SEARCH · Geology Reports

Results for “Contributions in Science”

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

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources

USGS2014

Genetic evidence of local exploitation of Atlantic salmon in a coastal subsistence fishery in the Northwest Atlantic

Fisheries targeting mixtures of populations risk the over utilization of minor stock constituents unless harvests are monitored and managed. We evaluated stock composition and exploitation of Atlantic salmon in a subsistence fishery in coastal Labrador, Canada using genetic mixture analysis and individual assignment with a microsatellite baseline (15 loci, 11 829 individuals, 12 regional groups) encompassing the species western Atlantic range. Bayesian and maximum likelihood mixture analyses of fishery samples over six years (2006-2011; 1 772 individuals) indicate contributions of adjacent stocks of 96-97%. Estimates of fishery associated exploitation were highest for Labrador salmon (4.2-10.6% per year) and generally < 1% for other regions. Individual assignment of fishery samples indicated non-local contributions to the fishery (e.g., Quebec, Newfoundland) were rare and primarily in southern Labrador, consistent with migration pathways utilizing the Strait of Belle Isle. This work illustrates how genetic analysis of mixed stock Atlantic salmon fisheries in the northwest Atlantic using this new baseline can disentangle exploitation and reveal complex migratory behaviours.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2016

Invasive European bird cherry disrupts stream-riparian linkages: effects on terrestrial invertebrate prey subsidies for juvenile coho salmon

The spread of invasive species in riparian forests has the potential to affect both terrestrial and aquatic organisms linked through cross-ecosystem resource subsidies. However, this potential had not been explored in regards to terrestrial prey subsidies for stream fishes. To address this, we examined the effects of an invasive riparian tree, European bird cherry (EBC, Prunus padus ), spreading along urban Alaskan salmon streams, by collecting terrestrial invertebrates present on the foliage of riparian trees, their subsidies to streams, and their consumption by juvenile coho salmon ( Oncorhynchus kisutch ). Riparian EBC supported four to six times less terrestrial invertebrate biomass on its foliage and contributed two to three times lower subsidies relative to native deciduous trees. This reduction in terrestrial invertebrate biomass was consistent between two watersheds over 2 years. In spite of this reduction in terrestrial prey resource input, juvenile coho salmon consumed similar levels of terrestrial invertebrates in stream reaches bordered by EBC. Although we did not see ecological effects extending to stream salmonids, reduced terrestrial prey subsidies to streams are likely to have negative consequences as EBC continues to spread.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2024

Preparing for a Bsal invasion into North America has improved multi-sector readiness

Western palearctic salamander susceptibility to the skin disease caused by the amphibian chytrid fungus Batrachochytrium salamandrivorans (Bsal) was recognized in 2014, eliciting concerns for a potential novel wave of amphibian declines following the B. dendrobatidis (Bd) chytridiomycosis global pandemic. Although Bsal had not been detected in North America, initial experimental trials supported the heightened susceptibility of caudate amphibians to Bsal chytridiomycosis, recognizing the critical threat this pathogen poses to the North American salamander biodiversity hotspot. Here, we take stock of 10 years of research, collaboration, engagement, and outreach by the North American Bsal Task Force. We summarize main knowledge and conservation actions to both forestall and respond to Bsal invasion into North America. We address the questions: what have we learned; what are current challenges; and are we ready for a more effective reaction to Bsal’s eventual detection? We expect that the many contributions to preemptive planning accrued over the past decade will pay dividends in amphibian conservation effectiveness and can inform future responses to other novel wildlife diseases and extreme threats.

North America↗

USGS2009

Toward immunogenetic studies of amphibian chytridiomycosis: Linking innate and acquired immunity

Recent declines in amphibian diversity and abundance have contributed significantly to the global loss of biodiversity. The fungal disease chytridiomycosis is widely considered to be a primary cause of these declines, yet the critical question of why amphibian species differ in susceptibility remains unanswered. Considerable evidence links environmental conditions and interspecific variability of the innate immune system to differential infection responses, but other sources of individual, population, or species-typical variation may also be important. In this article we review the preliminary evidence supporting a role for acquired immune defenses against chytridiomycosis, and advocate for targeted investigation of genes controlling acquired responses, as well as those that functionally bridge the innate and acquired immune systems. Immunogenetic data promise to answer key questions about chytridiomycosis susceptibility and host-pathogen coevolution, and will draw much needed attention to the importance of considering evolutionary processes in amphibian conservation management and practice. ?? 2009 by American Institute of Biological Sciences.

BioScience↗

USGS2026

Temperature and precipitation source variability and glacial dynamics in the southwestern United States at Fish Lake, Utah, since late MIS 4

An improved understanding of hydroclimate response to natural climate forcings is needed to evaluate impacts of changing seasonal circulation patterns on current and future drought in the southwestern United States (‘the Southwest’). However, few terrestrial records from the Southwest preserve changes in moisture availability continuously prior to the Last Glacial Maximum (LGM, ∼24.5 ka). Fish Lake, in the Upper Colorado River Basin, preserves a long (∼67 ka), continuous, high-resolution (∼3.3 cm/century) sedimentary record spanning from late Marine Isotope Stage (MIS) 4 to present. Here, we investigate the relative contributions of seasonal precipitation and moisture source using the hydrogen isotope value of the n -C 29 leaf wax alkane and changes in temperature using branched glycerol dialkyl glycerol tetraethers (brGDGTs). During the warm post glacial period (14 ka to present), a greater contribution of annual precipitation is sourced from the North American Monsoon (NAM) in response to declining winter insolation and rising greenhouse gases, weakening westerly storms and shifting them northward. MIS 3 (∼61 to 29 ka) is also influenced by NAM inputs, however, to a smaller magnitude than during the post glacial period when temperatures were warmer. However, stadial periods (MIS 2, 29 to 14.1 ka) show 2 H-enriched values, suggesting warm conditions and large contributions of NAM precipitation during the LGM, contradicting other proxies and regional records. The LGM is the only period in the record where glaciers are present in the catchment, thus we hypothesize glacial erosion reworked pre-LGM aged soil organic matter and biased the record during this time.

Utah↗

USGS2015

Role of anaerobic ammonium oxidation (anammox) in nitrogen removal from a freshwater aquifer

Anaerobic ammonium oxidation (anammox) couples the oxidation of ammonium with the reduction of nitrite, producing N 2 . The presence and activity of anammox bacteria in groundwater were investigated at multiple locations in an aquifer variably affected by a large, wastewater-derived contaminant plume. Anammox bacteria were detected at all locations tested using 16S rRNA gene sequencing and quantification of hydrazine oxidoreductase ( hzo ) gene transcripts. Anammox and denitrification activities were quantified by in situ 15 NO 2 – tracer tests along anoxic flow paths in areas of varying ammonium, nitrate, and organic carbon abundances. Rates of denitrification and anammox were determined by quantifying changes in 28 N 2 , 29 N 2 , 30 N 2 , 15 NO 3 – , 15 NO 2 – , and 15 NH 4 + with groundwater travel time. Anammox was present and active in all areas tested, including where ammonium and dissolved organic carbon concentrations were low, but decreased in proportion to denitrification when acetate was added to increase available electron supply. Anammox contributed 39–90% of potential N 2 production in this aquifer, with rates on the order of 10 nmol N 2 –N L –1 day –1 . Although rates of both anammox and denitrification during the tracer tests were low, they were sufficient to reduce inorganic nitrogen concentrations substantially during the overall groundwater residence times in the aquifer. These results demonstrate that anammox activity in groundwater can rival that of denitrification and may need to be considered when assessing nitrogen mass transport and permanent loss of fixed nitrogen in aquifers.

Environmental Science & Technology↗

USGS2017

Organic chemical characterization and mass balance of a hydraulically fractured well: From fracturing fluid to produced water over 405 days

A long-term field study (405 days) of a hydraulically fractured well from the Niobrara Formation in the Denver-Julesburg Basin was completed. Characterization of organic chemicals used in hydraulic fracturing and their changes through time, from the preinjected fracturing fluid to the produced water, was conducted. The characterization consisted of a mass balance by dissolved organic carbon (DOC), volatile organic analysis by gas chromatography/mass spectrometry, and nonvolatile organic analysis by liquid chromatography/mass spectrometry. DOC decreased from 1500 mg/L in initial flowback to 200 mg/L in the final produced water. Only ∼11% of the injected DOC returned by the end of the study, with this 11% representing a maximum fraction returned since the formation itself contributes DOC. Furthermore, the majority of returning DOC was of the hydrophilic fraction (60–85%). Volatile organic compound analysis revealed substantial concentrations of individual BTEX compounds (0.1–11 mg/L) over the 405-day study. Nonvolatile organic compounds identified were polyethylene glycols (PEGs), polypropylene glycols (PPG), linear alkyl-ethoxylates, and triisopropanolamine (TIPA). The distribution of PEGs, PPGs, and TIPA and their ubiquitous presence in our samples and the literature illustrate their potential as organic tracers for treatment operations or in the event of an environmental spill.

Environmental Science & Technology↗

USGS2018

Understanding how microbiomes influence the systems they inhabit

Translating the ever-increasing wealth of information on microbiomes (environment, host, or built environment) to advance the understanding of system-level processes is proving to be an exceptional research challenge. One reason for this challenge is that relationships between characteristics of microbiomes and the system-level processes they influence are often evaluated in the absence of a robust conceptual framework and reported without elucidating the underlying causal mechanisms. The reliance on correlative approaches limits the potential to expand the inference of a single relationship to additional systems and advance the field. We propose that research focused on how microbiomes influence the systems they inhabit should work within a common framework and target known microbial processes that contribute to the system-level processes of interest. Here we identify three distinct categories of microbiome characteristics (microbial processes, microbial community properties, and microbial membership) and propose a framework to empirically link each of these categories to each other and the broader system level processes they affect. We posit that it is particularly important to distinguish microbial community properties that can be predicted from constituent taxa (community aggregated traits) from and those properties that are currently unable to be predicted from constituent taxa (emergent properties). Existing methods in microbial ecology can be applied to more explicitly elucidate properties within each of these categories and connect these three categories of microbial characteristics with each other. We view this proposed framework, gleaned from a breadth of research on environmental microbiomes and ecosystem processes, as a promising pathway with the potential to advance discovery and understanding across a broad range of microbiome science.

Nature Microbiology↗

USGS1983

Eruption prediction aided by electronic tiltmeter data at Mount St. Helens

Telemetry from electronic tiltmeters in the crater at Mount St. Helens contributed to accurate predictions of all six effusive eruptions from June 1981 to August 1982. Tilting of the crater floor began several weeks before each eruption, accelerated sharply for several days, and then abruptly changed direction a few minutes to days before extrusion began. Each episode of uplift was caused by the intrusion of magma into the lava dome from a shallow source, causing the dome to inflate and eventually rupture. Release of magma pressure and increased surface loading by magma added to the dome combined to cause subsidence just prior to extrusion.

Washington↗

USGS1994

Hubble Space Telescope observations of comet P/Shoemaker-Levy 9 (1993e)

The Hubble Space Telescope observed the fragmented comet P/Shoemaker-Levy 9 (1993e) (P indicates that it is a periodic comet) on 1 July 1993. Approximately 20 individual nuclei and their comae were observed in images taken with the Planetary Camera. After subtraction of the comae light, the 11 brightest nuclei have magnitudes between ∼23.7 and 24.8. Assuming that the geometric albedo is 0.04, these magnitudes imply that the nuclear diameters are in the range ∼2.5 to 4.3 kilometers. If the density of each nucleus is 1 gram per cubic centimeter, the total energy deposited by the impact of these 11 nuclei into Jupiter's atmosphere next July will be ∼4 × 10 30 ergs (∼10 8 megatons of TNT). This latter number should be regarded as an upper limit because the nuclear magnitudes probably contain a small residual coma contribution. The Faint Object Spectrograph was used to search for fluorescence from OH, which is usually an excellent indicator of cometary activity. No OH emission was detected, and this can be translated into an upper limit on the water production rate of ∼2 × 10 27 molecules per second.

Science↗

USGS2020

A 36-year record of rock avalanches in the Saint Elias Mountains of Alaska, with implications for future hazards

Glacial retreat and mountain-permafrost degradation resulting from rising global temperatures have the potential to impact the frequency and magnitude of landslides in glaciated environments. Several recent events, including the 2015 Taan Fiord rock avalanche, which triggered a tsunami with one of the highest wave runups ever recorded, have called attention to the hazards posed by landslides in regions like southern Alaska. In the Saint Elias Mountains, the presence of weak sedimentary and metamorphic rocks and active uplift resulting from the collision of the Yakutat and North American tectonic plates create landslide-prone conditions. To differentiate between the typical frequency of landsliding resulting from the geologic and tectonic setting of this region, and landslide processes that may be accelerated due to changes in climate, we used Landsat imagery to create an inventory of rock avalanches in a 3700 km2 area of the Saint Elias Mountains. During the period from 1984-2019, we identified 220 rock avalanches with a mean recurrence interval of 60 days. We compared our landslide inventory with a catalog of M ≥ 4 earthquakes to identify potential coseismic events, but only found three possible earthquake-triggered rock avalanches. We observed a distinct temporal cluster of 41 rock avalanches from 2013 through 2016 that correlated with above average air temperatures (including the three warmest years on record in Alaska, 2014-2016); this cluster was similar to a temporal cluster of recent rock avalanches in nearby Glacier Bay National Park and Preserve. The majority of rock avalanches initiated from bedrock ridges in probable permafrost zones, suggesting that ice loss due to permafrost degradation, as opposed to glacial thinning, could be a dominant factor contributing to rock-slope failures in the high elevation areas of the Saint Elias Mountains. Although earthquake-triggered landslides have episodically occurred in southern Alaska, evidence from our study suggests that area-normalized rates of non-coseismic rock avalanches were greater during the period from 1964 to 2019, and that the frequency of these events will continue to increase as the climate continues to warm. These findings highlight the need for hazard assessments in Alaska that address changes in landslide patterns related to climate change.

Alaska↗

USGS2014

Continuous estimation of baseflow in snowmelt-dominated streams and rivers in the Upper Colorado River Basin: A chemical hydrograph separation approach

Effective science-based management of water resources in large basins requires a qualitative understanding of hydrologic conditions and quantitative measures of the various components of the water budget, including difficult to measure components such as baseflow discharge to streams. Using widely available discharge and continuously collected specific conductance (SC) data, we adapted and applied a long established chemical hydrograph separation approach to quantify daily and representative annual baseflow discharge at fourteen streams and rivers at large spatial (> 1,000 km 2 watersheds) and temporal (up to 37 years) scales in the Upper Colorado River Basin. On average, annual baseflow was 21-58% of annual stream discharge, 13-45% of discharge during snowmelt, and 40-86% of discharge during low-flow conditions. Results suggest that reservoirs may act to store baseflow discharged to the stream during snowmelt and release that baseflow during low-flow conditions, and that irrigation return flows may contribute to increases in fall baseflow in heavily irrigated watersheds. The chemical hydrograph separation approach, and associated conceptual model defined here provide a basis for the identification of land use, management, and climate effects on baseflow.

Colorado, Utah↗

USGS2020

The historic events at Kilauea Volcano in 2018: Summit collapse, rift zone eruption, and Mw 6.9 earthquake: Preface to the special issue

Kīlauea Volcano, on the Island of Hawaiʻi, has had a prominent role in the science of volcanology, and a long history of generating new insights into how volcanoes operate (Tilling et al. 2014; Garcia 2015). Native Hawaiians shared ideas on the behavior of the volcano with early Western visitors to Kīlauea, addressing the basic geometry of magma supply and transport (Ellis 1825; Bishop 1827). The recognition that magma originated at the summit and was transferred at shallow levels to the flanks implied that these ideas were rooted in centuries of observation preceding Western contact. The lava lake activity at Kīlauea’s summit in the 1800s and early 1900s fascinated early geologists, such as James Dana (1890), who published one of the first inquiries into the fundamental processes of Hawaiian volcanoes. The sustained activity led to the 1912 founding of the Hawaiian Volcano Observatory, one of the world’s first volcano observatories, by Thomas Jaggar (Tilling et al. 2014). Kīlauea’s activity in the 20th century contributed to the development of many modern volcano monitoring techniques (Tilling et al. 2014), which helped refine conceptual models of how volcanoes behave (Eaton and Murata, 1960).

Hawaii↗

USGS2021

Groundwater development leads to decreasing arsenic concentrations in the San Joaquin Valley, California

In the San Joaquin Valley (SJV), California, about 10% of drinking water wells since 2010 had arsenic concentrations above the US maximum contaminant level of 10 μg/L. High concentrations of arsenic are often associated with high pH (greater than 7.8) or reduced geochemical conditions. Although most wells have low arsenic (<3 μg/L) and do not have changing arsenic concentrations, this study found that most wells with concentrations above 10 μg/L had arsenic trends. Overall, about 24% of wells had time-series trends since 2010 and 59% had paired-sample trends since 2000. Most wells had decreasing arsenic trends, even in wells with higher arsenic concentrations. These wells often had co-detections of increasing nitrate and sulfate trends that reflect oxic groundwater likely derived from agricultural recharge. Wells with increasing arsenic trends were deeper or located in the valley trough where aquifer materials are more fine-grained and where reducing conditions favor arsenic mobility. Wells with arsenic trends also tend to be clustered near areas of higher well density. Groundwater pumping in these areas has likely increased the contribution of younger, more oxic groundwater in wells with declining arsenic or, less frequently, increased the contribution of higher pH or reduced groundwater in wells with rising arsenic. Projections of arsenic trends indicate that 37 wells with high arsenic presently will be below 10 μg/L in ten years. Unfortunately, these improvements will be largely offset by 31 wells that are expected to increase above 10 μg/L in addition to expected rises in nitrate in wells where arsenic decreased. This study shows how human-altered flow systems can impact the natural geochemical character of water in both beneficial and deleterious ways.

California↗

USGS2020

Landfill leachate contributes per-/poly-fluoroalkyl substances (PFAS) and pharmaceuticals to municipal wastewater

Widespread disposal of landfill leachate to municipal sewer infrastructure in the United States calls for an improved understanding of the relative organic-chemical contributions to the wastewater treatment plant (WWTP) waste stream and associated surface-water discharge to receptors in the environment. Landfill leachate, WWTP influent, and WWTP effluent samples were collected from three landfill-WWTP systems and compared with analogous influent and effluent samples from two WWTPs that did not receive leachate. Samples were analyzed for 73 per-/poly-fluoroalkyl substances (PFAS), 109 pharmaceuticals, and 21 hormones and related compounds. PFAS were detected more frequently in leachate (92%) than in influent (55%). Total PFAS concentrations in leachate (93,100 ng/L) were more than ten times higher than in influent (6,950 ng/L), and effluent samples (3,730 ng/L). Concentrations of bisphenol A; the nonprescription pharmaceuticals cotinine, lidocaine, nicotine; and the prescription pharmaceuticals amphetamine, carisoprodol, pentoxifylline, and thiabendazole were an order of magnitude higher in landfill leachate than WWTP influent. Leachate load contributions for PFAS (0.78 to 31 g/d), bisphenol A (0.97 to 8.3 g/d), and nonprescription (2.0 to 3.1 g/d) and prescription (0.48 to 2.5 g/d) pharmaceuticals to WWTP influent were generally low (<10 g/d) for most compounds because of high influent-to-leachate volumetric ratios (0.983). No clear differences in concentrations were apparent between effluents from WWTPs receiving landfill leachate and those that did not receive landfill leachate.

Environmental Science: Water Research & Technology↗

USGS2010

EAARL coastal topography-western Florida, post-Hurricane Charley, 2004: seamless (bare earth and submerged.

Project Description These remotely sensed, geographically referenced elevation measurements of lidar-derived seamless (bare-earth and submerged) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Coastal and Marine Geology Program (CMGP), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the western Florida coastline beachface, acquired post-Hurricane Charley on August 17 and 18, 2004. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative airborne lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multispectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for sub-meter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or sub-aerial topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation. For more information about similar projects, please visit the Decision Support for Coastal Science and Management website. Selected References Brock, J.C., Wright, C.W., Sallenger, A.H., Krabill, W.B., and Swift, R.N., 2002, Basis and methods of NASA airborne topographic mapper Lidar surveys for coastal studies: Journal of Coastal Research, v. 18, no. 1, p. 1-13. Crane, Michael, Clayton, Tonya, Raabe, Ellen, Stoker, Jason, Handley, Larry, Bawden, Gerald, Morgan, Karen, and Queija, Vivian, 2004, Report of the U.S. Geological Survey Lidar workshop sponsored by the Land Remote Sensing Program and held in St. Petersburg, FL, November 2002: U.S. Geological Survey Open-File Report 2004-1456, 72 p. Nayegandhi, Amar, Brock, J.C., and Wright, C.W., 2009, Small-footprint, waveform-resolving Lidar estimation of submerged and sub-canopy topography in coastal environments: International Journal of Remote Sensing, v. 30, no. 4, p. 861-878. Sallenger, A.H., Wright, C.W., and Lillycrop, Jeff, 2005, Coastal impacts of the 2004 hurricanes measured with airborne Lidar; initial results: Shore and Beach, v. 73, nos. 2-3, p. 10-14. Resources Included Readme.txt File

Data Series↗

USGS2025

Tracing invasion routes of Cuban treefrogs into Louisiana using mitochondrial DNA

Understanding the origin and spread of invasive species is critical for predicting when and where new introductions will establish, and impact native species. However, due to the complexity of contributing factors such as multiple introductions, dispersal method, genetic admixture in founding populations, and variable propagule pressure, genetic patterns observed in invasive species may not always conform to a single theoretical expectation. Cuban treefrogs ( Osteopilus septentrionalis ) are invasive in peninsular Florida and sporadically in the Florida panhandle. Though O. septentrionalis has been occasionally reported in Louisiana since the 1990s, established populations were not present until the discovery of a breeding population in New Orleans in 2017. In this study we investigated the source of this novel population using existing and newly generated cytochrome B (cyt-b) mitochondrial gene sequences from the native and invasive range of O. septentrionalis . We recovered a total of 14 cyt-b haplotypes, nine novel and five previously published. Within the 95 Louisiana invasion samples, we recovered seven haplotypes including five novel haplotypes. The haplotypes most common in Louisiana were shared exclusively with west and east Florida localities in central Florida, indicating a possible source population. The presence of haplotypes private to the Louisiana locality suggests other unsampled localities may also be contributing to the Louisiana settlement. Metrics of genetic diversity across native and invasive localities did not significantly differ. Furthermore, the Louisiana samples had higher genetic diversity than any single location sampled within Florida. Thus, genetic diversity and our haplotype connectivity suggest the Louisiana population is derived from multiple introductions from Florida. Our study highlights how demographic and genetic analyses can be utilized to understand the source and future expansion potential of invasive populations.

Florida, Louisiana↗

USGS2016

Seasonal flows of international British Columbia-Alaska rivers: The nonlinear influence of ocean-atmosphere circulation patterns

The northern portion of the Pacific coastal temperate rainforest (PCTR) is one of the least anthropogenically modified regions on earth and remains in many respects a frontier area to science. Rivers crossing the northern PCTR, which is also an international boundary region between British Columbia, Canada and Alaska, USA, deliver large freshwater and biogeochemical fluxes to the Gulf of Alaska and establish linkages between coastal and continental ecosystems. We evaluate interannual flow variability in three transboundary PCTR watersheds in response to El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Arctic Oscillation (AO), and North Pacific Gyre Oscillation (NPGO). Historical hydroclimatic datasets from both Canada and the USA are analyzed using an up-to-date methodological suite accommodating both seasonally transient and highly nonlinear teleconnections. We find that streamflow teleconnections occur over particular seasonal windows reflecting the intersection of specific atmospheric and terrestrial hydrologic processes. The strongest signal is a snowmelt-driven flow timing shift resulting from ENSO- and PDO-associated temperature anomalies. Autumn rainfall runoff is also modulated by these climate modes, and a glacier-mediated teleconnection contributes to a late-summer ENSO-flow association. Teleconnections between AO and freshet flows reflect corresponding temperature and precipitation anomalies. A coherent NPGO signal is not clearly evident in streamflow. Linear and monotonically nonlinear teleconnections were widely identified, with less evidence for the parabolic effects that can play an important role elsewhere. The streamflow teleconnections did not vary greatly between hydrometric stations, presumably reflecting broad similarities in watershed characteristics. These results establish a regional foundation for both transboundary water management and studies of long-term hydroclimatic and environmental change.

Alaska, British Columbia↗