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

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At least 73 records · Page 4Linked to original sources
USGS2013

To the editor: Reply confuses newsprint with media

“Is Science in Danger of Sanctifying the Wolf” (Mech, 2012), contends that some scientists have claimed that wolf (Canis lupus) restoration has led to many ecological benefits lower in the food chain but that other scientists have questioned the evidence for those claims. Furthermore, my article claims that “the media become complicit [in promoting positive studies about wolves] by immediately publicizing such studies (Table 1)….” Dr. Bruskotter’s letter (Bruskotter, 2012) contends that Houston et al. (2010) refute that statement. However, Houston et al. (2010) covered only newsprint, including many local newspapers dating back to 1999 before most of the scientific articles I mentioned were published. My article said nothing about newsprint or news media. It stated “media” which of course includes radio, TV, blogs, websites, magazines, social media, etc. These types of media reach a wider and often different audience than newsprint. The Houston et al. (2010)analysis included none of these latter types of media so does not refute my statements.

Biological Conservation↗
USGS2011

Glacial flour dust storms in the Gulf of Alaska: hydrologic and meteorological controls and their importance as a source of bioavailable iron

Iron is an essential micronutrient that limits primary productivity in much of the ocean, including the Gulf of Alaska (GoA). However, the processes that transport iron to the ocean surface are poorly quantified. We combine satellite and meteorological data to provide the first description of widespread dust transport from coastal Alaska into the GoA. Dust is frequently transported from glacially-derived sediment at the mouths of several rivers, the most prominent of which is the Copper River. These dust events occur most frequently in autumn, when coastal river levels are low and riverbed sediments are exposed. The dust plumes are transported several hundred kilometers beyond the continental shelf into iron-limited waters. We estimate the mass of dust transported from the Copper River valley during one 2006 dust event to be between 25–80 ktons. Based on conservative estimates, this equates to a soluble iron loading of 30–200 tons. We suggest the soluble Fe flux from dust originating in glaciofluvial sediment deposits from the entire GoA coastline is two to three times larger, and is comparable to the annual Fe flux to GoA surface waters from eddies of coastal origin. Given that glaciers are retreating in the coastal GoA region and in other locations, it is important to examine whether fluxes of dust are increasing from glacierized landscapes to the ocean, and to assess the impact of associated Fe on marine ecosystems.

Geophysical Research Letters↗
USGS2005

High dispersal in a frog species suggests that it is vulnerable to habitat fragmentation

Global losses of amphibian populations are a major conservation concern and their causes have generated substantial debate. Habitat fragmentation is considered one important cause of amphibian decline. However, if fragmentation is to be invoked as a mechanism of amphibian decline, it must first be established that dispersal is prevalent among contiguous amphibian populations using formal movement estimators. In contrast, if dispersal is naturally low in amphibians, fragmentation can be disregarded as a cause of amphibian declines and conservation efforts can be focused elsewhere. We examined dispersal rates in Columbia spotted frogs ( Rana luteiventris ) using capture–recapture analysis of over 10 000 frogs in combination with genetic analysis of microsatellite loci in replicate basins. We found that frogs had exceptionally high juvenile dispersal rates (up to 62% annually) over long distances (>5 km), large elevation gains (>750 m) and steep inclines (36° incline over 2 km) that were corroborated by genetic data showing high gene flow. These findings show that dispersal is an important life-history feature of some amphibians and suggest that habitat fragmentation is a serious threat to amphibian persistence.

Montana↗
USGS2016

MT3D-USGS version 1: A U.S. Geological Survey release of MT3DMS updated with new and expanded transport capabilities for use with MODFLOW

MT3D-USGS, a U.S. Geological Survey updated release of the groundwater solute transport code MT3DMS, includes new transport modeling capabilities to accommodate flow terms calculated by MODFLOW packages that were previously unsupported by MT3DMS and to provide greater flexibility in the simulation of solute transport and reactive solute transport. Unsaturated-zone transport and transport within streams and lakes, including solute exchange with connected groundwater, are among the new capabilities included in the MT3D-USGS code. MT3D-USGS also includes the capability to route a solute through dry cells that may occur in the Newton-Raphson formulation of MODFLOW (that is, MODFLOW-NWT). New chemical reaction Package options include the ability to simulate inter-species reactions and parent-daughter chain reactions. A new pump-and-treat recirculation package enables the simulation of dynamic recirculation with or without treatment for combinations of wells that are represented in the flow model, mimicking the above-ground treatment of extracted water. A reformulation of the treatment of transient mass storage improves conservation of mass and yields solutions for better agreement with analytical benchmarks. Several additional features of MT3D-USGS are (1) the separate specification of the partitioning coefficient ( K d ) within mobile and immobile domains; (2) the capability to assign prescribed concentrations to the top-most active layer; (3) the change in mass storage owing to the change in water volume now appears as its own budget item in the global mass balance summary; (4) the ability to ignore cross-dispersion terms; (5) the definition of Hydrocarbon Spill-Source Package (HSS) mass loading zones using regular and irregular polygons, in addition to the currently supported circular zones; and (6) the ability to specify an absolute minimum thickness rather than the default percent minimum thickness in dry-cell circumstances. Benchmark problems that implement the new features and packages test the accuracy of new code through comparison to analytical benchmarks, as well as to solutions from other published codes. The input file structure for MT3D-USGS adheres to MT3DMS conventions for backward compatibility: the new capabilities and packages described herein are readily invoked by adding three-letter package name acronyms to the name file or by setting input flags as needed. Memory is managed in MT3D-USGS using FORTRAN modules in order to simplify code development and expansion.

Techniques and Methods↗
USGS2023

Can preserved museum specimens be to be used to reconstruct fish mercury burden and sources through time?

To evaluate the utility of preserved fishes for reconstructing historical and spatial patterns of mercury (Hg) exposure, we experimentally tested the stability of Hg concentrations and Hg stable isotope ratios under standard museum practices of specimen preservation. We found that loss of unidentified constituents during preservation changed Hg concentrations in fish muscle. Fish reared in the lab with minimal Hg exposure were susceptible to exogenous contamination with inorganic mercury (iHg) when preservative fluids were intentionally spiked or iHg leached passively from contaminated wild fishes in the same container. This contamination impacted Hg isotope values of total Hg, but the conservative nature of MeHg allows us to quantitatively correct for iHg contamination. Our findings validate the potential to use fishes from the world’s museums to generate spatiotemporal baselines for the Minamata Convention on Mercury, but we indicate precautionary strategies to maximize inference strength. Selecting the largest specimens of a target species helps dilute any iHg contamination. Specimens should be drawn from lots that were not comingled with fishes from other collections, to minimize risk of iHg transfer among fish with different contamination histories. Focusing on low-lipid species will enhance the comparability of Hg concentrations between historical and contemporary collections.

Environmental Science and Technology Letters↗
USGS2003

Extraordinary phase separation and segregation in vent fluids from the southern East Pacific Rise

The discovery of Brandon vent on the southern East Pacific Rise is providing new insights into the controls on midocean ridge hydrothermal vent fluid chemistry. The physical conditions at the time ofsampling (287 bar and 405??C) place the Brandon fluids very close to the critical point of seawater (298 bar and 407??C). This permits in situ study of the effects of near criticalphenomena, which are interpreted to be the primary cause of enhanced transition metal transport in these fluids. Of the five orifices on Brandon sampled, three were venting fluids with less than seawater chlorinity, and two were venting fluids with greater than seawater chlorinity. The liquid phase orifices contain 1.6-1.9 times the chloride content of the vapors. Most other elements, excluding the gases, have this same ratio demonstrating the conservative nature of phase separation and the lack of subsequent water-rock interaction. The vapor and liquid phases vent at the same time from orifices within meters of each other on the Brandon structure. Variations in fluid compositions occur on a time scale of minutes. Our interpretation is that phase separation and segregation must be occurring 'real time' within the sulfide structure itself. Fluids from Brandon therefore provide an unique opportunity to understand in situ phase separation without the overprinting of continued water-rock interaction with the oceanic crust, as well as critical phenomena. ?? 2002 Elsevier Science B.V. All rights reserved.

Earth and Planetary Science Letters↗
USGS2020

Phosphorus runoff risk assessment in karstic regions of the U.S.

The Phosphorus (P) Index risk assessment tool has been widely adopted across the U.S. to identify and rank site vulnerability to P runoff as part of the Natural Resources Conservation Service (NRCS) nutrient management planning (NMP) process. However, limited success has been achieved in addressing the risk of P loss by subsurface flow pathways, despite its relative importance in certain areas of the U.S., particularly in those States dominated by karst terrain. Here we review how States with varying land areas classified as having karst features address the risk of P runoff during the NMP process. Indices adopted in Illinois and Indiana require setbacks (15 – 72 m widths) around surface karst features. The remaining States with karst, address the risk of P loss in NMP development rather than the application of a P Index. Given the spatially variable hydrogeologic properties of karst, technically rigorous field‐scale factors are unlikely to be developed in the near future.

Agricultural & Environmental Letters↗
USGS2024

Strengths and opportunities in gopher tortoise population modeling: Reply to Loope et al.

We read the letter written by Loope et al. (2024) that evaluated the predictive population model for gopher tortoises from our previous paper ( Folt et al., 2022 ), and, despite criticism raised, we contend that our effort remains a valuable contribution. In our previous paper, we performed an unprecedented and exhaustive review of gopher tortoise population demography, which synthesized a large volume of literature about the current state of knowledge on gopher tortoise population dynamics and factors that influence demographic rates, including anthropogenic threats ( Folt et al., 2022 ). We then built a predictive population model that examined the relative influence of multiple anthropogenic stressors on tortoise populations into the future, while accounting for important geographic variation ( Folt et al., 2022 ).

Global Ecology and Conservation↗
USGS2016

Climate-induced warming of lakes can be either amplified or suppressed by trends in water clarity

Climate change is rapidly warming aquatic ecosystems including lakes and reservoirs. However, variability in lake characteristics can modulate how lakes respond to climate. Water clarity is especially important both because it influences the depth range over which heat is absorbed, and because it is changing in many lakes. Here, we show that simulated long-term water clarity trends influence how both surface and bottom water temperatures of lakes and reservoirs respond to climate change. Clarity changes can either amplify or suppress climate-induced warming, depending on lake depth and the direction of clarity change. Using a process-based model to simulate 1894 north temperate lakes from 1979 to 2012, we show that a scenario of decreasing clarity at a conservative yet widely observed rate of 0.92% yr −1 warmed surface waters and cooled bottom waters at rates comparable in magnitude to climate-induced warming. For lakes deeper than 6.5 m, decreasing clarity was sufficient to fully offset the effects of climate-induced warming on median whole-lake mean temperatures. Conversely, a scenario increasing clarity at the same rate cooled surface waters and warmed bottom waters relative to baseline warming rates. Furthermore, in 43% of lakes, increasing clarity more than doubled baseline bottom temperature warming rates. Long-term empirical observations of water temperature in lakes with and without clarity trends support these simulation results. Together, these results demonstrate that water clarity trends may be as important as rising air temperatures in determining how waterbodies respond to climate change.

Limnology and Oceanography Letters↗
USGS2010

Generalizing a nonlinear geophysical flood theory to medium-sized river networks

The central hypothesis of a nonlinear geophysical flood theory postulates that, given space-time rainfall intensity for a rainfall-runoff event, solutions of coupled mass and momentum conservation differential equations governing runoff generation and transport in a self-similar river network produce spatial scaling, or a power law, relation between peak discharge and drainage area in the limit of large area. The excellent fit of a power law for the destructive flood event of June 2008 in the 32,400-km 2 Iowa River basin over four orders of magnitude variation in drainage areas supports the central hypothesis. The challenge of predicting observed scaling exponent and intercept from physical processes is explained. We show scaling in mean annual peak discharges, and briefly discuss that it is physically connected with scaling in multiple rainfall-runoff events. Scaling in peak discharges would hold in a non-stationary climate due to global warming but its slope and intercept would change.

Geophysical Research Letters↗
USGS2021

Authors’ reply to letter to the editor: Continued improvement to genetic diversity indicator for CBD

We appreciate the encouraging response to our call for indicators for genetic diversity within the post-2020 Global Biodiversity Framework of the Convention on Biological Diversity, CBD (Laikre et al. 2020 ; Hoban et al. 2020 ). In agreement with us, Frankham ( 2021 ) highlights the urgent necessity for the CBD to include an indicator that tracks the maintenance of genetic diversity within populations of all species—wild and domestic. Draft CBD Headline indicators (which all CBD Parties will need to report) do not include genetic diversity within populations of wild species (CBD/SBSTTA/24/3Add.1).

Conservation Genetics↗
USGS2026

First application of a coastal-dune model (AeoLiS) to simulate fluvial-aeolian morphodynamics

Quantifying aeolian processes is important to decision-making in river management and for optimizing strategies for ecosystem conservation, natural resource management, and recreation. We applied the AeoLiS aeolian transport model, originally developed for coastal environments, to a dryland river corridor to evaluate its ability to simulate sediment dynamics in a fluvial-aeolian system. The model reproduced spatial and temporal patterns of geomorphic change at a Grand Canyon sandbar, including aeolian dune formation, observed in field data. The model effectively captured trends in observed sediment movement in the spring and summer months. Thus, despite assuming a single grain-size, static vegetation, and not directly accounting for variable sediment supply from fluvial sources, the model performs well at capturing aeolian processes in a complex fluvial-aeolian system. AeoLiS demonstrates strong potential for dryland river applications and management, due to its flexibility and compatibility with coupled modeling frameworks.

Arizona↗
USGS2014

A stage-structured, spatially explicit migration model for Myotis bats: mortality location affects system dynamics

Bats are ecologically and economically important species because they consume insects, transport nutrients, and pollinate flowers. Many species of bats, including those in the Myotis genus, are facing population decline and increased extinction risk. Despite these conservation concerns, few models exist for providing insight into the population dynamics of bats in a spatially explicit context. We developed a model for bats by considering the stage-structured colonial life history of Myotis bats with their annual migration behavior. This model provided insight into network dynamics. We specifically focused on two Myotis species living in the eastern United States: the Indiana bat ( M. sodalis ), which is a Federally listed endangered species, and the little brown bat ( M. lucifugus ), which is under consideration for listing as an endangered species. We found that multiple equilibria exist for the local, migratory subpopulations even though the total population was constant. These equilibria suggest the location and magnitude of stressors such as White-nose Syndrome, meteorological phenomena, or impacts of wind turbines on survival influence system dynamics and risk of population extirpation in difficult to predict ways.

Letters in Biomathematics↗
USGS2021

Why disease ecology needs life-history theory: A host perspective

When facing an emerging infectious disease of conservation concern, we often have little information on the nature of the host‐parasite interaction to inform management decisions. However, it is becoming increasingly clear that the life‐history strategies of host species can be predictive of individual‐ and population‐level responses to infectious disease, even without detailed knowledge on the specifics of the host‐parasite interaction. Here, we argue that a deeper integration of life‐history theory into disease ecology is timely and necessary to improve our capacity to understand, predict and mitigate the impact of endemic and emerging infectious diseases in wild populations. Using wild vertebrates as an example, we show that host life‐history characteristics influence host responses to parasitism at different levels of organisation, from individuals to communities. We also highlight knowledge gaps and future directions for the study of life‐history and host responses to parasitism. We conclude by illustrating how this theoretical insight can inform the monitoring and control of infectious diseases in wildlife.

Ecology Letters↗
USGS2002

The lizard fauna of Guam's fringing islets: Island biogeography, phylogenetic history, and conservation implications

We sampled the lizard fauna of twenty-two small islets fringing the Pacific island of Guam and used these data to shed light on the processes responsible for present-day diversity. Habitat diversity, measured by islet area and vegetation complexity, was significantly correlated with the number of species found on an islet. However, islet distance and elevation were not significant predictors of diversity. Distribution patterns were slightly different for the two major families in our sample, Scincidae and Gekkonidae: skinks needed larger islets to maintain a population than did geckos. Presence/absence patterns were highly and significantly nested, and population density was correlated with the number of islets on which a species was found. An area cladogram was poorly supported and showed no faunal similarity between nearby islands. These patterns indicate that extinctions on most islets were due mostly to non-catastrophic, long-acting biological causes. The presence on the islets of species extirpated on Guam and the lack of significant nestedness on islands with greater maximum elevation highlight the impact that predators (primarily brown treesnakes) can have. Our findings also show that small reserves will not suffice to protect endangered lizard faunas, and that the islets may serve as a short-term repository of such species until snake-free areas can be established on Guam.

Global Ecology and Biogeography Letters↗
USGS2021

Seasonally dynamic nutrient modeling quantifies storage lags and time-varying reactivity across large river basins

Nutrients that have gradually accumulated in soils, groundwaters, and river sediments in the United States over the past century can remobilize and increase current downstream loading, obscuring effects of conservation practices aimed at protecting water resources. Drivers of storage accumulation and release of nutrients are poorly understood at the spatial scale of basins to watersheds. Predicting water quality outcomes in large river basins demands modeling storage lags and time varying reactivity that models of mean conditions typically cannot elucidate. We developed a seasonally dynamic approach to large-scale nutrient modeling based on a multiscale framework and nutrient storage lags were quantified for the nearly 190 000 small catchments that feed the rivers across the northeastern United States where catchment mean transit times were found to be around 4.7 (2–10) years for nitrogen and 1.3 (0.7–2) years for phosphorus. Nutrient loads carried in river flow in the current season contained a significant—and sometimes dominant—portion of mass lagged in its release from catchment storage repositories. Our approach of integrating storage releases with seasonally dynamic hydroclimatic drivers sets the stage to assess the accumulated effects of nutrient storage and lagged releases to the river interacting with seasonally varying nutrient reactivity and societal management actions throughout large river basins.

Environmental Research Letters↗
USGS2009

Hybridization rapidly reduces fitness of a native trout in the wild

Human-mediated hybridization is a leading cause of biodiversity loss worldwide. How hybridization affects fitness and what level of hybridization is permissible pose difficult conservation questions with little empirical information to guide policy and management decisions. This is particularly true for salmonids, where widespread introgression among non-native and native taxa has often created hybrid swarms over extensive geographical areas resulting in genomic extinction. Here, we used parentage analysis with multilocus microsatellite markers to measure how varying levels of genetic introgression with non-native rainbow trout (Oncorhynchus mykiss) affect reproductive success (number of offspring per adult) of native westslope cutthroat trout (Oncorhynchus clarkii lewisi) in the wild. Small amounts of hybridization markedly reduced fitness of male and female trout, with reproductive success sharply declining by approximately 50 per cent, with only 20 per cent admixture. Despite apparent fitness costs, our data suggest that hybridization may spread due to relatively high reproductive success of first-generation hybrids and high reproductive success of a few males with high levels of admixture. This outbreeding depression suggests that even low levels of admixture may have negative effects on fitness in the wild and that policies protecting hybridized populations may need reconsideration. ?? 2009 The Royal Society.

Biology Letters↗
USGS2016

Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines

Loss of Arctic sea ice owing to climate change is the primary threat to polar bears throughout their range. We evaluated the potential response of polar bears to sea-ice declines by (i) calculating generation length (GL) for the species, which determines the timeframe for conservation assessments; (ii) developing a standardized sea-ice metric representing important habitat; and (iii) using statistical models and computer simulation to project changes in the global population under three approaches relating polar bear abundance to sea ice. Mean GL was 11.5 years. Ice-covered days declined in all subpopulation areas during 1979–2014 (median −1.26 days year −1 ). The estimated probabilities that reductions in the mean global population size of polar bears will be greater than 30%, 50% and 80% over three generations (35–41 years) were 0.71 (range 0.20–0.95), 0.07 (range 0–0.35) and less than 0.01 (range 0–0.02), respectively. According to IUCN Red List reduction thresholds, which provide a common measure of extinction risk across taxa, these results are consistent with listing the species as vulnerable. Our findings support the potential for large declines in polar bear numbers owing to sea-ice loss, and highlight near-term uncertainty in statistical projections as well as the sensitivity of projections to different plausible assumptions.

Biology Letters↗