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At least 1,423 records · Page 79Linked to original sources
USGS2019

Patterns of acoustical activity of bats prior to and 10 years after WNS on Fort Drum Army Installation, New York

Previous acoustic surveys, netting, and count data have shown that overall bat activity patterns have shifted among most species between pre- and post-white-nose syndrome (WNS) years in much of North America where WNS has occurred. However, the significance of these changes is based on the species-specific susceptibility to WNS. We used acoustically recorded echolocation passes obtained at Fort Drum, New York to describe changes in bat activity pre-WNS (2004–2007) to post-WNS (2008–2018). We examined seasonal and yearly changes in bat activity as they relate to the presence of WNS at hibernacula near (<25 km) Fort Drum. A priori , we expected that overall activity for communal hibernating species would be less in years following WNS, and migratory bats or those hibernating bats that are less affected by WNS would show no response or a positive response, due to niche relaxation/competitive release. Our results indicated both an overall and seasonal decrease in activity for Myotis spp. post-WNS. For WNS-susceptible species, our results reflect the high level of mortality in regional winter hibernacula post-WNS and possibly variable reproductive effort and recruitment thereafter. Although migratory bats did show increases in post-WNS activity throughout the summer, we found little evidence that community displacement was occurring on a nightly level by any species. The continuous spread of WNS across North America has had strong negative effects on bat populations of affected species, and our research identifies how individual species (both impacted and non-impacted) respond to WNS.

New York↗
USGS2015

Masked expression of life-history traits in a highly variable environment

Differing life-history strategies may act as a constraint on reproductive expression that ultimately limits the ability of individual species to respond to changes in the magnitude or frequency of environmental variation, and potentially underlies the variation often inherent in phenotypic and evolved responses to anthropogenic change. Alternatively, if there are environmental cues that predict reproductive potential, differential expression of life-history strategies may represent differences in the adaptive capacity to optimize current reproductive value given variation in environmental conditions. We compared several aspects of walleye Sander vitreus spawning ecology at two reservoirs that differ in environmental variability (i.e., annual water-level fluctuation) to identify the capacity of phenotypic expression and the corresponding association with age. Despite significant differences in female body and liver masses between reservoirs that differ in environmental variability, we found no difference in reproductive investment measured by egg size and fecundity. Walleye in a highly variable environment appear to exhibit reproductive traits more typical of a short-lived life-history strategy, which may be resultant from the interaction of environmental and anthropogenic pressures. This finding emphasizes the need to identify the degree to which life-history expression represents physiological constraints versus ecological optimization, particularly as anthropogenic change continues to alter environmental conditions.

Great Plains Research↗
USGS2017

Oxygen stable isotopic disparities among sympatric small land snail species from northwest Minnesota, USA

The oxygen isotopic composition (δ 18 O) of land snail shells can be a valuable paleoenvironmental archive if the climatic parameters that influence the isotopic system are fully understood. Previous calibration studies have examined a limited number of species or individuals, and most have focused on larger (> 10 mm) taxa, which do not represent the dominant shell material in the Quaternary fossil record. In this study, we evaluate the δ 18 O values of small land snails (< 10 mm), which are common in modern settings and are often preserved in a wide array of Quaternary geologic and archeologic deposits. Our primary goal was to determine if coexisting species record equivalent isotopic information in their shells, regardless of differences in their ecology, dietary habits, behavior, and/or body size. We collected and analyzed 265 individuals of 11 species from 12 sites in northwest Minnesota (USA), which exhibits extremely abundant and diverse terrestrial malacofauna in North America. We did not observe significant correlations between shell δ 18 O values and the type of ecosystem (forest/grassland) or hydrologic setting (upland/lowland). However, the majority of species differed significantly in shell δ 18 O values. Larger taxa ( Catinella , Succinea , Discus ) consistently yielded higher δ 18 O values than smaller taxa ( Euconulus , Gastrocopta , Hawaiia , Vallonia ), by up to ~ 3‰. These isotopic offsets among sympatric taxa could be attributed to a number of physical, behavioral, and/or evolutionary traits, including the ability of larger species to tolerate drier conditions better than their smaller counterparts, differences in their preferred microhabitats or phylogentic non-independence. Regardless of the reason, our results imply that researchers should not combine isotopic data from different types of land snails without first investigating modern specimens to determine if it is appropriate. Moreover, our data suggest that combining instrumental climate data, a snail flux-balance model, and shell δ 18 O values can help us to better understand the ecology of land snails.

Minnesota↗
USGS2017

Biocrust ecology: Unifying micro- and macro-scales to confront global change

Biological soil crusts (biocrusts) are communities of microbes, lichens and bryophytes living at the soil surface in drylands (Fig. 1; Belnap et al ., 2016). Biocrusts occur on all continents and can comprise a majority of cover in some systems (Belnap et al ., 2016). While species diversity and distributions have long been a research focus, interest in controls on community composition and cover has expanded as biocrusts are increasingly recognized for their roles in ecosystem functioning (Deane-Coe and Stanton, 2017). For example, biocrust organisms can stabilize soils (Belnap et al ., 2016; Faist et al ., 2017), fix atmospheric carbon (C) (Sancho et al ., 2016), and serve as the foremost source of ‘new’ soil nitrogen (N) in drylands, via N 2 fixation (Barger et al ., 2016) These contributions to gross primary production and soil fertility could be quite large, as high-end estimates suggest biocrusts and similar communities of bryophytes and lichens might account for 10% of terrestrial C- and 50% of N-fixation globally (Elbert et al ., 2012). Yet verifying these and other biocrust roles in ecosystem functioning is complicated by limited knowledge of biocrust cover and composition across the vast dryland biome (Ferrenberg et al ., 2017). It was against this backdrop that ‘Biocrust3: the 3 rd International workshop on biological soil crusts’ was held in Moab, UT, USA, on 26-30 September 2016. The workshop brought together over 50 scientists from 21 countries and six continents, and included numerous biocrust science pioneers (Fig. 2). The meeting was notable for its cross-scale focus, discussion of novel molecular and imaging techniques, and sessions on mapping and restoring biocrusts in a changing world. Here, we synthesize a central theme that emerged from Biocrust3, namely the potential for combining cutting edge tools with studies focused on organismal traits, ecosystem functions, and global change biology to advance the frontier of biocrust ecology.

New Phytologist↗
USGS2014

Using scenario planning to evaluate the impacts of climate change on wildlife populations and communities in the Florida Everglades

It is uncertain how climate change will impact hydrologic drivers of wildlife population dynamics in freshwater wetlands of the Florida Everglades, or how to accommodate this uncertainty in restoration decisions. Using projections of climate scenarios for the year 2060, we evaluated how several possible futures could affect wildlife populations (wading birds, fish, alligators, native apple snails, amphibians, threatened and invasive species) across the Everglades landscape and inform planning already underway. We used data collected from prior research and monitoring to parameterize our wildlife population models. Hydrologic data were simulated using a spatially explicit, regional-scale model. Our scenario evaluations show that expected changes in temperature, precipitation, and sea level could significantly alter important ecological functions. All of our wildlife indicators were negatively affected by scenarios with less rainfall and more evapotranspiration. Under such scenarios, habitat suitability was substantially reduced for iconic animals such as wading birds and alligators. Conversely, the increased rainfall scenario benefited aquatic prey productivity and apex predators. Cascading impacts on non-native species is speculative, but increasing temperatures could increase the time between cold events that currently limit expansion and abundance of non-native fishes, amphibians, and reptiles with natural ranges in the tropics. This scenario planning framework underscored the benefits of proceeding with Everglades restoration plans that capture and clean more freshwater with the potential to mitigate rainfall loss and postpone impacts of sea level rise.

Florida↗
USGS2002

Interactions between groundwater and surface water: The state of the science

The interactions between groundwater and surface water are complex. To understand these interactions in relation to climate, landform, geology, and biotic factors, a sound hydrogeoecological framework is needed. All these aspects are synthesized and exemplified in this overview. In addition, the mechanisms of interactions between groundwater and surface water (GW-SW) as they affect recharge-discharge processes are comprehensively outlined, and the ecological significance and the human impacts of such interactions are emphasized. Surface-water and groundwater ecosystems are viewed as linked components of a hydrologic continuum leading to related sustainability issues. This overview concludes with a discussion of research needs and challenges facting this evolving field. The biogeochemical processes within the upper few centimeters of sediments beneath nearly all surface-water bodies (hyporheic zone) have a profound effect on the chemistry of the water interchange, and here is where most of the recent research has been focusing. However, to advance conceptual and other modeling of GW-SW systems, a broader perspective of such interactions across and between surface-water bodies is needed, including multidimensional analyses, interface hydraulic characterization and spatial variability, site-to-region regionalization approaches, as well as cross-disciplinary collaborations.

Hydrogeology Journal↗
USGS2023

Future marsh evolution due to tidal changes induced by human adaptation to sea level rise

With sea level rise threatening coastal development, decision-makers are beginning to act by modifying shorelines. Previous research has shown that hardening or softening shorelines may change the tidal range under future sea level rise. Tidal range can also be changed by natural factors. Coastal marshes, which humans increasingly depend on for shoreline protection, are ecologically sensitive to tidal range. Therefore, it is critical to examine how changes in tidal range could influence marsh processes. A marsh accretion model was used to investigate the ecological response of a San Francisco Bay, California, USA marsh to multiple tidal range scenarios and sea level rise from 2010 to 2100. The scenarios include a baseline scenario with no shoreline modifications in the estuary, a shoreline hardening scenario that amplifies the tidal range, and 14 tidal range scenarios as a sensitivity analysis that span tidal amplification and reduction of the baseline scenario. The modeling results expose key tradeoffs to consider when planning for sea level rise. Compared to the baseline, the hardening scenario shows minor differences. However, further tidal amplification prolongs marsh survival but decreases Sarcocornia pacifica cover, an important species for certain threatened wildlife and an effective attenuator of wave energy. Conversely, tidal reduction precipitates marsh drowning but shows gains in Sarcocornia pacifica cover. These mixed impacts of tidal amplification and reduction shown by the model indicate potential tradeoffs in relation to marsh survival, habitat characteristics, and shoreline protection. This study suggests the need for a cross-sectoral, regional approach to sea level rise adaptation.

California↗
USGS2020

The role of sand lances (Ammodytes sp.) in the Northwest Atlantic Ecosystem: A synthesis of current knowledge with implications for conservation and management

The American sand lance ( Ammodytes americanus , Ammodytidae) and the Northern sand lance ( A. dubius , Ammodytidae) are small forage fishes that play an important functional role in the Northwest Atlantic Ocean (NWA). The NWA is a highly dynamic ecosystem currently facing increased risks from climate change, fishing and energy development. We need a better understanding of the biology, population dynamics and ecosystem role of Ammodytes to inform relevant management, climate adaptation and conservation efforts. To meet this need, we synthesized available data on the (a) life history, behaviour and distribution; (b) trophic ecology; (c) threats and vulnerabilities; and (d) ecosystem services role of Ammodytes in the NWA. Overall, 72 regional predators including 45 species of fishes, two squids, 16 seabirds and nine marine mammals were found to consume Ammodytes . Priority research needs identified during this effort include basic information on the patterns and drivers in abundance and distribution of Ammodytes , improved assessments of reproductive biology schedules and investigations of regional sensitivity and resilience to climate change, fishing and habitat disturbance. Food web studies are also needed to evaluate trophic linkages and to assess the consequences of inconsistent zooplankton prey and predator fields on energy flow within the NWA ecosystem. Synthesis results represent the first comprehensive assessment of Ammodytes in the NWA and are intended to inform new research and support regional ecosystem‐based management approaches.

Northwest Atlantic↗
USGS2021

Iñupiaq knowledge of polar bears (Ursus maritimus) in the southern Beaufort Sea, Alaska

Successful wildlife management depends upon coordination and consultation with local communities. However, much of the research used to inform management is often derived solely from data collected directly from wildlife. Indigenous people living in the Arctic have a close connection to their environment, which provides unique opportunities to observe their environment and the ecology of Arctic species. Further, most northern Arctic communities occur within the range of polar bears ( nanuq , Ursus maritimus ) and have experienced significant climatic changes. Here, we used semi-structured interviews from 2017 to 2019 to document Iñupiaq knowledge of polar bears observed over four decades in four Alaskan communities in the range of the Southern Beaufort Sea polar bear subpopulation: Wainwright, Utqiaġvik, Nuiqsut, and Kaktovik. All but one of 47 participants described directional and notable changes in sea ice, including earlier ice breakup, later ice return, thinner ice, and less multiyear pack ice. These changes corresponded with observations of bears spending more time on land during the late summer and early fall in recent decades—observations consistent with scientific and Indigenous knowledge studies in Alaska, Canada, and Greenland. Participants noted that polar bear and seal body condition and local abundance either varied geographically or exhibited no patterns. However, participants described a recent phenomenon of bears being exhausted and lethargic when arriving on shore in the summer and fall after extensive swims from the pack ice. Further, several participants suggested that maternal denning is occurring more often on land than sea ice. Participants indicated that village and regional governments are increasingly challenged to obtain resources needed to keep their communities safe as polar bears spend more time on land, an issue that is likely to be exacerbated both in this region and elsewhere as sea ice loss continues.

Alaska↗
USGS1975

The geologic story of Isle Royale National Park

Isle Royale is an outstanding example of relatively undisturbed northwoods lake wilderness. But more than simple preservation of such an environment is involved in its inclusion in our National Park System. Its isolation from the mainland provides an almost untouched laboratory for research in the natural sciences, especially those studies whose very nature depends upon such isolation. One excellent example of such research is the intensive study of the predator-prey relationship of the timber wolf and moose, long sponsored by the National Park Service and Purdue University. In probably no other place in North America are the necessary ecological conditions for such a study so admirably fulfilled as on Isle Royale. The development of a natural laboratory with such conditions is ultimately dependent upon geologic processes and events that although not unique in themselves, produced in their interplay a unique result, the island archipelago as we know it today, with its hills and valleys, swamps and bogs the ecological framework of the plant and animal world. Even the most casual visitor can hardly fail to be struck by the fiordlike nature of many of the bays, the chains of fringing islands, the ridge-and-valley topography, and the linear nature of all these features. The distinctive topography of the archipelago is, of course, only the latest manifestation of geologic processes in operation since time immemorial. Fragments of geologic history going back over a billion years can be read from the rocks of the island, and with additional data from other parts of the Lake Superior region, we can fill in some of the story of Isle Royale. After more than a hundred years of study by man, the story is still incomplete. But then, geologic stories are seldom complete, and what we do know allows a deeper appreciation of one of our most naturally preserved parks and whets our curiosity about the missing fragments.

Michigan↗
USGS2017

Canyons microbiology studies

Off the eastern coast of the United States, several deep canyons cut through the continental shelf, acting like funnels to move sediment from the shelf out to the deep seafloor. Exposed rock outcrops and ledges along the walls of these canyons provide important habitat for deepsea corals and sponges. Although a few scientific expeditions have visited these canyons in the 1970s (Hecker and Blechschmidt 1979, Hecker et al. 1980), their purpose was mainly to map the contours and capture photographs of the bottom using manned submersibles and towed cameras. Our knowledge of the biodiversity in these complex ecosystems is limited; we know little about the macrofauna (e.g., fishes, crabs, sponges, and deepsea corals) and even less about the microbiota. The research described in this report was conducted from 2011 to 2015 as part of the Bureau of Ocean Energy Management (BOEM) study, entitled “Atlantic Deepwater Canyons” study. This work used molecular and microbiological techniques to examine the microbial ecology and diversity associated with Baltimore and Norfolk canyons. Specifically, this work focused on the microbial ecology of four species of octocorals (Acanthogorgia aspera, Anthothela grandiflora, Paramuricea placomus, and Primnoa resedaeformis), the microbial diversity in sediments within and outside the canyons, and a settling plate experiment designed to characterize microbial biofilm formation on a variety of hard substrates.

OCS Study↗
USGS2022

Golden Eagle (Aquila chysaetos)

The golden eagle ( Aquila chrysaetos ) is commonly recognized as an indicator of ecosystem health and was selected as an important indicator species for the ecological health of lands owned and managed by East Bay Stewardship Network (Network) partner agencies within the area of focus for this project (See map, Chapter 1). Based on national conservation goals and past and current golden eagle research in the area of focus, the desired condition and trend for this indicator species are to: (1) maintain or improve site occupancy by territorial pairs (i.e., the proportion of sites surveyed with at least 1 pair of eagles), (2) maximize reproductive rate (i.e., the proportion of sites surveyed with at least 1 pair of productive eagles), and (3) minimize the occurrence of territorial subadults in the local breeding population. The condition and trend in these three primary metrics were assessed for golden eagles in the area of focus using data from a large-scale demographic study conducted in 2014–2021 by the U.S. Geological Survey (USGS) and others. Overall, we found a condition of “caution” and an “unchanging” trend for golden eagles in the area of focus. Analyses of site occupancy and reproductive rate indicated that the local breeding population was unchanging (i.e., no evidence of increasing or decreasing time trends in these metrics during 2014–2021). However, a consistently high occurrence of territorial subadults (22%–35%) has been observed at breeding territories near the Altamont Pass Wind Resource Area (APWRA) relative to occupied territories monitored in surrounding regions (~3%). The heightened occurrence of territorial subadults suggested a possible increase in the adult mortality rate of territorial eagles occupying the Mt. Diablo Range and Mt. Hamilton subregions in the area of focus. Thus, although no trends were detected in site occupancy or reproductive rate, caution is warranted given the high observed frequency of territorial subadults, which was predominately associated with pairs monitored near the APWRA. The USGS golden eagle study was conducted during a period of prolonged and severe drought in the area of focus, which has been shown elsewhere to reduce the reproductive rate of golden eagles. Although we detected no trends in reproductive rate, we identified a condition of “caution” for this metric in the area of focus given that annual estimates were relatively low during the study period, which primarily included years of severe drought conditions in west-central California. A primary goal of the analysis was to provide a benchmark against which managers can measure future changes and understand the likely trajectory of this species. Baseline data and analyses provided here can be used to identify projects that could help support golden eagle conservation. Given the constraint of using only existing and available data, this evaluation also identified areas where not enough was known to draw meaningful conclusions. Gaps in our understanding include the long-term effects of repeated, extreme climate events (e.g., drought and wildfire) on golden eagle demographics and population sustainability, refined estimates of eagle survivorship and sources of mortality, and whether the APWRA represents a population sink for golden eagles within the northern Diablo Range and surrounding regions. These are described as data gaps at the end of this chapter and may be areas to focus on for future research and collaborations among land managers.

Book chapter↗
USGS2024

A guide to environmental DNA extractions for non-molecular trained biologists, ecologists, and conservation scientists

Ecologists, biologists, and conservation scientists are increasingly interested in the use of environmental DNA (eDNA) data for research and potentially decision-making. While commercial DNA extraction kits are typically user-friendly and accessible, they may fail to deliver the desired results with inherently complex eDNA samples, necessitating protocol optimization or educated selection of alternative approaches. To this end, knowledge of the basic steps and principles of DNA extractions is essential, but traditional education tracks in ecology, conservation, and environmental management typically do not include in-depth training in molecular methods. The primary objective of this paper is to enable scientists with an ecological background and limited molecular training to understand the four key steps of eDNA isolations, and to use this expertise to their advantage. We describe the purpose of commonly used reagents and chemicals, point out alternatives for each key step, explain the impact of certain choices regarding isolation approaches on DNA integrity and purity, and highlight the possibility of a tailor-made “mix and match” approach. We anticipate that this paper will enable field ecologists to develop a deeper understanding of the mechanisms and chemistry underlying eDNA extractions, thus allowing them to make informed decisions regarding the best eDNA extraction method for their research goals. Our intention is not to provide comprehensive, step-by-step protocols, but to offer guiding principles while highlighting alternative solutions. Finally, we hope that this paper will act as a useful resource to support knowledge transfer and teaching.

Environmental DNA↗
USGS2026

Ecological diffusion models are still useful in ecology

Context Connecting animal movement across scales—both among spatial scales and between individual and population level processes—is a central theme in ecology, including the sub-fields of movement and landscape ecology. However, most modeling frameworks operate at either the individual (Lagrangian) or population (Eulerian) level. Objectives We aimed to review how a partial differential equation (PDE) known as the ecological diffusion equation (EDE) offers connections among the scales of animal movement and how it can be embedded in commonly used statistical frameworks (e.g., hierarchical models) and fit to multiple types of data, such as count, presence-only, presence-absence, and telemetry data. In doing so, we also highlight emerging and promising avenues of research related to statistical EDE models. Methods We present how the EDE is derived from a simple set of first principles, can be used to represent both individual animal movement and spatiotemporal population dynamics, and can be fit to data by being applied in a hierarchical statistical framework. Finally, we review literature on recent applications and advances related to EDE models. Results In presenting the derivation of the EDE and reviewing recent advances and applications of EDE models, we established that the EDE can enable a mechanistic understanding of animal movement across scales, as well as the integration of multiple types of data. We also identified a number of topics where EDE models can be advanced to gain additional ecological insight. Conclusions Ecological diffusion is a process that emerges naturally from first principles governing animal movement and can be used to model both individual and population-level spatiotemporal dynamics. Statistical EDE models are related to other modeling frameworks, such as species distribution models, occupancy models, and step-selection analysis. The flexibility of hierarchical statistical modeling allows combining different types of data collected on movement and population dynamics, and the theoretical underpinnings of the EDE allow it to connect ecological processes occurring at fine and coarse spatial scales, as well as individual animal movement and population dynamics.

Landscape Ecology↗
USGS2026

Small creatures, big challenge: A review of current knowledge and assessment of research needs to inform water withdrawal management for the Duck River's freshwater mussel fauna

The Duck River is a remarkable national resource, boasting outstanding biodiversity (Ahlstedt et al. 2017). It contains 151 fish species, over 60 mussel species, and 22 snail species, many of which are federally listed (Etnier and Starnes 1993; Johnson et al. 2013; Ahlstedt et al. 2017; Womble and Rosenberger 2025a). The Duck River watershed is at a pivotal time in its management and ecological history due to significant growth in human population and economic activity. The consequent increase in surface water demand presents challenges for sustainable water resource management. The Tennessee Department of Environment and Conservation (TDEC) has permitted or proposed to permit eight water utilities to withdraw over 77 million gallons per day (mgd) from the Duck River, representing > 40% increase from previously permitted amounts (USFWS 2025). On November 20, 2024, Tennessee Governor Bill Lee signed Executive Order No 108 to ensure long-term stability of the Duck River watershed through balancing economic growth, water resource management, and environmental conservation. Some primary components of this plan are the creation of a Comprehensive Regional Drought Management Plan, the development of a Habitat Conservation Plan, and the establishment of the Duck River Watershed Planning Partnership (DRWPP). Although the planning partnership is not focused on a sole aspect of the Duck River, but the watershed as a whole, the mussel assemblages of the Duck River have been a particular focus due to their importance in providing ecosystem services, sensitivity to water quality, conservation status, and sensitivity to periodic drought conditions in this system. With multiple state and federal agencies involved in managing the Duck River’s unique water resources, a focused review on how future water management could affect the freshwater mussel communities in the Duck River will contribute to this process. Our objectives of this review are to: 1. Review the effects of changing flow regimes on mussels, with emphasis on the effect of droughts/low flows, highlighting key processes/factors affecting mussels. 2. Highlight critical data gaps that could allow future, evidence-based water management decisions in this system. 3. Propose research topics to address critical data gaps and enable evidence-based water management decisions that consider the needs of freshwater mussels. Freshwater mussels are a critical component of riverine ecosystems, providing ecosystem services including water filtration, nutrient cycling, and habitat provision (Vaughn et al. 2004; Haag 2012) that benefit human communities. Environmental flows, also referred to as ecological or e-flows, refer to the quantity, timing, and quality of water flows necessary to maintain the ecological health of rivers, wetlands, and other aquatic ecosystems (Acreman and Dunbar 2004; Acreman 2016). For freshwater mussels, environmental flows include maintaining a flow regime and associated water quality regimes that are favorable for both juveniles and adults while also seasonally supporting host fish and the survival of settling glochidia (i.e., larval mussels) in suitable environments (Gates et al. 2015). Freshwater mussels are adapted to the natural flow regime of their native streams, including seasonal variability in flows. As sedentary filter feeders, mussels require adequate water flow to provide oxygen and food (Allen and Vaughn 2009); however, they also require periods of low flow to increase access to fish hosts and to ensure juveniles are not displaced (Gates et al 2015). Mussels are sensitive to water quality conditions, including pollutants, sedimentation, and artificial alterations of temperature and pH (Strayer and Malcom 2012). Mussel community characteristics, including presence, abundance, and species richness, generally increase with stream size (e.g., stream order); however, responses to changes in flow conditions are often species-specific, and the magnitude and timing of extreme flow conditions have more predictive power for mussel community response than general changes in flow (Lopez and Vaughn 2021). Complex hydraulic variables, such as relative shear stress and Reynolds number, can be strong predictors of mussel community responses because they combine simple hydraulic variables (e.g., velocity, depth) with stream channel characteristics, such as substrate composition and dynamics. Droughts directly and indirectly affect mussels by influencing their physiology, behavior, reproduction, and ecosystem roles. Mass mussel die-offs during droughts and low water conditions are widely documented (Vaughn et al. 2015; Sousa et al. 2018; Dubose et al. 2019). Droughts can also lead to a shift in mussel community composition, with drought-tolerant species becoming more dominant while more sensitive species experience declines (Galbraith et al, 2010; Lopez et al. 2022; Vaughn and Atkinson 2025). Droughts affect mussels through direct mortality from stranding as well as physiological stress from altered water temperature and quality, reduced habitat and food availability and quality, increased predation and competition, disruption of reproductive cycles, and increased susceptibility to disease and pathogens. Although the effects of droughts, water withdrawals, and low flow conditions on mussels are an increasing area of study, there is a general paucity of data-driven consensus regarding optimal mitigation approaches and strategies (Cushway et al. 2024). Long-term management decisions regarding water withdrawals, particularly during extended or multi-year drought conditions, may consider factors beyond direct mortality such as the sublethal effects of drought and low flow conditions on freshwater mussels for a comprehensive understanding of the effects of prolonged low flows on freshwater mussels and aquatic communities.

Tennessee↗
USGS2005

Assessing uncertainty in ecological systems using global sensitivity analyses: A case example of simulated wolf reintroduction effects on elk

Often landmark conservation decisions are made despite an incomplete knowledge of system behavior and inexact predictions of how complex ecosystems will respond to management actions. For example, predicting the feasibility and likely effects of restoring top-level carnivores such as the gray wolf ( Canis lupus ) to North American wilderness areas is hampered by incomplete knowledge of the predator-prey system processes and properties. In such cases, global sensitivity measures, such as Sobol’ indices, allow one to quantify the effect of these uncertainties on model predictions. Sobol’ indices are calculated by decomposing the variance in model predictions (due to parameter uncertainty) into main effects of model parameters and their higher order interactions. Model parameters with large sensitivity indices can then be identified for further study in order to improve predictive capabilities. Here, we illustrate the use of Sobol’ sensitivity indices to examine the effect of parameter uncertainty on the predicted decline of elk ( Cervus elaphus ) population sizes following a hypothetical reintroduction of wolves to Olympic National Park, Washington, USA. The strength of density dependence acting on survival of adult elk and magnitude of predation were the most influential factors controlling elk population size following a simulated wolf reintroduction. In particular, the form of density dependence in natural survival rates and the per-capita predation rate together accounted for over 90% of variation in simulated elk population trends. Additional research on wolf predation rates on elk and natural compensations in prey populations is needed to reliably predict the outcome of predator–prey system behavior following wolf reintroductions.

Ecological Modelling↗
USGS2017

What determines water temperature dynamics in the San Francisco Bay-Delta system?

Water temperature is an important factor determining estuarine species habitat conditions. Water temperature is mainly governed by advection (e.g., from rivers) and atmospheric exchange processes varying strongly over time (day-night, seasonally) and the spatial domain. On a long time scale, climate change will impact water temperature in estuarine systems due to changes in river flow regimes, air temperature, and sea level rise. To determine which factors govern estuarine water temperature and its sensitivity to changes in its forcing, we developed a process-based numerical model (Delft3D Flexible Mesh) and applied it to a well-monitored estuarine system (the San Francisco Estuary) for validation. The process-based approach allows for detailed process description and a physics-based analysis of governing processes. The model was calibrated for water year 2011 and incorporated 3-D hydrodynamics, salinity intrusion, water temperature dynamics, and atmospheric coupling. Results show significant skill in reproducing temperature observations on daily, seasonal, and yearly time scales. In North San Francisco Bay, thermal stratification is present, enhanced by salinity stratification. The temperature of the upstream, fresh water Delta area is captured well in 2-D mode, although locally—on a small scale—vertical processes (e.g., stratification) may be important. The impact of upstream river temperature and discharge and atmospheric forcing on water temperatures differs throughout the Delta, possibly depending on dispersion and residence times. Our modeling effort provides a sound basis for future modeling studies including climate change impact on water temperature and associated ecological modeling, e.g., clam and fish habitat and phytoplankton dynamics.

California↗
USGS2025

Estimating polar bear (Ursus maritimus) age based on an epigenetic DNA methylation clock

Knowledge of animal age is essential to wildlife managers for obtaining meaningful and accurate insights into demographic parameters. A common approach to aging wildlife, including bears ( Ursus spp.), has been extracting a tooth during physical capture and counting the cementum annuli. Limitations to tooth-based aging include questionable accuracy and differing results based on the observer and laboratory. DNA methylation-based epigenetic aging clocks have been developed for many species but not yet for polar bears ( Ursus maritimus ). We generated DNA methylation data from whole blood samples ( n = 109) obtained during live capture operations from polar bears of known age in the Chukchi Sea and southern Beaufort Sea subpopulations. We used these samples to calibrate a species-specific epigenetic clock to estimate polar bear chronological age from DNA methylation (DNAm) age. The final polar bear clock was highly accurate ( r = 0.97) with a median absolute error of approximately 9 months. We applied the polar bear clock to 74 blood samples from live-captured polar bears with a cementum annuli-estimated age. Predicted age estimates for these bears ranged from 1.43 to 18.63 years compared to the estimated tooth age range of 3.23–25.27. These epigenetic clocks can be used for polar bear research and management where accurate estimates of age are needed for estimating demographic parameters.

Ecology and Evolution↗