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At least 775 records · Page 43Linked to original sources
USGS2019

Phylogeny and foraging mode correspond with thiaminase activity in freshwater fishes: Potential links to environmental factors

Knowledge of the dietary components of fish species is important for understanding their growth, survival, and recruitment. Deficiency in thiamine (vitamin B1) leading to reproductive failure and physiological illness among freshwater fishes has been attributed to thiaminase activity in fish in the Great Lakes and the New York Finger Lakes, but the causes of variation in thiaminase activity among freshwater fishes is unclear. We characterized thiaminase activity in 29 species of freshwater fishes across 7 ray-finned and 1 jawless family. All fish were further categorized by phylogeny, trophic category (trophic level and feeding mode), and native or non-native status to evaluate how ecological processes correspond with thiaminase activity. Thiaminase activity varied significantly across species, families, trophic factors, phylogenetic groups, and sites. Teleosts that were more recently derived had higher thiaminase activity than more basal species. Thiaminase activity was also higher among herbivores than omnivores or carnivores. This trend was clearest in the Cyprinidae family, which had the greatest range in thiaminase activity and a wide range in trophic-level position and trophic categories (herbivores, omnivores, and carnivores). Variation in average thiaminase activity of Spotfin Shiners (Cyprinella spiloptera) among sites within a watershed was correlated with anthropogenic and natural components of land cover. Our study contributes much-needed quantitative ecological information related to thiaminase activity in a suite of fish species that vary in evolutionary history, trophic level, and foraging modes. However, more studies are needed to identify interacting causes of thiaminase variation and examine the implications of these findings on the overall health of aquatic populations and freshwater ecosystems.

Freshwater Science↗
USGS2013

Thermal tolerance of meltwater stonefly Lednia tumana nymphs from an alpine stream in Waterton–Glacier International Peace Park, Montana, USA

Global climate change threatens to affect negatively the structure, function, and diversity of aquatic ecosystems worldwide. In alpine systems, the thermal tolerances of stream invertebrates can be assessed to understand better the potential effects of rising ambient temperatures and continued loss of glaciers and snowpack on alpine stream ecosystems. We measured the critical thermal maximum (CTM) and lethal temperature maximum (LTM) of the meltwater stonefly ( Lednia tumana ), a species limited to glacial and snowmelt-driven alpine streams in the Waterton–Glacier International Peace Park area and a candidate for listing under the US Endangered Species Act. We collected L. tumana nymphs from Lunch Creek in Glacier National Park, Montana (USA) and transported them to a laboratory at the University of Montana Flathead Lake Biological Station, Polson, Montana. We placed nymphs in a controlled water bath at 1 of 2 acclimation temperatures, 8.5 and 15°C. We increased water temperature at a constant rate of 0.3°C/min. We calculated the average CTM and LTM (± SD) for each acclimation temperature and compared them with Student’s t-tests. Predicted chronic temperature maxima were determined using the ⅓ rule. Mean LTMs were 32.3 ± 0.28°C and 31.05 ± 0.78°C in the 8.5 and 15°C acclimation treatments, respectively. CTM and LTM metrics were lower in the 15 than in the 8.5°C acclimation treatment, but these differences were not statistically significant (p > 0.05). The predicted chronic temperature maxima were 20.6 and 20.2°C for the 8.5 and 15°C acclimation treatments, respectively. More research is needed on the effects of chronic exposures to rising stream temperatures, but our results can be used to assess the potential effects of warming water temperatures on L. tumana and other aquatic macroinvertebrates in alpine ecosystems.

Montana↗
USGS2014

Metal Mixture Modeling Evaluation project: 2. Comparison of four modeling approaches

As part of the Metal Mixture Modeling Evaluation (MMME) project, models were developed by the National Institute of Advanced Industrial Science and Technology (Japan), the U.S. Geological Survey (USA), HDR⎪HydroQual, Inc. (USA), and the Centre for Ecology and Hydrology (UK) to address the effects of metal mixtures on biological responses of aquatic organisms. A comparison of the 4 models, as they were presented at the MMME Workshop in Brussels, Belgium (May 2012), is provided herein. Overall, the models were found to be similar in structure (free ion activities computed by WHAM; specific or non-specific binding of metals/cations in or on the organism; specification of metal potency factors and/or toxicity response functions to relate metal accumulation to biological response). Major differences in modeling approaches are attributed to various modeling assumptions (e.g., single versus multiple types of binding site on the organism) and specific calibration strategies that affected the selection of model parameters. The models provided a reasonable description of additive (or nearly additive) toxicity for a number of individual toxicity test results. Less-than-additive toxicity was more difficult to describe with the available models. Because of limitations in the available datasets and the strong inter-relationships among the model parameters (log KM values, potency factors, toxicity response parameters), further evaluation of specific model assumptions and calibration strategies is needed.

Environmental Toxicology and Chemistry↗
USGS2019

Current trends and future directions in swan research: Insights from the 6th International Swan Symposium

Given their popularity with researchers and public alike, together with their welldocumented importance in aquatic and terrestrial ecosystems, fundamental and applied research on swans continues to develop in the 21st century. The 6th International Swan Symposium (6th ISS), was held at the Estonian University of Life Sciences in Tartu, Estonia, in October 2018. The symposium brought together 101 delegates from 17 countries, with presentations on a range of topics on Cygnus and Coscoroba species, including monitoring, habitat and resource use, demography, movements and migration, and threats and conservation. The proceedings of the 6th ISS in this special issue of Wildfowl include select papers on swan research presented at the 6th ISS, covering a wide range of species, systems and issues. This paper presents a synthesis of the 6th ISS and an overview of current trends and future directions in swan research. Despite progress on many topics, southern hemisphere swan species continue to receive less attention than their northern hemisphere counterparts, whilst facing many of the same pressures. It is clear that, given the challenges facing swan researchers in the twenty-first century, international cooperation will continue to be vital. Swans are highly mobile animals and many populations undertake migrations spanning thousands of kilometres, and crucially do not recognise human geographic and political borders. Such international collaborations will be particularly important in coordinating future monitoring and conservation activities. The IUCN-SSC/Wetlands International Swan Specialist Group (SSG) will continue to facilitate international collaborations and communication among the global network of swan researchers, through its activities, website and annual newsletter. Given the substantial challenges and knowledge gaps documented here, there is no doubt that swan researchers will continue to benefit from regular symposia to share information and develop collaborations towards understanding and addressing emerging conservation issues. As such, we recommend holding International Swan Symposia every 4–5 years.

Wildfowl↗
USGS2015

Predicting the resilience and recovery of aquatic systems: a framework for model evolution within environmental observatories

Maintaining the health of aquatic systems is an essential component of sustainable catchmentmanagement, however, degradation of water quality and aquatic habitat continues to challenge scientistsand policy-makers. To support management and restoration efforts aquatic system models are requiredthat are able to capture the often complex trajectories that these systems display in response to multiplestressors. This paper explores the abilities and limitations of current model approaches in meeting this chal-lenge, and outlines a strategy based on integration of flexible model libraries and data from observationnetworks, within a learning framework, as a means to improve the accuracy and scope of model predictions.The framework is comprised of a data assimilation component that utilizes diverse data streams from sensornetworks, and a second component whereby model structural evolution can occur once the model isassessed against theoretically relevant metrics of system function. Given the scale and transdisciplinarynature of the prediction challenge, network science initiatives are identified as a means to develop and inte-grate diverse model libraries and workflows, and to obtain consensus on diagnostic approaches to modelassessment that can guide model adaptation. We outline how such a framework can help us explore thetheory of how aquatic systems respond to change by bridging bottom-up and top-down lines of enquiry,and, in doing so, also advance the role of prediction in aquatic ecosystem management.

Water Resources Research↗
USGS2014

Response to L. Land comment on Bricker, Rice, Bricker (2014) From Headwaters to Coast: Influence of human activities on water quality of the Potomac River Estuary. Aquatic Geochemistry 20: 291-324

Overabundance of nutrients is considered one of the top challenges to most populated coastal water bodies, including Chesapeake Bay (Executive Order 13508). As scientists, one of our responsibilities is to contribute to the discussion and evaluation of management actions that have the potential to decrease pollution with concomitant improvement of water quality. Results of our science should inform the legislative process for public policy. Bricker et al. (2014) consider the use of shellfish (i.e., oysters) to remediate nutrient pollution in the Potomac River Estuary (PRE), a tributary to Chesapeake Bay. This concept, termed bioextraction, has generated interest around the globe and has shown promise as a nutrient-removal method in other estuaries and with other shellfish species (Lindahl et al. 2005; Ferreira et al. 2009; Shumway 2011; Silva et al. 2011; Carmichael et al. 2012; Pollack et al. 2013; Rose et al. 2014).

Aquatic Geochemistry↗
USGS2024

Flow cytometric assessments of metabolic activity in bacterial assemblages provide insight into ecosystem condition along the Buffalo National River, Arkansas

The Buffalo National River (BNR), on karst terrain in Arkansas, is considered an extraordinary water resource. Water collected in Spring 2017 along BNR was metagenomically analyzed using 16S rDNA, and for 17 months (5/2017–11/2018), bacterial responses were measured in relation to nutrients sampled along a stretch of BNR near a concentrated animal feed operation (CAFO) on Big Creek. Because cell count and esterase activity can increase proportionally with organic enrichment, they were hypothesized to be elevated near the CAFO. Counts (colony forming units; CFUs) were different among sites for 73 % of the months; Big Creek generated highest CFUs 27 % of the time, with the closest downstream site at 13.3 %. Esterase activity was different among sites 94 % of the time, with Big Creek exhibiting lowest activity 71 % of the time. Over the months, activity was similar across sites at ~70 % active, except at Big Creek (56 %). The α-diversity of BNR microbial consortia near a wastewater treatment plant (WWTP) and the CAFO was related to distance from the WWTP and CAFO. The inverse relationship between high CFUs and low esterase activity at Big Creek ( r = −0.71) actuated in vitro exposures of bacteria to organic wastewater contaminants (OWC) previously identified in the watershed. Exponential-phase Escherichia coli (stock strain), Streptococcus suis (avirulent, from swine), and S. dysgalactiae (virulent, from silver carp, Hypophthalmichthys molitrix ) were incubated with atrazine, pharmaceuticals (17 α-ethynylestradiol and trenbolone), and antimicrobials (tylosin and butylparaben). Bacteria were differentially responsive. Activity varied with exposure time and OWC type, but not concentration; atrazine decreased it most. Taken together - the metagenomic taxonomic similarities along BNR, slightly higher bacterial growth and lower bacterial esterase at the CAFO, and the lab exposures of bacterial strains showing that OWC altered metabolism - the results indicated that bioactive OWC entering the watershed can strongly influence microbial processes in the aquatic ecosystem.

Science of the Total Environment↗
USGS2024

Factors contributing to pesticide contamination in riverine systems: The role of wastewater and landscape sources

Wastewater treatment plant (WWTP) discharges can be a source of organic contaminants, including pesticides, to rivers. An integrated model was developed for the Potomac River watershed (PRW) to determine the amount of accumulated wastewater percentage of streamflow (ACCWW) and calculate predicted environmental concentrations (PECs) for 14 pesticides in non-tidal National Hydrography Dataset Plus Version 2.1 stream segments. Predicted environmental concentrations were compared to measured environmental concentrations (MECs) from 32 stream sites that represented a range of ACCWW and land use to evaluate model performance and to assess possible non-WWTP loading sources. Statistical agreement between PECs and MECs was strongest for insecticides, followed by fungicides and herbicides. Principal component analysis utilizing optical fluorescence and ancillary water quality data identified wastewater and urban runoff sources. Pesticides that indicated relatively larger sources from WWTPs included dinotefuran, fipronil, carbendazim, thiabendazole, and prometon whereas imidacloprid, azoxystrobin, propiconazole, tebuconazole, and diuron were more related to urban runoff. In addition, PECs generally comprised a low proportion of MECs, which indicates possible dominant loading sources beyond WWTP discharges. Cumulative potential toxicity was higher for sites with greater ACCWW and/or located in developed areas. Imidacloprid, fipronil, and carbendazim accounted for the largest portion of predicted potential toxicity across sites. The chronic aquatic life toxicity benchmarks for freshwater invertebrates were exceeded for 82 % of the imidacloprid detections ( n = 28) and 47 % of the fipronil detections ( n = 19). These results highlight the ecological implications of pesticide contamination from WWTP discharges and also the potential legacy effects from accumulated soil and groundwater sources. Pesticide management strategies that mitigate both current and historical impacts may improve the health of aquatic ecosystems.

Potomac River watershed↗
USGS2014

Metamorphosis alters contaminants and chemical tracers in insects: implications for food webs

Insects are integral to most freshwater and terrestrial food webs, but due to their accumulation of environmental pollutants they are also contaminant vectors that threaten reproduction, development, and survival of consumers. Metamorphosis from larvae to adult can cause large chemical changes in insects, altering contaminant concentrations and fractionation of chemical tracers used to establish contaminant biomagnification in food webs, but no framework exists for predicting and managing these effects. We analyzed data from 39 studies of 68 analytes (stable isotopes and contaminants), and found that metamorphosis effects varied greatly. δ 15 N, widely used to estimate relative trophic position in biomagnification studies, was enriched by 1‰ during metamorphosis, while δ 13 C used to estimate diet, was similar in larvae and adults. Metals and polycyclic aromatic hydrocarbons (PAHs) were predominantly lost during metamorphosis leading to 2 to 125-fold higher larval concentrations and higher exposure risks for predators of larvae compared to predators of adults. In contrast, manufactured organic contaminants (such as polychlorinated biphenyls) were retained and concentrated in adults, causing up to 3-fold higher adult concentrations and higher exposure risks to predators of adult insects. Both food web studies and contaminant management and mitigation strategies need to consider how metamorphosis affects the movement of materials between habitats and ecosystems, with special regard for aquatic-terrestrial linkages.

Environmental Science & Technology↗
USGS2008

Aquatic toxicity of airfield-pavement deicer materials and implications for airport runoff

Concentrations of airfield-pavement deicer materials (PDM) in a study of airport runoff often exceeded levels of concern regarding aquatic toxicity. Toxicity tests on Vibrio fischeri, Pimephales promelas, Ceriodaphnia dubia, and Pseudokirchneriella subcapitata (commonly known as Selenastrum capricornutum) were performed with potassium acetate (K-Ac) PDM, sodium formate (Na-For) PDM, and with freezing- point depressants (K-Ac and Na-For). Results indicate that toxicity in PDM is driven by the freezing-point depressants in all tests except the Vibrio fisheri test for Na-For PDM which is influenced by an additive. Acute toxicity end points for different organisms ranged from 298 to 6560 mg/L (as acetate) for K-Ac PDM and from 1780 to 4130 mg/L (as formate) for Na- For PDM. Chronic toxicity end points ranged from 19.9 to 336 mg/L (as acetate) for K-Ac PDM and from 584 to 1670 mg/L (as formate) for Na-For PDM. Sample results from outfalls at General Mitchell International Airport in Milwaukee, Wl (GMIA) indicated that 40% of samples had concentrations greater than the aquatic-life benchmark for K-Ac PDM. K-Ac has replaced urea during the 1990s as the most widely used PDM at GMIA and in the United States. Results of ammonia samples from airport outfalls during periods when urea-based PDM was used at GMIA indicated that41% of samples had concentrations exceeding the U.S. Environmental Protection Agency (USEPA) 1 -h water-quality criterion. The USEPA 1-h water-quality criterion for chloride was exceeded in 68% of samples collected in the receiving stream, a result of road-salt runoff from urban influence near the airport. Results demonstrate that PDM must be considered to comprehensively evaluate the impact of chemical deicers on aquatic toxicity in water containing airport runoff. ?? 2009 American Chemical Society.

Environmental Science & Technology↗
USGS2011

Effects of acid deposition on ecosystems: Advances in the state of the science

Chapter 2 focused on the environmental results of the ARP, presenting data from national monitoring networks on SO2 and NOx emissions, air quality, atmospheric deposition, surface water chemistry, and visibility. This chapter expands on this information by examining the most recent research into how ecosystems respond to acid deposition, especially the processes that control the recovery of ecosystems as acid deposition decreases. In Chapter 2, two general trends were discussed regarding the current recovery status of affected ecosystems: (1) these ecosystems are trending generally towards recovery, but improvements in ecosystem condition shown by surface water chemistry monitoring data thus far have been less than the improvements in deposition; and (2) ecosystem impacts and trends vary widely by geographic region, but the evidence of improvement is strongest and most evident in the Northeast. These trends are not uniform across the United States, however, and in some regions (e.g., central Appalachian Mountain region), trends in improved water quality are generally not evident. Despite the strong link in many areas between reduced emissions and reduced acidity of atmospheric deposition, the link is less clear between reduced acidity and recovery of the biological communities that live in aquatic and terrestrial ecosystems that have experienced deleterious effects from acid deposition. The recovery of these communities is proceeding at a slower pace than, for example, the improvements in stream and lake ANC would indicate. The goal of this chapter is to synthesize the science in a weightof-evidence manner to provide policy makers with tangible evidence and likely causative factors regarding ecosystem status and recovery patterns to date. This chapter serves as an update to the 2005 NAPAP RTC (NSTC, 2005), with an emphasis on scientific studies and monitoring since 2003, which was the last year for consideration of research results in the 2005 report. Several issues pertinent to ecosystem response to emission controls and acid deposition are receiving increasing attention in the scientific literature and will be discussed in this chapter, including the (1) observed delay in ecosystem recovery in the eastern United States, even with decreases in emissions and deposition over the past 30 years; (2) emerging ecosystem impacts of nitrogen deposition in the western United States; (3) the application of critical deposition loads as a tool for scientists to better inform air quality policies; (4) the role of changes in climate and the carbon cycle as factors that affect the response of ecosystems to acid deposition; and (5) the interaction of multiple pollutants in ecosystems. Throughout this chapter, the value of long-term environmental monitoring data in informing air quality policy will be highlighted, including the limitations of assessing the current status of some ecosystem indicators for which continuous, long-term data are lacking.

Report↗
USGS2012

A science plan for a comprehensive assessment of water supply in the region underlain by fractured rock in Maryland

The fractured rock region of Maryland, which includes land areas north and west of the Interstate 95 corridor, is the source of water supply for approximately 4.4 million Marylanders, or approximately 76 percent of the State's population. Whereas hundreds of thousands of residents rely on wells (both domestic and community), millions rely on surface-water sources. In this region, land use, geology, topography, water withdrawals, impoundments, and other factors affect water-flow characteristics. The unconfined groundwater systems are closely interconnected with rivers and streams, and are affected by seasonal and climatic variations. During droughts, groundwater levels drop, thereby decreasing well yields, and in some cases, wells have gone dry. Low ground-water levels contribute to reduced streamflows, which in turn, can lead to reduced habitat for aquatic life. Increased demand, over-allocation, population growth, and climate change can affect the future sustainability of water supplies in the region of Maryland underlain by fractured rock. In response to recommendations of the 2008 Advisory Committee on the Management and Protection of the State's Water Resources report, the Maryland Department of the Environment's Water Supply Program, the Maryland Geological Survey, the Maryland Department of Natural Resources, Monitoring and Non-Tidal Assessment (MANTA) Division, and the U.S. Geological Survey have developed a science plan for a comprehensive assessment that will provide new scientific information, new data analysis, and new tools for the State to better manage water resources in the fractured rock region of Maryland. The science plan lays out five goals for the comprehensive assessment: (1) develop tools for the improved management and investigation of groundwater and surface-water resources; (2) characterize factors affecting reliable yields of individual groundwater and surface-water supplies; (3) investigate impacts on nearby water withdrawal users caused by groundwater and surface-water withdrawals; (4) assess the role of streamflow and water withdrawals on the ecological integrity of streams; and (5) improve understanding of the distribution of water-quality conditions in fractured rock aquifers. To accomplish these goals, accurate data collection, review, and analysis are needed, including the study of "Research Watersheds" that can provide detailed information about the potential effects that climate change and water withdrawals may have on groundwater, streamflow, and aquatic life. The assessment planning started in 2009 and is being conducted with close interagency coordination. A Fractured Rock Aquifer Information System is currently (2012) undergoing initial development. Other major tasks that will be performed include the development of work plans for each science goal, the estimation of daily streamflow at ungaged streams, and the design and implementation of Research Watersheds. Finally, scenarios will be modeled to evaluate current water allocation permitting methodologies, investigate effects on nearby water withdrawal users caused by groundwater and surface-water withdrawals, and assess the potential impacts of climate change on water resources. Desktop and Web-based tools will be developed in order to meet the diverse research needs of the assessment. These tools, including the Fractured Rock Aquifer Information System will be continuously improved during the assessment to store relevant groundwater and surface-water data in spatially referenced databases, estimate streamflows, locate higher-yielding wells, estimate the impacts of withdrawals on nearby users, and assess the cumulative impacts of withdrawals on the aquatic resource. Tools will be developed to serve the needs of many audiences, including water resource managers, water suppliers, planners, policymakers, and other scientific investigators.

Maryl↗
USGS2012

Science to support the understanding of Ohio's water resources

Ohio’s water resources support a complex web of human activities and nature—clean and abundant water is needed for drinking, recreation, farming, and industry, as well as for fish and wildlife needs. The distribution of rainfall can cause floods and droughts, which affects streamflow, groundwater, water availability, water quality, recreation, and aquatic habitats. Ohio is bordered by the Ohio River and Lake Erie and has over 44,000 miles of streams and more than 60,000 lakes and ponds (State of Ohio, 1994). Nearly all the rural population obtain drinking water from groundwater sources. The U.S. Geological Survey (USGS) works in cooperation with local, State, and other Federal agencies, as well as universities, to furnish decisionmakers, policymakers, USGS scientists, and the general public with reliable scientific information and tools to assist them in management, stewardship, and use of Ohio’s natural resources. The diversity of scientific expertise among USGS personnel enables them to carry out large- and small-scale multidisciplinary studies. The USGS is unique among government organizations because it has neither regulatory nor developmental authority—its sole product is reliable, impartial, credible, relevant, and timely scientific information, equally accessible and available to everyone. The USGS Ohio Water Science Center provides reliable hydrologic and water-related ecological information to aid in the understanding of use and management of the Nation’s water resources, in general, and Ohio’s water resources, in particular. This fact sheet provides an overview of current (2012) or recently completed USGS studies and data activities pertaining to water resources in Ohio. More information regarding projects of the USGS Ohio Water Science Center is available at http://oh.water.usgs.gov/.

Ohio↗
USGS2019

Columbia Environmental Research Center

The U.S. Geological Survey Columbia Environmental Research Center performs research to solve challenging environmental problems related to contaminants and habitat alterations in aquatic and terrestrial ecosystems. The research is interdisciplinary and pursued through partnerships within the U.S. Geological Survey and with national, international, state, and local agencies; nongovernmental organizations; and universities. Research is prioritized to provide science to the U.S. Department of the Interior and other natural resource management agencies to inform rehabilitation of degraded habitats and imperiled fish and wildlife populations. The Columbia Environmental Research Center was established in 1966 in Columbia, Missouri, as the U.S. Fish and Wildlife Service’s Fish Pesticide Research Laboratory; the Columbia Environmental Research Center was incorporated into the U.S. Geological Survey in 1996. The U.S. Geological Survey’s staff of 130 includes 90 scientists of which one-half have advanced degrees in ecology, toxicology, biology, biochemistry, chemistry, hydrology, geology, and information technology.

Missouri↗
USGS2008

Removal of phosphorus from wastewater using ferroxysorb sorption media produced from amd sludge

Treatment of acid mine drainage (AMD), whether with lime, limestone, caustic or simple aeration, nearly always results in generation of a metal hydroxide sludge. Disposal of the sludge often constitutes a significant fraction of the operating cost for the AMD treatment plant. Research at the USGS - Leetown Science Center has shown that AMD sludge, with its high content of aluminum and iron oxides, has a high affinity of phosphorus (P). Anthropogenic sources of P are associated with eutrophication and degradation of aquatic environments, resulting in anoxic dead zones in certain sensitive waterways. In this paper, we describe a method of converting the AMD sludge from a liability into an asset - Ferroxysorb P removal media - which can be used to remove excess P from wastewater. Three different Ferroxysorb media samples were produced from differing AMD sources and tested for P removal. Adsorption isotherms confirmed that the media had a high sorption capacity for P, as high as 19,000 mg/kg. The technology was demonstrated at an active fish hatchery, where the media remained in service for over three months without stripping or regeneration. Over that period of time, the calculated P removal was 50%, even at a very low influent P concentration of 60 parts per billion. In summary, use of the AMD-derived Ferroxysorb sorption media will reduce AMD treatment costs while at the same time helping to resolve the pressing environmental issue of eutrophication and degradation of sensitive waterways.

Conference Paper↗
USGS2024

PCB concentrations in riparian spiders (Tetragnathidae) consistently reflect concentrations in water and aquatic macroinvertebrates, but not sediment: Analysis of a seven-year field study

Tetragnathid spiders have been used as sentinels to study the biotransport of contaminants between aquatic and terrestrial environments because a significant proportion of their diet consists of adult aquatic insects. A key knowledge gap in assessing tetragnathid spiders as sentinels is understanding the consistency of the year-to-year relationship between contaminant concentrations in spiders and sediment, water, and macroinvertebrates. We collected five years of data over a seven-year investigation at a PCB contaminated-sediment site to investigate if concentrations in spiders were consistently correlated with concentrations in sediment, water, and aquatic macroinvertebrates. Despite significant year-to-year variability in spider PCB concentrations, they were not correlated with sediment concentrations ( p = 0.186). However, spider PCB concentrations were significantly, positively correlated with PCB concentrations in water ( p < 0.0001, annual r 2 = 0.35–0.84) and macroinvertebrates (p < 0.0001; annual r 2 = 0.59–0.71). Analysis of covariance (ANCOVA) showed that spider PCB concentrations varied consistently with water (β = 0.63) and macroinvertebrate PCB concentrations (β = 1.023) among years. Overall, this study filled a critical knowledge gap in the utilization of tetragnathid spiders as sentinels of aquatic pollution by showing that despite year-to-year changes in PCB concentrations across environmental compartments, consistent relationships existed between spiders and water and aquatic macroinvertebrates.

Science of the Total Environment↗
USGS2012

Absence of fractionation of mercury isotopes during trophic transfer of methylmercury to freshwater fish in captivity

We performed two controlled experiments to determine the amount of mass-dependent and mass-independent fractionation (MDF and MIF) of methylmercury (MeHg) during trophic transfer into fish. In experiment 1, juvenile yellow perch ( Perca flavescens ) were raised in captivity on commercial food pellets and then their diet was either maintained on unamended food pellets (0.1 μg/g MeHg) or was switched to food pellets with 1.0 μg/g or 4.0 μg/g of added MeHg, for a period of 2 months. The difference in δ 202 Hg (MDF) and Δ 199 Hg (MIF) between fish tissues and food pellets with added MeHg was within the analytical uncertainty (δ 202 Hg, 0.07 ‰; Δ 199 Hg, 0.06 ‰), indicating no isotope fractionation. In experiment 2, lake trout ( Salvelinus namaycush ) were raised in captivity on food pellets and then shifted to a diet of bloater ( Coregonus hoyi ) for 6 months. The δ 202 Hg and Δ 199 Hg of the lake trout equaled the isotopic composition of the bloater after 6 months, reflecting reequilibration of the Hg isotopic composition of the fish to new food sources and a lack of isotope fractionation during trophic transfer. We suggest that the stable Hg isotope ratios in fish can be used to trace environmental sources of Hg in aquatic ecosystems.

Environmental Science & Technology↗