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At least 883 records · Page 49Linked to original sources

USGS2002

Submarine landslides: advances and challenges

Due to the recent development of well-integrated surveying techniques of the sea floor, significant improvements were achieved in mapping and describing the morphology and architecture of submarine mass movements. Except for the occurrence of turbidity currents, the aquatic environment (marine and fresh water) experiences the same type of mass failure as that found on land. Submarine mass movements, however, can have run-out distances in excess of 100 km, so their impact on any offshore activity needs to be integrated over a wide area. This great mobility of submarine mass movements is still not very well understood, particularly for cases like the far-reaching debris flows mapped on the Mississippi Fan and the large submarine rock avalanches found around many volcanic islands. A major challenge ahead is the integration of mass movement mechanics in an appropriate evaluation of the hazard so that proper risk assessment methodologies can be developed and implemented for various human activities offshore, including the development of natural resources and the establishment of reliable communication corridors. Key words : submarine slides, hazards, risk assessment, morphology, mobility, tsunami. Le dveloppement rcent de techniques de levs hydrograhiques pour les fonds marins nous a permis d'atteindre une qualit ingale dans la cartographie et la description des glissements sous marins. l'exception des courants de turbidit, on retrouve dans le domaine aquatique les mmes types de mouvements de terrain que sur terre. Par contre, les glissements sous-marins peuvent atteindre des distances excdant 100 km de telle sorte que leur impact sur les activits offshore doit tre pris en compte sur de grandes tendues. La grande mobilit des glissements sous-marins n'est pas encore bien comprise, comme pour le cas des coules de dbris cartographies sur le cne du Mississippi ainsi que pour les grandes avalanches rocheuses sous-marines retrouves au pourtour des les volcaniques. Un dfi majeur auquel nous faisons face est celui de dterminer les alas associs aux divers types de mouvements sous-marins ainsi que les risques associs l'activit humaine, telle que l'exploitation des ressources naturelles et l'tablissement de routes de communications fiables. Mots cls : glissements sous-marins, morphologie, ala, risque, mobilit, tsunami.

Canadian Geotechnical Journal↗

USGS2026

VegET evapotranspiration for Africa: Continental-scale simulation, multi-product evaluation, and drought assessment

Study region Continental Africa, encompassing diverse climatic zones—tropical, arid, and temperate—and spanning major transboundary river basins such as the Nile, Niger, Congo, Volta, and Zambezi River Basins. The region exhibits pronounced hydroclimatic gradients and heterogeneous land use systems ranging from rainfed croplands and rangelands to dense tropical forests and irrigated schemes. Study focus Actual evapotranspiration (ETa) is a central component of the terrestrial water balance, governing the redistribution of water and energy between the land surface and the atmosphere. Accurate estimation of ETa at continental scale is critical for hydrological monitoring, water resource management, and climate adaptation, as well as for quantifying water, energy, and carbon fluxes that underpin sustainable development. In this study, we applied the agro-hydrologic VegET v2 model to simulate a new, high-resolution, continental-scale ETa dataset for Africa (2000–2021). The model results were benchmarked against four widely used remote sensing-based products—MODIS16 v6.1, SSEBop v6.1, WaPOR v3, and GLEAM v4.1a—across major climate zones, land use types, and River Basins, providing a comprehensive multi-product evaluation of evapotranspiration dynamics across the continent. New hydrological insights for the region Validation against eddy covariance flux tower observations at eight representative sites confirmed that VegET v2 accurately reproduces the seasonal dynamics of observed ETa, achieving a correlation (r) of 0.8 and an RMSE of 25 mm month⁻¹ —accuracy that is comparable to or higher than accuracies of satellite-based products MODIS16, SSEBop, and GLEAM. This study represents one of the first Africa-wide hydrological simulations of ETa, extending the VegET model beyond basin-scale applications. Intercomparisons reveal that VegET aligns closely with MODIS16, SSEBop, and GLEAM in humid and tropical regions (r = 0.80–0.90; RMSE < 20 mm month⁻¹), while greater discrepancies appear in arid and semi-arid zones, where WaPOR tends to overestimate ETa (RMSE ≥ 28 mm month⁻¹). Despite these differences, VegET effectively captures spatial and temporal ETa variability across rainfed croplands, forests, and savannas, supporting its utility in regional water balance assessments, water accounting, and drought monitoring. A key application of VegET v2 is the Evapotranspiration Deficit Index (ETDI), derived by integrating VegET-based ETa with potential evapotranspiration (PET) to quantify water stress. ETDI successfully captured major drought episodes across Africa, including persistent Sahelian and southern African dry spells, the 2020–2021 winter drought in the Maghreb, and the 2018–2019 austral summer drought in southern Africa, while identifying positive anomalies over central Africa indicative of recurrent wetness. These results underscore VegET’s capability as a hydrologically consistent, operational tool for continental ETa monitoring and drought assessment, offering support for basin-scale water balance studies, food security planning, and climate resilience across Africa’s diverse hydrological environments.

Journal of Hydrology: Regional Studies↗

USGS2019

Distribution and movement of steelhead and anglers in the Clearwater River, Idaho

Steelhead Oncorhynchus mykiss is a species that is of high economic value that supports popular sport fisheries across the Pacific Northwest. The Clearwater River in Idaho provides a trophy steelhead fishery, and it is home to both wild- and hatchery-origin steelhead. To manage the fishery effectively, information is needed about the spatial and temporal overlap of wild and hatchery steelhead in the Clearwater River, as well as the activity of anglers. We conducted a radiotelemetry study to describe the distribution of steelhead and their final fate in the Clearwater River, and creel surveys were used to describe the distribution of anglers. In total, 289 wild (Potlatch River and Lochsa River) and hatchery (from Dworshak National Fish Hatchery and South Fork Clearwater River) steelhead were radio-tagged at Lower Granite Dam, 51 river kilometers (rkm) downstream from the mouth of the Clearwater River. Fish were monitored upon their entry into the Clearwater River by using mobile tracking surveys (boat and vehicle) and stationary antennas. The majority of wild and hatchery steelhead arrived in the Clearwater River in the fall with the exception of those from the Lochsa River, which arrived in the fall and following spring. Average daily movement of the fish was minimal (range = 0.3–4.7 km/d) and dependent on water temperature and flow. The fates of wild and hatchery steelhead varied. Fish returned to spawning grounds, were harvested by anglers (hatchery fish only), or had unknown fates. Both wild and hatchery steelhead returned at high rates to their natal tributaries and release locations. No straying was observed in either group; however, occasions when steelhead have overshot their natal tributaries and release locations were documented. Spatial and temporal overlap of the distributions of wild and hatchery steelhead was minimal. The distribution of anglers overlapped with that of hatchery steelhead in the fall, winter, and spring. The distributional overlap of anglers and wild steelhead was minimal and largely occurred in September in the lower Clearwater River. This suggests that the Clearwater River has a highly compartmentalized fishery and that current fishing regulations in the Clearwater River are providing for a diversity of angling opportunities while conserving wild steelhead and offering harvest of hatchery fish. The results from this study have important implications for the conservation and management of wild and hatchery steelhead.

Idaho↗

USGS2017

Trends in snowmelt-related streamflow timing in the conterminous United States

Changes in snowmelt-related streamflow timing have implications for water availability and use as well as ecologically relevant shifts in streamflow. Historical trends in snowmelt-related streamflow timing (winter-spring center volume date, WSCVD) were computed for minimally disturbed river basins in the conterminous United States. WSCVD was computed by summing daily streamflow for a seasonal window then calculating the day that half of the seasonal volume had flowed past the gage. We used basins where at least 30 percent of annual precipitation was received as snow, and streamflow data were restricted to regionally based winter-spring periods to focus the analyses on snowmelt-related streamflow. Trends over time in WSCVD at gages in the eastern U.S. were relatively homogenous in magnitude and direction and statistically significant; median WSCVD was earlier by 8.2 days (1.1 days/decade) and 8.6 days (1.6 days/decade) for 1940–2014 and 1960–2014 periods respectively. Fewer trends in the West were significant though most trends indicated earlier WSCVD over time. Trends at low-to-mid elevation (<1600 m) basins in the West, predominantly located in the Northwest, had median earlier WSCVD by 6.8 days (1940–2014, 0.9 days/decade) and 3.4 days (1960–2014, 0.6 days/decade). Streamflow timing at high-elevation (⩾1600 m) basins in the West had median earlier WSCVD by 4.0 days (1940–2014, 0.5 days/decade) and 5.2 days (1960–2014, 0.9 days/decade). Trends toward earlier WSCVD in the Northwest were not statistically significant, differing from previous studies that observed many large and (or) significant trends in this region. Much of this difference is likely due to the sensitivity of trend tests to the time period being tested, as well as differences in the streamflow timing metrics used among the studies. Mean February–May air temperature was significantly correlated with WSCVD at 100 percent of the study gages (field significant, p < 0.0001), demonstrating the sensitivity of WSCVD to air temperature across snowmelt dominated basins in the U.S. WSCVD in high elevation basins in the West, however, was related to both air temperature and precipitation yielding earlier snowmelt-related streamflow timing under warmer and drier conditions.

Journal of Hydrology↗

USGS2025

Identifying precursors and tracking pulses of magma ascent in multidisciplinary data during the 2018–2023 phreatomagmatic eruption at Semisopochnoi Island, Alaska

The 2018–2023 phreatomagmatic eruptions at Semisopochnoi Island, Alaska produced abundant long-period (LP) seismicity, harmonic and broadband tremor, and explosion signals over several well-monitored periods of eruption and quiescence. The corresponding dataset provides an excellent opportunity to investigate precursory and syn -eruptive geophysical signals of long-lived phreatomagmatic eruptions using multiparameter observations. We generated explosion and LP event catalogs through novel implementations of the REDPy ( Hotovec-Ellis, 2024 ) repeating event detector in mid-2021 following a network upgrade and the onset of a new phase of the eruption. The hundreds of detected explosions show a high degree of infrasound waveform similarity over more than a year, indicating a repeating source mechanism likely associated with explosive magma-water interaction. The seismic LP catalog shows that events began over a month prior to renewed explosive activity at the beginning of August 2021, and that lower frequency index (FI) LPs were generated in the week prior to the onset of explosions. We applied a recently developed machine learning tool (VOISS-Net, Tan et al., 2024 ) to catalog abundant broadband and harmonic seismic tremor recorded before and during the renewed explosive activity, along with LPs and explosions. The tremor catalogs complement the LP and explosion catalogs by filling out the seismic sequence with the dominant signal types. Together, these catalogs reveal a seismic sequence of renewed unrest that started with several weeks of LP events, followed by LPs with lower FI values and harmonic tremor in the days prior to explosive activity, and finally the onset of discrete explosions and broadband eruption tremor. We interpret this sequence as the ascent of a new pulse of magma that first interacted with the hydrothermal/groundwater system to produce LPs, followed by harmonic tremor, and that ultimately drove explosive magma-water interactions and periods of continuous ash emissions. The 2021 seismic sequence, in combination with long-term records of satellite SO 2 emissions, deformation from interferometric synthetic aperture radar (InSAR) analysis, ash sample analysis, infrasound, and volcano tectonic seismicity, allows us to interpret the entire 9-year period of unrest and eruption that began with an intrusion and earthquake swarm in 2014.

Alaska↗

USGS2023

Differential hypoxia tolerance of eastern oysters from the northern Gulf of Mexico at elevated temperature

Increasing prevalence of hypoxia in shallow waters of U.S. Gulf of Mexico (GoM) estuaries can pose a serious threat to eastern oysters ( Crassostrea virginica ). Their tolerance to hypoxia, however, is not well characterized, especially at elevated temperatures (>30 °C) typical of GoM estuaries in summer. Moreover, it is unknown whether differences in hypoxia tolerance exist between GoM oyster populations growing in estuaries differing in local environmental conditions. Wild oyster broodstocks were collected from four estuarine sites in Texas (Packery Channel, PC and Aransas Bay, AB) and Louisiana (Calcasieu Lake, CL and Vermilion Bay, VB) and their adult progenies (F1) were tested (Study 1) under continuous hypoxia (<2.0 mg O 2 L −1 ) at 32 °C. Significant differences in hypoxia tolerance were found between F1 populations with calculated median lethal time (LT 50 ) ranging from 3.9 to 12.5 days. PC and CL oysters were the most and least tolerant populations, respectively. The study was repeated twice more (Studies 2 and 3) using PC and CL oysters, and their responses at the organismic, cellular, and biochemical levels were investigated. Valve movement was monitored, and oysters were sampled to measure hemocyte density, plasma protein, calcium and glutathione concentrations, and digestive gland alanine and succinate concentrations after either 3–5 days (Study 2) or 1–3 days (Study 3) of hypoxia exposure. From the onset of hypoxia until their death, oysters stayed opened 13–32% of the time compared to 53–64% under normoxia, but no differences between populations were detected under hypoxia. PC oyster but not CL oyster plasma glutathione concentrations increased significantly in both studies. Under longer (3–5 days) hypoxia exposure, plasma calcium and glutathione concentrations of PC oysters were significantly higher than CL oysters. These results suggest PC oysters were better able to protect tissues against acidosis and oxidative damage during hypoxia and high temperature stress than CL oysters. Overall, our results indicate that oyster populations originating from the GoM vary in their response to hypoxia and high temperature stress and possess differential tolerance.

Alabama, Louisiana, Mississippi, Texas↗

USGS2016

Uncertainty analysis of the Operational Simplified Surface Energy Balance (SSEBop) model at multiple flux tower sites

Evapotranspiration (ET) is an important component of the water cycle – ET from the land surface returns approximately 60% of the global precipitation back to the atmosphere. ET also plays an important role in energy transport among the biosphere, atmosphere, and hydrosphere. Current regional to global and daily to annual ET estimation relies mainly on surface energy balance (SEB) ET models or statistical and empirical methods driven by remote sensing data and various climatological databases. These models have uncertainties due to inevitable input errors, poorly defined parameters, and inadequate model structures. The eddy covariance measurements on water, energy, and carbon fluxes at the AmeriFlux tower sites provide an opportunity to assess the ET modeling uncertainties. In this study, we focused on uncertainty analysis of the Operational Simplified Surface Energy Balance (SSEBop) model for ET estimation at multiple AmeriFlux tower sites with diverse land cover characteristics and climatic conditions. The 8-day composite 1-km MODerate resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) was used as input land surface temperature for the SSEBop algorithms. The other input data were taken from the AmeriFlux database. Results of statistical analysis indicated that the SSEBop model performed well in estimating ET with an R2 of 0.86 between estimated ET and eddy covariance measurements at 42 AmeriFlux tower sites during 2001–2007. It was encouraging to see that the best performance was observed for croplands, where R2 was 0.92 with a root mean square error of 13 mm/month. The uncertainties or random errors from input variables and parameters of the SSEBop model led to monthly ET estimates with relative errors less than 20% across multiple flux tower sites distributed across different biomes. This uncertainty of the SSEBop model lies within the error range of other SEB models, suggesting systematic error or bias of the SSEBop model is within the normal range. This finding implies that the simplified parameterization of the SSEBop model did not significantly affect the accuracy of the ET estimate while increasing the ease of model setup for operational applications. The sensitivity analysis indicated that the SSEBop model is most sensitive to input variables, land surface temperature (LST) and reference ET ( ET o ); and parameters, differential temperature ( dT ), and maximum ET scalar ( K max ), particularly during the non-growing season and in dry areas. In summary, the uncertainty assessment verifies that the SSEBop model is a reliable and robust method for large-area ET estimation. The SSEBop model estimates can be further improved by reducing errors in two input variables ( ET o and LST) and two key parameters ( K max and dT ).

Journal of Hydrology↗

USGS2012

Shear stress and bed roughness estimates for combined wave and current flows over a rippled bed

High‐quality bottom boundary layer measurements and bottom photographs were obtained over a sand substrate during a 10‐day deployment of the GEOPROBE tripod at an inner shelf (35‐m water depth) location off northern California. The seafloor surrounding the tripod was composed of well‐sorted medium‐grained (mean diameter, 0.25 mm) sand which was formed into symmetrical wave ripples with heights of 3–4 cm and wavelengths of 22–30 cm. Mean velocity profiles in the region from 23 cm to 102 cm above the rippled bed were highly logarithmic ( R > 0.95) approximately 30% of the time. Nineteen profiles exhibiting R > 0.997 were analyzed to obtain the shear velocity ( U * c ) and roughness length (Z 0 c ) for the mean current. The near‐bottom flow field was composed of quasi‐steady currents (up to 12 cm s −1 at z = 102 cm) and wave‐induced, oscillatory currents (up to 14 cm s −1 ). The data‐derived estimates of U * c and Z 0 c were 0.3–0.93 cm s −1 and 0.82–1.5 cm, respectively. The mean shear estimates are 50–100% larger than those predicted using a drag coefficient ( C D ) of 3 × 10 −3 that is typical for rough boundaries, and the roughness lengths are up to an order of magnitude larger than the maximum expected values based on the observed wave‐rippled bottom. These results indicate the importance of the combined flow turbulent interaction in producing a large apparent Z 0 c . However, comparison of the shear and roughness estimates derived from the velocity profile analysis to predictions made by the combined flow model of Grant and Madsen (1979) show that direct application of the wave‐ripple roughness equation of Grant and Madsen (1982) yields large overestimates of z 0 c and U * c . Selecting the physical roughness length k b (=30 z 0 ) that produced the best agreement with the data resulted in z 0 values ranging from 0.03 to 0.43 cm. Moreover, a direct correlation exists between these physical roughness estimates and the angle (θ cr ) formed by the mean current and the trend of the wave ripple crests. A simple linear relationship between k b and θ cr is suggested by our limited data set.

California↗

USGS2024

Abiotic and biotic factors related to growth of non-native Walleyes in Lake Pend Oreille, Idaho

Objective Growth is one of the primary drivers of fish population dynamics and understanding factors influencing growth is vital to effective management of fish populations. This study investigated potential factors influencing growth of a recently established, non-native population of Walleye Sander vitreus in the Lake Pend Oreille system in northern Idaho. Methods We used relative growth index to describe growth of Walleyes relative to populations across North America. Mixed‐effects modeling was used to relate growth to abiotic (i.e., mean summer water temperature, river inflow) and biotic (i.e., kokanee Oncorhynchus nerka abundance and biomass; opossum shrimp Mysis diluviana density) variables. Models were ranked using Akaike's information criterion corrected for small sample size. Individual variability in growth was related to diet represented by stable isotopes (i.e., δ 15 N, δ 13 C) using linear regression for age‐1, age‐2, age‐3, and age‐5 individuals. Subsequently, for each age‐class, we evaluated differences in δ 15 N and δ 13 C between fast‐growing (i.e., 75th and higher percentiles of growth) and slow‐growing (i.e., 25th and lower percentiles of growth) individuals. Results The relative growth index suggested that Walleye grew fast relative to other populations, particularly those at similar latitudes to the Lake Pend Oreille system. Mixed-effects regression modeling indicated that growth of Walleyes was positively associated with temperature as well as abundance and biomass of kokanee; growth was negatively associated with inflow from the Clark Fork River and Mysis diluviana density. The top model explaining growth of Walleyes contained temperature and abundance of kokanee as environmental variables. The second equally plausible (i.e., within 2 AICc) model contained temperature. Growth of Walleyes varied among individuals. Generally, fast-growing Walleyes had higher δ15N than slow-growing Walleyes. Similarly, δ13C was more depleted in the fast-growing individuals for all age classes, except age 1, suggesting that age-1 individuals used higher proportions of littoral prey items compared to other age classes. Conclusion This study showed that kokanee abundance and temperature appeared to be important factors influencing growth of Walleyes in the Lake Pend Oreille system. Additionally, variability in growth appeared to be related to variability in diet, particularly for age-1 Walleyes. Impact statement Growth of Walleyes has been extensively studied, yet few studies have evaluated growth of Walleyes in novel systems or assessed individual variability in growth. Our research adds to the understanding of individual variability in growth and factors influencing population dynamics of non-native Walleyes.

Idaho↗

USGS2007

A new towed platform for the unobtrusive surveying of benthic habitats and organisms

Maps of coral ecosystems are needed to support many conservation and management objectives, as well as research activities. Examples include ground-truthing aerial and satellite imagery, characterizing essential habitat, assessing changes, and monitoring the progress of restoration efforts. To address some of these needs, the U.S. Geological Survey developed the Along-Track Reef-Imaging System (ATRIS), a boat-based sensor package for mapping shallow-water benthic environments. ATRIS consists of a digital still camera, a video camera, and an acoustic depth sounder affixed to a moveable pole. This design, however, restricts its deployment to clear waters less than 10 m deep. To overcome this limitation, a towed version has been developed, referred to as Deep ATRIS. The system is based on a light-weight, computer-controlled, towed vehicle that is capable of following a programmed diving profile. The vehicle is 1.3 m long with a 63-cm wing span and can carry a wide variety of research instruments, including CTDs, fluorometers, transmissometers, and cameras. Deep ATRIS is currently equipped with a high-speed (20 frames · s-1) digital camera, custom-built light-emitting-diode lights, a compass, a 3-axis orientation sensor, and a nadir-looking altimeter. The vehicle dynamically adjusts its altitude to maintain a fixed height above the seafloor. The camera has a 29° x 22° field-of-view and captures color images that are 1360 x 1024 pixels in size. GPS coordinates are recorded for each image. A gigabit ethernet connection enables the images to be displayed and archived in real time on the surface computer. Deep ATRIS has a maximum tow speed of 2.6 m · s-1and a theoretical operating tow-depth limit of 27 m. With an improved tow cable, the operating depth can be extended to 90 m. Here, we present results from the initial sea trials in the Gulf of Mexico and Biscayne National Park, Florida, USA, and discuss the utility of Deep ATRIS for map-ping coral reef habitats. Several example mosaics illustrate the high-quality imagery that can be obtained with this system. The images also reveal the potential for unobtrusive animal observations; fish and sea turtles are unperturbed by the presence of Deep ATRIS

Florida↗

USGS2002

Complex earthquake rupture and local tsunamis

In contrast to far-field tsunami amplitudes that are fairly well predicted by the seismic moment of subduction zone earthquakes, there exists significant variation in the scaling of local tsunami amplitude with respect to seismic moment. From a global catalog of tsunami runup observations this variability is greatest for the most frequently occurring tsunamigenic subduction zone earthquakes in the magnitude range of 7 < M w < 8.5. Variability in local tsunami runup scaling can be ascribed to tsunami source parameters that are independent of seismic moment: variations in the water depth in the source region, the combination of higher slip and lower shear modulus at shallow depth, and rupture complexity in the form of heterogeneous slip distribution patterns. The focus of this study is on the effect that rupture complexity has on the local tsunami wave field. A wide range of slip distribution patterns are generated using a stochastic, self-affine source model that is consistent with the falloff of far-field seismic displacement spectra at high frequencies. The synthetic slip distributions generated by the stochastic source model are discretized and the vertical displacement fields from point source elastic dislocation expressions are superimposed to compute the coseismic vertical displacement field. For shallow subduction zone earthquakes it is demonstrated that self-affine irregularities of the slip distribution result in significant variations in local tsunami amplitude. The effects of rupture complexity are less pronounced for earthquakes at greater depth or along faults with steep dip angles. For a test region along the Pacific coast of central Mexico, peak nearshore tsunami amplitude is calculated for a large number ( N = 100) of synthetic slip distribution patterns, all with identical seismic moment ( M w = 8.1). Analysis of the results indicates that for earthquakes of a fixed location, geometry, and seismic moment, peak nearshore tsunami amplitude can vary by a factor of 3 or more. These results indicate that there is substantially more variation in the local tsunami wave field derived from the inherent complexity subduction zone earthquakes than predicted by a simple elastic dislocation model. Probabilistic methods that take into account variability in earthquake rupture processes are likely to yield more accurate assessments of tsunami hazards.

Journal of Geophysical Research B: Solid Earth↗

USGS2021

Microbial and viral indicators of pathogens and human health risks from recreational exposure to waters impaired by fecal contamination

Fecal indicator bacteria (FIB) (e.g., fecal coliforms, Escherichia coli , and enterococci) have been used for decades to monitor for and protect the public from waterborne pathogens from fecal contamination. However, FIB may not perform well at predicting the presence of waterborne pathogens or human health outcomes from recreational exposure to fecal-contaminated surface waters. Numerous factors can influence the relationship between FIB and pathogens or human health outcomes, including the source(s) of contamination, the type of pathogen(s) present, differences in the survival and behavior of FIB and pathogens in the wastewater conveyance and treatment process, and varying environmental conditions. As a result, different indicators, such as source-specific microbial source tracking (MST) markers and viral fecal indicators, have been used as possible surrogates to better approximate pathogen abundance and human health risks in recreational waters. The performance of these alternative indicators has been mixed, with some promise of viral indicators better approximating viral pathogens than bacterial fecal indicators, and FIB generally more closely associated with bacterial and protozoal pathogen presence than human MST markers. Many of the assays to detect and quantify fecal indicators and pathogens are polymerase chain reaction-based assays, which detect and quantify nucleic acid [deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)] sequences specific to a target of interest. Recent advances in DNA and RNA sequencing technologies may push the field toward metabarcoding approaches, where multiple targets can be detected and quantified simultaneously. Metabarcoding is currently more applicable to bacterial and protozoal assessments than viral assessments based on a lack of universal metabarcoding markers for viruses. Innovative technologies, such as biosensors and nanotechnologies, may provide more sensitive and accurate tools to detect and quantify pathogens. When a specific pathogen is of concern for a recreational water body, a practical approach in estimating the likelihood of human health outcomes is the application of quantitative microbial risk assessments (QMRAs). Quantitative microbial risk assessments can be used to model the likelihood of pathogen-specific human health outcomes from recreational exposure as a function of a surrogate indicator. Inputs for QMRAs include the ratio between the indicator to be monitored and the pathogen of interest, the concentration of the indicator, the amount of water ingested, and the likelihood of the health outcome based on the estimated amount of pathogen consumed. There are numerous unknowns about the behavior and survival of fecal indicators and pathogens in environmental waters. Developing accurate models to predict pathogen concentrations from fecal indicators in recreational waters will require a better understanding of these unknowns. Current methods and technologies for detecting and quantifying fecal indicators and pathogens are limited due to the rare and patchy nature of pathogens. Technological advances may help improve sensitivity for detecting and quantifying pathogens.

Journal of Sustainable Water in the Built Environm↗

USGS2014

High-resolution delineation of chlorinated volatile organic compounds in a dipping, fractured mudstone: depth- and strata-dependent spatial variability from rock-core sampling

Synthesis of rock-core sampling and chlorinated volatile organic compound (CVOC) analysis at five coreholes, with hydraulic and water-quality monitoring and a detailed hydrogeologic framework, was used to characterize the fine-scale distribution of CVOCs in dipping, fractured mudstones of the Lockatong Formation of Triassic age, of the Newark Basin in West Trenton, New Jersey. From these results, a refined conceptual model for more than 55 years of migration of CVOCs and depth- and strata-dependent rock-matrix contamination was developed. Industrial use of trichloroethene (TCE) at the former Naval Air Warfare Center (NAWC) from 1953 to 1995 resulted in dense non-aqueous phase liquid (DNAPL) TCE and dissolved TCE and related breakdown products, including other CVOCs, in underlying mudstones. Shallow highly weathered and fractured strata overlie unweathered, gently dipping, fractured strata that become progressively less fractured with depth. The unweathered lithology includes black highly fractured (fissile) carbon-rich strata, gray mildly fractured thinly layered (laminated) strata, and light-gray weakly fractured massive strata. CVOC concentrations in water samples pumped from the shallow weathered and highly fractured strata remain elevated near residual DNAPL TCE, but dilution by uncontaminated recharge, and other natural and engineered attenuation processes, have substantially reduced concentrations along flow paths removed from sources and residual DNAPL. CVOCs also were detected in most rock-core samples in source areas in shallow wells. In many locations, lower aqueous concentrations, compared to rock core concentrations, suggest that CVOCs are presently back-diffusing from the rock matrix. Below the weathered and highly fractured strata, and to depths of at least 50 meters (m), groundwater flow and contaminant transport is primarily in bedding-plane-oriented fractures in thin fissile high-carbon strata, and in fractured, laminated strata of the gently dipping mudstones. Despite more than 18 years of pump and treat (P&T) remediation, and natural attenuation processes, CVOC concentrations in aqueous samples pumped from these deeper strata remain elevated in isolated intervals. DNAPL was detected in one borehole during coring at a depth of 27 m. In contrast to core samples from the weathered zone, concentrations in core samples from deeper unweathered and unfractured strata are typically below detection. However, high CVOC concentrations were found in isolated samples from fissile black carbon-rich strata and fractured gray laminated strata. Aqueous-phase concentrations were correspondingly high in samples pumped from these strata via short-interval wells or packer-isolated zones in long boreholes. A refined conceptual site model considers that prior to P&T remediation groundwater flow was primarily subhorizontal in the higher-permeability near surface strata, and the bulk of contaminant mass was shallow. CVOCs diffused into these fractured and weathered mudstones. DNAPL and high concentrations of CVOCs migrated slowly down in deeper unweathered strata, primarily along isolated dipping bedding-plane fractures. After P&T began in 1995, using wells open to both shallow and deep strata, downward transport of dissolved CVOCs accelerated. Diffusion of TCE and other CVOCs from deeper fractures penetrated only a few centimeters into the unweathered rock matrix, likely due to sorption of CVOCs on rock organic carbon. Remediation in the deep, unweathered strata may benefit from the relatively limited migration of CVOCs into the rock matrix. Synthesis of rock core sampling from closely spaced boreholes with geophysical logging and hydraulic testing improves understanding of the controls on CVOC delineation and informs remediation design and monitoring.

New Jersey, New York, Pennsylvania↗

USGS2004

Limnological and climatic environments at Upper Klamath Lake, Oregon during the past 45 000 years

Upper Klamath Lake, in south-central Oregon, contains long sediment records with well-preserved diatoms and lithological variations that reflect climate-induced limnological changes. These sediment archives complement and extend high resolution terrestrial records along a north-south transect that includes areas influenced by the Aleutian Low and Subtropical High, which control both marine and continental climates in the western United States. The longest and oldest core collected in this study came from the southwest margin of the lake at Caledonia Marsh, and was dated by radiocarbon and tephrochronology to an age of about 45 ka. Paleolimnological interpretations of this core, based upon geochemical and diatom analyses, have been augmented by data from a short core collected from open water environments at nearby Howards Bay and from a 9-m core extending to 15 ka raised from the center of the northwestern part of Upper Klamath Lake. Pre- and full-glacial intervals of the Caledonia Marsh core are characterized and dominated by lithic detrital material. Planktic diatom taxa characteristic of cold-water habitats (Aulacoseira subarctica and A. islandica) alternate with warm-water planktic diatoms (A. ambigua) between 45 and 23 ka, documenting climate changes at millennial scales during oxygen isotope stage (OIS) 3. The full-glacial interval contains mostly cold-water planktic, benthic, and reworked Pliocene lacustrine diatoms (from the surrounding Yonna Formation) that document shallow water conditions in a cold, windy environment. After 15 ka, diatom productivity increased. Organic carbon and biogenic silica became significant sediment components and diatoms that live in the lake today, indicative of warm, eutrophic water, became prominent. Lake levels fell during the mid-Holocene and marsh environments extended over the core site. This interval is characterized by high levels of organic carbon from emergent aquatic vegetation (Scirpus) and by the Mazama ash (7.55 ka), generated by the eruption that created nearby Crater Lake. For a brief time the ash increased the salinity of Upper Klamath Lake. High concentrations of molybdenum, arsenic, and vanadium indicate that Caledonia Marsh was anoxic from about 7 to 5 ka. After the mid-Holocene, shallow, but open-water environments returned to the core site. The sediments became dominated (>80%) by biogenic silica. The open-water cores show analogous but less extreme limnological and climatic changes more typical of mid-lake environments. Millennial-scale lake and climate changes during OIS 3 at Upper Klamath Lake contrast with a similar record of variation at Owens Lake, about 750 km south. When Upper Klamath Lake experienced cold-climate episodes during OIS 3, Owens Lake had warm but wet episodes; the reverse occurred during warmer intervals at Upper Klamath Lake. Such climatic alternations apparently reflect the variable position and strength of the Aleutian Low during the mid-Wisconsin.

Oregon↗

USGS2024

Does the extent of glacial cover across watersheds and discharge periods affect dietary resource use of nearshore fishes in the Northern Gulf of Alaska?

Northern high-latitude glaciers impact nearshore marine ecosystems through the discharge of cold and fresh waters, including nutrients and organic matter. Fishes are important integrators of ecosystem processes and hold key positions in the transfer of energy to higher trophic positions in such systems. This study used a natural gradient in space and time, including watershed glacial cover (0–60%) of five adjacent estuaries and three sequential discharge periods (pre-peak, peak, post-peak) in the northern Gulf of Alaska (Kachemak Bay) to test whether differences in glacial cover of watersheds upstream of estuaries affect dietary resource use of nearshore fishes. Dietary resource use was assessed using stomach content and stable carbon and nitrogen isotope analyses to determine fish diet composition and trophic niche width. Crescent gunnel ( Pholis laeta ), a mostly sedentary species, was our focal species for comparisons across estuaries and discharge periods. Discharge period had a greater influence on diet composition and trophic niche width of crescent gunnels than watershed glacial coverage. Niche width of crescent gunnel was larger during the post-peak discharge period compared to pre-peak and peak periods, coincident with a shift in prey spectrum. However, watershed glacial cover was not a suitable predictor of niche width of crescent gunnel. Trophic resource use was also considered along this glacial cover gradient for two other fish species, Pacific staghorn sculpin ( Leptocottus armatus ) and starry flounder ( Platichthys stellatus ), but within the post-peak discharge period only. These species exploited a larger prey base compared to crescent gunnel, likely due to their greater mobility. Similar to crescent gunnel, there were no relationships in trophic niche width associated with watershed glacial coverage for these other species during the post-peak discharge period. Instead, trophic resource use of these three nearshore fish species was influenced by a more complex set of dynamic environmental variables (salinity, temperature, turbidity, and discharge), as well as static watershed characteristics, especially vegetation cover. Such drivers can act through changes in metabolic rates, modulating foraging strategies and trophic connectivity, as well as terrestrial nutrient delivery to support estuarine production. The environmental conditions associated with the glacially influenced estuaries during our study period (2020−2021) seemed within a range that allowed nearshore fishes to maintain energy pathways and prey bases across these estuaries, but it is unknown how these estuarine food webs may be influenced in years of extreme conditions such as during heat waves, droughts, or floods.

Alaska↗

USGS2017

Late Cretaceous inoceramid bivalves of the Kuskokwim Basin, southwestern Alaska, and their implications for basin evolution

Upper Cretaceous rocks of the Kuskokwim Group are exposed in a large region of southwestern Alaska and are mainly composed of deformed turbidite deposits that contain few fossils other than inoceramid bivalves. This paper documents the taxonomy of the inoceramids in the Kuskokwim Group, develops an inoceramid biostratigraphy based on known ranges in other regions, and analyzes biogeographic patterns, paleoecology, and depositional history of the Kuskokwim Group. Most of the inoceramid bivalves present in the Kuskokwim Group are of Cenomanian and Turonian age, and an assemblage of species typical of late Turonian age rocks is particularly well developed. Only two localities appear to be as young as Santonian age. The following 16 species or subspecies are discussed and illustrated in detail: Birostrina tamurai Matsumoto and Noda, Inoceramus virgatus Schlüter, I. pennatulus Pergament, I. pictus minus Matsumoto, I. cf. I. yabei Nagao and Matsumoto, I. ? sp. aff. I. costatus Nagao and Matsumoto, I. hobetsensis Nagao and Matsumoto, I. longealatus Tröger, I. frechi Flegel, I. waltersdorfensis waltersdorfensis Andert, I. cf. I. waltersdorfensis hannovrensis Heinz, I. kuskokwimensis n. sp., Mytiloides cf. M. opalensis (Böse), M. teraokai (Matsumoto and Noda), M. cf. M. incertus (Jimbo), and Sphenoceramus naumanni (Yokoyama). In addition, a specimen with affinities to Mytiloides striatoconcentricus carpathicus (Simionescu) and a specimen that may belong to the I. (Cremnoceramus?) rotundatus–I. ( C .) erectus lineage are illustrated. Most of the taxa present in the Kuskokwim region are found in other regions of the North Pacific, particularly Japan and eastern Siberia, or are found throughout the Northern Hemisphere. Only one species, I. kuskokwimensis n. sp., is new and may be endemic. North Pacific taxa are predominant in the Kuskokwim region, but intervals near the Cenomanian–Turonian Stage boundary and in the upper Turonian contain taxa characteristic of Europe and the Western Interior basin of North America; some of these taxa have not been recorded previously in the North Pacific region. Turonian heteromorph ammonite assemblages associated with inoceramids in the finer grained facies of the Kuskokwim region are similar to those found in coeval rocks of Japan and Germany. The depositional area of the Kuskokwim Group can be broken into two northeast-trending subbasins, the Kuskokwim River subbasin to the northwest and the Mulchatna River subbasin to the southeast, connected by the Nushagak Hills corridor. Within the Kuskokwim River subbasin, deposition apparently started earlier in the north (middle Cenomanian) than in the south (late Cenomanian to early Turonian), and prograding deltaic sedimentation along the western margin also appears to have started earlier in the north. No marine fossils younger than latest Turonian to earliest Coniacian are known from the Kuskokwim River subbasin. The youngest fossils identified are Santonian in age and are from deep-water deposits in the Nushagak Hills corridor. Few fossils are known from the Mulchatna River subbasin and age control is limited.

Journal of Paleontology↗

USGS2020

Phytoremediation of slightly brackish, polycyclic aromatic hydrocarbon‐contaminated groundwater from 250 ft below land surface: A pilot‐scale study using salt‐tolerant, endophyte‐enhanced hybrid poplar trees at a Superfund site in the Central Valley of California, April‒November 2019

Slightly brackish groundwater contaminated by polycyclic aromatic hydrocarbons (PAHs) at a Superfund site in the Central Valley of California was pumped from 250 feet below land surface to a water storage tank using solar power and then gravity‐fed into 18, 330‐gallon intermediate bulk containers (totes) as follows: (1) Five totes contained planting medium with three salt‐tolerant hybrid poplar trees per tote ( n = 15); (2) Seven totes contained planting medium with three salt‐tolerant hybrid poplar trees per tote and inoculated with the naturally occurring, PAH‐degrading endophyte Pseudomonas putida PD1 ( n = 21); (3) Three totes contained planting medium only ( n = 0); (4) One tote contained groundwater with three PD1‐inoculated trees ( n = 3) and one tote contained groundwater with three regular trees ( n = 3); and (5) One tote contained groundwater only ( n = 0). All trees grew well during the 7‐month growing season in spite of the area's hot, dry air temperature, little precipitation, tote‐influent chloride concentrations of 290 mg/L, and tote‐influent naphthalene concentrations that ranged from 650 to 5100 mg/L. PD1‐inoculated trees initially had 56% larger tree area (tree height × tree width) than regular trees and up to 69% larger tree area by the end of the growing season, indicating some conferred phytoprotection to the PAH contamination. All trees had similar trunk caliper (diameter) and leaf chlorophyll content by the end of the growing season. Total naphthalene removal ranged from 88% to 100% across all totes. The lowest naphthalene removal of 88% was observed in a tote that contained only planting medium and indicates substantial adsorption of naphthalene onto the high organic content of the planting medium. Contaminant removal due to uptake by the hybrid poplar trees was confirmed by the detection of naphthalene in in vivo passive samplers placed in tree trunks. Benzene, toluene, ethylbenzene, total xylenes, 2‐methylnaphthalene, 1,2,4‐trimethylbenzene, and isopropylbenzene were also detected. These results from the pilot‐scale study indicate that a full‐scale application of using salt‐tolerant hybrid poplar trees at this site could effectively decrease naphthalene concentrations in groundwater pumped from the deep aquifer. These initial results provide hope for similar application at other contaminated sites characterized by groundwater at considerable depths, especially at Superfund sites where costly pump‐and‐treat systems have been used long term to treat low levels of groundwater contamination.

California↗

USGS2008

Distribution and variability of redox zones controlling spatial variability of arsenic in the Mississippi River Valley alluvial aquifer, southeastern Arkansas

Twenty one of 118 irrigation water wells in the shallow (25-30??m thick) Mississippi River Valley alluvial aquifer in the Bayou Bartholomew watershed, southeastern Arkansas had arsenic (As) concentrations (< 0.5 to 77????g/L) exceeding 10????g/L. Sediment and groundwater samples were collected and analyzed from the sites of the highest, median, and lowest concentrations of As in groundwater in the alluvial aquifers located at Jefferson County, Arkansas. A traditional five-step sequential extraction was performed to differentiate the exchangeable, carbonate, amorphous Fe and Mn oxide, organic, and hot HNO3-leachable fraction of As and other compounds in sediments. The Chao reagent (0.25??M hydroxylamine hydrochloride in 0.25??M HCl) removes amorphous Fe and Mn oxides and oxyhydroxides (present as coatings on grains and amorphous minerals) by reductive dissolution and is a measure of reducible Fe and Mn in sediments. The hot HNO3 extraction removes mostly crystalline metal oxides and all other labile forms of As. Significant total As (20%) is complexed with amorphous Fe and Mn oxides in sediments. Arsenic abundance is not significant in carbonates or organic matter. Significant (40-70????g/kg) exchangeable As is only present at shallow depth (0-1??m below ground surface). Arsenic is positively correlated to Fe extracted by Chao reagent (r = 0.83) and hot HNO3 (r = 0.85). Arsenic extracted by Chao reagent decreases significantly with depth as compared to As extracted by hot HNO3. Fe (II)/Fe (the ratio of Fe concentration in the extracts of Chao reagent and hot HNO3) is positively correlated (r = 0.76) to As extracted from Chao reagent. Although Fe (II)/Fe increases with depth, the relative abundance of reducible Fe decreases noticeably with depth. The amount of reducible Fe, as well as As complexed to amorphous Fe and Mn oxides and oxyhydroxides decreases with depth. Possible explanations for the decrease in reducible Fe and its complexed As with depth include historic flushing of As and Fe from hydrous ferric oxides (HFO) by microbially-mediated reductive dissolution and aging of HFO to crystalline phases. Hydrogeochemical data suggests that the groundwater in the area falls in the mildly reducing (suboxic) to relatively highly reducing (anoxic) zone, and points to reductive dissolution of HFO as the dominant As release mechanism. Spatial variability of gypsum solubility and simultaneous SO42- reduction with co-precipitation of As and sulfide is an important limiting process controlling the concentration of As in groundwater in the area. ?? 2008 Elsevier B.V. All rights reserved.

Journal of Contaminant Hydrology↗