Using Mussel Isotope Ratios to Assess Anthropogenic Nitrogen Inputs to Freshwater Ecosystems

Stable nitrogen isotope ratios (¹⁵N) of freshwater mussels from a series of lakes and ponds wererelated to watershed land use characteristics to assess their utility in determining the source ofnitrogen inputs to inland water bodies. Nitrogen isotope ratiosmeasured in freshwater musselsfrom 19 lakes and ponds in Rhode Island, U.S.A., ranged from4.9–12.6 and were found tosignificantly correlate with the fraction of residential development in 100 and 200 m bufferzones around the ponds. Mussel ¹⁵N values in 12 of the 19 ponds also showed significantcorrelation with average dissolved nitrate concentrations, which ranged from 23–327 g L^-1.These observations, in light of previous studies which link elevated¹⁵N values of nitrogenderived from septic wastewater with those seen in biota, suggest that mussel isotope ratios mayreflect nitrogen source in freshwater ecosystems. We followed aniterative approach usingmultiple regression analysis to assess the relationship between mussel¹⁵N and the land usecategories fraction residential development, fraction feedlotagriculture, fraction row-cropagriculture, and fraction natural vegetation in 100 and 200 m bufferzones and pond watersheds.From this we developed a simple regression model to predict mussel¹⁵N from the fraction ofresidential development in the 200 m buffer zone around the pond.Subsequent testing with datafrom 16 additional sites in the same ecoregion led us to refine themodel by incorporating thefraction of natural vegetation. The overall average absolute differencebetween measured andpredicted ¹⁵N values using the two-parameter model was 1.6. Potential sources of error inthe model include differences in the scale and categorization ofland-use data used to generate andtest the model, differences in physical characteristics, such asretention time and range ofresidential development, and exclusion of sources of enrichednitrogen such as runoff from feedlot operations or increased nitrogen loading from inefficient or failed septic systems.     

Economic Impacts of Zebra Mussels on Drinking Water Treatment and Electric Power Generation Facilities

Invasions of nonnative species such as zebra mussels can have both ecological and economic consequences. The economic impacts of zebra mussels have not been examined in detail since the mid-1990s. The purpose of this study was to quantify the annual and cumulative economic impact of zebra mussels on surface water-dependent drinking water treatment and electric power generation facilities (where previous research indicated the greatest impacts). The study time frame was from the first full year after discovery in North America (Lake St. Clair, 1989) to the present (2004); the study area was throughout the mussels’ North American range. A mail survey resulted in a response rate of 31% for electric power companies and 41% for drinking water treatment plants. Telephone interviews with a sample of nonrespondents assessed nonresponse bias; only one difference was found and adjusted for. Over one-third (37%) of surveyed facilities reported finding zebra mussels in the facility and almost half (45%) have initiated preventive measures to prevent zebra mussels from entering the facility operations. Almost all surveyed facilities (91%) with zebra mussels have used control or mitigation alternatives to remove or control zebra mussels. We estimated that 36% of surveyed facilities experienced an economic impact. Expanding the sample to the population of the study area, we estimated $267 million (BCa 95% CI = $161 million–$467 million) in total economic costs for electric generation and water treatment facilities through late 2004, since 1989. Annual costs were greater ($44,000/facility) during the early years of zebra mussel infestation than in recent years ($30,000). As a result of this and other factors, early predictions of the ultimate costs of the zebra mussel invasion may have been excessive.     

Cadmium in aquatic ecosystems in Western Australia: A legacy of nutrient-deficient soils

More than 273 tonnes of cadmium have been added to Western Australian ecosystems through the application of superphosphate fertilisers since 1982. Fifty percent of this is water soluble and therefore eventually leaches into waterbodies and accumulates in the sediments. From this source, it enters the food web through algae and benthic animals and may ultimately be passed to humans. This is reflected in the cadmium levels of the freshwater mussels (Westralunio carteri) that exceeded statutory Australia New Zealand Food Authority (ANZFA) guidelines for Maximum Permissible Concentrations (MPCs) with respect to human consumption. The cadmium levels bioaccumulated in freshwater mussels elevated with increasing catchment clearing, being highest in degraded catchments. The MPC for Cd in crustaceans have recently been removed, yet tissues within the freshwater crayfish (Cherax tenuimanus) frequently exceeded the old MPC (0·2 μCd g⁻¹wet weight). Marron are sometimes consumed in considerable quantities and the risk to human health posed by a high Cd intake is briefly summarised. Finally, a number of management options concerned with reducing the level of Cd from fertilisers passing to humans are reviewed.     

Reach‐Scale Comparison of Habitat and Mollusk Assemblages for Select Sites in the Clinch River with Regional Context

Several hypotheses, including habitat degradation and variation in fluvial geomorphology, have been posed to explain extreme spatial and temporal variation in Clinch River mollusk assemblages. We examined associations between mollusk assemblage metrics (richness, abundance, recruitment) and physical habitat (geomorphology, streambed composition, fish habitat, and riparian condition) at 10 sites selected to represent the range of current assemblage condition in the Clinch River. We compared similar geomorphological units among reaches, employing semi‐quantitative and quantitative protocols to characterize mollusk assemblages and a mix of visual assessments and empirical measurements to characterize physical habitat. We found little to no evidence that current assemblage condition was associated with 54 analyzed habitat metrics. When compared to other sites in the Upper Tennessee River Basin (UTRB) that once supported or currently support mollusk assemblages, Clinch River sites were more similar to each other, representing a narrower range of conditions than observed across the larger geographic extent of the UTRB. A post‐hoc analysis suggested stream size and average boundary shear stress at bankfull stage may have historically limited species richness in the UTRB (p < 0.001). Associations between mollusk assemblages and physical habitat in the UTRB and Clinch River currently appear obscured by other factors limiting richness, abundance, and recruitment.     

Infant health impacts of freshwater algal blooms: Evidence from an invasive species natural experiment

Economists are increasingly interested in causally interpretable estimates of environmental health externalities, particularly on infant health. This paper focuses on a specific case by investigating microcystin, a toxin produced by freshwater blue-green algal blooms. We exploit a natural experiment caused by a zebra mussel die-off in a large lake located in the state of Michigan, USA to identify changes in microcystin-related infant outcomes surrounding the lake. Using both the synthetic control method and a difference-in-differences strategy, we find that instances of low birth weight around the lake fell by 1.4 percentage points after lake water quality improved. Along the intensive margin, birth weight and length of gestation increased by 17.1 g and 0.47 weeks, respectively. Improvements to low birth weight result in $768,500 in average annual hospitalization cost savings. Many robustness and falsification tests are performed including using both annual and monthly data and accounting for possible weather confounders and seasonality. Results suggest that microcystin can affect infant health at levels below current water advisory guidelines.     

Organochlorines in sediments and mussels collected from coastal sites along the Pearl River Delta, South China

IntroductionContaminationofthemarineenvironmentassociatedwithorganochlorineshasreceivedincreasingattentionoverthelastthirtyyears.Particularattentionhasbeenfocusedonthecoastalzoneandestuaries ,especiallynearmetropolitanregion(Sericano ,1990 ) .ThePearlRiverestuarine ,rangefromDayaBayintheeasttoChangshanIslandsinthewest,supportslargepopulationsofmarineorganismsandextensivefisheriesintheSouthChina .Sincethe 1980s ,therehasbeenrapideconomicdevelopmentinthePearlRiverDeltaresultinginexcessivedi…     

Measured and modelled tritium concentrations in freshwater Barnes mussels (Elliptio complanata) exposed to an abrupt increase in ambient tritium levels

To improve understanding of environmental tritium behaviour, the International Atomic Energy Agency (IAEA) included a Tritium and C-14 Working Group (WG) in its EMRAS (Environmental Modelling for Radiation Safety) program. One scenario considered by the WG involved the prediction of time-dependent tritium concentrations in freshwater mussels that were subjected to an abrupt increase in ambient tritium levels. The experimental data used in the scenario were obtained from a study in which freshwater Barnes mussels (Elliptio complanata) were transplanted from an area with background tritium concentrations to a small Canadian Shield lake that contains elevated tritium. The mussels were then sampled over 88 days, and concentrations of free-water tritium (HTO) and organically-bound tritium (OBT) were measured in the soft tissues to follow the build-up of tritium in the mussels over time.The HTO concentration in the mussels reached steady state with the concentration in lake water within one or two hours. Most models predicted a longer time (up to a few days) to equilibrium. All models under-predicted the OBT concentration in the mussels one hour after transplantation, but over-predicted the rate of OBT formation over the next 24 h. Subsequent dynamics were not well modelled, although all participants predicted OBT concentrations that were within a factor of three of the observation at the end of the study period. The concentration at the final time point was over-predicted by all but one of the models. The relatively low observed concentration at this time was likely due to the loss of OBT by mussels during reproduction.     

A study of radium bioaccumulation in freshwater mussels, Velesunio angasi, in the Magela Creek catchment, Northern Territory, Australia

Freshwater mussels, Velesunio angasi, along Magela Creek in Australia’s Northern Territory were examined to study radionuclide activities in mussel flesh and to investigate whether the Ranger Uranium mine is contributing to the radium loads in mussels downstream of the mine. Radium loads in mussels of the same age were highest in Bowerbird Billabong, located 20 km upstream of the mine site. Variations in the ratio of [Ra]:[Ca] in filtered water at the sampling sites accounted for the variations found in mussel radium loads with natural increases in calcium (Ca) in surface waters in a downstream gradient along the Magela Creek catchment gradually reducing radium uptake in mussels. At Mudginberri Billabong, 12 km downstream of the mine, concentration factors for radium have not significantly changed over the past 25 years since the mine commenced operations and this, coupled with a gradual decrease of the ²²⁸Ra/²²⁶Ra activity ratios observed along the catchment, indicates that the ²²⁶Ra accumulated in mussels is of natural rather than mine origin. The ²²⁸Th/²²⁸Ra ratio has been used to model radium uptake and a radium biological half-life in mussels of approximately 13 years has been determined. The long biological half-life and the low Ca concentrations in the water account for the high radium concentration factor of 30,000-60,000 measured in mussels from the Magela Creek catchment.     

用斑马鱼超弱光技术检测水体污染

用斑马鱼超弱光测量技术调测北京地区东南郊工业区和石油化工区,并设非污染对照点.结果表明:①斑马鱼超弱光强度与水体水质污染分级基本相平行;②与非污染对照点比较,灵敏地鉴别水质的清洁和污染的差别;③东南郊工业区,铬、钢、锌和镉等元素的影响小于氰、砷和氟化物,但是增强斑马鱼超弱光强度和引致水样间光强度差别的主要影响是化学需氧量、生化需氧量、氨氮和酚,即有机化合物类.石油化工区,除COD、BOD、氨氮和酚存在一定影响外,主要是石油类.斑马鱼超弱光测量方法是一项可拓展于环保领域的分析技术,有潜在应用前景。     

Clinch River Freshwater Mussels Upstream of Norris Reservoir,Tennessee and Virginia: A Quantitative Assessment from 2004 to 2009

The Clinch River is located in northeastern Tennessee (TN) and southwestern Virginia (VA) of the United States, and contains a diverse mussel assemblage of 46 extant species, including 20 species listed as federally endangered. To facilitate quantitative monitoring of the fauna, quadrat data were collected from 2004 to 2009 at 18 sites in the river, including 12 sites in TN and 6 sites in VA. Thirty‐eight mussel species were collected alive in total from quadrat samples taken annually at sites in the TN section of the river. Over the five‐year study period, mussel density averaged 25.5 m^?2 at all sites sampled in TN. In contrast, mussel density averaged only 3.1 m^?2 at sites sampled in VA. The best historical site in VA was Pendleton Island in Scott County, where mussel density was estimated as high as 25 m^?2 in 1979, comparable to current densities recorded in TN. Mussel densities are now <1 m^?2, indicating a collapse of the fauna. A severe reduction in mussel abundance has occurred in a 68‐km section of the river from St. Paul, VA, downstream to approximately Clinchport, VA (river kilometers 411.5‐343.3). While the environmental factors responsible for the faunal decline are largely unknown, they must have been severe and sustained to reduce such large populations to their current low levels. Long‐term water and habitat quality monitoring is needed to determine whether environmental degradation is still occurring in the river.