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At least 1,081 records · Page 60Linked to original sources
USGS2020

Fluoride occurrence in United States groundwater

Data from 38,105 wells were used to characterize fluoride (F) occurrence in untreated United States (U.S.) groundwater. For domestic wells (n = 11,032), water from which is generally not purposely fluoridated or monitored for quality, 10.9% of the samples have F concentrations >0.7 mg/L (U.S. Public Health Service recommended optimal F concentration in drinking water for preventing tooth decay) (87% are <0.7 mg/L); 2.6% have F > 2 mg/L (EPA Secondary Maximum Contaminant Level, SMCL); and 0.6% have F > 4 mg/L (EPA MCL). The data indicate the biggest concern with F in domestic wells at the national scale could be one of under consumption of F with respect to the oral-health benchmark (0.7 mg/L). Elevated F concentrations relative to the SMCL and MCL are regionally important, particularly in the western U.S. Statistical comparisons of potentially important controlling factors in four F-concentration categories (<0.1–0.7 mg/L; >0.7–2 mg/L; >2–4 mg/L; >4 mg/L) at the national scale indicate the highest F-concentration category is associated with groundwater that has significantly greater pH values, TDS and alkalinity concentrations, and well depths, and lower Ca/Na ratios and mean annual precipitation, than the lowest F-concentration category. The relative importance of the controlling factors appears to be regionally variable. Three case studies illustrate the spatial variability in controlling factors using groundwater-age (groundwater residence time), water-isotope (evaporative concentration), and water-temperature (geothermal processes) data. Populations potentially served by domestic wells with F concentrations <0.7, >0.7, >2, and >4 mg/L are estimated to be ~28,200,000, ~3,110,000; ~522,000; and ~172,000 people, respectively, in 40 principal aquifers with at least 25 F analyses per aquifer.

Science of the Total Environment↗
USGS2026

Escherichia coli monitoring and assessment in 2022 and 2023 after beach restoration at Lake St. Clair Metropark Beach, Macomb County, Michigan

Lake St. Clair Metropark Beach in Michigan has a history of closures because of elevated Escherichia coli ( E. coli ) concentrations in its recreational waters. To reduce closures, restoration projects were implemented in 2021 to deter waterfowl from congregating on the beach. In this study, the U.S. Geological Survey, in cooperation with the Michigan Department of the Environment, Great Lakes, and Energy and in collaboration with Huron-Clinton Metroparks and the Macomb County Health Department, monitored E. coli from 2022–23 in surface water, shallow groundwater, and sediment at Lake St. Clair Metropark Beach. Results were compared to data from a prerestoration (2018–19) study. A significant decrease in daily geometric mean E. coli concentrations in surface water was observed postrestoration, but the number of high concentration events increased. This resulted in more frequent beach closures postrestoration. Surface-sediment E. coli concentrations significantly decreased after restoration, and waterfowl populations generally decreased from 2021 to 2023, suggesting that the deterrence measures could be influencing E. coli concentrations in surface sediments and surface water. Groundwater E. coli concentrations were orders of magnitude higher than those in surface water and revealed no change correlated with restoration. Seepage measurements indicated that groundwater occasionally discharges into surface water, potentially providing a transport mechanism for E. coli to reach the lake. Continued monitoring and consideration of environmental factors could help to better understand the beach system.

Michigan↗
USGS2002

Occurrence and distribution of microbiological contamination and enteric viruses in shallow ground water in Baltimore and Harford counties, Maryland

The U.S. Geological Survey, in cooperation with the Maryland Department of the Environment and the Wisconsin State Laboratory of Hygiene, conducted a study to characterize the occurrence and distribution of viral contamination in small (withdrawing less than 10,000 gallons per day) public water-supply wells screened in the shallow aquifer in the Piedmont Physiographic Province in Baltimore and Harford Counties, Maryland. Two hundred sixty-three small public water-supply wells were in operation in these counties during the spring of 2000. Ninety-one of these sites were selected for sampling using a methodology that distributed the samples evenly over the population and the spatial extent of the study area. Each site, and its potential susceptibility to microbiological contamination, was evaluated with regard to hole depth, casing interval, and open interval. Each site was evaluated using characteristics such as on-site geology and on-site land use.Samples were collected by pumping between 200 and 400 gallons of untreated well water through an electropositive cartridge filter. Water concentrates were subjected to cell-culture assay for the detection of culturable viruses and reverse-transcription polymerase chain reaction/gene probe assays to detect viral ribonucleic acid; grab samples were analyzed for somatic and male-specific coliphages, Bacteroides fragilis, Clostridium perfringens, enterococci, Escherichia coli, total coliforms, total oxidized nitrogen, nitrite, organic nitrogen, total phosphate, ortho-phosphate, calcium, magnesium, sodium, potas-sium, chloride, sulfate, iron, acid-neutralizing capacity, pH, specific conductance, temperature, and dissolved oxygen.One sample tested positive for the presence of the ribonucleic acid of rotavirus through poly-merase chain-reaction analysis. Twenty-nine per-cent of the samples (26 of 90) had bacterial con-tamination. About 7 percent of the samples (6 of 90) were contaminated with either male-specific coliphage, somatic coliphage, or bacteriophages of Bacteroides fragilis. About 3 percent of the sam-ples (3 of 87) had oxidized nitrogen concentra-tions that exceeded the U.S. Environmental Protection Agency?s Maximum Contaminant Level of 10.0 milligrams per liter. A statistical analysis showed that no significant relation exists between the presence of bacteria or coliphage and all variables, except the mean temperature of the water sample as measured in the field. Additionally, the concentration of total coliform bacteria had a statistically significant, moderately strong cor-relation with the concentration of sulfate and sample pH as measured at the U.S. Geological Survey National Water-Quality Laboratory in Denver, Colorado.

Water-Resources Investigations Report↗
USGS2002

Ground-water quality and discharge to Chincoteague and Sinepuxent Bays adjacent to Assateague Island National Seashore, Maryland

The U.S. Geological Survey, in cooperation with the Maryland Department of the Environment and the Wisconsin State Laboratory of Hygiene, conducted a study to characterize the occurrence and distribution of viral contamination in small (withdrawing less than 10,000 gallons per day) public water-supply wells screened in the shallow aquifer in the Piedmont Physiographic Province in Baltimore and Harford Counties, Maryland. Two hundred sixty-three small public water-supply wells were in operation in these counties during the spring of 2000. Ninety-one of these sites were selected for sampling using a methodology that distributed the samples evenly over the population and the spatial extent of the study area. Each site, and its potential susceptibility to microbiological contamination, was evaluated with regard to hole depth, casing interval, and open interval. Each site was evaluated using characteristics such as on-site geology and on-site land use.Samples were collected by pumping between 200 and 400 gallons of untreated well water through an electropositive cartridge filter. Water concentrates were subjected to cell-culture assay for the detection of culturable viruses and reverse-transcription polymerase chain reaction/gene probe assays to detect viral ribonucleic acid; grab samples were analyzed for somatic and male-specific coliphages, Bacteroides fragilis, Clostridium perfringens, enterococci, Escherichia coli, total coliforms, total oxidized nitrogen, nitrite, organic nitrogen, total phosphate, ortho-phosphate, calcium, magnesium, sodium, potas-sium, chloride, sulfate, iron, acid-neutralizing capacity, pH, specific conductance, temperature, and dissolved oxygen.One sample tested positive for the presence of the ribonucleic acid of rotavirus through poly-merase chain-reaction analysis. Twenty-nine per-cent of the samples (26 of 90) had bacterial con-tamination. About 7 percent of the samples (6 of 90) were contaminated with either male-specific coliphage, somatic coliphage, or bacteriophages of Bacteroides fragilis. About 3 percent of the sam-ples (3 of 87) had oxidized nitrogen concentra-tions that exceeded the U.S. Environmental Protection Agency?s Maximum Contaminant Level of 10.0 milligrams per liter. A statistical analysis showed that no significant relation exists between the presence of bacteria or coliphage and all variables, except the mean temperature of the water sample as measured in the field. Additionally, the concentration of total coliform bacteria had a statistically significant, moderately strong cor-relation with the concentration of sulfate and sample pH as measured at the U.S. Geological Survey National Water-Quality Laboratory in Denver, Colorado.

Water-Resources Investigations Report↗
USGS2004

Seafloor habitat mapping and classification in Glacier Bay, Alaska: Phase 1 & 2 1996-2004

Glacier Bay is a diverse fjord ecosystem with multiple sills, numerous tidewater glaciers and a highly complex oceanographic system. The Bay was completely glaciated prior to the 1700’s and subsequently experienced the fastest glacial retreat recorded in historical times. Currently, some of the highest sedimentation rates ever observed occur in the Bay, along with rapid uplift (up to 2.5 cm/year) due to a combination of plate tectonics and isostatic rebound. Glacier Bay is the second deepest fjord in Alaska, with depths over 500 meters. This variety of physical processes and bathymetry creates many diverse habitats within a relatively small area (1,255 km 2 ). Habitat can be defined as the locality, including resources and environmental conditions, occupied by a species or population of organisms (Morrison et al 1992). Mapping and characterization of benthic habitat is crucial to an understanding of marine species and can serve a variety of purposes including: understanding species distributions and improving stock assessments, designing special management areas and marine protected areas, monitoring and protecting important habitats, and assessing habitat change due to natural or human impacts. In 1996, Congress recognized the importance of understanding benthic habitat for fisheries management by reauthorizing the Magnuson-Stevens Fishery Conservation and Management Act and amending it with the Sustainable Fisheries Act (SFA). This amendment emphasizes the importance of habitat protection to healthy fisheries and requires identification of essential fish habitat in management decisions. Recently, the National Park Service’s Ocean Stewardship Strategy identified the creation of benthic habitat maps and sediment maps as crucial components to complete basic ocean park resource inventories (Davis 2003). Glacier Bay National Park managers currently have very limited knowledge about the bathymetry, sediment types, and various marine habitats of ecological importance in the Park. Ocean floor bathymetry and sediment type are the building blocks of marine communities. Bottom type and shape affects the kinds of benthic communities that develop in a particular environment as well as the oceanographic conditions that communities are subject to. Accurate mapping of the ocean floor is essential for park manager’s understanding of existing marine communities and will be important in assessing human induced changes (e.g., vessel traffic and commercial fishing), biological change (e.g., rapid sea otter recolonization), and geological processes of change (e.g., deglaciation). Information on animal-habitat relationships, particularly within a marine reserve framework, will be valuable to agencies making decisions about critical habitats, marine reserve design, as well as fishery management. Identification and mapping of benthic habitat provides National Park Service mangers with tools to increase the effectiveness of resource management. The primary objective of this project is to investigate the geological characteristics of the biological habitats of halibut, Dungeness crab, king crab, and Tanner crab within Glacier Bay National Park. Additionally, habitat classification of shallow water regions of Glacier Bay will provide crucial information on the relationship between benthic habitat features and the abundance of benthic prey items for a variety of marine predators, including sea ducks, the rapidly increasing population of sea otters, and other marine mammals.

Alaska↗
USGS2002

A terrain-based paired-site sampling design to assess biodiversity losses from eastern hemlock decline

Biodiversity surveys are often hampered by the inability to control extraneous sources of variability introduced into comparisons of populations across a heterogenous landscape. If not specifically accounted for a priori, this noise can weaken comparisons between sites, and can make it difficult to draw inferences about specific ecological processes. We developed a terrain-based, paired-site sampling design to analyze differences in aquatic biodiversity between streams draining eastern hemlock (Tsuga canadensis) forests, and those draining mixed hardwood forests in Delaware Water Gap National Recreation Area (USA). The goal of this design was to minimize variance due to terrain influences on stream communities, while representing the range of hemlock dominated stream environments present in the park. We used geographic information systems (GIS) and cluster analysis to define and partition hemlock dominated streams into terrain types based on topographic variables and stream order. We computed similarity of forest stands within terrain types and used this information to pair hemlock-dominated streams with hardwood counterparts prior to sampling. We evaluated the effectiveness of the design through power analysis and found that power to detect differences in aquatic invertebrate taxa richness was highest when sites were paired and terrain type was included as a factor in the analysis. Precision of the estimated difference in mean richness was nearly doubled using the terrain-based, paired site design in comparison to other evaluated designs. Use of this method allowed us to sample stream communities representative of park-wide forest conditions while effectively controlling for landscape variability.

Environmental Monitoring and Assessment↗
USGS2018

A social–ecological perspective for riverscape management in the Columbia River Basin

Riverscapes are complex, landscape-scale mosaics of connected river and stream habitats embedded in diverse ecological and socioeconomic settings. Social–ecological interactions among stakeholders often complicate natural-resource conservation and management of riverscapes. The management challenges posed by the conservation and restoration of wild salmonid populations in the Columbia River Basin (CRB) of western North America are one such example. Because of their ecological, cultural, and socioeconomic importance, salmonids present a complex management landscape due to interacting environmental factors (eg climate change, invasive species) as well as socioeconomic and political factors (eg dams, hatcheries, land-use change, transboundary agreements). Many of the problems in the CRB can be linked to social–ecological interactions occurring within integrated ecological, human–social, and regional–climatic spheres. Future management and conservation of salmonid populations therefore depends on how well the issues are understood and whether they can be resolved through effective communication and collaboration among ecologists, social scientists, stakeholders, and policy makers.

Columbia River Basin↗
USGS2021

Biological and chemical recovery of acidified Catskill Mountain streams in response to the Clean Air Act Amendments of 1990

Decades of acidic deposition have adversely affected aquatic and terrestrial ecosystems in acid-sensitive watersheds in parts of the eastern United States. The national Acid Rain Program (Title IV of the 1990 Clean Air Act Amendments - CAAA) helped reduce emissions of sulfur dioxide (SO 2 ) and nitrogen oxides (NO x ) and resulted in sharp decreases in the acidity of atmospheric deposition. The decrease in acidic deposition produced a steady decline in the acidity of streams in many poorly buffered waters across the western Adirondacks and parts of the Catskill Mountains of New York. Until recently, however, there has been little evidence of biological recovery in most acid-sensitive streams in both regions. Long-term deposition and stream-chemistry records and fish-community data from quantitative surveys done during 1991–93 and again during 2012–19 at 13 sites in the upper Neversink River and its tributaries were evaluated to determine if chemical and biological recovery were evident in this Catskill Mountain watershed and if they could be linked to regional declines in acidic deposition. Between 1991 and 2019, large decreases in sulfate and nitrate deposition in the basin mirrored declines in total nationwide SO 2 and NO x emissions. There were corresponding decreases in sulfate and nitrate concentrations in deposition at a National Trends Network station at Frost Valley (NY68) and coincident declines in sulfate concentrations at four long-term monitoring sites in the Neversink River watershed. Mean acid neutralizing capacity and pH increased and inorganic aluminum (Al i ) concentrations from routine summertime samples decreased significantly at most moderately to severely acidified sites between the two study periods. Richness, density, and biomass of fish communities increased at most sites, while the density and biomass of brook trout Salvelinus fontinalis populations increased at fewer sites that were undergoing chemical recovery. Although recovery is far from complete, trends in deposition chemistry, water quality, and fish assemblages in streams of the upper Neversink watershed indicate that the 1990 CAAA is having positive impacts on aquatic ecosystems in the Catskill Mountain region, New York.

New York↗
USGS2013

Interactions between chemical and climate stressors: A role for mechanistic toxicology in assessing climate change risks

Incorporation of global climate change (GCC) effects into assessments of chemical risk and injury requires integrated examinations of chemical and nonchemical stressors. Environmental variables altered by GCC (temperature, precipitation, salinity, pH) can influence the toxicokinetics of chemical absorption, distribution, metabolism, and excretion as well as toxicodynamic interactions between chemicals and target molecules. In addition, GCC challenges processes critical for coping with the external environment (water balance, thermoregulation, nutrition, and the immune, endocrine, and neurological systems), leaving organisms sensitive to even slight perturbations by chemicals when pushed to the limits of their physiological tolerance range. In simplest terms, GCC can make organisms more sensitive to chemical stressors, while alternatively, exposure to chemicals can make organisms more sensitive to GCC stressors. One challenge is to identify potential interactions between nonchemical and chemical stressors affecting key physiological processes in an organism. We employed adverse outcome pathways, constructs depicting linkages between mechanism-based molecular initiating events and impacts on individuals or populations, to assess how chemical- and climate-specific variables interact to lead to adverse outcomes. Case examples are presented for prospective scenarios, hypothesizing potential chemical–GCC interactions, and retrospective scenarios, proposing mechanisms for demonstrated chemical–climate interactions in natural populations. Understanding GCC interactions along adverse outcome pathways facilitates extrapolation between species or other levels of organization, development of hypotheses and focal areas for further research, and improved inputs for risk and resource injury assessments.

Environmental Toxicology and Chemistry↗
USGS2007

Use of multiple chemical tracers to define habitat use of Indo-Pacific mangrove crab, Scylla serrata (Decapoda: Portunidae)

The mangrove or mud crab, Scylla serrata, is an important component of mangrove fisheries throughout the Indo-Pacific. Understanding crab diets and habitat use should assist in managing these fisheries and could provide additional justification for conservation of the mangrove ecosystem itself. We used multiple chemical tracers to test whether crab movements were restricted to local mangrove forests, or extended to include adjacent seagrass beds and reef flats. We sampled three mangrove forests on the island of Kosrae in the Federated States of Micronesia at Lelu Harbor, Okat River, and Utwe tidal channel. Samples of S. serrata and likely food sources were analyzed for stable carbon (??13C), nitrogen (??15N), and sulfur (??34S) isotopes. Scylla serrata tissues also were analyzed for phosphorus (P), cations (K, Ca, Mg, Na), and trace elements (Mn, Fe, Cu, Zn, and B). Discriminant analysis indicated that at least 87% of the crabs remain in each site as distinct populations. Crab stable isotope values indicated potential differences in habitat use within estuaries. Values for ??13C and ??34S in crabs from Okat and Utwe were low and similar to values expected from animals feeding within mangrove forests, e.g., feeding on infauna that had average ??13C values near -26.5???. In contrast, crabs from Lelu had higher ?? 13C and ??34S values, with average values of -21.8 and 7.8???, respectively. These higher isotope values are consistent with increased crab foraging on reef flats and seagrasses. Given that S. serrata have been observed feeding on adjacent reef and seagrass environments on Kosrae, it is likely that they move in and out of the mangroves for feeding. Isotope mixing model results support these conclusions, with the greatest mangrove ecosystem contribution to S. serrata diet occurring in the largest mangrove forests. Conserving larger island mangrove forests (> 1 km deep) appears to support crab foraging activities. ?? 2007 Coastal and Estuarine Research Federation.

Estuaries and Coasts↗
USGS2008

Remote sensing and GIS approach for water-well site selection, southwest Iran

The Pabdeh-Lali Anticline of northern Khuzestan province is located in southwestern Iran and occupies 790 km2. This structure is situated in the Zagros folded belt. As a result of well-developed karst systems in the anticlinal axis, the water supply potential is high and is drained by many peripheral springs. However, there is a scarcity of water for agriculture and population centers on the anticlinal flanks, which imposes a severe problem in terms of area development. This study combines remotely sensed (RS) data and a geographical information system (GIS) into a RSGIS technique to delineate new areas for groundwater development and specific sites for drilling productive water wells. Toward these goals, RS data were used to develop GIS layers for lithology, structural geology, topographic slope, elevation, and drainage density. Field measurements were made to create spring-location and groundwater-quality GIS layers. Subsequently, expert choice and relational methods were used in a GIS environment to conjunctively analyze all layers to delineate preferable regions and 43 individual sites in which to drill water wells. Results indicate that the most preferred areas are, in preferential order, within recent alluvial deposits, the Bakhtiyari Conglomerates, and the Aghajari Sandstone. The Asmari Limestone and other units have much lower potential for groundwater supplies. Potential usefulness of the RSGIS method was indicated when six out of nine producing wells recently drilled by the Khozestan Water and Power Authority (which had no knowledge of this study) were located in areas preferentially selected by this technique.

Environmental & Engineering Geoscience↗
USGS2004

Nutritional ecology of ursids: A review of newer methods and management implications

The capability to understand the nutritional ecology of free-ranging bears has increased dramatically in the last 20 years. Advancements have occurred because (1) managers and biologists recognized the need to link habitat quality, productivity, and variability with bear movements, home ranges, and demographic parameters like reproductive output, survival, and population growth, and (2) several research teams are using new methods to build on the results of earlier field studies. Our ability to couple new field methods and empirical field research with controlled experiments using captive bears has been central to our increased understanding of bear nutrition. Newer methods include the use of stable isotopes to quantify assimilated diet and nutrient flows within ecosystems, bioelectrical impedance to measure body composition, and naturally occurring mercury to estimate fish intake. Controlled experiments using captive bears have been integral to developing methods, isolating specific variables by controlling the environment, and providing additional nutritional understanding necessary to interpret field observations. We review new methods and apply our increased understanding of bear nutritional ecology to 3 management issues: (1) the importance of salmon ( Oncorhynchus spp.) to brown bears ( Ursus arctos ) in the Pacific Northwest, (2) the consequences of the closure of the Yellowstone garbage dumps to grizzly bears, and (3) the relocation of problem bears.

Ursus↗
USGS2014

Integrated synoptic surveys of the hydrodynamics and water-quality distributions in two Lake Michigan rivermouth mixing zones using an autonomous underwater vehicle and a manned boat

The U.S. Geological Survey (USGS), in cooperation with the National Monitoring Network for U.S. Coastal Waters and Tributaries, launched a pilot project in 2010 to determine the value of integrated synoptic surveys of rivermouths using autonomous underwater vehicle technology in response to a call for rivermouth research, which includes study domains that envelop both the fluvial and lacustrine boundaries of the rivermouth mixing zone. The pilot project was implemented at two Lake Michigan rivermouths with largely different scales, hydrodynamics, and settings, but employing primarily the same survey techniques and methods. The Milwaukee River Estuary Area of Concern (AOC) survey included measurements in the lower 2 to 3 miles of the Milwaukee, Menomonee, and Kinnickinnic Rivers and inner and outer Milwaukee Harbor. This estuary is situated in downtown Milwaukee, Wisconsin, and is the most populated basin that flows directly into Lake Michigan. In contrast, the Manitowoc rivermouth has a relatively small harbor separating the rivermouth from Lake Michigan, and the Manitowoc River Watershed is primarily agricultural. Both the Milwaukee and Manitowoc rivermouths are unregulated and allow free exchange of water with Lake Michigan. This pilot study of the Milwaukee River Estuary and Manitowoc rivermouth using an autonomous underwater vehicle (AUV) paired with a manned survey boat resulted in high spatial and temporal resolution datasets of basic water-quality parameter distributions and hydrodynamics. The AUV performed well in these environments and was found primarily well-suited for harbor and nearshore surveys of three-dimensional water-quality distributions. Both case studies revealed that the use of a manned boat equipped with an acoustic Doppler current profiler (ADCP) and multiparameter sonde (and an optional flow-through water-quality sampling system) was the best option for riverine surveys. To ensure that the most accurate and highest resolution velocity data were collected concurrently with the AUV surveys, the pilot study used a manned boat equipped with an ADCP. Combining the AUV and manned boat datasets resulted in datasets that are essentially continuous from the fluvial through the lacustrine zones of a rivermouth. Whereas the pilot studies were completed during low flows on the tributaries, completion of surveys at higher flows using the same techniques is possible, but the use of the AUV would be limited to areas with relatively low velocities (less than 2 feet per second) such as the harbors and nearshore zones of Lake Michigan. Overall, this pilot study aimed at evaluation of AUV technology for integrated synoptic surveys of rivermouth mixing zones was successful, and the techniques and methods employed in this pilot study should be transferrable to other sites with similar success. The use of the AUV provided significant time savings compared to traditional sampling techniques. For example, the survey of outer Milwaukee Harbor using the AUV required less than 7 hours for approximately 600 profiles compared to the 150 hours it would have taken using traditional methods in a manned boat (a 95 percent reduction in man-hours). The integrated datasets resulting from the AUV and manned survey boat are of high value and present a picture of the mixing and hydrodynamics of these highly dynamic, highly variable rivermouth mixing zones from the relatively well-mixed fluvial environment through the rivermouth to the stratified lacustrine receiving body of Lake Michigan. Such datasets not only allow researchers to understand more about the physical processes occurring in these rivermouths, but they provide high spatial resolution data required for interpretation of relations between disparate point samples and calibration and validation of numerical models.

Wisconsin↗
USGS2012

Drought and cooler temperatures are associated with higher nest survival in Mountain Plovers

Native grasslands have been altered to a greater extent than any other biome in North America. The habitats and resources needed to support breeding performance of grassland birds endemic to prairie ecosystems are currently threatened by land management practices and impending climate change. Climate models for the Great Plains prairie region predict a future of hotter and drier summers with strong multiyear droughts and more frequent and severe precipitation events. We examined how fluctuations in weather conditions in eastern Colorado influenced nest survival of an avian species that has experienced recent population declines, the Mountain Plover (Charadrius montanus). Nest survival averaged 27.2% over a 7-yr period (n = 936 nests) and declined as the breeding season progressed. Nest survival was favored by dry conditions and cooler temperatures. Projected changes in regional precipitation patterns will likely influence nest survival, with positive influences of predicted declines in summer rainfall yet negative effects of more intense rain events. The interplay of climate change and land use practices within prairie ecosystems may result in Mountain Plovers shifting their distribution, changing local abundance, and adjusting fecundity to adapt to their changing environment.

Avian Conservation and Ecology↗
USGS2008

Using Molecular Genetic Markers to Resolve a Subspecies Boundary: The Northern Boundary of the Southwestern Willow Flycatcher in the Four-Corner States

*Executive Summary* The northern boundary of the endangered Southwestern Willow Flycatcher (Empidonax traillii extimus) is currently approximated as running through southern Colorado and Utah, but the exact placement is uncertain because this subspecies shares a border with the more northern and non-endangered E. t. adastus. To help resolve this issue, we evaluated the geographic distribution of mitochondrial and nuclear DNA by sampling breeding sites across the four-corner states (Arizona, Colorado, New Mexico, and Utah). We found that breeding sites clustered into two major groups generally consistent with the currently designated boundary, with the exception of three sites situated along the current boundary. However, delineating a precise boundary that would separate the two subspecies is made difficult because (1) we found evidence for a region of intergradation along the boundary area, suggesting the boundary is not discreet, and (2) the boundary region is sparsely populated, with too few extant breeding populations to precisely locate a boundary. The boundary region encompasses an area where elevation changes markedly over relatively short distances, with low elevation deserts to the south and more mesic, higher elevation habitats to the north. We hypothesized that latitudinal and elevational differences and their concomitant ecological effects could form an ecological barrier that inhibited gene flow between the subspecies, forming the basis for the subspecies boundary. We modeled changes in geographic patterns of genetic markers as a function of latitude and elevation finding significant support for this relationship. The model was brought into a GIS environment to create multiple subspecies boundaries, with the strength of each predicted boundary evaluated on the basis of how much genetic variation it explained. The candidate boundary that accounted for the most genetic variation was situated generally near the currently recognized subspecies boundary, but should be more biologically meaningful because it incorporates the landscape features that may be driving separation of the subspecies. Even so, we caution that using any narrow boundary line as an indicator of subspecies identity could be misleading because biologically the boundary is a region of intergradation rather than a discrete line. Designating, a boundary ultimately becomes a regulatory and management decision based on how much of the genetic variation unique to a subspecies should be protected. We discuss how the results of this study can help guide this decision process by wildlife policy makers.

Open-File Report↗
USGS2018

Field diagnostics and seasonality of Ophidiomyces ophiodiicola in wild snake populations

Snake fungal disease (SFD) is an emerging disease caused by the fungal pathogen, Ophidiomyces ophiodiicola . Clinical signs of SFD include dermal lesions, including regional and local edema, crusts, and ulcers. Snake fungal disease is widespread in the Eastern United States, yet there are limited data on how clinical signs of SFD compare with laboratory diagnostics. We compared two sampling methods for O. ophiodiicola , scale clip collection and swabbing, to evaluate whether collection method impacted the results of polymerase chain reaction (PCR). In addition, we evaluated the use of clinical signs to predict the presence of O. ophiodiicola across seasons, snake habitat affiliation (aquatic or terrestrial) and study sites. We found no significant difference in PCR results between sampling methods. Clinical signs were a strong predictor of O. ophiodiicola presence in spring and summer seasons. Snakes occupying terrestrial environments had a lower overall probability of testing positive for O. ophiodiicola compared to snakes occupying aquatic environments. Although our study indicates that both clinical signs of SFD and prevalence of O. ophiodiicola vary seasonally and based on habitat preferences of the host, our analysis suggests that clinical signs can serve as a reliable indicator of O. ophiodiicola presence, especially during spring and summer.

Kentucky↗
USGS2023

Increased aridity is associated with stronger tradeoffs in ponderosa pine vital functions

Trees must allocate resources to core functions like growth, defense, and reproduction. These allocation patterns have profound effects on forest health, yet little is known about how core functions trade off over time, and even less is known about how a changing climate will impact tradeoffs. We conducted a 21-year survey of growth, defense, and reproduction in 80 ponderosa pine individuals spanning eight populations across environmental gradients along the Colorado Front Range, USA. We used linear mixed models to describe tradeoffs among these functions and to characterize variability among and within individuals over time. Growth and defense were lower in years of high cone production, and local drought conditions amplified year-to-year tradeoffs between reproduction and growth, where trees located at sites with hotter and drier climates showed stronger tradeoffs between reproduction and growth. Our results support the environmental stress hypothesis of masting, which predicts that greater interannual variation in tree functions will be associated with more marginal environments, such as those that are prone to drought. With warming temperatures and increased exposure to drought stress, trees will be faced with stronger interannual tradeoffs, which could lead to further decreases in growth and defensive efforts, ultimately increasing risks of mortality.

Ecology↗
USGS2021

Mismatch-induced growth reductions in a clade of Arctic-breeding shorebirds are rarely mitigated by increasing temperatures

In seasonal environments subject to climate change, organisms typically show phenological changes. As these changes are usually stronger in organisms at lower trophic levels than those at higher trophic levels, mismatches between consumers and their prey may occur during the consumers’ reproduction period. While in some species a trophic mismatch induces reductions in offspring growth, this is not always the case. This variation may be caused by the relative strength of the mismatch, or by mitigating factors like increased temperature-reducing energetic costs. We investigated the response of chick growth rate to arthropod abundance and temperature for six populations of ecologically similar shorebirds breeding in the Arctic and sub-Arctic (four subspecies of Red Knot Calidris canutus , Great Knot C . tenuirostris and Surfbird C . virgata ). In general, chicks experienced growth benefits (measured as a condition index) when hatching before the seasonal peak in arthropod abundance, and growth reductions when hatching after the peak. The moment in the season at which growth reductions occurred varied between populations, likely depending on whether food was limiting growth before or after the peak. Higher temperatures led to faster growth on average, but could only compensate for increasing trophic mismatch for the population experiencing the coldest conditions. We did not find changes in the timing of peaks in arthropod availability across the study years, possibly because our series of observations was relatively short; timing of hatching displayed no change over the years either. Our results suggest that a trend in trophic mismatches may not yet be evident; however, we show Arctic-breeding shorebirds to be vulnerable to this phenomenon and vulnerability to depend on seasonal prey dynamics.

Global Change Biology↗