Geology topics

Research about United States

Source-linked reports with geographic coverage including United States.

At least 127 records · Page 7Linked to original sources

USGS2026

Null models reveal differing drivers of multidimensional beta diversity change in invaded metacommunities

Aim Invasion-driven changes in beta diversity (Δβ) are multifaceted (taxonomic, functional, and phylogenetic) and are comprised of three components (total beta diversity, replacement, and richness difference); therefore, they represent a nine-dimensional phenomenon. Invasion-driven trajectories of multidimensional Δβ are inconsistent and can vary based on the geographic origin of nonnative species, native community structure, and site attributes. Here, we examine the drivers of multidimensional Δβ to better understand how nonnative species alter biodiversity. Location 1023 wadable-stream fish communities across the conterminous United States. Methods We characterized nine dimensions of Δβ as changes in local contribution to beta diversity (ΔLCBD) derived from pairwise beta diversity of all 1023 sites between contemporary and native-only assemblages at each site. We used redundancy analysis and variance partitioning to identify and estimate the relative importance of 18 Δβ drivers related to nonnative species origin, propagule pressure, abiotic factors, and native community structure. We compared results between those from raw and null model standardized LCBD. Results We found an overall trend of taxonomic homogenization due to nonnative species occurrences. However, null model standardization revealed inconsistent directional change in functional and phylogenetic Δβ, and also revealed Δβ patterns and drivers that differed from those of raw values. Sites did not contribute evenly to overall Δβ trends, with nonnative species origin and native community structure explaining the most variation in ΔLCBD (16% and 15% respectively). Nonnative occurrences, regardless of origin, contributed to taxonomic homogenization, with the magnitude of change dependent on origin. Native community structure dictated the direction of phylogenetic Δβ, with phylogenetically distinct sites contributing to homogenization. Conclusions Our findings demonstrate the utility in using LCBD to identify site-level drivers of Δβ and the need for null model standardization of multidimensional Δβ metrics. Additionally, our results show that spatially explicit definitions of nonnative species are needed to gain robust estimates of Δβ.

conterminous United States↗

USGS2026

Estimating habitat availability for Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) to inform reintroduction planning in the middle Snake River basin, USA

Anadromous fishes have been blocked from the middle Snake River basin since the construction of flood control, irrigation, and hydroelectric projects during the 19 th and 20 th centuries, culminating with the construction of Hells Canyon Dam (river kilometer [rkm] 398) in 1967. Seven large watersheds in the blocked area of the basin are under consideration for Pacific salmon reintroduction. The primary objective of this study was to identify and characterize potential reintroduction sites with high-quality rearing and spawning habitat for Chinook salmon ( Oncorhynchus tshawytscha ) and steelhead ( O. mykiss ) upstream of the Hells Canyon Complex in Idaho, Oregon, and Nevada, USA. We created and tested habitat models to predict rearing presence/absence, rearing abundance, and spawning presence/absence using channel morphology, hydrology, and stream temperature variables obtained from regional peer-reviewed datasets. Habitat models were trained with salmonid presence and abundance records collected in the lower Snake River basin (downstream of Hells Canyon Dam), where anadromous fish can currently access, from 1993 to 2011. Model performance was tested with set-aside data comprised of randomly selected reaches and independent environmental DNA data. An index model was created in the middle Snake River basin for each species by combining results from the habitat models. Modeling covariates differed by species and life stage and included different combinations of August stream temperature, summer flow, channel slope, and quadratic terms for temperature and slope. The habitat models predicted high versus low Chinook salmon and steelhead probability and abundance with 66% to 85% accuracy depending on species and life stage. The index models predicted a total of 2,887 km of Chinook salmon habitat and 2,434 km of steelhead habitat in the blocked area. The three basins in the blocked area with the greatest amount of predicted habitat were the Powder River, South Fork Payette River, and North Fork Payette River for Chinook salmon, and the Powder River, South Fork Boise River, and South Fork Payette River for steelhead. The modeling approach presented here is complementary to other planning efforts for Chinook salmon and steelhead reintroduction in the blocked area of the Snake River basin, and similar approaches may be useful for reintroduction planning in other systems.

Idaho, Nevada, Oregon, Utah, Washington, Wyoming↗

USGS2026

Core microbiomes as a potential fingerprinting method of Western USA dust sources

Introduction: Changing frequency and intensity of dust emissions impacts ecosystems and human health. Dust carries microbes, nutrients, heavy metals, and other materials that may change environmental biogeochemistry at deposition sites. Identifying dust sources provides key information on where and when mitigation strategies should be employed. However, commonly used geochemical or isotopic tracers are often not capable of distinguishing between geographic regions. Methods: We explored whether soil bacterial communities may provide distinct fingerprints of dust sources in the western United States. We identified bacterial core communities of dust from ten locations monitored by the National Wind Erosion Research Network (NWERN) with varied land use (cropland, rangeland, and playa), and compared communities to location, soil, and regional characteristics. Samples were collected monthly from Modified Wilson and Cooke (MWAC) samplers, composited by season (spring, summer, and fall), and analyzed using 16S rRNA sequencing. Results: We found distinct bacterial core communities that reflected dust source characteristics. In order of importance, precipitation levels ( p = 0.0001), location ( p = 0.0001), soil texture ( p = 0.0001), seasonality ( p = 0.0001), and elevation (p = 0.0002) were correlated with bacterial community composition. Discussion: Distinct bacterial core communities were associated with site characteristics such as biocrusts, playas, and military base proximity. Our results suggest that the use of core microbiomes may offer a fingerprinting method to identify dust source regions.

Colorado, Nevada, New Mexico, North Dakota, Oklaho↗

USGS2026

Permeability and compressibility of “seal” sediment overlying the B1 sand gas hydrate reservoir: Hydrate 02 Geo Data Well, Prudhoe Bay unit, Alaska North Slope

An important element in evaluating the viability of extracting methane from a gas hydrate-bearing reservoir is establishing the effectiveness of the overlying bounding sediment as a seal to prevent gas loss, to enable effective depressurization, and to prevent fluid from entering the reservoir during production. This laboratory study presents results for index properties (e.g., grain density, grain size, and liquid limit), compressibility and swelling indices, and permeability measurements on sediment overlying the gas hydrate-bearing reservoir that was the target of the recent JOGMEC-DOE-USGS collaborative gas hydrate production testing project on the Alaska North Slope (ANS). Sediment analyzed in this study was collected during pressure coring operations in the HYDRATE 02 Geo Data Well (GDW). The ∼6.1 m sediment interval recovered in Cores 13P and 14P (878.74–884.88 m measured depth, MD) exhibited heterogeneous sedimentologic characteristics at the centimeter scale, with sediments ranging from clay to thin silty-sand lithologies. Permeability measurements and index-property correlations indicate the interval’s overall in situ vertical permeability ranges from 0.2 to 3.6 microdarcy (μD). Results for compressibility ( C C = 0.255 ± 0.02) and swelling index ( C S = 0.04 ± 0.01) are consistent with estimates based on mineralogy and liquid limit correlations. Based on the measured compressibility, the ∼3 MPa increase in effective stress during the stable phase of depressurization-induced production is anticipated to have imposed 2.43 cm of compaction per meter in the reservoir overburden, reducing permeability by ∼36%. The overburden sediment’s low in situ permeability (3 to 4 orders of magnitude below permeabilities measured in the gas hydrate-bearing part of the B1 sand (unit B)) suggests the B1 sand′s overburden provides an effective seal. Such a seal promotes efficient production by limiting fluid flow into the reservoir during depressurization-induced gas hydrate dissociation.

Alaska↗

USGS2026

Strength, stiffness, and Poisson’s ratio measurements for cements used in the well completions for the extended-duration gas production test on the Alaskan North Slope

As part of an extended-duration production test from a natural gas hydrate reservoir on the Alaska North Slope, a suite of optical-fiber sensors was encased in the completion cement to provide stable downhole monitoring around each of the four project wells. How the sensors respond to changes in the reservoir over time depends in part on properties of the LiteCRETE, ArcticCem, or Tuned Light cement in which each sensor is encased, and on how well the cement bonded to the well casing, sensors, and sediment formation. Here, we report on physical properties of the cements (compressive and tensile strength, stiffness, and Poisson’s ratio), on the downhole distribution of the cements used in each well, and on the cement bond quality. Physical property measurements are presented for cements sampled during the completion activities for the three wells completed in 2022–2023. Samples were cured while being submerged in water at 2–4 °C, then tested at intervals from ∼30 days to more than one year. After an initial period of rapid increase, cement strengths largely stabilized around 120 days in all cases, meaning that cements in all wells reached their nominal strength plateau four months or more before the production test began. Calculations based on recorded volumes of pumped cement show the subpermafrost, main hole portion of each well is encased only in the higher-density “tail” cement used in that well. Downhole cement evaluation logs from two wells demonstrate how the presence of sensors and other hardware outside the casing interferes with the cement evaluation assessment. Nonetheless, the cement evaluations indicate a generally good bond with the formation and sensors over the gas hydrate reservoir intervals.

Alaska↗

USGS2026

Lithological control of gas hydrate saturation determined by pressure core analysis in sub-permafrost reservoirs of the Alaska North Slope (HYDRATE 02 Geo Data Well)

Quantitatively degassing pressure cores by controlled depressurization is a key approach to characterizing gas hydrate reservoirs by measuring the gas hydrate saturation (S h ) of sediments. We measured S h for 53 core sections from the Alaska North Slope during the JOGMEC-DOE-USGS Collaborative Gas Hydrate R&D Project in Alaska, from subpermafrost sediments that were later subjected to an extended-duration gas production test. We characterized lithologic influences on S h using physical property core scans (P-wave velocity, gamma ray attenuation density, and X-ray computed tomography) and grain size measurements. Pressure cores were recovered from the Hydrate-02 Geo Data Well (GDW) at the Kuparuk State 7-11-12 site through two hydrate-bearing sand reservoirs, the B1 and D1 sands, and their finer-grained bounding sediments. S h reaches very high values (68 to 91% of the pore space) in silty fine sands within the B1 sand, which also contains two lower P-wave velocity intervals (one measured at 30% S h ) within the main reservoir. S h and grain sizes of the B1 sand are generally higher than the D1 sand, which hosts high S h (53 to 73%) within its sandy silt to silty fine sands. The heterogeneous silty clay to silt “seal” sediments directly overlying both reservoirs have low S h (0 to 13%) even in thin, coarser beds, suggesting minimal methane transport between the reservoir and seal. S h decreases with depth downward toward the base of both the D1 and B1 sands, corresponding to decreasing grain size. These transitions are underlain by silty clay to clayey silt sediments with low S h (<10%), similar to the seal sediments. Slow depressurization was used to estimate a brackish salinity based on the pressure and temperature of the onset of hydrate dissociation for two core sections within the B1 sand. We show that S h increases with median grain size, sand content, and porosity but exhibits some variation within the sand beds that is not directly explained by lithology.

Alaska↗

USGS2026

Emergent headwater types for watershed monitoring, research, and planning

Headwaters—that is headwater streams and the watersheds they drain—strongly influence water quality, ecosystem services, and hydrologic connectivity, yet remain poorly mapped, monitored, and understood at large spatial scales. Using available spatial data to classify headwater “types” could therefore enhance the utility of sparse monitoring data to advance research and watershed planning—and help update literature-based perceptual models of headwaters as steep, forested, and minimally disturbed watersheds. Here, we analyze headwaters across the contiguous United States to quantify how their attributes (climate, topography, land cover, soils) vary regionally and differ from their downstream watersheds. Our analysis (a) identified seven dominant headwater types with distinct combinations of biophysical and climatic attributes and (b) revealed systematic contrasts with downstream watersheds, with strongest differences in attributes representing potential flowpath depth. Our findings offer a transferable framework for classifying, modeling, and managing these critical yet understudied components of the hydrologic network.

conterminous United States↗

USGS2026

Cost-efficient filtration and replication strategies match or exceed detection sensitivity for marine eDNA diversity at an intertidal site under a standardized laboratory workflow

Optimizing environmental DNA (eDNA) metabarcoding to maximize species detection while minimizing costs and effort remains a challenge, particularly in high-throughput workflows. In the marine intertidal zone off Point Conception, California, we compared eDNA richness accumulation between filtration approaches that differed in filter type and downstream processing, field and laboratory replicates, and independent and pooled polymerase chain reaction (PCR) replicates. Ten 10-cm 2 capsule filters and 10 5-cm 2 syringe disc filters were processed using a standardized laboratory workflow for 12S ribosomal ribonucleic acid (rRNA) (marine vertebrates) and 18S rRNA (metazoans and phytoplankton) metabarcoding, with 10 independent PCR replicates per filter. Because capsules generated larger lysate volumes than discs, the fixed extraction input volume under the standardized workflow resulted in less lysate being processed. A follow-up study pooled 10 PCR replicates for 12S rRNA. When comparing individual PCR replicates, individual filters, or all filters aggregated, discs detected greater marine vertebrate richness than capsules. Probabilistic models indicated that varying effective volume alone could produce similar richness accumulation patterns to those observed, though other filter characteristics were unaccounted for. Minimal differences in richness accumulation were detected between filters for 18S rRNA, and modeling indicated that this was not explained by higher initial copies of 18S rRNA. Meanwhile, vertebrate richness accumulation was similar when adding PCR replicates from the same sample or independent field samples across the short, relatively homogenous intertidal transect. Pooling PCR replicates had no detectable difference on richness compared to sequencing PCR replicates independently: a single pooled PCR replicate detected the same vertebrate richness as the sum of 10 independent PCR replicates. These results show that, under the standardized workflow and conditions tested here, eDNA programs may reduce costs and effort without detectable loss of richness by using filtration approaches aligned with extraction input and pooling technical replicates.

California↗

USGS2026

Evaluation of best management practices at an edge-of-field site in the Eagle Creek watershed, Ohio, 2012–20

In 2010, the U.S. Geological Survey worked in partnership with the Great Lakes Restoration Initiative and the Natural Resources Conservation Service to identify farm fields in priority watersheds—watersheds critically important to Great Lake health. Intensive best management practices were implemented in five States to test the efficacy of best management practices, also referred to as agricultural conservation practices, to reduce sediment and nutrient runoff on agricultural fields. These fields were chosen as representatives of the priority watersheds because their farming practices and geographical conditions were common among farms in those watersheds. A farm site located near Findlay, Ohio, in the Eagle Creek watershed used two conservation practices, cover crop (Natural Resources Conservation Service practice standard 340) and variable rate technology (VRT; Natural Resources Conservation Service practice standard 590), which represent common practices in the Maumee priority watershed. This study monitored surface runoff and subsurface tile runoff at the Eagle Creek watershed site. The effects of cover crop and VRT nutrient application on sediment and nutrient runoff were assessed from October 2012 to September 2020. Cover crops were applied in fall of 2016, 2017, and 2018, coinciding with VRT applications. The following parameters were analyzed as part of the study: runoff discharge; peak discharge; and concentrations and loads of total phosphorus, particulate phosphorus, dissolved reactive phosphorus, and suspended sediment. High peak runoff events disproportionally affected nutrient concentrations and loads in runoff. A threshold of the 85th percentile of the peak discharge was chosen to assess the effect of cover crop and VRT nutrient application on nutrient mitigation at each gage. Runoff events below the 85th percentile were considered small, and runoff events over the 85th percentile were considered large. Concentrations from collected water-quality samples were used for the analysis; estimated concentrations were excluded from the statistical evaluation. All surface runoff parameters during small runoff events, except surface runoff volume, were significantly lower in the period with cover crops and VRT implementation. Contrarily, subsurface runoff parameters during small events were not statistically different between the periods with and without cover crops and VRT implementation. Surface and subsurface parameters during large events were also not statistically different between the periods with and without cover crops and VRT implementation. These results indicate cover crops and VRT may improve water quality during small runoff events, but additional best management practices that mitigate large runoff events may lead to greater water-quality improvement given the contribution of large events to overall losses.

Ohio↗

USGS2026

Continuous monitoring and temporal variability of fluorescence of dissolved organic matter in karst groundwater of the Edwards aquifer, south-central Texas, 2019–24

Widespread urbanization on the Edwards aquifer recharge zone in south-central Texas has prompted the development of new approaches and tools for evaluating the current and future status of water quality in the San Antonio and Barton Springs segments of the Edwards aquifer. The U.S. Geological Survey, in cooperation with the San Antonio Water System and the City of Austin, applied continuous monitoring of fluorescence of dissolved organic matter (fDOM) to characterize the sources and transport of dissolved organic matter and associated constituents in the Edwards aquifer. Continuous fDOM time-series data were adjusted using empirically derived temperature, turbidity, and inner-filter-effect correction factors prior to analysis and interpretation. Fully corrected fDOM time-series data from the study sites were evaluated for short- and long-term temporal variability in fDOM in the context of the hydrologic and climatic conditions that occurred during the 5-year study period to understand vulnerability of the aquifer to potential contaminants in recharge. Study results indicate that fDOM is an effective proxy for dissolved organic carbon that, in turn, is indicative of the influx of recent surface water and associated contaminants, and thus, aquifer vulnerability to those contaminants. Although other continuously monitored water-quality parameters provide insights into changes in water quality in response to varying hydrologic conditions, the quantitative relation between fDOM and dissolved organic carbon directly indicates the timing and magnitude of pulses of organic constituents derived from the land surface, whereas other water-quality parameters do not.

Texas↗

USGS2026

Vessel avoidance behavior in green turtles off the west coast of Florida

Vessel strikes are an increasing source of mortality for sea turtles in coastal waters with high recreational vessel traffic. We quantified flight initiation distance (FID) and avoidance behavior of green turtles Chelonia mydas in response to an approaching vessel traveling at different speeds in shallow coastal waters of Florida. Observational boat surveys were conducted at 3 vessel speeds, and observed FID was evaluated in relation to vessel speed, turtle size class (<60 cm vs. ≥60 cm estimated carapace length), and environmental conditions using a regression tree analysis. Observed FID was most strongly partitioned by vessel speed, with shorter mean distances consistently associated with higher speeds. Mean observed FID ranged from approximately 7.7 m at low vessel speed under specific environmental conditions to approximately 5 m or less at higher speeds. Turtle size class was not associated with differences in observed FID. Flight behavior was non-random, with turtles most frequently fleeing directly away from the vessel’s trajectory, and was independent of vessel speed and turtle size. Observed FID reflects the combined effects of turtle behavior and observer detection. Nevertheless, the consistent association between higher vessel speed and reduced observed FID supports management strategies that would reduce boat speeds and increase boater awareness to protect green turtles in shallow coastal habitats.

Florida↗

USGS2026

Creation of aerial camera system boresight installations in Bangor, Maine; Monroe, Louisiana; and Bassville Park, Florida

Aerial camera systems rely on boresights for defining internal and external metrics. The U.S. Fish and Wildlife Service’s Migratory Bird Surveys Branch required boresights to calibrate their camera systems for creating georeferenced imagery that can then be used in geographic information systems. The U.S. Geological Survey created high-accuracy boresight installations in Bangor, Maine, in July 2024; Monroe, Louisiana, in September 2024; and Bassville Park, Florida, in January 2025 to provide this metric-defining capacity to the U.S. Fish and Wildlife Service. This U.S. Geological Survey Data Report details the methods and results of the boresight installation process and provides camera operators with the data needed to use each of the installations.

Florida, Louisiana, Maine↗

USGS2026

White light reduces flight height of birds in low-density migration corridor

Artificial light at night (ALAN) has been shown to influence the behavior of migratory birds, yet how different light spectra modulate these effects remains unclear. We conducted a field experiment for 31 nights at a remote site in northern Colorado, USA, using 2 800-W light-emitting diode (LED) floodlights with white, red, amber, and blue lighting treatments during fall migration in 2023 and 2024. Using a vertical-looking radar system, we quantified avian in-flight responses in migration traffic rate, flight height, and flight direction between paired control periods with no light and periods with lighting treatments. Although we found no effects of our treatments on migration traffic rate and weak effects on flight direction, we found that broad-spectrum white light with emissions across a 400–600 nm spectrum reduced mean avian flight height by an estimated 22.57 m (±10.53 SE) compared to dark periods, and this response was stronger than red and blue lighting treatments. Our ability to detect behavior changes from a point source in a rural, low-density migration system supports the notion that the effects of artificial light at night on bird behavior may be more pervasive than is often recognized, and that this varies by ALAN spectra. Beyond providing insight into avian orientation and in-flight behavior, our results have implications for future research, the conservation management of artificial light at night, and lighting designs that minimize effects on migratory birds.

Colorado↗

USGS2026

Fueling the fire: Predicting cogongrass (Imperata cylindrica) impacts on fire behavior across environmental and seasonal gradients

Invasive species can fundamentally alter fire regimes by modifying fuel characteristics, yet predicting their impacts on fire behavior remains challenging. Cogongrass ( Imperata cylindrica ), a highly invasive grass spreading across the southeastern US, has been associated with increased fuel loads and fire intensity, but it is unclear how its impacts on fuel load and fire behavior vary across environmental and seasonal gradients. We measured fuel characteristics across 159 cogongrass invaded and non-invaded plots spanning from central Florida to southern Mississippi across multiple seasons. Using these data, we developed custom fuel models in BehavePlus to predict cogongrass effects on surface fire behavior and tree torching across spatial and temporal gradients. Cogongrass invasion increased live fuel loads by up to 1.96 t/ha, with effects strongest in summer and at lower latitudes, and dead fuel loads by up to 1.88 t/ha across all sites. Latitude × invasion interactions indicated that fuel load differences between invaded and non-invaded plots diminished toward northern sites. Cogongrass-driven fuel load alterations elevated surface fire rate of spread (median + 0.75 m/min), and flame length (+ 0.16 m), with the largest increases observed in spring (rate of spread: + 2.60 m/min; flame length: + 0.80 m). Invasion also consistently increased the crown fire transition probability, with magnitudes mirroring those of surface fire effects. Our findings highlight the potential for cogongrass to substantially alter fire behavior across a range of environmental conditions, although the magnitude of these effects varies geographically and tends to be strongest at lower latitudes. These results underscore the importance of targeted management in regional fire planning of invaded landscapes.

Alabama, Florida, Mississippi↗

USGS2026

Satellite observations, plume dynamics and volcanic lightning from the 2023 eruption of Shishaldin Volcano, Alaska

The 2023 eruption of Shishaldin Volcano, Alaska, provided an unusually well-monitored example of a “dry” (non-hydromagmatic) explosive basaltic eruption with sustained, buoyant plumes, and pyroclastic density currents. Here, we examine the 13 basaltic paroxysms that occurred between July and November 2023 using geostationary satellite observations, plume modeling, and volcanic lightning detection to characterize mass eruption rates and plume dynamics. We show that seven volcanic plumes reached 10–14 km above sea level, sustained for minutes to tens of minutes. Translating plume heights into mass eruption rates, using both empirical scaling and one-dimensional plume modeling, gives peak rates of 10 4 –10 7 kg·s −1 and a total erupted volume of ~ 0.05 km 3 (dense rock equivalent) across the eruption sequence. Despite the moderate intensity of this eruption, automated satellite detection algorithms generally failed to detect volcanic ash. We attribute this persistent challenge to the fines-poor grain size distribution of the eruption. Volcanic lightning provides an additional window into the eruption dynamics. A total of 491 volcanic lightning flashes were detected, concentrated during seven of the most energetic phases. The timing of this electrical activity suggests that lightning only became detectable by the global lightning monitoring network when plumes ascended to atmospheric levels favorable for ice formation. Based on the available data, we infer that the low fine ash content of the plumes, combined with minimal water and ice, led to the overall modest rates of lightning (1–13 flashes per minute) compared to “wet” eruptions of similar intensity. These results show that combining satellite observations, plume modeling, and lightning detection provides a valuable timeline of eruptive intensity, even for “dry” basaltic eruptions in remote locations.

Alaska↗

USGS2026

Acute toxicity and tissue concentrations of 6PPD-quinone in Arctic grayling (Thymallus arcticus, Thymallinae)

Studies of N -(1,3-dimethylbutyl)- N' -phenyl- p -phenylenediamine-quinone (6PPDQ) toxicity have identified sensitive and resistant species within the subfamily Salmoninae, but thus far fewer than 10 species, all in two genera ( Oncorhynchus and Salvelinus ), have shown sensitivity in experiments. The Arctic grayling ( Thymallus arcticus , Salmonidae, Thymallinae) was extirpated from its range in the Great Lakes region of the United States, but because of the importance of this species to the Native American tribes of Michigan, a reintroduction effort is underway. Because high 6PPDQ concentrations have been found in Great Lakes tributaries, it is important to understand if this species is at risk from 6PPDQ exposure. Using standard methods with flow-through exposures to provide stable 6PPDQ concentrations, we exposed Arctic grayling at 3 weeks after swim-up to a series of 6PPDQ concentrations for 96 hr, evaluating mortality and measuring tissue concentrations of 6PPDQ in surviving and dying fish. We observed that grayling were sensitive to 6PPDQ, with 24- and 96-hr median lethal concentrations of 5,136 and 3,137 ng/L, respectively. Tissue concentrations were much higher than those observed in other sensitive salmonines in previous studies. While this is only the third genus found to be sensitive to 6PPDQ leading to acute lethality and the first species outside of Salmoninae, the median lethal concentrations determined for the Arctic grayling exposed in this study are at 6PPDQ water concentrations unlikely to be encountered in situ.

Great Lakes↗

USGS2026

Bulk location and source mechanisms of repetitive long-period seismicity at Mount St. Helens in July 2005

The 2004–2008 eruption of Mount St. Helens exemplified the practical challenges of processing high seismic event rates and data volumes. This protracted multi-year eruptive sequence was accompanied by a near-continuous occurrence of long-period (LP, 0.5–5 Hz) seismicity, but network-based picks and locations have previously been performed for only a relatively small subset of the overall seismicity, and full-waveform source–mechanism inversions have previously been performed for just two event types during the eruption. We present a new workflow for the bulk detection, cluster picking, 3-D location, and full-waveform source–mechanism inversion of repetitive LP volcanic seismicity recorded by a local broadband seismic network. Our emphasis is on methods that: exploit waveform similarity (multiplets) commonly observed for volcanic LP seismicity swarms; can take into account 3-D topographic and velocity structure heterogeneity typical of volcanoes; can process high event rates with relatively low analyst burden; and do not require a priori catalogue picks or known waveform templates. We develop and illustrate the workflow using data from Mount St. Helens from 2005 June 29 to July 31, a time-window characterized by high-rate LP seismicity, including numerous lower amplitude small LPs, and for which relatively dense seismic network coverage is available. Approximately 40 per cent of seismicity (20 561 events out of 52 141 triggers) during 2005 June 29 to July 31 is repetitive enough to be grouped into 17 multiplets of at least 300 events. We present 3-D locations of the 17 multiplets, representing 20 076 events having picks from at least eight stations, along with full-waveform source mechanism inversions of the 17 separate multiplet stacks. Collectively, our seismic 3-D hypocentre distributions for 2005 June 29 to July 31 are compatible with sources around the margins of the upper conduit section that is associated with plug solidification. All location results indicate compact seismicity clusters, with the 17 multiplets spatially connected and collectively located at shallow depth, approximately ~ 775 m depth beneath the 1980s crater floor and directly beneath, or immediately adjacent to, the extruding dacite spine. The full-waveform source–mechanism inversions for the 17 multiplets generally indicate mechanisms dominated by volumetric components consistent with subhorizontal cracks along with minor contributions from subvertical cracks. The overall picture is that of a stack or plexus of subhorizontal cracks located at shallow depth beneath the extruding dacite spines, consistent with subhorizontal hydrofractures extending from the conduit margins into the surrounding wall rock; minor subvertical crack components of the mechanisms could possibly arise from surfaces parallel to the conduit wall, such as within the damage halo associated with degassing pathways.

Washington↗

USGS2026

Black Carp Mylopharyngodon piceus reproductive development and maturation in the Mississippi River basin

Black Carp Mylopharyngodon piceus are native to most major east Asian drainages and are internationally cultured for use as a food-fish or a biological control for molluscs. We describe the reproductive biology of Black Carp from the growing invasive population in the Mississippi River basin through examination of incidental commercial fisheries and biologist captures. Our objectives were to assess (1) reproductive development by combined macroscopic and histological staging to compare reproductive maturation by total length, estimated age, and latitude; (2) population functions of gonadosomatic index, length and age, and weight and length relationships; and (3) absolute fecundity. We identified length as a better predictor of reproductive maturation than age, with variation among individuals, and between males and females, with higher probability of maturation anticipated for larger and older individuals predicted around 1050 mm total length (TL; 6 years) for females and 950 mm TL (5 years) for males ( n = 548). Proposed sizes and ages are representative minimum and should be interpreted with the understanding that spawning and recruitment success increase for older, more mature fish than in early stages. Observed growth rates were rapid relative to both native and introduced ranges. We confirmed that Black Carp are developmentally indeterminate batch spawners due to the simultaneous presence of advanced growth oocytes via histology and egg measurements, with preserved egg average diameters ranging from 0.395 to 3.215 mm ( n = 23). Absolute fecundity estimates ranged from 72,748 to 3,542,789 eggs across the 966 to 1412 mm TL size range of individuals, with substantial variability among individuals attributed to poor relative fecundity estimates. These results represent the first step in assessing the reproductive rates of Mississippi River Black Carp via the size of reproductive development and potential contributions through fecundity. The results and population rates presented here may be used or adapted for future studies on regional spawning phenology and reproductive development, or in population growth models for control.

Arkansas, Illinois, Indiana, Kentucky, Louisiana, ↗