Geology topics

Research about Wyoming

Source-linked reports with geographic coverage including Wyoming.

At least 109 records · Page 6Linked to original sources

USGS2023

The relation between decadal droughts and eruptions of Steamboat Geyser in Yellowstone National Park, USA

In the past century, most eruptions of Steamboat Geyser in Yellowstone National Park's Norris Geyser Basin were mainly clustered in three episodes: 1961–1969, 1982–1984, and ongoing since 2018. These eruptive episodes resulted in extensive disturbance to surrounding trees. To characterize tree response over time as an indicator of geyser activity adjustments to climate variability, aerial and ground images were analyzed to document changes in tree coverage around the geyser since 1954. Radiocarbon dating of silicified tree remnants from within 14 m of the geyser vent was used to examine geyser response to possible variations in decadal to centennial precipitation patterns. We searched for atypical or absent growth rings in cores from live trees in years associated with large geyser eruptions. Photographs indicate that active eruptive phases have adversely affected trees up to 30 m from the vent, primarily in the dominant downwind direction. Radiocarbon dates indicate that the geyser formed before 1878, in contrast to the birthdate reported in historical documents. Further, the ages of the silicified trees cluster within three episodes that are temporally correlated with periods of relative drought in the Yellowstone region during the 15th–17th centuries. The discontinuous growth of trees around the geyser suggests that changes in eruptive patterns occur in response to decadal to multidecadal droughts. This inference is supported by the lack of silicified specimens with more than 20 annual rings and by the existence of atypical or missing rings in live trees during periods of extended geyser activity.

Wyoming↗

USGS2023

Decomposition rates of suppression-produced fish carcasses in a large, deep, high-elevation lake in North America

The decomposition of vertebrates in lake ecosystems has been largely understudied despite being a vital part of ecosystem processes. Invasive lake trout ( Salvelinus namaycush ) invaded Yellowstone Lake and caused a decline in the native Yellowstone cutthroat trout ( Oncorhynchus clarkii bouvieri ) population. To restore Yellowstone cutthroat trout, lake trout were suppressed by gillnetting annually since 1995 and has continued to present, with most carcasses deposited in the profundal zone (>70 m). As a part of suppression management, a fraction of carcasses from gillnetting were ground and placed on littoral spawning sites (causing lake trout embryo mortality via hypoxia). We conducted experiments (2018 and 2019) to determine how carcass state (i.e., whole vs. ground) and location of deposition (i.e., profundal or littoral) affected decomposition rates. Whole carcasses in the depths of Yellowstone Lake decomposed nine times slower (rate of decay, k = −0.0075 day −1 ; 95% CI = −0.0063–−0.0089) than ground carcasses in the littoral zone (k = −0.0679 day −1 ; 95% CI = −0.0590–−0.0768). Whole carcasses had a half-life of 91 days while ground carcasses had a half-life of 10 days. We showed that carcass state and location cause a differential decomposition for lake trout carcasses in Yellowstone Lake. Understanding carcass persistence in lakes can inform the management of suppression-produced carcasses in large lakes and provide insight into potential effects of carcass deposition from other sources, such as spawning events or fish kills, on nutrient cycling.

Wyoming↗

USGS2023

Hidden Markov movement models reveal diverse seasonal movement patterns in two North American ungulates

Animal movement is the mechanism connecting landscapes to fitness, and understanding variation in seasonal animal movements has benefited from the analysis and categorization of animal displacement. However, seasonal movement patterns can defy classification when movements are highly variable. Hidden Markov movement models (HMMs) are a class of latent-state models well-suited to modeling movement data. Here, we used HMMs to assess seasonal patterns of variation in the movement of pronghorn ( Antilocapra americana ), a species known for variable seasonal movements that challenge analytical approaches, while using a population of mule deer ( Odocoileus hemionus ), for whom seasonal movements are well-documented, as a comparison. We used population-level HMMs in a Bayesian framework to estimate a seasonal trend in the daily probability of transitioning between a short-distance local movement state and a long-distance movement state. The estimated seasonal patterns of movements in mule deer closely aligned with prior work based on indices of animal displacement: a short period of long-distance movements in the fall season and again in the spring, consistent with migrations to and from seasonal ranges. We found seasonal movement patterns for pronghorn were more variable, as a period of long-distance movements in the fall was followed by a winter period in which pronghorn were much more likely to further initiate and remain in a long-distance movement pattern compared with the movement patterns of mule deer. Overall, pronghorn were simply more likely to be in a long-distance movement pattern throughout the year. Hidden Markov movement models provide inference on seasonal movements similar to other methods, while providing a robust framework to understand movement patterns on shorter timescales and for more challenging movement patterns. Hidden Markov movement models can allow a rigorous assessment of the drivers of changes in movement patterns such as extreme weather events and land development, important for management and conservation.

Wyoming↗

USGS2023

Invasive Brook Stickleback Culaea inconstans occurrence, habitat drivers, and spatial overlap with native fishes in Wyoming, USA

A central focus of modern fisheries management is eradicating invaders that threaten imperiled native fishes. However, vast landscapes and limited funding and personnel resources demand a prioritized approach to management. Brook Stickleback Culaea inconstans (Kirtland, 1840) is an aquatic invasive species in Wyoming, USA, that may pose a risk to native biodiversity. Our aim was to evaluate Brook Stickleback’s invasive potential in the North Platte River drainage. We updated the current distribution of Brook Stickleback, evaluated for possible range expansion, and determined landscape-level habitat drivers and occurrence potential for streams across the North Platte River drainage. Additionally, we examined Brook Stickleback’s spatial overlap with native nongame fishes. At the landscape scale, Brook Stickleback preferred low-gradient streams with moderate disturbance risk. Though we did not find evidence of current Brook Stickleback range expansion 61% of streams in the drainage have landscape-level environmental characteristics that are likely suitable for Brook Stickleback, creating potential for future expansion. Brook Stickleback overlapped spatially with 13 native nongame species, though spatial overlap was less common than expected for species with similar habitat preferences. Our work serves as a case study of the factors to consider when assessing a species’ invasive potential in a previously unstudied region.

Wyoming↗

USGS2023

Dynamic spatiotemporal modeling of a habitat-defining plant species to support wildlife management at regional scales

Sagebrush ( Artemisia spp.) ecosystems provide critical habitat for the Greater sage-grouse ( Centrocercus urophasianus ), a species of conservation concern. Thus, future loss of sagebrush habitat because of land use change and global climate change is of concern. Here, we use a dynamic additive spatiotemporal model to estimate the effects of climate on sagebrush cover dynamics at 32 sage-grouse management (core) areas in Wyoming. We use the fitted models to quantify the sensitivity of each management area to precipitation and temperature, and to make probabilistic projections of sagebrush cover from present to 2100 under three climate change scenarios. Global circulation models predict an increase in temperature and no change in precipitation for Wyoming. Sensitivity to climate varied among management areas, but the most common response (70% of management areas) was a positive effect of temperature on sagebrush performance. The combination of positive sensitivity to temperature and the predicted increase in temperature under all climate change scenarios resulted in projections of increased sagebrush cover for most management areas. We characterized management areas as “optimal” or “suboptimal” based on the percentage of grid cells in each management area with sagebrush cover exceeding a nesting habitat target value. Only 18% of management areas are projected to switch from being currently optimal to suboptimal in the future. Thirty-five percent of management areas are projected to switch from being suboptimal to optimal. The most common outcome (47%) was for currently suboptimal management areas to remain suboptimal, even though average cover tended to increase in those areas. The direct effects of climate change appear to favor sagebrush performance in the future for most sage-grouse core areas in Wyoming. Our approach is broadly applicable to quantitative climate change assessments where remotely sensed estimates of habitat-defining vegetation are available.

Wyoming↗

USGS2023

Diverse migratory portfolios drive inter-annual switching behavior of elk across the Greater Yellowstone Ecosystem

A growing body of evidence shows that some ungulates alternate between migratory and nonmigratory behaviors over time. Yet it remains unclear whether such short-term behavioral changes can help explain reported declines in ungulate migration worldwide, as opposed to long-term demographic changes. Furthermore, advances in tracking technology reveal that a simple distinction between migration and nonmigration may not sufficiently describe all individual behaviors. To better understand the dynamics and drivers of ungulate switching behavior, we investigated 14 years of movement data from 361 elk in 20 herds across the Greater Yellowstone Ecosystem (GYE). First, we categorized yearly individual behaviors using a clustering algorithm that identified similar migratory tactics across a continuum of behaviors. Then, we tested seven hypotheses to explain why some ungulates switch behaviors, and we evaluated how behavioral changes affected the proportions of different behaviors across the system. We identified four distinct behavioral tactics: residents (4.8% of elk-years), short-distance migrants (53.7%), elevational migrants (21.9%) and long-distance migrants (19.6%). Of the 20 herds, 18 were partially migratory, and 5 had all four movement tactics present. We observed switches between migratory tactics in all sets of consecutive years during our study period, with an average of 22.5% of individual elk changing movement tactics from one year to the next. Elk in herds with higher movement tactic diversity were significantly more likely to switch tactics and often responded more effectively to adverse environmental conditions, compared to those in herds with low movement tactic diversity. During our study period, switching increased the prevalence of both short- and long-distance migrants, decreased the prevalence of elevational migrants, and had no effect on the prevalence of residents. Our findings suggest that rather than contributing to the declining migratory behavior found in the GYE, switching behavior may enable greater resiliency to continuously changing environmental and anthropogenic conditions.

Wyoming↗

USGS2023

Yellowstone Volcano Observatory 2022 annual report

The Yellowstone Volcano Observatory (YVO) monitors volcanic and hydrothermal activity associated with the Yellowstone magmatic system, carries out research into magmatic processes occurring beneath Yellowstone Caldera, and issues timely warnings and guidance related to potential future geologic hazards. This report summarizes the activities and findings of YVO during the year 2022, focusing on the Yellowstone volcanic system. Highlights of YVO research and related activities during 2022 include deployments of seismometers in Norris Geyser Basin and Upper Geyser Basin to investigate interactions between hydrothermal features and influences from external influences, geological studies of post-glacial hydrothermal activity, refining the ages of Yellowstone volcanic units and updating existing maps of geologic deposits, new mapping of ash-flow deposits on the Sour Creek dome, installation of a new continuous gas monitoring station near Mud Volcano, sampling of gas emissions and thermal waters around Yellowstone National Park to monitor water chemistry over space and time, research into the age and history of Steamboat Geyser in Norris Geyser Basin, and assessment of thermal output based on satellite imagery and chloride flux in rivers. The most noteworthy event of the year was not geophysical, but meteorological. Combined runoff from rain and snowmelt caused substantial flooding in Yellowstone National Park, which caused damage to park roads and infrastructure. Steamboat Geyser, in Norris Geyser Basin, continued the pattern of frequent eruptions that began in 2018 with 11 water eruptions in 2022, the lowest number of annual eruptions in the current eruptive sequence. Total seismicity—2,429 located earthquakes—was slightly less than the 2,773 earthquakes located in 2021 and at the upper end of the historical average range of about 1,500–2,500 earthquakes per year. Overall subsidence of the caldera floor, ongoing since late 2015 or early 2016, continued at rates of a few centimeters (1–2 inches) per year. Satellite deformation measurements indicated the possibility of slight uplift amounting to about 1 centimeter (less than 1 inch) along the north caldera rim in 2021, but satellite data spanning 2022 show no uplift in that area. Throughout 2022, the aviation color code for Yellowstone Caldera remained at “green” and the volcano alert level remained at “normal.”

Wyoming↗

USGS2023

Using neutral landscape models to evaluate the umbrella species concept in an ecotone

Context Steep declines in North American rangeland biodiversity have prompted researchers and managers to use umbrella species as a tool to manage diverse suites of co-occurring wildlife, but efficacy of this method has been variable. Evaluation of prairie and shrubland grouse as umbrellas is typically restricted to observed overlap between umbrella and background species, but this approach does not distinguish between overlap due to ubiquity or niche overlap. Objectives We demonstrate a novel application of neutral landscape models (NLMs) to test the effectiveness of greater sage-grouse ( Centrocercus urophasianus ) as an umbrella species for grassland songbirds at a grassland-sagebrush ecotone in northeastern Wyoming, USA. Methods We leveraged existing spatial data representing sage-grouse habitat in two distinct seasons (nesting and late brood-rearing) and density and distribution of eight grassland songbirds. We applied a permutation-based analysis using NLMs to determine whether overlap between background species and greater sage-grouse was greater than expected by chance. Results Three species (western meadowlark Sturnella neglecta , loggerhead shrike Lanius ludovicianus , and lark bunting Calamospiza melanocorys ) had greater overlap than expected with at least one type of greater sage-grouse habitat, while western kingbirds ( Tyrannus verticalis ) indicated avoidance of all sage-grouse habitat assessed. Conclusions NLMs provided a more nuanced evaluation of the umbrella species concept than previously available and allowed us to differentiate between overlap due to ubiquity (e.g., vesper sparrow; Pooecetes gramineus ) rather than overlap in habitat use. All grassland passerine species with greater than expected overlap with sage-grouse habitat either nest in sagebrush (loggerhead shrike) or often select nest locations underneath small shrubs (western meadowlark, lark bunting). These results indicate that nesting substrate is a potential niche axis to consider when evaluating the umbrella species concept, especially within sagebrush-grassland ecotones.

Wyoming↗

USGS2023

Migrating mule deer compensate en route for phenological mismatches

Billions of animals migrate to track seasonal pulses in resources. Optimally timing migration is a key strategy, yet the ability of animals to compensate for phenological mismatches en route is largely unknown. Using GPS movement data collected from 72 adult female deer over a 10-year duration, we study a population of mule deer ( Odocoileus hemionus ) in Wyoming that lack reliable cues on their desert winter range, causing them to start migration 70 days ahead to 52 days behind the wave of spring green-up. We show that individual deer arrive at their summer range within an average 6-day window by adjusting movement speed and stopover use. Late migrants move 2.5 times faster and spend 72% less time on stopovers than early migrants, which allows them to catch the green wave. Our findings suggest that ungulates, and potentially other migratory species, possess cognitive abilities to recognize where they are in space and time relative to key resources. Such behavioral capacity may allow migratory taxa to maintain foraging benefits amid rapidly changing phenology.

Wyoming↗

USGS2023

Evaluating management alternatives for Wyoming elk feedgrounds in consideration of chronic wasting disease

Executive Summary The authors used decision and modeling analyses to evaluate management alternatives for a decision on whether to permit Cervus canadensis (elk) feeding on two sites on Bridger-Teton National Forest, Dell Creek and Forest Park. Supplemental feeding of elk could increase the transmission of chronic wasting disease (CWD) locally and disease spread regionally, potentially impacting elk populations over time with wider implications for Odocoileus hemionus (mule deer) and Odocoileus virginianus (white-tailed deer) populations and hunting, tourism, and regional revenue. Supplemental feeding is thought to improve overwinter elk survival and reduce the commingling of elk with cattle during months when brucellosis transmission risk is highest. We worked with the U.S. Department of Agriculture Forest Service to identify their fundamental objectives and associated performance metrics related to this feedground decision. We then developed disease and habitat selection models to quantify the effect of four management alternatives on select performance metrics. The four alternatives were to continue to permit feeding, phaseout permits to feed in three years, permit feeding on an emergency basis, or stop permitting feeding. In this report, we present methods and summarized results on disease and habitat selection models and summaries of other performance metrics analyzed by BIO-WEST, Inc. and Cirrus Ecological Solutions as part of an Environmental Impact Statement. Data from Wyoming Game and Fish Department (WGFD) supported the assumption that supplemental elk feeding allows for larger elk populations in a region. We documented that herd units (HU) without feedgrounds had 23 percent lower densities of elk per area of winter range when compared against HUs with feedgrounds, after accounting for differences in sightability of elk during counts on and off feedgrounds. Thus, throughout our analyses, we assumed feedground closures would reduce elk carrying capacity resulting in an average decline of previously fed elk population segments by 23 percent (5th and 95th percentiles = [11 percent, 35 percent]) by year 20. Most of that decline occurred within the first few years after a feedground ceases to operate. We used a panel of CWD experts to help estimate CWD trans-mission in fed and unfed elk population segments. In aggregate, the expert panel estimated that median values of direct and indirect transmission of CWD are expected to be 1.9 and 4 times higher, respectively, in fed elk populations compared to unfed elk. We used these disease transmission estimates in combination with local elk demographic rates and carrying capacity estimates to project disease and population dynamics. In year 20, we predicted CWD prevalence would increase to 42 percent (5th and 95th percentiles = [29 percent, 55 percent]), and 13 percent (5th and 95th percentiles = [4 percent, 26 percent]) on average for fed and unfed elk population segments, respectively, given a starting prevalence of 1.6 percent. The prevalence estimates for the unfed elk population segments are in the range of previous observations of CWD in elk in the western United States. The average CWD prevalence from 2016 to 2018 in the unfed elk population of Wind Cave National Park in South Dakota was 18 percent overall but up to 30 percent in some regions (Sargeant and others, 2021). Meanwhile, CWD prevalence in the Iron Mountain and Laramie Peak elk herds in Wyoming from 2016 to 2018 was 14 percent and 7 percent, respectively, despite being present since at least 2002 (Wyoming Game and Fish Department, 2020b). From 2016 to 2020, elk that were fed at Dell Creek and Forest Park constituted on average 12–20 percent of the total elk on their respective HUs. As a result, the differences between management alternatives are modest when considering the closure of only one feedground on a HU. The no feeding alternative for Forest Park resulted in a CWD prevalence of 17 percent (SD = 7 percent) in the Afton HU compared to 20 percent (SD = 7 percent) with continued feeding by year 20. In the Upper Green River HU, no feeding on Dell Creek resulted in a CWD prevalence of 27 percent (SD = 6 percent) compared to 30 percent (SD = 5 percent) with continued feeding. In terms of disease-associated mortality, we predicted the closure of Forest Park and Dell Creek feedgrounds would reduce the total number of CWD mortalities by 9 percent in the Upper Green River HU and 26 percent in the Afton HU during the 20-year timespan. Our spatial analyses predicted that management alternative effects vary by HU as a function of private property and other wildlife winter ranges proximity relative to feedground location. The predicted number of elk abortions on private land, as a proxy for brucellosis risk to cattle, may increase by 8–21 percent in the absence of feeding at Dell Creek and Forest Park. Eight feedgrounds are located on Bridger-Teton National Forest, all of which have permits that have expired or will expire prior to 2028. In addition, WGFD could change their management of feedgrounds given new information; therefore, we also assessed the cumulative effects of continued feeding, phaseout, and no feeding management alternatives across five HUs south of Jackson, Wyoming (Afton HU, Fall Creek HU, Piney HU, Pinedale HU, and Upper Green River HU). These five HUs ranged from about 41 to 85 percent of the elk herd using feedgrounds, which corresponded to a CWD prevalence at year 20 of 23–34 percent if all feedgrounds in those five HUs remained open relative to 12 to 14 percent if all feedgrounds were closed. We predicted feedground closures may result in immediate reductions in population size relative to alternatives that continue feeding (for example, continued feeding and emergency feeding alternatives); however, over longer periods of time, CWD-associated mortality leads to larger population reductions. The no feeding alternative resulted in higher elk population sizes compared to the continued feeding alternative after about 10 years of implementation. Delayed action under a phaseout alternative resulted in increasing the CWD prevalence to 20 percent relative to 12 to 14 percent, on average, without feeding on HUs with a large population of fed elk such as the Upper Green River HU. Summarizing our cumulative results across all five of the analyzed HUs, we predicted continued feeding will lead to fewer elk by year 20 (mean = 8,300, standard deviation [SD] = 740) compared to no feeding at U.S. Department of Agri-culture Forest Service sites (10,700, SD = 890). The closure of all feedgrounds was projected to result in the largest elk populations at year 20 (12,500, SD = 980). No feeding at all sites also resulted in the largest cumulative harvest of 57,700 (SD = 2,600) compared to 51,100 (SD = 3,800) for continued feeding at all current feedground sites on the five HUs. Continued feeding also resulted in the lowest brucellosis costs to producers ($194,600, SD = $11,500) compared to no feeding on all feedgrounds ($243,000, SD = $13,700). Assuming moderate reductions in hunter interest because of increasing CWD prevalence in elk, we predicted that no feeding resulted in regional revenues generated by hunting activities of $190 million (SD = $10 million) compared to $173 million (SD = $10 million) for continued feeding over the 20-year timeframe. Recent CWD detections in mule deer and elk in Grand Teton National Park has elevated the importance of the cur-rent decision on whether, and how, to permit elk feeding on Dell Creek and Forest Park and the management of the other feedgrounds. Aggressive male harvest has slowed, but not stopped, the increasing prevalence of CWD in mule deer (Conner and others, 2021). It is unclear whether harvest management can be an effective tool to slow the spread of CWD in elk. There are also no effective treatments or vaccines for CWD, and it is unlikely that any will be developed that can be easily deployed in the near future. Thus, reducing artificial aggregations is one of the few management approaches suggested by the Western Association of Fish and Wildlife Agencies (Almberg and others, 2017). Future surveillance and monitoring can be designed to resolve uncertainties that can improve future decision-making. If feedgrounds close, research could quantify elk population reductions in the absence of feeding, the redistribution of fed elk to other places, or the consequences of elk movement on private property. If feedgrounds remain open, research could assess how rapidly CWD spreads in artificial aggregations of elk; however, surveillance programs would need to be designed with sufficient power to detect initial changes of CWD prevalence. Delaying action on feedground management was projected to be costly. Results of the phaseout alternative relative to the no feeding alternative suggested a 3-year delay was enough for substantial long-term changes in CWD prevalence. The long-term persistence of infectious CWD prions in the environment suggests that feedground management decisions may have long-lasting consequences. Our results indicated tradeoffs in the ability of a management agency to achieve all their objectives, and all management alternatives resulted in significant reductions in elk population size. This report contains the foundational elements for formal decision analysis methods, which can be implemented to help decision makers transparently evaluate the consequences of decision alternatives and identify the set of actions that best achieve agency and stakeholder priorities.

Wyoming↗

USGS2023

Interaction of a legacy groundwater contaminant plume with the Little Wind River from 2015 through 2017, Riverton Processing site, Wyoming

The Riverton Processing site was a uranium mill 4 kilometers southwest of Riverton, Wyoming, that prepared uranium ore for nuclear reactors and weapons from 1958 to 1963. The U.S. Department of Energy completed surface remediation of the uranium tailings in 1989; however, groundwater below and downgradient from the tailings site and nearby Little Wind River was not remediated. Beginning in 2010, a series of floods along the Little Wind River began to mobilize contaminants in the unsaturated zone, resulting in substantial increases of uranium and other contaminants of concern in monitoring wells completed inside the contaminant plume. In 2011, the U.S. Department of Energy started a series of university and Government agency retrospective and field investigations to understand the processes controlling contaminant increases in the groundwater plume. The goals of the field investigations described in this report were to (1) identify and quantify the contaminant flux and potential associated biological effects from groundwater associated with the legacy plume as it enters a perennial stream reach, and (2) assess chemical exposure and potential effects to biological receptors from the interaction of the contaminant plume and the river. Field investigations along the Little Wind River were completed by the U.S. Geological Survey during 2015–17 in cooperation with the U.S. Department of Energy Office of Legacy Management to characterize: (1) seepage areas and seepage rates; (2) pore-water and bed sediment chemistry and hyporheic exchange and reactive loss; and (3) exposure pathways and biological receptors. All data collected during the study are contained in two U.S. Geological Survey data releases, available at https://doi.org/10.5066/F7BR8QX4 and https://doi.org/10.5066/P9J9VJBR . A variety of tools and methods were used during the field characterizations. Streambed temperature mapping, electrical resistivity tomography, electromagnetic induction, fiber-optic distributed temperature sensing, tube seepage meters, vertical thermal sensor arrays, and an environmental tracer (radon) were used to identify areas of groundwater seepage and associated seepage rates along specific sections of the study reach of the river. Drive points, minipiezometers, diffusive equilibrium in thin-film/diffusive gradients in thin-film probes, bed-sediment samples, and equal discharge increment sampling methods were used to characterize pore-water chemistry, estimate hyporheic exchange and reactive loss of selected chemical constituents, and quantify contaminant loadings entering the study reach. Sampling and analysis of surface sediments, filamentous algae, periphytic algae, and macroinvertebrates were used to characterize biological exposure pathways, metal uptake, and receptors. Areas of focused groundwater discharge identified by the fiber-optic distributed temperature sensing surveys corresponded closely with areas of elevated electrical conductivity identified by the electromagnetic induction survey results in the top 5 meters of sediment. During three monitoring periods in 2016, the mean vertical seepage rate measured with tube seepage meters was 0.45 meter per day, ranging from −0.02 to 1.55 meters per day. Five of the 11 locations where vertical thermal profile data were collected along the study reach during August 2017 indicated mean upwelling values ranging from 0.11 to 0.23 meter per day. Radon data collected from the Little Wind River during June, July, and August 2016 indicated a consistent inflow of groundwater to the central part of the study reach, in the area congruous with the center of the previously mapped groundwater plume discharge zone. During August 2017, the greatest attenuation of uranium from reactive loss in pore-water samples was observed at three locations along the study reach, at depths between 6 and 15 centimeters, and similar trends in molybdenum attenuation were also observed. Bed-sediment concentration profiles collected during 2017 also indicated attenuation of uranium and molybdenum from groundwater during hyporheic mixing of surface water with the legacy plume during groundwater upwelling into the river. Streamflow measurements combined with equal discharge increment water sampling along the study reach indicated an increase in dissolved uranium concentrations in the downstream direction during 2016 and 2017. Net uranium load entering the Little Wind River study reach was about 290 and 435 grams per day during 2016 and 2017, respectively. Biological samples indicated that low levels of uranium and molybdenum exposure were confined to the benthos in the Little Wind River within and immediately downstream from the perimeter of the groundwater plume. Concentrations of molybdenum and uranium in filamentous algae were consistently low at all sites in the study reach with no indication of increased exposure of dissolved bioavailable molybdenum or uranium at sites next to or downstream from the groundwater plume. Comparison of the August 2017 results from electromagnetic induction, tube seepage meters, vertical thermal profiling, and pore-water chemistry surveys were in general agreement in identifying areas with upwelling groundwater conditions along the study reach. However, the electroconductivity values measured with electromagnetic induction in the top 100 centimeters of sediment did not agree with sodium concentrations measured in pore-water samples collected at similar streambed depths. Differences and similarities between multiple methods can result in additional insights into hydrologic and biogeochemical processes that may be occurring along a reach of a river system interacting with shallow groundwater inputs. It may be advantageous to apply a variety of geophysical, geochemical, hydrologic, and biological tools at other Uranium Mill Tailings Remedial Action ( https://www.energy.gov/sites/prod/files/2014/10/f19/UMTRCA.pdf ) sites during the investigation of legacy contaminant plume interactions with surface-water systems.

Wyoming↗

USGS2023

Wind-energy development alters pronghorn migration at multiple scales

Migration is a critical behavioral strategy necessary for population persistence and ecosystem functioning, but migration routes have been increasingly disrupted by anthropogenic activities, including energy development. Wind energy is the world's fastest growing source of electricity and represents an important alternative to hydrocarbon extraction, but its effects on migratory species beyond birds and bats are not well understood. We evaluated the effects of wind-energy development on pronghorn migration, including behavior and habitat selection, to assess potential effects on connectivity and other functional benefits including stopovers. We monitored GPS-collared female pronghorn from 2010 to 2012 and 2018 to 2020 in south-central Wyoming, USA, an area with multiple wind-energy facilities in various stages of development and operation. Across all time periods, we collected 286 migration sequences from 117 individuals, including 121 spring migrations, 123 fall migrations, and 42 facultative winter migrations. While individuals continued to migrate through wind-energy facilities, pronghorn made important behavioral adjustments relative to turbines during migration. These included avoiding turbines when selecting stopover sites in spring and winter, selecting areas farther from turbines at a small scale in spring and winter, moving more quickly near turbines in spring (although pronghorn moved more slowly near turbines in the fall), and reducing fidelity to migration routes relative to wind turbines under construction in both spring and fall. For example, an increase in distance to turbine from 0 to 1 km translated to a 33% and 300% increase in the relative probability of selection for stopover sites in spring and winter, respectively. The behavioral adjustments pronghorn made relative to wind turbines could reduce the functional benefits of their migration, such as foraging success or the availability of specific routes, over the long term.

Wyoming↗

USGS2023

Aerial application of organic pellets eliminates Lake Trout recruitment from a primary spawning reef in Yellowstone Lake

Invasive Lake Trout Salvelinus namaycush in the Yellowstone Lake ecosystem have been gillnetted since 1995 to suppress the population and allow for recovery of native Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri . Although gillnetting is effective (Lake Trout population growth rate λ ≤ 0.6 during 2012–2022), the effort only targets free-swimming, age-2 and older Lake Trout. We developed a complementary suppression method using organic (soy and wheat) pellets to cause Lake Trout embryo mortality and reduce recruitment from spawning areas. The entire Carrington Island spawning reef (0.5 ha) was aerially treated with 3.56 and 3.00 kg/m 2 of pellets in 2019 and 2020, respectively. Pellet decomposition caused dissolved oxygen concentrations to decline to lethal levels at 20 cm depth in the substrate, and pellets mostly dissipated from the reef within 12 d. Lake Trout fry trap CPUE was reduced to zero after ice-off each spring after the treatments. Prior to the treatments, 71 fry were captured during 58 trap-nights of effort in 2017–2019. After the treatments, no fry were captured during 273 trap-nights in 2020 and 2021. Lake Trout CPUE in large-mesh gill nets set near Carrington Island in September did not decline during 2017–2021 and fry were again trapped on the reef in spring 2022, suggesting that adults were not deterred from spawning there in the years after the pellet treatments. Complementary methods that increase mortality of prerecruits may allow for a reduction in gill-netting effort and the long-term costs of maintaining Lake Trout population suppression in Yellowstone Lake. Treatment of spawning areas may improve suppression efficiency for Lake Trout and invasive fish populations elsewhere because entire cohorts are targeted while immobile and temporarily concentrated in relatively small areas.

Wyoming↗

USGS2023

Invasive Brook Stickleback Culaea inconstans minimally alters the trophic ecology of four native fishes in Wyoming, USA

Invasive species introductions are a primary threat facing populations of native freshwater fishes. There are multiple mechanisms by which an invader can affect native species, with competition for food resources being one mechanism that can lead to declines in the distribution and abundance of native species. Invaders that are trophic generalists may cause shifts in the trophic ecology of native species and may be better suited for long-term persistence amid environmental stochasticity. Therefore, trophic studies can provide valuable information on the risk an invader poses to native species. Brook Stickleback Culaea inconstans is an invasive fish species in Wyoming whose effect on native fish assemblages is poorly understood. Our goal was to understand the potential for competitive interactions between Brook Stickleback and native fishes. We used stable isotopes of carbon (ẟ 13 C) and nitrogen (ẟ 15 N) to evaluate the feeding ecology of Brook Stickleback relative to four native fishes, and to explore whether native fish isotopic niches changed in sympatry with Brook Stickleback. We hypothesized that the isotopic niche of Brook Stickleback would be larger than that of native fishes, suggesting broader resource use. Additionally, we hypothesized that the isotopic niche of native fish populations sympatric with Brook Stickleback would contract. We did not find support for our hypotheses as the isotopic niche of Brook Stickleback was not substantially different from that of native fishes. Further, the isotopic niche of native fishes was not substantially affected by Brook Stickleback presence. As a result, we do not currently see evidence of Brook Stickleback altering the trophic ecology of native fish species. Our results provide insight to the effects of a small-bodied invasive fish species on native fishes in a previously unstudied region, and can help managers prioritize management actions to conserve native fishes.

Wyoming↗

USGS2023

The dynamic influence of subsurface geological processes on the assembly and diversification of thermophilic microbial communities in continental hydrothermal systems

An accepted paradigm of hydrothermal systems is the process of phase separation, or boiling, of a deep, homogeneous hydrothermal fluid as it ascends through the subsurface resulting in gas rich and gas poor fluids. While phase separation helps to explain first-order patterns in the chemistry and biology of a hot spring’s surficial expression, we know little about the subsurface architecture beneath “phase-separated” pools and the timescales over which phase separation processes occur. Essentially, we have a two-dimensional understanding of a four-dimensional process. By combining geophysical, geochemical, isotopic, and microbiological measurements of two adjacent phase-separated hot springs in Norris Geyser Basin, Yellowstone National Park, we provide a four-dimensional assessment of phase separation processes and their biological manifestation. We uniquely show that Yellowstone’s hydrothermal waters originate from a deep sedimentary aquifer and that both meteoric recharge and shallow reactive transport processes are required to establish the geobiological feedbacks that drive bimodal distributions in the geochemical and microbial composition of hot springs. Specifically, over periods of tens of years, gas-enriched fluids containing volcanic sulfide mix with meteoric waters resulting in microbially-mediated production of sulfuric acid by thermoacidophilic Archaea in the near subsurface. In contrast, over periods of hundreds of years, anoxic residual liquid rises to the surface where it is infused with atmospheric gas fostering Archaea and Bacteria that are largely dependent on oxygen. As such, our results provide formative insight into the causative links between subsurface geological processes, the development of geochemical fluids, and the assembly and diversification of thermophilic microbial communities in hydrothermal systems.

Wyoming↗

USGS2023

Luminescence ages and new interpretations of the timing and deposition of Quaternary sediments at Natural Trap Cave, Wyoming

Natural Trap Cave, located in the Big Horn Mountains of north-central Wyoming, has a history of trapping and preserving a range of North American fauna that plummeted into the deep vertical entrance. These animal remains were buried and preserved within sediments of the main chamber and, in turn, have helped elucidate the procession of faunal dynamics during the latest glacial cycle. The cave location, south of the Laurentide and Cordilleran Ice Sheets, and proximal to Yellowstone, is at an ideal geographical juncture to provide insights to ecological changes in North America. The sediments that the animals are buried in inform us about transport and deposition both inside and outside of the cave that relate to catchment dynamics. We report on a series of optically stimulated luminescence (OSL) ages derived from samples obtained within the cave during excavation work in 2014 and in 2018. We also examine chronology produced by argon, tephrochronology, fission track, and luminescence techniques that have been used for understanding the infilling of the cave. The cave sediment ages and in situ measured gamma spectroscopy as measured in this study helped resolve an improved chronological age model when combined with previous data. The suite of OSL ages is interpreted through the stratigraphic relationships (and vertebrates contained within) which requires the use of an adequate age model; we use either the central age model or minimum age model where appropriate and with justification. Lowest sediments are dated to ∼150 ka with a hiatus at ∼130 to 52 ka. Above this, sediment deposition and entrainment of paleontological materials are representative of Pleistocene and early Holocene times, between 37 ± 6 ka and 7.6 ± 0.5 ka. The stratigraphic architecture suggests that deposition of materials into the cave is episodic and rapid, followed by quiescent periods where hydrologic scour, heavy overland flow , or possibly a cryo-hydrologic process may have altered unit relationships. Thus, the complementary geochronometers and the characteristics of quartz versus feldspar luminescence signals improve temporal interpretations of these complex deposits. This adapted understanding of mixing also sets the stage for future work with the aim to improve our understanding of ages and sources for ash units within these cave deposits. The three ash units recognized in the cave may represent an in-situ reworking of the same ash or may be representative of previously undocumented eruptions from the Yellowstone Caldera.

Wyoming↗

USGS2023

Winners and losers over a ½ century of change in crayfish assemblages of Wyoming, USA

Crayfish have experienced extensive assemblage reorganization as a result of global change, with some species becoming globally invasive and others becoming rare or extinct. We combined historical and contemporary sampling data to determine temporal trends of crayfish assemblages of Wyoming, USA, identifying winners and losers over a ½ century of change (1969–2020). We first documented range expansions of several species, including the Virile Crayfish Faxonius virilis (Hagen, 1870), Ringed Crayfish Faxonius neglectus (Faxon, 1885), and Rusty Crayfish Faxonius rusticus (Girard, 1852) as well as range contractions of the Calico Crayfish Faxonius immunis (Hagen, 1870) and Pilose Crayfish Pacifastacus gambelii (Girard, 1852). We then used multispecies occupancy models to investigate potential mechanisms behind the replacement of F. immunis by F. virilis as the most commonly detected crayfish species in Wyoming over time. We hypothesized that F. virilis is more likely to competitively displace F. immunis from more permanent waterbodies, whereas F. immunis is more likely to persist in more ephemeral habitats because of its superior burrowing ability and tolerance of low dissolved oxygen concentrations. Our occupancy models supported this prediction, with F. immunis occupancy declining at more permanent sites in the presence of F. virilis , but F. immunis occupancy was unaffected by F. virilis in less permanent sites. We also found positive associations of F. virilis occupancy and detection probability with water temperature, suggesting that warmer streams may be more vulnerable to new invasions or spread by this species in nonnative regions of western North America. Our results highlight the value of regular, statewide crayfish surveys through documenting substantial changes in Wyoming’s crayfish assemblage structure that may be driven by habitat-mediated competitive interactions.

Wyoming↗

USGS2023

Redd superimposition mediates the accuracy, precision, and significance of redd counts for cutthroat trout

Redd counts are commonly applied to estimate spawning population size for salmonids and allow for broad spatial and temporal coverage in monitoring efforts. However, the utility of redd counts may be compromised by observation error, particularly with respect to superimposition, where later arriving spawners construct redds overlapping existing redds. Here, we provide a mechanistic evaluation of the effects of superimposition on the error structure and biological significance of redd count data for Yellowstone cutthroat trout ( Oncorhynchus clarkii bouvieri ) spawning within tributaries to the Snake River, Wyoming. We used a Bayesian framework to parse observation error into distinct components and found low detection of redd clusters (i.e., areas of superimposition) was offset by overestimates of the number of redds per cluster, such that observed counts accurately reflected census redd abundance. However, a saturating relationship between redd counts and spawner abundance indicated that counts is best interpreted as effective reproductive effort rather than spawner abundance. Our results provide a mechanistic understanding of redd count data that can be used to assess their application and interpretation for monitoring.

Wyoming↗