Improving arsenopyrite oxidation rate laws: implications for arsenic mobilization during aquifer storage and recovery (ASR)

Aquifer storage and recovery (ASR) and aquifer recharge (AR) provide technical solutions to address water supply deficits and growing future water demands. Unfortunately, the mobilization of naturally present arsenic due to ASR/AR operations has undermined its application on a larger scale. Predicting arsenic mobility in the subsurface during ASR/AR is further complicated by site-specific factors, including the arsenic mobilization mechanisms, groundwater flow conditions, and multi-phase geochemical interactions. In order to ensure safe and sustainable ASR/AR operation, a better understanding of these factors is needed. The current study thus aims to better characterize and model arsenic remobilization at ASR/AR sites by compiling and analyzing available kinetic data on arsenic mobilization from arsenopyrite under different aqueous conditions. More robust and widely applicable rate laws are developed for geochemical conditions relevant to ASR/AR. Sensitivity analysis of these new rate laws gives further insight into the controlling geochemical factors for arsenic mobilization. When improved rate laws are incorporated as the inputs for reactive transport modeling, arsenic mobilization in ASR/AR operations can be predicted with an improved accuracy. The outcomes will be used to guide groundwater monitoring and specify ASR/AR operational parameters, including water pretreatment requirements prior to injection.     

Why Economics Matters for Endangered Species Protection

Abstract: We offer three reasons why economics matters more to species protection than many people think and what this implies for the ongoing debate over the reauthorization of the Endangered Species Act of 1973. Economics matters because (1) human behavior generally, and economic parameters in particular, help determine the degree of risk to a species; (2) in a world of scarce resources, the opportunity cost of species protection—the costs of reduced resources for other worthwhile causes—must be taken into account in decision making; and (3) economic incentives are critical in shaping human behavior, and consequently the recovery of species. Endangered species protection that explicitly addresses these basic principles can avoid wasting valuable resources that yield no gain in species protection.     

Aquatic plant community invasibility and scale-dependent patterns in native and invasive species richness

Invasive species richness often is negatively correlated with native species richness at the small spatial scale of sampling plots, but positively correlated in larger areas. The pattern at small scales has been interpreted as evidence that native plants can competitively exclude invasive species. Large-scale patterns have been understood to result from environmental heterogeneity, among other causes. We investigated species richness patterns among submerged and floating-leaved aquatic plants (87 native species and eight invasives) in 103 temperate lakes in Connecticut (northeastern USA) and found neither a consistently negative relationship at small (3-m2) scales, nor a positive relationship at large scales. Native species richness at sampling locations was uncorrelated with invasive species richness in 37 of the 60 lakes where invasive plants occurred; richness was negatively correlated in 16 lakes and positively correlated in seven. No correlation between native and invasive species richness was found at larger spatial scales (whole lakes and counties). Increases in richness with area were uncorrelated with abiotic heterogeneity. Logistic regression showed that the probability of occurrence of five invasive species increased in sampling locations (3 m2, n = 2980 samples) where native plants occurred, indicating that native plant species richness provided no resistance against invasion. However, the probability of three invasive species' occurrence declined as native plant density increased, indicating that density, if not species richness, provided some resistance with these species. Density had no effect on occurrence of three other invasive species. Based on these results, native species may resist invasion at small spatial scales only in communities where density is high (i.e., in communities where competition among individuals contributes to community structure). Most hydrophyte communities, however, appear to be maintained in a nonequilibrial condition by stress and/or disturbance. Therefore, most aquatic plant communities in temperate lakes are likely to be vulnerable to invasion.     

Population structure of <Emphasis Type="Italic">Symbiodinium</Emphasis> sp. associated with the common sea fan, <Emphasis Type="Italic">Gorgonia ventalina</Emphasis>, in the Florida Keys across distance,depth, and time

Numerous marine invertebrates form endosymbiotic relationships with dinoflagellates in the genus Symbiodinium. However, few studies have examined the fine-scale population structure of these symbionts. Here, we describe the genetic structure of Symbiodinium type “B1/B184” inhabiting the gorgonian Gorgonia ventalina along the Florida Keys. Six polymorphic microsatellite loci were utilized to examine 16 populations along the Upper, Middle, and Lower Keys spanning a range of ~200 km. Multiple statistical tests detected significant differentiation in 54–92% of the 120 possible pairwise comparisons between localities, suggesting low levels of gene flow in these dinoflagellates. In general, populations clustered by geographic region and/or reefs in close proximity. Some of the sharpest population differentiation was detected between Symbiodinium from deep and shallow sites on the same reef. In spite of the high degree of population structure, alleles and genotypes were shared among localities, indicating some connectivity between Symbiodinium populations associated with G. ventalina. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Developing a circumpolar programme for the monitoring of Arctic terrestrial biodiversity

The Arctic is undergoing biological and environmental changes, and a coordinated effort to monitor is critical to detect these changes. The Circumpolar Biodiversity Monitoring Programme (CBMP) of the Arctic Council biodiversity working group, Conservation of Arctic Flora and Fauna (CAFF), has developed pan-Arctic biodiversity monitoring plans that aims to improve the ability to detect and report on long-term changes. Whilst introducing this special issue, this paper also presents the making of the terrestrial monitoring plan and discusses how the plan follows the steps required for an adaptive and ecosystem-based monitoring programme. In this article, we discuss how data on key findings can be used to inform circumpolar and global assessments, including the State of the Arctic Terrestrial Biodiversity Report, which will be the first terrestrial assessment made by the CBMP. Key findings, advice for future monitoring and lessons learned will be used in planning next steps of pan-Arctic coordinated monitoring.     

Are soils beneath coniferous tree stands more acidic than soils beneath deciduous tree stands?

Environmental Science and Pollution Research - In 2008, the Mulberry River, a National Wild and Scenic River, was listed as impaired due to low pH (below pH&nbsp;6.0). Over the last...     

An approach to determining functional parameters of microperiphyton fauna in colonization surveys for marine bioassessment based on rarefaction curves

The functional parameters, i.e., the estimated equilibrium species number (S _eq ), the colonization rate constant, and the time taken to reach 90 % of S _eq (T ₉₀ ), of microperiphyton fauna have been widely used to determine the water quality status in aquatic ecosystems. The objective of this investigation was to develop a protocol for determining functional parameters of microperiphyton fauna in colonization surveys for marine bioassessment based on rarefaction and regression analyses. The temporal dynamics in species richness of microperiphyton fauna during the colonization period was analyzed based on a dataset of periphytic ciliates in Chinese coastal waters of the Yellow Sea. The results showed that (1) based on observed species richness and estimated maximum species numbers, a total of 16 glass slides were required in order to achieve coefficients of variation of <5 % in the functional parameters; (2) the rarefied average species richness and functional parameters showed weak sensitivity to sampling effort; (3) the temporal variations in average species richness were well-fitted to the MacArthur-Wilson model; and (4) the sampling effort of ~8 glass slides was sufficient to achieve coefficients of variation of <5 % in equilibrium average species number (AvS _eq ), colonization rate (AvG), and the time to reach 90 % of AvS _eq (AvT ₉₀ ) based on the average species richness. The findings suggest that the AvS _eq , AvG, and AvT ₉₀ values based on rarefied average species richness of microperiphyton might be used as reliable ecological indicators for the bioassessment of marine water quality in coastal habitats.     

Small farm ponds: overlooked features with important impacts on watershed sediment transport

Despite their size, small farm ponds are important features in many landscapes. Yet hydrographical databases often fail to capture these ponds, and their impacts on watershed processes remain unclear. For a 230‐km² portion of central Texas, United States (U.S.), we created a historical inventory of ponds and quantified the accuracy of automated detection methods under varying drought conditions. In addition, we documented pond dredging/enlargement events and identified sites that had been abandoned. We also analyzed sediment cores from downstream reservoirs to track changes in watershed sediment transport. Over 75 years, pond densities increased more than 350% — to among the highest documented in the U.S. — and the ability of automated methods to detect these ponds was highly dependent on drought severity (R² = 0.96). Approximately 5% of ponds present in the 1950s were no longer present in 2012, while 33% were dredged between 1937 and 2012. Downstream reservoir sedimentation has decreased by an average of 55% as ponds have increased in number. These findings suggest that small ponds and the maintenance of trapping efficiency have large‐scale impacts on sediment dynamics. Accurately accounting for these storage effects is vital to water resource planning efforts.     

Social Demand for Ecosystem Services and Implications for Watershed Management

We performed a sociocultural preference assessment for a suite of ecosystem services provided by the Kiamichi River watershed in the south‐central United States, a region with intense water conflict. The goal was to examine how a social assessment of services could be used to weigh tradeoffs among water resource uses for future watershed management and planning. We identified the ecosystem services beneficiaries groups, analyzed perception for maintaining services, assessed differences in the importance and perceived trends for ecosystem services, and explored the perceived impact on ecosystem services arising from different watershed management scenarios. Results show habitat for species and water regulation were two ecosystem services all beneficiaries agreed were important. The main discrepancies among stakeholder groups were found for water‐related services. The identification of potential tradeoffs between services under different flow scenarios promotes a dynamic management strategy for allocating water resources, one that mitigates potential conflicts. While it is widely accepted the needs of all beneficiaries should be considered for the successful incorporation of ecosystem services into watershed management, the number of studies actually using the sociocultural perspective in ecosystem service assessment is limited. Our study demonstrates it is both possible and useful to quantify social demand of ecosystem services in watershed management.