#psuenvironmentalscienceandmanagement

Methylmercury (MeHg) bioaccumulation in freshwater aquatic systems is impacted by anthropogenic stressors, including climate change and nutrient enrichment. The goal of this study was to determine how warmer water temperatures and excess nutrients would alter zooplankton communities and phytoplankton concentrations, and whether those changes would in turn increase or decrease MeHg concentrations in freshwater zooplankton. To test this, we employed a 2 × 2 factorial experimental design with nutrient and temperature treatments. Mesocosms were filled with ambient water and plankton from Cottage Grove Reservoir, Oregon, U.S.A., a waterbody that has experienced decades of elevated MeHg concentrations and corresponding fish consumption advisories due to run-off from Black Butte Mine tailings, located within the watershed. Treatment combinations of warmer temperature (increased by 0.7 °C) and nutrient addition (a single pulse of 10× ambient concentrations of nitrogen and phosphorous), control, and a combination of temperature and nutrients were applied to mesocosms. The individual treatments altered phytoplankton densities and community structure, but alone the effects on MeHg concentrations were muted. Importantly, we found a significant interactive effect of nutrients and temperature: the nutrient addition appeared to buffer against increased MeHg concentrations associated with elevated temperature. However, there was variability in this response, which seems to be related to the abundance of Daphnia and edible phytoplankton. Nutrients at low temperature were associated with marginal increases (1.1×) in zooplankton MeHg. Our findings suggest that global change drivers that influence community composition and ecosystem energetics of both zooplankton and phytoplankton can alter MeHg pathways through food webs.

Dramatic growth in herbicide-resistant (HR) weeds in the United States threatens farm profitability and may undercut environmentally beneficial farming practices. When HR weeds move across farm boundaries due to ecological processes or human action, a common pool resource challenge emerges, requiring farmer cooperation to manage such weeds effectively. We investigate the scope for cooperative management using responses to a national survey on HR weed issues to test a recursive model of three preconditions for collective action: (1) concern about HR weeds migrating from nearby lands; (2) communication with neighbors about HR weeds; and (3) belief that cooperation is necessary for effective resistance management. Results suggest that farmers who relied more on Extension educators regarding weed management, were more likely to satisfy each precondition. Further, concern about weeds resistant to multiple herbicides as well as concern about HR weed mobility positively influence concern about migration and views toward cooperation. Farmer time constraints and “techno-optimism” (a belief that herbicide discoveries will solve resistance problems) detract from the perceived need for cooperative approaches. A different set of factors significantly affect each precondition, suggesting heterogeneity in the underlying casual mechanisms. The findings can help tailor collective action to different socio-ecological settings experiencing HR weed resistance issues.

Disentangling the environmental and spatial drivers of biological communities across large scales increasingly challenges modern ecology in a rapidly changing world. Here, we investigate the hierarchical and trait‐based organization of regional and local factors of zooplankton communities at a macroscale of 1240 mountain lakes and ponds spanning western North America (California, USA, to Yukon Territory, Canada). Variation partitioning was used to test the hypothesized importance of climate, connectivity, catchment features, and exotic sportfish to zooplankton beta‐diversity in the context of key functional traits (body size and reproductive dispersal potential) given the pronounced environmental heterogeneity (e.g. thermal gradients), topographic barriers, and legacy of stocked fish in mountainous regions. Dispersal limitation was inferred from multispecies patch connectivity estimates based on nearest and average distances to occupied patches. Environmental heterogeneity best explained community composition as catchment/lake features (morphometry, land cover, and lithology) collectively captured greater variation than did climate (temperature, precipitation, and solar radiation), local stocking, or connectivity; however, single climatic variables captured the most variation individually. Macrospatial variation by larger obligate sexual species was better explained than that by smaller cyclically parthenogenetic asexual species. Our results provide several novel insights into the macroecology of zooplankton of the North American Cordillera, demonstrating their stronger associations to climatically driven aquatic‐terrestrial habitat coupling than dynamics arising from introduced salmonids, human land‐use, or species dispersal. These findings highlight the clear and important role of these communities as bioindicators of the limnological impacts of accelerating rates of climate change, as their responses appear relatively not confounded by local human perturbations or dispersal limitation.

Risk management typologies and their resulting archetypes can structure the many social and biophysical drivers of community wildfire risk into a set number of strategies to build community resilience. Existing typologies omit key factors that determine the scale and mechanism by which exposure from large wildfires occur. These factors are particularly important for land managing agencies like the US Forest Service, which must weigh community wildfire exposure against other management priorities. We analyze community wildfire exposure from national forests by associating conditions that affect exposure in the areas where wildfires ignite to conditions where exposure likely occurs. Linking source and exposure areas defines the scale at which cross-boundary exposure from large wildfires occurs and the scale at which mitigation actions need to be planned. We find that the vast majority of wildfire exposure from national forests is concentrated among a fraction of communities that are geographically clustered in discrete pockets. Among these communities, exposure varies primarily based on development patterns and vegetation gradients and secondarily based on social and ecological management constraints. We describe five community exposure archetypes along with their associated risk mitigation strategies. Only some archetypes have conditions that support hazardous fuels programs. Others have conditions where managing community exposure through vegetation management is unlikely to suffice. These archetypes reflect the diversity of development patterns, vegetation types, associated fuels, and management constraints that exist in the western US and provide a framework to guide public investments that improve management of wildfire risk within threatened communities and on the public lands that transmit fires to them.

Identifying early signs of anthropogenic disturbances in protected areas is critical for determining overuse, safeguarding natural beauty, protecting biodiversity, and sustaining resource use and economy. Assessing disturbances to aquatic systems of such areas is challenging due to the low-dose, diffused, and cumulative nature of disturbances; high risk at iconic sites; and difficulty of linking human activities with degradation. Using Jiuzhaigou Nature Reserve as an example study to overcome such challenges, we developed an approach that integrated human activities known to impact aquatic systems to calculate a holistic disturbance index for assessing the extent of human uses at scales of entire reserve and individual sub-watersheds. We linked human disturbance index with benthic algae and macroinvertebrate indicators of individual waterbodies to identify early signs of degradation. We conducted in situ nutrient experiments and intensive sampling of biota at iconic sites with early signs of degradation to provide direct linkage between tourist activities and eutrophication, and to pinpoint mechanisms of how human disturbances have resulted in such degradations. We found that the human disturbance index significantly correlated with benthic algae and macroinvertebrate indicators, and Jiuzhaigou is largely in healthy condition. For the two identified iconic sites with early signs of degradation, intensive tourist activities at observation and rest areas of Five-Color Lake seemed to link to extra amount of nitrogen input into the lake and resulted in overgrowth of phytoplankton and filamentous algae during summer peak tourist months. Extra amount of phosphorus input from tourism activities at Pearl Shoal seemed the cause of changes in substrate colors and of shifts in attached moss and algal communities. Our example study demonstrates that early signs of degradation can be visually observed and should be further assessed by measuring water quality and sensitive biological indicators at high risk areas of a waterbody during summer and peak tourist seasons. Sensitive biological indicators (e.g., intolerant diatom and macroinvertebrates) are better indicators than nutrient concentrations because of rapid assimilation of nutrients by algae and macrophytes. Our assessment approach and findings of studying Jiuzhaigou have broad applications to other protected areas for determining overuse, and hence for making science-based policy and taking adequate management actions to prevent overuses.

This paper describes the results of several years of study of backyards in Portland that have been restored as backyard habitats. We measured the relative success of yard habitats in contributing to diversity and abundance of forest-habitat birds. We studied how the abundance and diversity of shrubs, arthropods, and birds were related. We compared two neighborhoods; one having high, native tree cover, and the second having lower, non-native tree cover. Both the amount of regional and local tree cover had a stronger statistical signal than shrub cover. The presence of native species of shrubs in these yards was not a good predictor for abundance of arthropods.

Abstract: Predators exert considerable top-down pressure on ecosystems by directly consuming prey or indirectly influencing their foraging behaviors and habitat use. Prey is, therefore, forced to balance predation risk with resource reward. A growing list of anthropogenic stressors such as rising temperatures and ocean acidification has been shown to influence prey risk behaviors and subsequently alter important ecosystem processes. Yet, limited attention has been paid to the effects of chronic pharmaceutical exposure on risk behavior or as an ecological stressor, despite widespread detection and persistence of these contaminants in aquatic environments. In the laboratory, we simulated estuarine conditions of the shore crab, Hemigrapsus oregonensis, and investigated whether chronic exposure (60 days) to field-detected concentrations (0, 3, and 30 ng/L) of the antidepressant fluoxetine affected diurnal and nocturnal risk behaviors in the presence of a predator, Cancer productus. We found that exposure to fluoxetine influenced both diurnal and nocturnal prey risk behaviors by increasing foraging and locomotor activity in the presence of predators, particularly during the day when these crabs normally stay hidden. Crabs exposed to fluoxetine were also more aggressive, with a higher frequency of agonistic interactions and increased mortality due to conflicts with conspecifics. These results suggest that exposure to field-detected concentrations of fluoxetine may alter the trade-off between resource acquisition and predation risk among crabs in estuaries. This fills an important data gap, highlighting how intra- and interspecific behaviors are altered by exposure to field concentrations of pharmaceuticals; such data more explicitly identify potential ecological impacts of emerging contaminants on aquatic ecosystems and can aid water quality management. Prozac in the water: Chronic fluoxetine exposure and predation risk interact to shape behaviors in an estuarine crab. Available from: https://www.researchgate.net/publication/320133543_Prozac_in_the_water_Chronic_fluoxetine_exposure_and_predation_risk_interact_to_shape_behaviors_in_an_estuarine_crab [accessed Oct 4, 2017].

Abstract: The 2011 East Japan earthquake generated a massive tsunami that launched an extraordinary transoceanic biological rafting event with no known historical precedent. We document 289 living Japanese coastal marine species from 16 phyla transported over 6 years on objects that traveled thousands of kilometers across the Pacific Ocean to the shores of North America and Hawai‘i. Most of this dispersal occurred on nonbiodegradable objects, resulting in the longest documented transoceanic survival and dispersal of coastal species by rafting. Expanding shoreline infrastructure has increased global sources of plastic materials available for biotic colonization and also interacts with climate change–induced storms of increasing severity to eject debris into the oceans. In turn, increased ocean rafting may intensify species invasions.