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Source-linked reports with geographic coverage including United States.

At least 91 records · Page 5Linked to original sources
USGS2026

Application of novel encounter and predation models to the natural behavior of slimy sculpin Cottus cognatus

Sculpins play a critical mid-trophic role in lacustrine food webs, converting production by benthic and migrating pelagic invertebrates into biomass available to higher trophic levels. Although sculpin diets and habitat choices are relatively well described, much less is known about their in situ behavior which governs trophic interactions and, in part, prey behavior. We measured the natural behavior of slimy sculpin Cottus cognatus in Lake Champlain using video data originally collected to quantify Mysis diluviana abundance in benthic habitat. After characterizing slimy sculpin movement behaviors according to body size, we incorporated these data into encounter and predation rate models at the individual and population levels, the latter based on bottom trawl data from Lake Champlain. Saltatory movement varied with body length in terms of distance traveled, duration traveled, and duration at rest, but strike distances at prey did not vary across individual sculpins. Slimy sculpin predation rate increased with depth and was limited by pursuit time rather than prey availability, and their populations exerted predation rates on Mysis up to 5 predation events/m 2 /day. Assessment of benthic predation risks affords the opportunity to test hypotheses about the role of predation risk in Mysis diel vertical migration (DVM), and DVM more broadly. Furthermore, the methods we describe here can easily be employed for other benthic fishes such as the invasive round goby Neogobius melanostomus .

New York, Vermont↗
USGS2026

Description of multiple cryptic species of Obovaria Rafinesque, 1819 (Bivalvia: Unionida) from the Mississippi Embayment and Gulf coastal rivers of North America

The freshwater mussel genus Obovaria (Bivalvia: Unionidae) has long been recognized as taxonomically challenging due to plastic shell morphology, historical misidentifications, and incomplete geographic sampling across the southeastern United States. Using an integrated approach combining shell morphology, comparative conchology, geographic distribution, and molecular phylogenetic evidence, we revise the taxonomy of Obovaria in the Gulf Coastal Plain and adjacent drainages. We describe five new species: Obovaria sipseyensis sp. nov. from the Tombigbee River basin of Alabama and Mississippi; Obovaria neeskaensis sp. nov. from the White River basin of Arkansas and Missouri; Obovaria pinetorum sp. nov. from the west Gulf Coast drainages of Louisiana and Texas; Obovaria tallahattae sp. nov. from lower Mississippi River tributaries of Mississippi; and Obovaria lumbo sp. nov. from Lake Pontchartrain, Pascagoula River, and Pearl River basins of Louisiana and Mississippi. We further recognize Pseudoon olivarium comb. nov. based on its phylogenetic distinctiveness from Obovaria . Our results reveal previously unrecognized endemism and cryptic diversity within Obovaria , with significant implications for conservation and management. Several species treated herein are rare and geographically restricted, underscoring how basin-specific conservation strategies and accurate taxonomic recognition can guide freshwater mussel recovery efforts.

Mississippi Embayment and Gulf Coastal Plain river↗
USGS2026

Detecting demographic patterns of old coast redwood forests in northern California

Forest demography is difficult to describe accurately. Tree recruitment and mortality are uncommon events, so that rates based on these observations often require long survey periods using large numbers of trees. Demographic rates can scale with tree size, so challenges describing demography are pronounced in coast redwood forests that are dominated by extremely large Sequoia sempervirens . Here, we present 10 years of observations from 15 1-ha plots in unmanaged primary coast redwood forests in northern California. The size distribution of live stems followed a “reverse-J” shape, with many small trees relative to large trees. Sequoia dominated these plots, particularly in terms of stem area. Mortality and recruitment rates varied among common species, with Sequoia having much lower mortality relative to co-occurring conifers and hardwoods. Mortality varied substantially among size classes and taxonomic groups, while little variability in recruitment occurred among taxonomic groups. Mortality rates were consistently greater than recruitment across taxonomic groups during our 10-year observation period. Our area experienced heavy winter storms in 2022–2023 resulting in numerous blowdowns, although mortality still outpaced recruitment when we excluded years affected by the storms. Simulations using current plot data found low statistical power to detect potential future changes in the mortality rate of Sequoia . We consider how these results could inform conservation of old Sequoia forests.

California↗
USGS2026

Predicting streamflow drought in the conterminous United States using machine learning and a donor-gage approach, 1982–2020

Drought is a highly consequential natural disaster that may likely increase in both severity and extent across the conterminous United States (CONUS). The mechanisms affecting the propagation of drought from the atmosphere to streamflow are complex and interactive, making the prediction of streamflow drought difficult with current modeling approaches. Machine learning is an emerging tool in the field of hydrology that may be well-suited to prediction of streamflow drought across large and topographically diverse areas. Here, we train and analyze 3198 random forest models at U.S. Geological Survey streamgages to understand common meteorological drivers of streamflow drought and to define physiographic characteristics of basins sensitive to these drivers. We also develop a novel dynamic regionalization approach using donor gages to predict daily streamflow drought at pseudo-ungaged locations. Our results show that teleconnections, temperature, evaporative demand, and snow–water equivalent are important drivers of streamflow drought in the West, Southwest, and Northern Rocky Mountains (Northern Rockies) regions of the United States, and precipitation and soil moisture are primary drivers of streamflow drought in the Northeast, Southeast, and the Northwest regions. Prediction using dynamic regionalization shows comparable performance to at-site models. This method may be applicable to other hydrologic prediction problems requiring transferability to ungaged locations.

conterminous United States↗
USGS2026

Fire regime shift reveals 17th century socio-ecological change in the Rio Grande del Norte National Monument, New Mexico

Humans have influenced ecosystems for millennia, and social changes can have notable ecological effects. Recent human influence on ecosystems is exemplified by the collapse of fire regimes circa 1900 in the western United States due to increased grazing, fire suppression, and declining Indigenous fire use. Climate can also drive fire regime changes, which is reflected by increasing area burned across the West in recent decades associated with warming and increased aridity. In the southwestern United States during the mid-1600s, large social changes accompanied Spanish colonization. These changes included increases in domestic livestock (e.g., sheep and horses), declines of Indigenous populations and cultural burning, and exploitation of Puebloans that led to the 1680 Pueblo Revolt, an Indigenous uprising that expelled Spanish colonizers for 12 years. The ecological effects of these large social changes are not well studied. The goal of this study was to use tree-ring fire histories to investigate fire dynamics of a sagebrush-dominated landscape in the Rio Grande del Norte National Monument (RGDN) in northern New Mexico, including the effects of historical social and climatic changes. We reconstructed fire history on four forested mountains that rise above the sagebrush/grass plateau. We asked: (1) What was the pre-1900 fire frequency, season, and fire–climate relationship in the RGDN? (2) Was there evidence for fire spread in the sagebrush/grass flats between the mountains? and (3) Did regional social or climate changes influence fire regimes? From 1400 to 1679, we found frequent fire within forests (8–12-year median fire intervals [mfi]) and potential evidence of spreading fire through the sagebrush/grass ecosystem based on greater-than-expected intermountain fire synchrony. However, beginning in the mid-1600s and continuing after the Pueblo Revolt of 1680, there was (1) a significant decline in fire frequency, including 38–166-year mfi and no fire for >350 years at two sites; and (2) only one synchronous fire between mountains. During this 17th century period of socio-ecological change there was no persistent shift in climate. We propose that reduced Indigenous ignitions and increased domestic grazing, which reduced herbaceous fuels and fire spread, are likely causes of the extraordinary early and persistent reduction in fire.

New Mexico↗
USGS2026

Water in, no water out—How a rain garden reduced stormwater at City Hall in Gary, Indiana

Introduction Urban stormwater runoff can be an issue in many communities because it may cause flooding, overwhelm sewage treatment plants, and negatively affect water quality in local streams, lakes, and other waterbodies. Stormwater runoff can be controlled by using "green infrastructure," which consists of engineered structures that imitate nature to collect stormwater runoff, reduce the amount of runoff, and improve water quality. In 2014, the city of Gary, Indiana implemented green infrastructure to reduce the negative effects of urban stormwater on Lake Michigan and its tributaries. From November 2016 to June 2017, the mostly impermeable parking lot in front of Gary City Hall was removed and rebuilt with a rain garden. The U.S. Geological Survey studied how the rain garden reduced stormwater runoff and published results in Scientific Investigations Report 2022–5101.

Indiana↗
USGS2026

Historical changes in streamflows important to diadromous fish in United States coastal regions

Diadromous fish species occupy freshwater habitats (rearing, spawning, migration) for a substantial part of their lives. The quality and quantity of these habitats is mainly driven by thermal and streamflow regimes; therefore, understanding trends in streamflow allows better management of diadromous species and their habitats. We investigated seasonal flows for many basins in two U.S. regions on the Pacific coast and two on the Atlantic coast and computed seasonal trends for eight streamflow metrics for each region from 1973 to 2022 and from 1943 to 2022. In the Atlantic regions, February through May maximum streamflows and frequency and duration of high flows mostly decreased from 1973 to 2022. These trends toward drier conditions coincide with migration windows of multiple diadromous species. Summer low-flow frequency and duration in the two Pacific regions increased (toward drier conditions) in many near-natural basins. More low-flow days can affect species directly through decreased river longitudinal connectivity, which can limit habitat access and food availability. Trends in highly regulated systems differed from trends in near-natural systems, especially in the Pacific regions, because large reservoirs often decrease peak flows and increase low flows. For example, in the southwestern U.S. coastal region, low-flow duration and frequency significantly decreased (wetter) in many regulated basins while near-natural basins were not similarly affected. Our results demonstrate how analysis of environmental flows at regional and seasonal scales can inform future habitat management and restoration plans.

Hydrological Processes↗
USGS2026

Landscape controls river continuum dissolved organic carbon in northeastern Alaska

Rivers draining continuous permafrost landscapes on the North Slope of Alaska span from the mountains to the coast, integrating gradients in vegetation, soil organic matter, and hydrologic flow. We investigated how these landscape transitions influence dissolved organic carbon (DOC) concentrations, radiocarbon ages, and export along the river continuum over seasonal timeframes in northeastern Alaska. Water samples were collected from the Canning River and its tributaries from the spring freshet through late summer via multiple campaigns during 2011–2024. A simulation from the Permafrost Water Balance Model (PWBM) estimated terrain-specific contributions to freshwater and DOC export. River DOC concentrations peaked during the spring and declined in summer, with episodic increases linked to summer rainfall. Summer river DOC concentrations from the Brooks Range remained low (0.41–0.64 mg C L −1 ) but increased downstream (0.5–3.0 mg C L −1 ), becoming younger from the mountains (805 yBP) to the river delta (525 yBP) as flow from DOC-enriched streams draining the foothills (6–18 mg C L −1 ; Modern yBP) entered the Canning. The PWBM simulation revealed that while the mountains dominate the Canning's annual (90%) and spring-summer (88%–93%) freshwater export, the foothills disproportionately influence its annual (56%) and spring-summer (44%–58%) DOC export. DOC yields from the coastal plain were also high but had little influence due to its small contributing area. Our findings highlight the outsized role of the foothills in modulating river-integrated DOC export to coastal ecosystems. Considering the impact of these landscapes on carbon source and runoff will aid in anticipating future DOC fluxes from Arctic rivers.

Alaska↗
USGS2026

Fine-scale factors affecting the abundance and thermal sensitivity of nonnative Brook Trout in coldwater Rocky Mountain streams

The Brook Trout ( Salvelinus fontinalis ) is a globally distributed nonnative species that threatens native salmonids in coldwater streams. Understanding the factors regulating Brook Trout densities in coldwater refugia is critical to effective management, so we investigated (a) fine-scale drivers of Brook Trout abundance and (b) factors affecting their thermal sensitivity in 49 coldwater streams in Idaho. Among the 14 candidate variables evaluated, Brook Trout density was most closely associated with mean August water temperature (dome-shaped response peaking at 11.0°C–11.1°C), wetted width (negative association), gradient (negative association), run habitat (positive association), and substrate size (negative association). Simulations indicated that densities were most sensitive to climate warming in low-velocity habitats, with the largest increases occurring in areas with baseline temperatures of 8.9°C and largest decreases in areas with temperatures of 12.2°C. We discuss our results in the context of Brook Trout behavior, effects on native salmonids, climate warming, and habitat restoration.

Idaho↗
USGS2026

Abundant ticks but limited Borrelia spp. pathogens in Mojave desert tortoise habitat

Ornithodoros ticks, a genus of soft ticks in the family Argasidae, occur worldwide including throughout deserts in the Southwestern United States. In the Mojave Desert, Ornithodoros parkeri and O. turicata are common ectoparasites of Mojave desert tortoises ( Gopherus agassizii ). These two tick species are vectors of Borrelia spp. that cause tick-borne relapsing fever (TBRF) in people. However, the distribution of O. parkeri and O. turicata and TBRF group Borrelia infection prevalence remain poorly known in the Mojave Desert. These ticks are commonly found in desert tortoise burrows. In this study, 1165 ticks were collected in the Mojave Desert, 1164 of those ticks were identified as belonging to the genus Ornithodoros, while the remaining tick was an Otobius species. We used morphologic characteristics and molecular genetic analysis to identify ticks as O. parkeri and O. turicata . Twenty-two of the 1165 tick samples tested positive for TBRF group Borrelia, five of which could be sequenced and were identified as Borrelia turicatae . This study sheds light on the distributions of tick species and pathogens in an understudied ecosystem, the Mojave Desert, and identifies group Borrelia as a potential risk factor in Mojave desert tortoise habitat.

California, Nevada↗
USGS2026

Impacts of transient critical zone evolution on landslide susceptibility and hazard Across the Utuado batholith, Puerto Rico

Landscapes in humid climates often experience rapid chemical and mechanical weathering that can change groundwater fluxes, drainage pathways, and frictional strength via alterations in subsurface mineral composition and matrix porosity. These changes to hillslope critical zone structure and strength should control landslide susceptibility, size, and failure style. Here we test the impact of differential weathering on landslide failure processes by exploiting a natural experiment along the dioritic Utuado batholith in Puerto Rico's Cordillera Central, where a sharp weathering gradient follows an upstream-propagating knickzone into an uplifted shoreline platform that was affected by Hurricane Maria in 2017. Through a combination of landslide mapping, field geophysical and geotechnical surveys, topographic analysis, calibrated stream profile inversion, 3D back-analysis of hillslope strength, and debris-flow inundation assessments, we show that differential weathering induces changes to critical zone structure and consequently landslide susceptibility and hazard. Our mapping reveals that the hurricane-induced landslides preferentially cluster along less weathered hillslopes despite a marked increase in frictional strength. Jointly inverted seismic refraction and electrical resistivity profiles show that the frictionally weak, heavily weathered hillslopes are highly porous and dry, which we posit acts to stabilize slopes through limiting deeper hydrologic connectivity that can produce shallow water tables with destabilizing lateral seepage forces during storms. Debris-flow inundation mapping and analysis reveals that major contributors to debris-flow growth, channel steepness and landslide coalescence, scale linearly with hillslope friction angle. This leads to higher-mobility debris flows along knickzone reaches, which disproportionately affects communities at the base of the plateau.

Puerto Rico↗
USGS2026

National-scale remotely sensed lake surface temperature in the contiguous United States

Temperature is a master variable in aquatic ecosystems. Despite its importance for ecosystem function, our capacity to measure temperature is often limited to focal systems with intensive in situ measurements or larger systems with readily accessible data from disparate data streams. These limitations are consequential for holistically understanding aquatic ecosystem status and change, especially considering that most lakes globally do not have consistent in situ data. To empower researchers with macroscale surface temperature observations, we present the first remotely sensed lake temperature dataset that includes measurements from Landsat 8 made every ~ 16 d for 137,394 lakes of at least 4 ha in surface area throughout the contiguous United States from 2013 through 2025. By aggregating data in a cloud computing framework, the dataset is amenable for continual update, thereby allowing end users to track local-to-continental scale changes in lake water temperature over time.

contiguous United States↗
USGS2026

Forecasting marsh resilience in the Plum Island Estuary: Integrating uncertainty to inform coastal management

Salt marshes provide critical ecosystem services yet face increasing threats from accelerated relative sea-level rise (SLR). The long-term persistence of these habitats depends on their ability to vertically accrete and laterally migrate into adjacent uplands. Predicting the location and viability of these future marsh corridors is therefore a primary challenge for coastal managers; one often hindered by uncertainties in future water levels and topographic data accuracy, particularly in vegetated wetlands where light detection and ranging (lidar) data systematically overestimate elevation. This study applies an uncertainty-informed modeling framework to forecast marsh resilience in the Plum Island Estuary, Massachusetts. We integrated the Sea Level Affecting Marshes Model (SLAMM) with a Monte Carlo error analysis, generating an ensemble of bias-corrected digital elevation models (DEMs) alongside three probabilistic SLR scenarios (Intermediate, Intermediate High, High) through 2100. We synthesized these simulations into a “marsh fate” classification map to distinguish between resilient core habitats, vulnerable zones requiring intervention, and likely migration corridors. While the marsh platform exhibits resilience under Intermediate scenarios, a critical tipping point emerges under the High SLR scenario. In this case, accelerating inundation overwhelms accretion capacities, driving a landscape-scale regime shift. By integrating the interacting uncertainties of SLR trajectories and initial marsh elevation, we project 2100 net marsh coverage outcomes ranging from a 10.5% gain to a 23.2% loss. These results demonstrate that incorporating elevation uncertainty is essential for detecting non-linear threshold behaviors that deterministic models often miss. The resulting framework empowers managers with a spatially explicit tool to prioritize land acquisition and restoration efforts in the face of climate uncertainty.

Massachusetts↗
USGS2026

Perceptions of relational organizing as a tool for human–bear coexistence

Conflict between humans and American black bears ( Ursus americanus ) is a growing concern in North America, especially in wildland–urban interfaces. Beyond ecological drivers, conflict reduction relies on changing human behavior. Neighbor-to-neighbor conversations, also known as relational organizing, may drive social diffusion of coexistence actions. However, little research has explored the behavioral conditions enabling (a) residents to initiate conversations and (b) neighbors to listen and adopt bear-safe practices. Using the capability, opportunity, motivations and behavior (COM-B) framework, we analyzed 34 semi-structured interviews with engaged residents in two western U.S. communities with ongoing coexistence efforts. Results highlight that interviewees have heterogeneous knowledge and skills (capability), are committed to leveraging interpersonal relationships but concerned about protecting these relationships (social opportunity), feel more able to engage in relational organizing with enabling programmatic support and regulatory frameworks (physical opportunity), and are motivated by identity, emotion, and beliefs about consequences.

Colorado, Montana↗
USGS2026

The cost of limited nocturnal roost availability on pre-migratory energy budgets in a central-place foraging shorebird, Numenius hudsonicus (Hudsonian Whimbrel)

Mobile species often travel long distances between the sites they use for different behaviors, such as central-place foragers that make daily commutes between a central roost and foraging sites. For migratory shorebird species that use coastal habitats, the limited availability of suitable nocturnal roost sites can lead individuals to commute long distances to their foraging territories, forcing them to balance the energetic cost of commuting with the need to refuel in between migratory flights. We investigated this potential trade-off in a population of Numenius hudsonicus (Hudsonian Whimbrel) that show wide variation in commute distance between a shared central nocturnal roost and individual foraging territories in coastal South Carolina, USA. We combined high-resolution movement data, behavioral state modeling, and empirical foraging behavior data to assess how increasing commute distances from a central nocturnal roost affect individual daily activity budgets, foraging habitat use, potential net energy gain, and breeding ground departure date. We found that N. hudsonicus that commute farther from their nocturnal roost spend a higher proportion of each day foraging and commuting, and that they delay their departure to the breeding grounds by 3–6 days. Our results indicate that roosting habitat close to foraging areas can reduce the energetic cost of commuting to help shorebirds avoid delays in migratory timing. Thus, protecting, restoring, and creating nocturnal roosting habitat close to foraging areas may enhance successful shorebird migration.

South Carolina↗
USGS2026

Ecological stability of zooplankton communities in changing arctic lakes over three decades

In the Arctic, rapid warming is altering disturbance regimes, creating an urgent need to assess the ecological stability of these relatively pristine ecosystems. The Arctic landscape has thousands of lakes that are experiencing both gradual, persistent disturbances (e.g., warming) and increased frequency and intensity of pulse disturbances (e.g., land-surface failures). To assess the ecological stability of lake communities in a changing environment, we analyzed long-term data (14–39 years) on zooplankton communities and environmental variables from 25 lakes in arctic Alaska. We characterized long-term change and evaluated the resistance and recovery of communities to natural or experimental disturbances. We hypothesized that reference lakes would demonstrate resistance to background environmental change, represented by variable but consistent relative abundances over time, while manipulated or disturbed lakes would show recovery after the disturbance ceased, as represented by directional changes in relative abundance with return to pre-disturbance conditions. Environmental variables including water conductivity, chlorophyll- a , NO 3 − , pH, dissolved oxygen, light extinction, and soluble reactive phosphorus changed directionally through time, suggesting press effects due to climate change. Zooplankton communities were resistant to environmental change in undisturbed lakes, but, despite monitoring lakes for up to 28 years after disturbance, few lakes showed evidence of recovery to pre-disturbance conditions. This lack of recovery may indicate shifting baselines due to environmental change. The variation we did observe was largely due to shifts in species relative abundance rather than in species turnover, and this variability was related to lake depth. Zooplankton communities and environmental variables displayed more interannual variation in shallow (depth ≤ 6 m) lakes than in deep lakes. Overall, our results demonstrate that arctic zooplankton communities have high resistance to the effects of climate change but potentially low recovery or long recovery times to pulse disturbances.

Alaska↗
USGS2026

Assessing low-dose copper treatment for dreissenid mussels: Effects on nontarget organisms

Zebra mussels ( Dreissena polymorpha ), an invasive dreissenid mussel, have been established and caused considerable effects in many North American aquatic ecosystems. In response, copper-based pesticides have been used to manage zebra mussel populations. We evaluated the effects of a low-dose (60 µg Cu/L for 10 d) copper-based molluscicide for zebra mussel suppression on nontarget species in Lake Minnetonka (Minnesota, USA). Specifically, we assessed changes in four fish species, a native mussel species, adult zebra mussels, chlorophyll-a concentrations (as a proxy for phytoplankton productivity), the zooplankton community, and the benthic invertebrate community before and after treatment. Chlorophyll- a concentration increased in both the treated and reference bays 1 and 4 d posttreatment. Non-target zooplankton community composition changed in both bays over the course of this study; zooplankton abundance and diversity initially decreased in the treated bay but gradually recovered and was back to pretreatment and reference bay levels after one year. We observed no significant differences in non-target benthic invertebrate abundance or diversity between the treated and reference bays, although abundance and diversity estimates were dynamic and uncertain. Among caged non-target organisms, copper bioaccumulation was higher in both mussel species than in fish, and among fish, was highest in fathead minnow ( Pimephales promelas ). These findings contribute to our understanding of the potential effects of copper-based pesticides on aquatic ecosystems and provide insights for zebra mussel management.

Minnesota↗