Spatio-temporal variability of solid, total dissolved and labile metal: passive vs. discrete sampling evaluation in river metal monitoring

In order to obtain representative dissolved and solid samples from the aquatic environment, a spectrum of sampling methods are available, each one with different advantages and drawbacks. This article evaluates the use of discrete sampling and time-integrated sampling in illustrating medium-term spatial and temporal variation. Discrete concentration index (CI) calculated as the ratio between dissolved and solid metal concentrations in grab samples are compared with time-integrated concentration index (CI) calculated from suspended particulate matter (SPM) collected in sediment traps and labile metals measured by the diffusive gel in thin films (DGT) method, collected once a month during one year at the Seine River, upstream and downstream of the Greater Paris Region. Discrete CI at Bougival was found to be significantly higher than at Triel for Co, Cu, Mn, Ni and Zn, while discrete metal partitioning at Marnay was found to be similar to Bougival and Triel. However, when using time-integrated CI, not only was Bougival CI significantly higher than Triel CI, CI at Marnay was also found to be significantly higher than CI at Triel which was not observed for discrete CI values. Since values are time-averaged, dramatic fluctuations were smoothed out and significant medium-term trends were enhanced. As a result, time-integrated concentration index (CI) was able to better illustrate urbanization impact between sites when compared to discrete CI. The impact of significant seasonal phenomenon such as winter flood, low flow and redox cycles was also, to a certain extent, visible in time-integrated CI values at the upstream site. The use of time-integrated concentration index may be useful for medium- to long-term metal studies in the aquatic environment.     

A Strategy for Prioritizing Threats and Recovery Actions for At-Risk Species

Ensuring the persistence of at-risk species depends on implementing conservation actions that ameliorate threats. We developed and implemented a method to quantify the relative importance of threats and to prioritize recovery actions based on their potential to affect risk to Mojave desert tortoises (Gopherus agassizii). We used assessments of threat importance and elasticities of demographic rates from population matrix models to estimate the relative contributions of threats to overall increase in risk to the population. We found that urbanization, human access, military operations, disease, and illegal use of off highway vehicles are the most serious threats to the desert tortoise range-wide. These results suggest that, overall, recovery actions that decrease habitat loss, predation, and crushing will be most effective for recovery; specifically, we found that habitat restoration, topic-specific environmental education, and land acquisition are most likely to result in the greatest decrease in risk to the desert tortoise across its range. In addition, we have developed an application that manages the conceptual model and all supporting information and calculates threat severity and potential effectiveness of recovery actions. Our analytical approach provides an objective process for quantifying threats, prioritizing recovery actions, and developing monitoring metrics for those actions for adaptive management of any at-risk species.     

Analyzing the Effects of Groundwater Pumping on an Urban Stream‐Aquifer System

When the cone of influence of a pumping well reaches a nearby river, the resulting hydraulic gradient can induce enhanced seepage of streamflow into the aquifer. The rate of seepage is often modeled using analytical solutions that are simple to apply but may not reproduce field data due to mathematical assumptions not being met in the field. Furthermore, the appropriateness of such models has not been investigated in detail due to difficulty in measuring streamflow loss in the field. In this study, a field experiment was conducted on a reach of the South Platte River near Denver, Colorado to estimate pumping‐induced streamflow loss. A network of stream gauges, monitoring wells, and in situ measurements was used to observe streamflow rates, groundwater levels, and temperature to assess if pumping wells have a significant impact on streamflow, and to compare observed streamflow depletion against analytical solutions. Data collected suggest that pumping wells have a noticeable impact on streamflow. The analytical solutions proved accurate if streamflow was low and constant but performed poorly if streamflow was high and variable. Therefore, for this reach, the use of analytical solutions to predict streamflow may only be appropriate under low‐flow, constant‐flow conditions. Methods and results can be used to guide other streamflow depletion studies and to inform cases of pumping‐induced streamflow depletion, particularly in regard to water rights.     

Climate Response by the Ski Industry: The Shortcomings of Snowmaking for Australian Resorts

Skier numbers, and revenues for the multi-billion-dollar ski industry, are highly sensitive to snow cover. Previous research projected that under climate change, natural snow cover will become inadequate at 65% of sites in the Australian ski resorts by 2020. Resorts plan to compensate for reduced snowfall through additional snowmaking. For the six main resorts, however, this would require over 700 additional snow guns by 2020, requiring approximately US $100 million in capital investment, and 2,500-3,300 ML of water per month, as well as increased energy consumption. This is not practically feasible, especially as less water will be available. Therefore, low altitude ski resorts such as these may not be able to rely on snowmaking even for short-term adaptation to climate change. Instead, they are likely to seek conversion to summer activities and increased property development.     

Ecosystem response to climatic change: the importance of the cold season

Winter climate and snow cover are the important drivers of plant community development in polar regions. However, the impacts of changing winter climate and associated changes in snow regime have received much less attention than changes during summer. Here, we synthesize the results from studies on the impacts of extreme winter weather events on polar heathland and lichen communities. Dwarf shrubs, mosses and soil arthropods were negatively impacted by extreme warming events while lichens showed variable responses to changes in extreme winter weather events. Snow mould formation underneath the snow may contribute to spatial heterogeneity in plant growth, arthropod communities and carbon cycling. Winter snow cover and depth will drive the reported impacts of winter climate change and add to spatial patterns in vegetation heterogeneity. The challenges ahead lie in obtaining better predictions on the snow patterns across the landscape and how these will be altered due to winter climate change.     

Expansion of Canopy-Forming Willows Over the Twentieth Century on Herschel Island,Yukon Territory,Canada

Canopy-forming shrubs are reported to be increasing at sites around the circumpolar Arctic. Our results indicate expansion in canopy cover and height of willows on Herschel Island located at 70° north on the western Arctic coast of the Yukon Territory. We examined historic photographs, repeated vegetation surveys, and conducted monitoring of long-term plots and found evidence of increases of each of the dominant canopy-forming willow species (Salix richardsonii, Salix glauca and Salix pulchra), during the twentieth century. A simple model of patch initiation indicates that the majority of willow patches for each of these species became established between 1910 and 1960, with stem ages and maximum growth rates indicating that some patches could have established as late as the 1980s. Collectively, these results suggest that willow species are increasing in canopy cover and height on Herschel Island. We did not find evidence that expansion of willow patches is currently limited by herbivory, disease, or growing conditions.     

Multi-decadal changes in tundra environments and ecosystems: synthesis of the International Polar Year-Back to the Future project (IPY-BTF)

Understanding the responses of tundra systems to global change has global implications. Most tundra regions lack sustained environmental monitoring and one of the only ways to document multi-decadal change is to resample historic research sites. The International Polar Year (IPY) provided a unique opportunity for such research through the Back to the Future (BTF) project (IPY project #512). This article synthesizes the results from 13 papers within this Ambio Special Issue. Abiotic changes include glacial recession in the Altai Mountains, Russia; increased snow depth and hardness, permafrost warming, and increased growing season length in sub-arctic Sweden; drying of ponds in Greenland; increased nutrient availability in Alaskan tundra ponds, and warming at most locations studied. Biotic changes ranged from relatively minor plant community change at two sites in Greenland to moderate change in the Yukon, and to dramatic increases in shrub and tree density on Herschel Island, and in subarctic Sweden. The population of geese tripled at one site in northeast Greenland where biomass in non-grazed plots doubled. A model parameterized using results from a BTF study forecasts substantial declines in all snowbeds and increases in shrub tundra on Niwot Ridge, Colorado over the next century. In general, results support and provide improved capacities for validating experimental manipulation, remote sensing, and modeling studies.     

Heavy metal accumulation by recombinant mammalian metallothionein within Escherichia coli protects against elevated metal exposure

In an effort to minimize the impact on the environment or improve the properties of choice, most engineered nanoparticles used for commercial applications are surface functionalized. The release of these functionalized engineered nanoparticles (FENPs) into the environment can be either deliberate or accidental. Scientific research to date has tended to focus on evaluating the toxicity of FENPs, with less attention being given to exposure assessments or to the study of their general behavior in natural environments. We have therefore investigated the effects of environmental parameters such as pH, NaCl concentration, and natural organic matter concentration on the aggregation kinetics of FENPs with time resolved dynamic light scattering, using functionalized gold nanoparticles (FAuNPs) as a representative of these particles. We also investigated the effects of average particle size, the type of surface capping agent, and particle concentration on FAuNP aggregation kinetics. Our results show that the physico-chemical properties of the capping agent have a greater influence on the aggregation behavior of FAuNPs than either their core composition or their particle size.     

Comparative study of biochemical and immunological biomarkers in three marine bivalves exposed at a polluted site

A battery of biochemical and immunological biomarkers used for pollution assessment were measured for first time in the clams Venus verrucosa and Callista chione and were compared with those of the mussel Mytilus galloprovincialis, a well-established indicator organism utilized in numerous environmental monitoring programs. Clams and mussel were transplanted at a polluted and a reference site or maintained at the laboratory. Among biochemical biomarkers, acetylcholinesterase did not differ at the polluted site in all species, but there was a significant difference between the mussel and the clams, glutathione S-transferase showed a clear inhibition at the polluted site in all species and a significant difference between the two clams was also indicated, while catalase activities were increased only in V. verrucosa at the polluted site and not in mussel or the other clam. Immunological biomarkers responses were also pronounced at the polluted site. Lysozyme activity was species-dependent whereas respiratory burst activity measured as luminol-dependent chemiluminescence (CL) was site and stimulus dependent, and it was evident in M. galloprovincialis and V. verrucosa and not in C. chione. Further investigation focused on biochemical and immunological biomarkers related with the oxidative mechanisms in clams will strengthen and expand their use as bioindicators for pollution assessment.     

Hybrid larch (Larix x eurolepis Henry): a good candidate for cadmium phytoremediation?

Studies related to phytoremediation by conifers are still at their beginning. Thus, we investigated the ability of a hybrid larch (Larix x eurolepis) to accumulate cadmium (Cd). One-month-old clonal plantlets grown in vitro were exposed for 1 week to a high Cd concentration (1.5 mM). No significant effect was observed on root and shoot biomass, root length, and needle number as a result of Cd treatment. Leaf photosynthetic pigment content and total soluble protein concentration in roots and shoots remained unchanged compared to control plantlets. Taken together, these results suggested that hybrid larch tolerated Cd in our conditions. The high Cd concentration in shoots (200 μg Cd gram^?1 dry weight) showed the good capacity of larch to translocate Cd and thus a potential use of this species for phytoremediation. Furthermore, under our conditions, phytochelatin biosynthesis pathway was slightly stimulated, suggesting that this pathway did not reach the threshold and/or another mechanism of Cd storage may be involved to explain larch tolerance to Cd.