SEARCH · Geology Reports

Results for “Environmental Modeling & Assessment”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources

USGS2021

Seasonally dynamic nutrient modeling quantifies storage lags and time-varying reactivity across large river basins

Nutrients that have gradually accumulated in soils, groundwaters, and river sediments in the United States over the past century can remobilize and increase current downstream loading, obscuring effects of conservation practices aimed at protecting water resources. Drivers of storage accumulation and release of nutrients are poorly understood at the spatial scale of basins to watersheds. Predicting water quality outcomes in large river basins demands modeling storage lags and time varying reactivity that models of mean conditions typically cannot elucidate. We developed a seasonally dynamic approach to large-scale nutrient modeling based on a multiscale framework and nutrient storage lags were quantified for the nearly 190 000 small catchments that feed the rivers across the northeastern United States where catchment mean transit times were found to be around 4.7 (2–10) years for nitrogen and 1.3 (0.7–2) years for phosphorus. Nutrient loads carried in river flow in the current season contained a significant—and sometimes dominant—portion of mass lagged in its release from catchment storage repositories. Our approach of integrating storage releases with seasonally dynamic hydroclimatic drivers sets the stage to assess the accumulated effects of nutrient storage and lagged releases to the river interacting with seasonally varying nutrient reactivity and societal management actions throughout large river basins.

Environmental Research Letters↗

USGS2006

Spatial variations in fish-tissue mercury concentrations in the St. Croix River basin, Minnesota and Wisconsin, 2004

Parts of the St. Croix River in Minnesota and Wisconsin are under fish-consumption advisories because of elevated mercury concentrations that have been measured in fish from this river. The U.S. Geological Survey, National Park Service, and the University of Wisconsin, LaCrosse, cooperated in a study to determine the spatial variation of mercury in fish in the St. Croix River and selected tributaries. Game and nongame fish were collected at 14 sites during summer 2004 and identified to species. One hundred ninety-three (193) composite tissue samples were analyzed for total mercury as whole fish, skin-on fillet, or skin-off fillet. A model of mercury in fish was used to standardize fish-tissue mercury concentrations to a common species, tissues sampled, and length of fish allowing for more consistent comparisons among sites. Rush Creek near Rush City, Minnesota, was identified as having high median standardized fish-tissue mercury concentrations compared to other tributaries sampled. Previous studies identified Rush Creek as having high concentrations of methylmercury in water and high concentrations of total mercury in sediment when compared to other sites in the St. Croix River Basin. Sites in the St. Croix River Basin that drained forest/wetland watersheds had significantly higher median fish-tissue mercury concentrations than sites draining agricultural/forested watersheds (p=0.0003). There also was a significant relation between fish-tissue mercury concentration and methylmercury concentration in water (rho=0.580, p=0.02) and between fish-tissue mercury and total mercury in sediment (rho=0.569, p=0.03). Observed fish-tissue mercury concentrations exceeding the U.S. Environmental Protection Agency’s (USEPA) human-health criterion of 300 micrograms per kilogram occurred at 7 of the 14 sampling sites. The model predicted concentrations exceeding USEPA’s criterion at all of the seven sites where exceedances were observed and four of the seven sites where exceedances were not observed. The implication is that fish-consumption advisories that are based on observed concentrations (of a subset of the species that occur at the site or smaller fish) could underestimate the threat to human health. Using the model to predict fish-tissue mercury concentrations allows site-specific fish-consumption advisories to be developed for multiple species and different lengths of fish. Potential mercury exposure to fish consumers may be reduced because an individual can choose to consume sizes and species of fish that are expected to have lower fish-tissue mercury concentrations. The National Park Service can use these results to more reliably monitor fish-tissue mercury concentrations in the St. Croix River Basin and better assess potential health effects of fish consumption to humans and wildlife.

Minnesota, Wisconsin↗

USGS2015

Monitoring and modeling wetland chloride concentrations in relationship to oil and gas development

Extraction of oil and gas via unconventional methods is becoming an important aspect of energy production worldwide. Studying the effects of this development in countries where these technologies are being widely used may provide other countries, where development may be proposed, with some insight in terms of concerns associated with development. A fairly recent expansion of unconventional oil and gas development in North America provides such an opportunity. Rapid increases in energy development in North America have caught the attention of managers and scientists as a potential stressor for wildlife and their habitats. Of particular concern in the Northern Great Plains of the U.S. is the potential for chloride-rich produced water associated with unconventional oil and gas development to alter the water chemistry of wetlands. We describe a landscape scale modeling approach designed to examine the relationship between potential chloride contamination in wetlands and patterns of oil and gas development. We used a spatial Bayesian hierarchical modeling approach to assess multiple models explaining chloride concentrations in wetlands. These models included effects related to oil and gas wells (e.g. age of wells, number of wells) and surficial geology (e.g. glacial till, outwash). We found that the model containing the number of wells and the surficial geology surrounding a wetland best explained variation in chloride concentrations. Our spatial predictions showed regions of localized high chloride concentrations. Given the spatiotemporal variability of regional wetland water chemistry, we do not regard our results as predictions of contamination, but rather as a way to identify locations that may require more intensive sampling or further investigation. We suggest that an approach like the one outlined here could easily be extended to more of an adaptive monitoring approach to answer questions about chloride contamination risk that are of interest to managers.

Montana, North Dakota↗

USGS2011

Are two systemic fish assemblage sampling programmes on the upper Mississippi River telling us the same thing?

We applied an Index of Biotic Integrity (IBI) used on Wisconsin/Minnesota waters of the upper Mississippi River (UMR) to compare data from two systemic sampling programmes. Ability to use data from multiple sampling programmes could extend spatial and temporal coverage of river assessment and monitoring efforts. We normalized for effort and tested fish community data collected by the Environmental Monitoring and Assessment Program-Great Rivers Ecosystems (EMAP-GRE) 2004–2006 and the Long Term Resource Monitoring Program (LTRMP) 1993–2006. Each programme used daytime electrofishing along main channel borders but with some methodological and design differences. EMAP-GRE, designed for baseline and, eventually, compliance monitoring, used a probabilistic, continuous design. LTRMP, designed primarily for baseline and trend monitoring, used a stratified random design in five discrete study reaches. Analysis of similarity indicated no significant difference between EMAP-GRE and LTRMP IBI scores ( n =238; Global R = 0.052; significance level=0.972). Both datasets distinguished clear differences only between 'Fair' and 'Poor' condition categories, potentially supporting a 'pass–fail' assessment strategy. Thirteen years of LTRMP data demonstrated stable IBI scores through time in four of five reaches sampled. LTRMP and EMAPGRE IBI scores correlated along the UMR's upstream to downstream gradient (df [3, 25]; F =1.61; p =0.22). A decline in IBI scores from upstream to downstream was consistent with UMR fish community studies and a previous, empirically modelled human disturbance gradient. Comparability between EMAP-GRE (best upstream to downstream coverage) and LTRMP data (best coverage over time and across the floodplain) supports a next step of developing and testing a systemic, multi-metric fish index on the UMR that both approaches could inform.

Illinois;Iowa;Minnesota;Missouri;Wisconsin↗

USGS2024

Immunomodulation in adult largemouth bass (Micropterus salmoides) exposed to a model estrogen or mixture of endocrine disrupting contaminants during early gonadal recrudescence

Disease outbreaks, skin lesions, fish kill events, and reproductive abnormalities have been observed in wild populations of Centrarchids in watersheds throughout the United States. Occurrence of synthetic and natural hormones from wastewater treatment plants and livestock operations, pesticides from agricultural land use, and phytoestrogens have been implicated as potential causes of these adverse effects. Our objective was to investigate possible immunomodulation in adult largemouth bass ( Micropterus salmoides ) in response to a seasonal exposure to environmentally relevant contaminants in outdoor experimental ponds. Exposures included 17α-ethinylestradiol (EE2; 3.6 ng/L) or a binary mixture of endocrine-active substances commonly detected in surface waters, estrone (E1; 85.6 ng/L) and atrazine (ATR; 5.4 µg/L). The 4-month exposure was conducted from July to November. Functional immune responses of anterior kidney-derived leukocytes were evaluated in December in the week following the end of the dosing period, and in the following April, four months after dosing ended and just prior to spawning. Concentrations of EE2 and E1 in the ponds fell below detectable levels in December, but detectable concentrations of ATR (2.9 µg/L) persisted at least through May. For each sampling time, anterior kidney leukocytes were isolated and grown in primary culture for the assessment of zymosan-stimulated respiratory burst and lectin-stimulated mitogenic responses. We observed seasonal differences in respiratory burst stimulation over time and treatment with a significantly greater response in April relative to December. Respiratory burst activity was also significantly greater in April for fish exposed to the E1+ATR relative to control. In April, prior to spawning, we observed a significantly dampened mitogenic response to PHAP (a T cell mitogen) and LPS (a B cell mitogen) in the EE2 treatment relative to control fish. There were no significant differences in mitogenic responses or respiratory burst between sexes. However, there was significantly higher alternative complement pathway hemolytic activity in males compared to females in both the control and E1+ATR treatment groups. Our results demonstrate that environmentally relevant concentrations of contaminants can alter immune function in a socioeconomically important fish species.

Comparative Immunology Reports↗

USGS2025

Examining the compositional selectivity of hydrocarbon oxidation products using liquid–liquid extraction and solid-phase extraction techniques

The effect of extraction methods on detecting hydrocarbon oxidation products (HOPs) in groundwater remains unclear. HOPs are polar, water-soluble byproducts of petroleum biodegradation. Our previous work showed that liquid–liquid extraction (LLE), a method commonly used in regulatory monitoring, has a significantly lower extraction efficiency for HOPs compared to solid-phase extraction (SPE). In this study, we evaluate the analytical limitations and compositional selectivity of LLE and SPE using groundwater samples from the Bemidji, MN, crude oil spill site. Optical properties were characterized using excitation–emission matrix spectroscopy (EEMs), and a three-component PARAFAC model was validated, showing consistent trends across both extracts and whole water samples. Ultrahigh-resolution mass spectrometry (UHR-MS) revealed that LLE selectively recovered aliphatic-like compounds but underrepresented more polar oxygenated HOPs. In contrast, SPE methods were more effective at isolating highly oxidized compound classes. These differences were consistent across a gradient of contamination. Overall, the LLE was less precise and less representative of polar HOPs, introducing bias in the characterization of HOPs. This study is the first to quantitatively demonstrate the compositional selectivity and analytical bias of LLE versus SPE for HOPs using combined EEM-PARAFAC and UHR-MS techniques, with implications for long-term monitoring and site assessment protocols.

Environmental Science and Technology↗

USGS2018

Quantifying uncertainty and tradeoffs in resilience assessments

Several frameworks have been developed to assess the resilience of social-ecological systems, but most require substantial data inputs, time, and technical expertise. Stakeholders and practitioners often lack the resources for such intensive efforts. Furthermore, most end with problem framing and fail to explicitly address trade-offs and uncertainty. To remedy this gap, we developed a rapid survey assessment that compares the relative resilience of social-ecological systems with respect to a number of resilience properties. This approach generates large amounts of information relative to stakeholder inputs. We targeted four stakeholder categories: government (policy, regulation, management), end users (farmers, ranchers, landowners, industry), agency/public science (research, university, extension), and NGOs (environmental, citizen, social justice) in four North American watersheds, to assess social-ecological resilience through surveys. Conceptually, social-ecological systems are comprised of components ranging from strictly human to strictly ecological, but that relate directly or indirectly to one another. They have soft boundaries and several important dimensions or axes that together describe the nature of social-ecological interactions, e.g., variability, diversity, modularity, slow variables, feedbacks, capital, innovation, redundancy, and ecosystem services. There is no absolute measure of resilience, so our design takes advantage of cross-watershed comparisons and therefore focuses on relative resilience. Our approach quantifies and compares the relative resilience across watershed systems and potential trade-offs among different aspects of the social-ecological system, e.g., between social, economic, and ecological contributions. This approach permits explicit assessment of several types of uncertainty (e.g., self-assigned uncertainty for stakeholders; uncertainty across respondents, watersheds, and subsystems), and subjectivity in perceptions of resilience among key actors and decision makers and provides an efficient way to develop the mental models that inform our stakeholders and stakeholder categories.

Ecology and Society↗

USGS2017

Five-year external reviews of the eight Department of Interior Climate Science Centers: Southeast Climate Science Center

In 2008, the U.S. Congress authorized the establishment of the National Climate Change and Wildlife Science Center (NCCWSC) within the U.S. Department of Interior (DOI). Housed administratively within the U.S. Geological Survey (USGS), NCCWSC is part of the DOI’s ongoing mission to meet the challenges of climate change and its effects on wildlife and aquatic resources. From 2010 through 2012, NCCWSC established eight regional DOI Climate Science Centers (CSCs). Each of these regional CSCs operated with the mission to “synthesize and integrate climate change impact data and develop tools that the Department’s managers and partners can use when managing the Department’s land, water, fish and wildlife, and cultural heritage resources” (Salazar 2009). The model developed by NCCWSC for the regional CSCs employed a dual approach of a federal USGS-staffed component and a parallel host-university component established competitively through a 5-year cooperative agreement with NCCWSC. At the conclusion of this 5-year agreement, a review of each CSC was undertaken, with the Southeast Climate Science Center (SE CSC) review in February 2016. The SE CSC is hosted by North Carolina State University (NCSU) in Raleigh, North Carolina, and is physically housed within the NCSU Department of Applied Ecology along with the Center for Applied Aquatic Ecology, the North Carolina Cooperative Fish and Wildlife Research Unit (CFWRU), and the North Carolina Agromedicine Institute. The U.S. Department of Agriculture Southeast Regional Climate Hub is based at NCSU as is the National Oceanic and Atmospheric Administration (NOAA) Southeast Regional Climate Center, the North Carolina Institute for Climate Studies, the North Carolina Wildlife Resources Commission, the NOAA National Weather Service, the State Climate Office of North Carolina, and the U.S. Forest Service Eastern Forest Environmental Threat Assessment Center. This creates a strong core of organizations operating in close proximity focused on climate issues. The geographic area covered by the SE CSC represents all or part of 16 states and the Caribbean Islands and has overlapping boundaries with seven Landscape Conservation Cooperatives (LCCs): Appalachian LCC, Eastern Tallgrass Prairie and Big Rivers LCC, Gulf Coast Prairie LCC, Gulf Coastal Plains and Ozarks LCC, Peninsular Florida LCC, South Atlantic LCC, and Caribbean LCC. The SE CSC region also encompasses 134 U.S. Fish and Wildlife Service refuges and 89 National Park Service (NPS) units and is home to 11 federally recognized and 54 state recognized tribes.

Report↗

USGS2023

Interactions among rainfall, fire, forbs and non-native grasses predict occupancy dynamics for the endangered Pacific pocket mouse (Perognathus longimembris pacificus) in a Mediterranean-type ecosystem

It is important to understand species-habitat relationships to implement effective adaptive management for rare species. However, it can be challenging to assess habitat associations and their relationships to abiotic stressors in dynamic habitats without the insights that can be gained from long-term monitoring. We report results from the first six years of extensive track tube monitoring of the largest two of three remaining extant populations of federally endangered Pacific pocket mouse ( Perognathus longimembris pacificus ) in a coastal Mediterranean-type ecosystem on Marine Corps Base, Camp Pendleton in southern California, USA. We used dynamic occupancy and structural equation modeling to assess potential drivers of population trends that included habitat, fire history, rainfall, disturbance, and the presence of other small mammals. We found that the variables that best predicted mouse occupancy were moderate to high forb and perennial herb cover (40–80%), and moderate to high open ground (20–70%) and low non-native grass cover (<20%), Non-native grass cover (>20%) was also a strong predictor of lower PPM colonization and increased extinction probabilities, with the extent of non-native grass cover being strongly influenced by annual rainfall and recency of fire. Our study adds to the growing literature on effects of invasive annual grasses on native species in Mediterranean-type ecosystems. We suggest that habitat management could be based upon promotion of open forb and perennial herb dominated habitats with reduction of non-native grasses by prescribed fire and other methods. These types of spatial and temporal monitoring programs can support land managers by creating a monitoring and management feedback loop. They can reveal landscape and environmental variables associated with species persistence, inform habitat management goals, and help managers to assess the success of management actions on populations of conservation concern.

California↗

USGS2014

Spatial structuring within a reservoir fish population: implications for management

Spatial structuring in reservoir fish populations can exist because of environmental gradients, species-specific behaviour, or even localised fishing effort. The present study investigated whether white crappie exhibited evidence of improved population structure where the northern more productive half of a lake is closed to fishing to provide waterfowl hunting opportunities. Population response to angling was modelled for each substock of white crappie (north (protected) and south (unprotected) areas), the entire lake (single-stock model) and by combining simulations of the two independent substock models (additive model). White crappie in the protected area were more abundant, consisting of larger, older individuals, and exhibited a lower total annual mortality rate than in the unprotected area. Population modelling found that fishing mortality rates between 0.1 and 0.3 resulted in sustainable populations (spawning potential ratios (SPR) >0.30). The population in the unprotected area appeared to be more resilient (SPR > 0.30) at the higher fishing intensities (0.35–0.55). Considered additively, the whole-lake fishery appeared more resilient than when modelled as a single-panmictic stock. These results provided evidence of spatial structuring in reservoir fish populations, and we recommend model assessments used to guide management decisions should consider those spatial differences in other populations where they exist.

Marine and Freshwater Research↗

USGS2020

Influenza A viruses remain infectious for more than seven months in northern wetlands of North America

In this investigation, we used a combination of field- and laboratory-based approaches to assess if influenza A viruses (IAVs) shed by ducks could remain viable for extended periods in surface water within three wetland complexes of North America. In a field experiment, replicate filtered surface water samples inoculated with duck swabs were tested for IAVs upon collection and again after an overwintering period of approximately 6–7 months. Numerous IAVs were molecularly detected and isolated from these samples, including replicates maintained at wetland field sites in Alaska and Minnesota for 181–229 days. In a parallel laboratory experiment, we attempted to culture IAVs from filtered surface water samples inoculated with duck swabs from Minnesota each month during September 2018–April 2019 and found monthly declines in viral viability. In an experimental challenge study, we found that IAVs maintained in filtered surface water within wetlands of Alaska and Minnesota for 214 and 226 days, respectively, were infectious in a mallard model. Collectively, our results support surface waters of northern wetlands as a biologically important medium in which IAVs may be both transmitted and maintained, potentially serving as an environmental reservoir for infectious IAVs during the overwintering period of migratory birds.

Proceedings of the Royal Society B: Biological Sci↗

USGS2019

Perfluoroalkyl contaminant exposure in tree swallows nesting at Clarks Marsh, Oscoda, Michigan, USA

A site in north eastern Michigan, Oscoda Township, has some of the highest recorded exposure in birds to perfluorinated substances (PFASs) in the U.S. Some egg and plasma concentrations at that location exceeded the lowest reproductive effect threshold established for two avian laboratory species. The objectives of this study were to determine whether there were reproductive effects or physiological responses in a model bird species, the tree swallow (Tachycineta bicolor), associated with this extremely high exposure to PFASs. The lack of exposure above background to other contaminants at this site allowed for an assessment of PFAS effects without the complication that responses may be caused by other contaminants. A secondary objective was to determine the distribution of PFASs in multiple tissue types to better understand and interpret residues in different tissues. This can best be done at highly exposed locations where tissue concentrations would be expected to be above detectable levels if they are present in that tissue. There were no demonstrable effects of PFAS exposure on reproduction nor on most physiological responses.

Michigan↗

USGS2010

The areal extent of brown shrimp habitat suitability in Mobile Bay, Alabama, USA: Targeting vegetated habitat restoration

The availability of wetlands and shallow water habitats significantly influences Gulf of Mexico (GOM) penaeid shrimp fishery productivity. However, the GOM region has the highest rate of wetland loss in the USA. Protection and management of these vital GOM habitats are critical to sustainable shrimp fisheries. Brown shrimp (Farfantepenaeus aztecus) are a major component of GOM fisheries. We present an approach for estimating the areal extent of suitable habitat for post-larval and juvenile brown shrimp in Mobile Bay, Alabama, using an existing habitat suitability index model for the northern GOM calculated from probabilistic survey of water quality and sediment data, land cover data, and submerged aquatic vegetation coverages. This estuarine scale approach is intended to support targeted protection and restoration of these habitats. These analyses indicate that approximately 60% of the area of Mobile Bay is categorized as suitable to near optimal for post-larval and juvenile shrimp and 38% of the area is marginally to minimally suitable. We identify potential units within Mobile Bay for targeted restoration to improve habitat suitability. ?? 2010 Springer Science+Business Media B.V.

Environmental Monitoring and Assessment↗

USGS1995

Geohydrology and water quality of stratified-drift aquifers in the middle Merrimack River basin, south-central New Hampshire

The U.S. Geological Survey, in cooperation with the State of New Hampshire, Department of Environmental Services, Water Resources Division has assessed the geohydrology and water quality of stratified-drift aquifers in the middle Merrimack River basin in south-central New Hampshire. The middle Merrimack River basin drains 469 square miles; 98 square miles is underlain by stratified-drift aquifers. Saturated thickness of stratified drift within the study area is generally less than 40 feet but locally greater than 100 feet. Transmissivity of stratified-drift aquifers is generally less than 2,000 feet squared per day but locally exceeds 6, 000 feet squared per day. At present (1990), ground-water withdrawals from stratified drift for public supply are about 0.4 million gallons per day within the basin. Many of the stratified-drift aquifers within the study area are not developed to their fullest potential. The geohydrology of stratified-drift aquifers was investigated by focusing on basic aquifer properties, including aquifer boundaries; recharge, discharge, and direction of ground-water flow; saturated thickness and storage; and transmissivity. Surficial geologic mapping assisted in the determination of aquifer boundaries. Data from 757 wells and test borings were used to produce maps of water-table altitude, saturated thickness, and transmissivity of stratified drift. More than 10 miles of seismic-refraction profiling and 14 miles of seismic-reflection profiling were also used to construct the water table and saturated-thickness maps. Stratified-drift aquifers in the southern, western, and central parts of the study area are typically small and discontinuous, whereas aquifers in the eastern part along the Merrimack River valley are continuous. The Merrimack River valley aquifers formed in glacial Lakes Merrimack and Hooksett. Many other smaller discontinuous aquifers formed in small temporary ponds during deglaciation. A stratified-drift aquifer in Goffstown was analyzed for aquifer yield by use of a two-dimensional, finite-difference ground-water-flow model. Yield of the Goffstown aquifer was estimated to be 2.5 million gallons per day. Sensitivity analysis showed that the estimate of aquifer yield was most sensitive to changes in hydraulic conductivity. The amount of water induced into the aquifer from the Piscataquog River was most affected by changes in estimates of streambed conductance. Results of analysis of water samples from 10 test wells indicate that, with some exceptions, water in the stratified-drift aquifers generally meets U.S. Environmental Protection Agency primary and secondary drinking-water regulations. Water from two wells had elevated sodium concentrations, waterfront two wells had elevated concentrations of dissolved iron, and waterfront seven wells had elevated concentrations of manganese. Known areas of contamination were avoided during water-quality sampling.

New Hampshire↗

USGS2021

Annual winter water-level drawdowns influence physical habitat structure and macrophytes in Massachusetts, USA, lakes

Annual wintertime water-level drawdowns are a common management strategy in recreational lakes; however, few studies have estimated their relative impact on lake littoral habitat among a set of typically co-occurring anthropogenic stressors including lakeshore development and herbicide application. Within 21 Massachusetts, USA lakes that represented a drawdown magnitude gradient (0.07–2.26 m), we assessed depth-specific littoral habitat (coarse wood, sediment, macrophytes) at two sites adjacent to forested or developed shorelines. Using generalized linear mixed models, we found coarse wood abundance and branching complexity was not correlated with drawdown magnitude but was primarily explained by the presence of lakeshore development. Drawdown magnitude was negatively correlated with silt cover and positively correlated with coarse substrate cover, with effects further varying by depth (0.5 m vs. 1 m). Macrophyte biomass and biovolume were negatively correlated with drawdown magnitude with effects also varying by depth for biomass. Macrophyte taxa with annual longevity strategies (e.g., Najas flexilis ) and amphibious growth forms increased in biomass proportions with drawdown magnitude. Distance-based redundancy analyses suggested macrophyte taxa composition was driven by drawdown magnitude, coarse substrate, alkalinity, water transparency, and herbicide use. These results suggest the importance of water quality and depth on macrophyte assemblage responses to winter drawdowns and the potential to develop drawdown-tolerant macrophyte assemblages. Altogether, understanding the unique impacts of anthropogenic stressors on littoral zone habitat across heterogeneous environmental lake conditions can help minimize impacts to lake ecological integrity while maintaining recreational value.

Massachusetts↗

USGS2005

Baseline models of trace elements in major aquifers of the United States

Trace-element concentrations in baseline samples from a survey of aquifers used as potable-water supplies in the United States are summarized using methods appropriate for data with multiple detection limits. The resulting statistical distribution models are used to develop summary statistics and estimate probabilities of exceeding water-quality standards. The models are based on data from the major aquifer studies of the USGS National Water Quality Assessment (NAWQA) Program. These data were produced with a nationally-consistent sampling and analytical framework specifically designed to determine the quality of the most important potable groundwater resources during the years 1991-2001. The analytical data for all elements surveyed contain values that were below several detection limits. Such datasets are referred to as multiply-censored data. To address this issue, a robust semi-parametric statistical method called regression on order statistics (ROS) is employed. Utilizing the 90th-95th percentile as an arbitrary range for the upper limits of expected baseline concentrations, the models show that baseline concentrations of dissolved Ba and Zn are below 500 ??g/L. For the same percentile range, dissolved As, Cu and Mo concentrations are below 10 ??g/L, and dissolved Ag, Be, Cd, Co, Cr, Ni, Pb, Sb and Se are below 1-5 ??g/L. These models are also used to determine the probabilities that potable ground waters exceed drinking water standards. For dissolved Ba, Cr, Cu, Pb, Ni, Mo and Se, the likelihood of exceeding the US Environmental Protection Agency standards at the well-head is less than 1-1.5%. A notable exception is As, which has approximately a 7% chance of exceeding the maximum contaminant level (10 ??g/L) at the well head.

Applied Geochemistry↗

USGS2019

Functional and geographic components of risk for climate sensitive vertebrates in the Pacific Northwest, USA

Rarity and life history traits inform multiple dimensions of intrinsic risk to climate and environmental change and can help systematically identify at-risk species. We quantified relative geographic rarity (area of occupancy), climate niche breadth, and life history traits for 114 freshwater fishes, amphibians, and reptiles in the U.S. Pacific Northwest. Our approach leveraged presence-only, publicly available data and traits-based inference to evaluate area of occupancy, climate sensitivity (i.e., climate niche breadth), and a Rarity and Climate Sensitivity (RCS) index of all species across multiple geographic extents, grain sizes, and data types. The RCS index was relatively stable across extents, grains, and data types, with climate sensitivity differentiating species with otherwise similar areas of occupancy. We also found that species with sensitivity-associated traits (e.g., long generation time, low fecundity) were not necessarily the same species identified as at-risk with geographical approaches (small range size, small climate niche breadth). Many multispecies assessments using coarse-scale data (e.g., entire range maps or convex-hull approaches) often focus on a single dimension of intrinsic risk; others rely on data-intensive models only applicable to a few well-studied species. What remains is a need for an approach that enables multispecies, multidimensional assessment efforts. This is particularly true at regional scales, where management needs require assessments that are intermediate to coarse- and fine-scale approaches. We demonstrate that by considering multiple dimensions of intrinsic risk to climate change (range size, climate sensitivity, and traits), site-specific locality data may offer a pathway for ensuring vulnerable, understudied species do not go overlooked in conservation.

Pacific Northwest↗

USGS2016

Integrating seasonal information on nutrients and benthic algal biomass into stream water quality monitoring

Benthic chlorophyll a (BChl a ) and environmental factors that influence algal biomass were measured monthly from February through October in 22 streams from three agricultural regions of the United States. At-site maximum BChl a ranged from 14 to 406 mg/m 2 and generally varied with dissolved inorganic nitrogen (DIN): 8 out of 9 sites with at-site median DIN >0.5 mg/L had maximum BChl a >100 mg/m 2 . BChl a accrued and persisted at levels within 50% of at-site maximum for only one to three months. No dominant seasonal pattern for algal biomass accrual was observed in any region. A linear model with DIN, water surface gradient, and velocity accounted for most of the cross-site variation in maximum chlorophyll a (adjusted R 2 = 0.7), but was no better than a single value of DIN = 0.5 mg/L for distinguishing between low and high-biomass sites. Studies of nutrient enrichment require multiple samples to estimate algal biomass with sufficient precision given the magnitude of temporal variability of algal biomass. An effective strategy for regional stream assessment of nutrient enrichment could be based on a relation between maximum BChl a and DIN based on repeat sampling at sites selected to represent a gradient in nutrients and application of the relation to a larger number of sites with synoptic nutrient information.

Journal of the American Water Resources Associatio↗