alcohol consumption is an effective means to reduce stress) and nonescapist (i.e. decreased drinking for those who are dissatisfied with their jobs but do not believe alcohol is an effective coping strategy) responses to work stress. These hypotheses were tested on a sample of 972 production workers in the Pacific northwest. Results show moderate support for the existence of both escapist and nonescapist responses to job-related stresses. © 1998 John Wiley & Sons, Ltd.     

Incorporating private lands in conservation planning: protected areas in Britain.

Evaluations of the effectiveness of protected areas often report their inadequate representation of regional variation in environmental conditions, land cover, and biological diversity. One frequent contributory explanation is the heavy reliance placed upon the designation of public as opposed to private lands for statutory protection. Given that protected area designation in Britain has no such constraint, and indeed that more than half of such areas are on private lands, we tested the a priori assumption that within this region the representation of environmental conditions and land cover within statutory protected areas would be more equitable. Despite the reduction in land ownership constraints on where protected areas can be established, a marked bias in protected area coverage remains. Protected areas in Britain tend toward regions of higher elevation, soils of lower economic potential, and coastal/estuarine habitat and fail adequately to represent areas of lower elevation and woodland habitats. Improving the current situation requires not only a more systematic approach to site selection, but a more equitable and diverse portfolio of incentives for private landowners to facilitate the decision to manage sites for conservation.     

Habitat type determines herbivory controls over CO2 fluxes in a warmer Arctic

High-latitude ecosystems store large amounts of carbon (C); however, the C storage of these ecosystems is under threat from both climate warming and increased levels of herbivory. In this study we examined the combined role of herbivores and climate warming as drivers of CO2 fluxes in two typical high-latitude habitats (mesic heath and wet meadow). We hypothesized that both herbivory and climate warming would reduce the C sink strength of Arctic tundra through their combined effects on plant biomass and gross ecosystem photosynthesis and on decomposition rates and the abiotic environment. To test this hypothesis we employed experimental warming (via International Tundra Experiment [ITEX] chambers) and grazing (via captive Barnacle Geese) in a three-year factorial field experiment. Ecosystem CO2 fluxes (net ecosystem exchange of CO2, ecosystem respiration, and gross ecosystem photosynthesis) were measured in all treatments at varying intensity over the three growing seasons to capture the impact of the treatments on a range of temporal scales (diurnal, seasonal, and interannual). Grazing and warming treatments had markedly different effects on CO2 fluxes in the two tundra habitats. Grazing caused a strong reduction in CO2 assimilation in the wet meadow, while warming reduced CO2 efflux from the mesic heath. Treatment effects on net ecosystem exchange largely derived from the modification of gross ecosystem photosynthesis rather than ecosystem respiration. In this study we have demonstrated that on the habitat scale, grazing by geese is a strong driver of net ecosystem exchange of CO2, with the potential to reduce the CO2 sink strength of Arctic ecosystems. Our results highlight that the large reduction in plant biomass due to goose grazing in the Arctic noted in several studies can alter the C balance of wet tundra ecosystems. We conclude that herbivory will modulate direct climate warming responses of Arctic tundra with implications for the ecosystem C balance; however, the magnitude and direction of the response will be habitat-specific.     

Tolerance of soil pathogens co-varies with shade tolerance across species of tropical tree seedlings

A negative feedback between local abundance and natural enemies could contribute to maintaining tree species diversity by constraining population growth of common species. Soil pathogens could be an important mechanism of such noncompetitive distance and density-dependent (NCDD) mortality, but susceptibility to local pathogens may be ameliorated by a life history strategy that favors survivorship. In a shade-house experiment (1% full sun), we tested seedling life span, growth, and mass allocation responses to microbial extract filtered from conspecific-cultured soil in 21 tree species that varied in abundance and shade tolerance in a wet tropical forest (La Selva Biological Station, Costa Rica). Forty-three percent of the species had significant reductions, and 10% of the species had significant increases in life span, growth, root length, or root surface area when inoculated with microbial extract; 10% of the species experienced opposing reductions and increases in these characteristics. Contrary to expectation, species' local abundance was not related to species-specific responses to microbial extracts from cultured soils. Across species, seedling shade tolerance (survival at 1% full sun) was negatively correlated with susceptibility to the microbial. treatment for both survival and total mass accumulation, thereby exaggerating shade tolerance differences among species. Thus, soil pathogens may contribute to species coexistence through heightening niche differentiation rather than through negative density dependence in common species.     

Dominant species identity, not community evenness, regulates invasion in experimental grassland plant communities

While there has been extensive interest in understanding the relationship between diversity and invasibility of communities, most studies have only focused on one component of diversity: species richness. Although the number of species can affect community invasibility, other aspects of diversity, including species identity and community evenness, may be equally important. While several field studies have examined how invasibility varies with diversity by manipulating species identity or evenness, the results are often confounded by resource heterogeneity, site history, or disturbance. We designed a mesocosm experiment to examine explicitly the role of dominant species identity and evenness on the invasibility of grassland plant communities. We found that the identity of the dominant plant species, but not community evenness, significantly impacted invasibility. Using path analysis, we found that community composition (dominant species identity) reduced invasion by reducing early-season light availability and increasing late-season plant community biomass. Nitrogen availability was an important factor for the survival of invaders in the second year of the experiment. We also found significant direct effects of certain dominant species on invasion, although the mechanisms driving these effects remain unclear. The magnitude of dominant species effects on invasibility we observed are comparable to species richness effects observed in other studies, showing that species composition and dominant species can have strong effects on the invasibility of a community.     

Success of collaboration for sustainable agriculture: a case study meta-analysis

Environment, Development and Sustainability - More and better collaboration between farmers and other stakeholders has repeatedly been identified as a key strategy for sustainable agriculture....