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

At least 1,711 records · Page 95Linked to original sources

USGS2026

Fifty years of riverine harmful algal bloom modeling: A global synthesis of approaches, challenges, and opportunities

This systematic literature review critically examines 162 articles on harmful algal bloom (HAB) modeling in riverine systems to uncover persistent gaps, redefine critical challenges, and propose trackable opportunities to advance future modeling efforts. Articles largely focused on site-specific applications (93%) across more than 80 rivers worldwide. Most modeled systems were large, eutrophic rivers with flow modifications or obstructions. Geographic clustering of modeled systems was pronounced, with South Korea accounting for 26% of articles, followed by Europe (25%), United States (21%), and China (12%). Modeling approaches were led by process-based models (59%), though use of data-driven models (37%) increased over time, reflecting advances in computing and monitoring technology. Modeling endpoints varied widely across the articles with many focused on gross measures of algal abundance and fewer representing more refined endpoints like algal toxins or community composition. Furthermore, inconsistent units and taxonomic resolution hindered comparability between models. Datasets used for model development and calibration typically spanned 5 years, with weekly to monthly sampling at 1–10 sites, though durations and site counts were positively skewed. Quantitative metrics of model skill were often absent and included a diverse set of metrics when reported. Across all models, nutrients, light availability, streamflow, algal physiological processes, and water temperature emerged as key predictors, though algal processes were rarely incorporated in data-driven models. Scenario analyses primarily were conducted with process-based models and addressed flow management, whereas forecasting applications were less common and typically used data-driven models. After almost 50 years of riverine HAB modeling, persistent challenges include underrepresentation of benthic habitats, neglect of side-channel and backwater influences, insufficient documentation of river features, and weak linkages between modeled endpoints and potential harms. Addressing these gaps through reporting of contextual information, models from other aquatic settings, benchmark datasets, and community-driven tools could advance riverine HAB modeling towards increased transferability and ultimately operational forecasts.

Water Research↗

USGS2026

Phylogenomic analyses reveal introgression and cryptic speciation in the globally distributed, vector-transmitted pathogen Plasmodium relictum

Establishing species limits is challenging, particularly for pathogens of wildlife. These pathogens can be difficult to sample and culture, and their genome sequencing must often be conducted in the presence of high levels of host DNA. Plasmodium relictum is a mosquito-vectored avian malaria pathogen that is a globally distributed host generalist, comprised of several genetic lineages. We used sequence capture data from 52 P. relictum infections originating from multiple continents to generate a genomic dataset of the pathogen. With this data, we established a robust phylogeny and determined species limits among P. relictum lineages. We generated phylogenomic trees by maximum likelihood and Bayesian methods with multi-species coalescent models and confirmed robustness of the topology by varying the amount of missing data in the analyses. Our results suggest the existence of two cryptic species among the infections we analyzed and provide evidence of genetic introgression between these species. One of the cryptic species, GRW4, devastated the endemic and immunologically naïve avifauna of Hawaii after its introduction to the islands ca. 100 years ago, and so was tested for positive selection in the GRW4 Hawaiian clade. Although we hypothesized it would be released from host selective pressures, we did not find evidence of positive selection in the Hawaiian GRW4 clade, and we discuss possible explanations. Overall, our results underscore the importance of genomic analyses for resolving pathogen species limits and understanding pathogen evolution.

Molecular Phylogenetics and Evolution↗

USGS2026

How to accelerate advances in ecological forecasting

Ecological forecasting offers critical insights for managing natural resources and safeguarding public well-being. Despite growing demand for these forecasts, progress is hindered by fragmented systems, redundant workflows, and limited interoperability. Drawing lessons from weather forecasting and recent successes like the NEON Ecological Forecasting Challenge, shared cyberinfrastructure is important for advancing ecological prediction. By adopting common standards, open-source tools, and scalable architectures, and fostering transdisciplinary collaboration, the ecological forecasting community can overcome technical and institutional barriers. Such investments could accelerate scientific understanding, improve forecast reliability, and empower decisionmakers to anticipate environmental change and respond effectively.

Eos, American Geophysical Union↗

USGS2026

A hybrid approach for revealing headwater hydrology

Coordinated work to compile existing data and apply models pairing physical understanding with machine learning could substantially improve streamflow predictions for little-known headwater basins.

Eos, American Geophysical Union↗

USGS2026

Socio-ecological impacts of the 2025 Los Angeles urban fires on communities, neighborhoods, and homes

Human settlements are increasingly being impacted by urban fires initiated by wildfires. Metrics such as area burned and number of structures destroyed are important, but research often overlooks the socio-ecological complexity of urban fires. We study the impacts of the 2025 Los Angeles fires on two communities at the neighborhood and residential parcel scales. Geospatial analyses and econometric modeling explore the relationships between urban morphology, socio-demographic factors, and home destruction. Here we show that socio-ecological characteristics and scale are key in parsing the dynamics of urban fires. Also, new socio-demographic populations are being affected and urban morphology metrics are more important than vegetation cover. Despite parallels with 19 th and early 20 th century urban conflagrations, understanding these re-emerging urban fires requires transdisciplinary approaches and unique metrics. Investigating the socio-ecological scales and dynamics of urban fires provides a valuable next step towards understanding and adapting to the risk associated with these disasters.

California↗

USGS2026

Extreme droughts shrink suitable habitats and reduce fitness for large mammals in the American West

Droughts are intensifying across the biosphere, yet the consequences of this phenomenon for wildlife habitat suitability and fitness are poorly studied. We analyzed 12 years of GPS telemetry data for three large mammal species—herbivorous mule deer ( N = 2854), omnivorous black bears ( N = 103), and carnivorous cougars ( N = 105)—to evaluate the effects of drought on each species’ habitat selection across a 500,000-km 2 aridity gradient in the interior West, USA. Additionally, we evaluated interannual variation in mule deer reproduction as a function of drought intensity. Severe drought reduced the area of highly selected habitat by 10.0% for mule deer, 14.3% for black bears, and 18.2% for cougars, suggesting stronger negative effects of drought at upper trophic levels. We also found that mule deer fawn recruitment decreased by >34% under extreme drought conditions. Our findings highlight the critical influence of drought on habitat selection of large mammals and common indices of mule deer fitness. Furthermore, we underscore the need for integrating predictions of climate-driven environmental changes into wildlife conservation planning.

Communications Earth & Environment↗

USGS2026

Per- and polyfluoroalkyl substances (PFAS) and other contaminants of concern in tribal waters of Montana

We assessed potential exposures to a broad suite of contaminants (inorganic, organic and microbial) in culturally important surface waters from three watersheds in a northern plains Native American community (Apsáalooke [Crow Tribe of Montana]) in south-central Montana, United States, with water insecurity concerns. Inorganic (37), organic (435) and microbial (3) constituents were assessed in 12 surface water sites from the Pryor Creek ( n = 2), Bighorn River ( n = 2) and Little Bighorn River ( n = 8) valleys. Twenty-six organics, 33 inorganics and Escherichia coli were detected. Despite relatively low concentrations in surface waters within the Crow Reservation, mixture toxicity indicated prevalent chronic ecological effects and human-health secondary contact (recreation) effects at multiple sites. Further, to address Tribal concerns over the prevalence and corresponding risks of per- and polyfluoroalkyl substances (PFAS), we sampled water, sediment, biofilms and fish at a limited number of locations in the Little Bighorn River. Results indicated that PFAS were prevalent in fish tissues, including whole blood and filets, and to a lesser extent in biofilms, despite few detections in water and sediment samples. This is the first attempt to document environmental PFAS contamination within the reservation and the potential human-health concerns for the general population from consumption of recreational/subsistence fish. Overall, this effort provided preliminary information on the contaminant mixtures present and their potential health implications, which can support the protection of community health and culturally meaningful resources across the Crow Reservation.

Montana↗

USGS2026

Transient methylmercury formation during wetland soil rewetting is governed by organic matter availability rather than coagulant history

Rewetting of previously drained wetland soils can induce rapid redox shifts that influence mercury (Hg) cycling and methylmercury (MeHg) production. We investigated how prior exposure to common metal-salt and biopolymer coagulants influences Hg transformations during wetland soil rewetting and whether organic matter (OM) availability modulates these effects. Wetland soils (∼300 µg kg −1 total Hg) were incubated in triplicate soil-water microcosms for 16 days following rewetting. Treatments included soils previously exposed to ferric sulfate, polyaluminum chloride, or a chitosan-based coagulant, alongside untreated controls. Upon rewetting without additional OM, redox potential declined to ∼250 mV, consistent with manganese-reducing conditions, and MeHg concentrations remained relatively low in water (0.05–0.18 ng L −1 ) and soils (1–2 µg kg −1 ) across all treatments. In contrast, addition of algal-derived OM (Spirulina powder) rapidly decreased redox potential to 0–100 mV and produced a short-lived pulse of MeHg formation in all treatments, with aqueous MeHg peaking at ∼30–40 ng L −1 and soil MeHg at ∼6–8 µg kg −1 on days 2–4 before declining. Coagulant treatments increased transient inorganic Hg concentrations in overlying water (45–75 ng L −1 ) relative to controls (∼30 ng L −1 ) but did not enhance higher MeHg production. Results demonstrate that OM-driven redox dynamics, rather than prior coagulant exposure, control transient MeHg production during wetland soil rewetting, highlighting how episodic carbon inputs can regulate mercury transformation in managed and natural wetlands.

California↗

USGS2026

Multireservoir allocation framework considering societal and ecological needs in a time-frequency domain

Existing reservoir management frameworks traditionally consider historical (predam) flow conditions to deliver environmental flows. Such frameworks may not be feasible because current demand and/or climate could be different from predam conditions. Hence, we developed a multireservoir framework that explicitly considers both human water demands and environmental flow requirements to minimize deviations under current hydroclimatic conditions and demand patterns. The multireservoir framework, Generalized Reservoir Analyses using Probabilistic Streamflow (GRAPS), was modified and implemented to solve the problem of minimizing the flow deviations using feasible sequential quadratic programming for three reservoirs in the Chattahoochee River Basin, Southeastern United States, which is known for its imperiled native biodiversity and productive estuarine ecosystem. Our results show that downstream reservoirs in the cascade system are less influenced by upstream reservoirs’ regulation because the downstream reservoirs receive a significant amount of natural flows. By comparing the average wavelet power spectrum at different periodicities between natural flows and downstream releases, we found that the current release policy and modified releases resulted in highly altered flows under shorter periodicities (e.g., less than 2 months) but synchronized flow variance between natural flow and downstream releases at longer periodicities (e.g., greater than 3 years). This framework of linking the multireservoir allocation model through the time–frequency analysis using wavelet power spectrum could not only advance sustainable water management policies to meet water for human and environmental needs but can also add additional value in meeting the downstream environmental demand at desired periodicities.

Alabama, Florida, Georgia↗

USGS2026

Fish introductions related to strong and diversifying effects on zooplankton assemblages in high-elevation mountain lakes

Freshwater environments are threatened by multiple anthropogenic stressors. High-elevation mountain lakes are particularly vulnerable to introduced nonnative fish and nutrient deposition because they were historically fishless and typically oligotrophic. To understand the potential effects of fish introduction and nutrient levels on high-elevation lake ecosystems, we assessed differences in zooplankton size, biomass, and density in 76 alpine and subalpine lakes in the Wind River Range, Wyoming, USA, and related those differences to the presence of introduced trout and to food quality (seston nutrient content) and quantity (chlorophyll a concentration). Trout presence, and to a lesser extent trout species, were the strongest predictors of zooplankton composition. Fishless lakes were dominated by low densities of copepods and other large-bodied taxa, and lakes with introduced trout were dominated by high densities of cladocerans, rotifers, and other small-bodied taxa. These assemblage differences are likely because trout reduce or eliminate all large zooplankton taxa by size-selective predation, including predation on Hesperodiaptomus shoshone (S. A. Forbes, 1893), a keystone species that effectively controls populations of rotifers and small crustacean zooplankton taxa. In contrast, the quantity and quality of seston was not associated with zooplankton assemblages. Zooplankton composition in lakes with Rocky Mountain Cutthroat Trout Oncorhynchus virginalis (Girard, 1856) or Golden Trout Oncorhynchus aguabonita (Jordan, 1892) was highly variable, but in lakes with primarily Brook Trout Salvelinus fontinalis (Mitchill, 1814), zooplankton composition was consistently distinct from that in fishless lakes, suggesting that Brook Trout introductions altered the zooplankton assemblage to a greater extent than Cutthroat or Golden trout did. These results contribute to global evidence that predatory fish introductions fundamentally restructure alpine lake food webs. The slow or incomplete recovery of native zooplankton assemblages following fish removal suggests long-term ecological legacies of fish introductions and highlights the importance of understanding factors that promote resilience in high-elevation lake ecosystems.

Wyoming↗

USGS2026

Higher methanotroph abundance and bottom-water methane in ponds with floating photovoltaic arrays

Floating photovoltaic (FPV) arrays alter the methane (CH 4 ) cycling dynamics of waterbodies on which they are deployed. Here, we investigated dissolved CH 4 dynamics and associated CH 4 cycling microbial communities (methanogens and methanotrophs) in the second year of FPV deployment (70% aerial coverage) in experimental ponds. We found that bottom-water CH 4 concentrations were twice as high in ponds with FPV compared to those without, while surface water CH 4 concentrations were orders of magnitude lower than bottom-waters, but did not differ between treatments. There was no change in the relative abundances of putative sediment methanogens or methanotrophs, but FPV restructured methanogen communities. FPV promoted late-summer methanotroph blooms in the water column, with abundances surpassing 1,000,000 cells mL -1 . We conclude that prolonged periods of CH 4 production in low oxygen FPV ponds favored blooms of methanotrophs, that may mitigate diffusive CH 4 emissions to the atmosphere by consuming dissolved CH 4 .

BioRxiv↗

USGS2026

Development and field testing of a UAS-based software-defined radar for measuring freshwater bathymetry

We provide an overview of an uncrewed aircraft system (UAS)-based software-defined radar (SDRadar) system for high-resolution geophysical observations. The radar transceiver is implemented on a Radio Frequency System-on-Chip (RFSoC) platform, along with an ultra-wideband Vivaldi antenna that has a starting operating frequency of 150 MHz, enabling the system to be used across different applications, including measurements of freshwater bathymetry. In addition to system design and subsystem performance assessments, this paper presents the results of field testing conducted along the Sacramento River near Glenn, California, USA. The radar-derived river depth measurements are compared with ground truth data collected from a crewed boat using an acoustic Doppler current profiler (ADCP). The results show good agreement, with a root mean square error (RMSE) of 0.079 m.

California↗

USGS2026

Satellite observations reveal widespread alteration of river thermal regimes by U.S. dams

Dams are well known to alter river thermal regimes, but assessments of downstream temperature changes have been constrained to single dams, single basins, or specific seasonal windows, thus limiting knowledge of their widespread impacts. We used satellite-based thermal infrared observations to quantify river surface temperature differences up- and downstream of 287 large dams in the United States from 2013 to 2024 across all seasons. We found downstream river temperature differences for the majority (71%) of longitudinal river profiles. These downstream changes were typically warmer (60%), and, on average, were sustained or continued to increase within 20 km downstream of the dam. We also found that the magnitude and frequency of downstream alterations varied by dam type, with 91% of extreme (≥ ±4°C) differences occurring at dams with reservoirs. This work documents the pervasive effects of large dams on downstream ecosystems across all seasons on a national scale.

Science Advances↗

USGS2026

Delayed submarine caldera subsidence creates extreme tsunami hazard

The 2022 Hunga volcano eruption generated one of the largest and most destructive volcanic tsunamis ever recorded. We interpret the timing, nature and relative hazard of volcanic-tsunamigenic processes by combining geophysical, oceanographic, atmospheric, and eye-witness observations of this event. Hydro-acoustic signal ( T waves) detected on seismic stations up to 2600 km away provided a key to discerning tsunami triggers from explosions, volcanic mass flows, and caldera subsidence. The largest tsunami was generated by the first of at least two sudden caldera-subsidence events. This occurred 1 hour after globally detected explosions that produced smaller tsunami. Our results provide rare insights into the rates of caldera subsidence and highlight the complex multiple sources of tsunamis resulting from eruptions of oceanic volcanoes.

Hunga volcano↗

USGS2026

Interacting effects of human presence and landscape modification on birds and mammals

Sustainable human–wildlife coexistence requires a mechanistic understanding of the many ways that humans affect animals. However, progress is hampered by the lack of accessible data measuring the dynamic presence of people. Here, we leverage mobile-device data to disentangle how human presence and landscape modification differentially influence the use of geographic and environmental space for 37 mammal and bird species across the United States. Human presence affected more than 65% of species, with substantial variation across species. For ~60% of species that responded to human activities, the effects were interdependent—animals tended to react more strongly to human presence in less modified habitats. Our results demonstrate that human presence and landscape modification have complex combined effects on wildlife, which need to be considered for effective management.

Science↗

USGS2026

Insights from more than a year of ongoing episodic lava fountaining at Kilauea

Episodic lava fountaining is rare globally, with only three occurrences from Kīlauea (Hawaii) since 1823. Beginning in December 2024, an eruption within the summit crater, Halemaʻumaʻu, has produced 52 fountaining episodes to date, each lasting typically for hours and separated by days to weeks. Although multiple mechanisms have been proposed, fundamental questions remain about how magma reservoir pressure, conduit permeability, and volatile exsolution control fountaining onset. We present a multi-parameter record of episodic fountaining at Kīlauea using modern geochemical, geophysical, and geologic monitoring. These observations revealed systematic correlations between fountaining and summit inflation, enabling unprecedented quantitative forecasts. This eruption will provide new constraints on the timing, evolution, and processes driving episodic fountaining globally, and highlights Kīlauea’s role as a natural laboratory for studying volcanic processes.

Hawaii↗

USGS2026

Mars sample return campaign: Biological risk and a proposed sample safety assessment protocol

Returning surface samples from Mars to Earth has been a major planetary science objective, with the potential for the detection of microbiological life and the possibility of improving our understanding of the origins of life. The National Aeronautics and Space Administration and the European Space Agency assembled a team to assess the level of risk that returned samples could contain potential biohazards. The team was chartered with optimizing previous sample safety assessment strategies, defining what constitutes a biological hazard, developing a protocol to test for biohazards, and establishing a statistical framework to determine if samples may be safe for release from a high-containment facility. This report presents the biological context for a proposed three-step protocol for testing returned samples, including how to determine if microorganisms are present, and if they could be (or were recently) alive.

Applied and Environmental Microbiology↗

USGS2026

Upper Triassic igneous rocks of the southern Kenai Peninsula, Alaska – Prelude to Early Jurassic subduction along the western Wrangellia composite terrane margin

New U–Pb zircon geochronology identifies a latest Triassic (ca 214–201 Ma) igneous suite of tuff, hypabyssal dikes, and a pluton on the southern Kenai Peninsula, Alaska. The igneous suite was emplaced within Upper Triassic sedimentary rocks along the southern margin of Western Wrangellia, the western-most fragment of the Wrangellia composite terrane. The igneous rocks range from mafic (50.6% SiO 2 ) to felsic (78.3% SiO 2 ), characteristically have less than 1.55% K 2 O, and generally have low trace element abundances. The tonalitic and trondhjemitic magmas were largely sourced in mafic-rich lower crust and incompletely assimilated quartz and other mineral xenocrysts are common. Fractionation involving plagioclase and amphibole is indicated for some magmas and composite intrusions and igneous xenoliths indicate magma mixing was possible. Paleozoic and Precambrian inherited zircons and initial 87 Sr/ 86 Sr (0.704103–0.705609) and 143 Nd/ 144 Nd (0.512396–0.512777) ratios indicate that the Western Wrangellia crustal sources are heterogeneous and contain sialic components. The latest Triassic magmatism reflects processes that preceded Early Jurassic subduction along the Wrangellia composite terrane and Pacific Ocean plate boundary. These processes involved heating and melting of mantle lithosphere and lower crust as mantle instabilities accompanied the breaking of the plate boundary linkages. The Late Triassic transition to subduction along the Wrangellia composite terrane margin coincided with the transition to subduction cessation in the Late Triassic arcs of the western Intermontane terranes of Canada. The shift to subduction along the outboard Wrangellia composite terrane margin marks the beginning of the Pacific Ocean–Cordillera plate interactions that came to dominate the tectonic evolution of the northern Cordillera from the Early Jurassic to today.

Alaska↗