SEARCH · Search USGS

Results for “Biology Direct”

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 163 records · Page 9Linked to original sources

USGS2012

Strategies for soil quality assessment using VNIR gyperspectral spectroscopy in a western Kenya Chronosequence

Visible and near-infrared reflectance spectroscopy (VNIRS) is a rapid and nondestructive method that can predict multiple soil properties simultaneously, but its application in multidimensional soil quality (SQ) assessment in the tropics still needs to be further assessed. In this study, VNIRS (350–2500 nm) was employed to analyze 227 air-dried soil samples of Ultisols from a soil chronosequence in western Kenya and assess 16 SQ indicators. Partial least squares regression (PLSR) was validated using the full-site cross-validation method by grouping samples from each farm or forest site. Most suitable models successfully predicted SQ indicators (R 2 ≥ 0.80; ratio of performance to deviation [RPD] ≥ 2.00) including soil organic matter (OM LOI ), active C, Ca, cation exchange capacity (CEC), and clay. Moderately-well predicted indicators (0.50 ≤ R 2 < 0.80; 1.40 ≤ RPD < 2.00) were water stable aggregation (WSA), Cu, silt, Mg, pH, sand, water content at permanent wilting point (Θ pwp ), and field capacity (Θ fc ). Poorly predicted indicators (R 2 < 0.50; RPD < 1.40) were EC, S, P, available water capacity (AWC), K, Zn, and penetration resistance. Combining VNIRS with selected field- and laboratory-measured SQ indicator values increased predictability. Furthermore, VNIRS showed moderate to substantial agreement in predicting interpretive SQ scores and a composite soil quality index (CSQI) especially when combined with directly measured SQ indicator values. In conclusion, VNIRS has good potential for low cost, rapid assessment of physical and biological SQ indicators but conventional soil chemical tests may need to be retained to provide comprehensive SQ assessments.

Western Kenya↗

USGS2015

Literature review of giant gartersnake ( Thamnophis gigas ) biology and conservation

This report reviews the available literature on giant gartersnakes ( Thamnophis gigas ) to compile existing information on this species and identify knowledge gaps that, if addressed, would help to inform conservation efforts for giant gartersnakes. Giant gartersnakes comprise a species of semi-aquatic snake precinctive to wetlands in the Central Valley of California. The diversion of surface water and conversion of wetlands to agricultural and other land uses resulted in the loss of more than 90 percent of natural giant gartersnake habitats. Because of this habitat loss, giant gartersnakes are now listed by the United States and California Endangered Species Acts as Threatened. Most extant populations occur in the rice-growing regions of the Sacramento Valley, which comprises the northern portion of the giant gartersnake’s former range. The huge demand for water in California for agriculture, industry, recreation, and other human consumption, combined with periodic severe drought, places remaining giant gartersnake habitats at increased risk of degradation and loss. This literature review summarizes the available information on giant gartersnake distribution, habitat relations, behavior, demography, and other aspects of its biology relevant to conservation. This information is then compiled into a graphical conceptual model that indicates the importance of different aspects of giant gartersnake biology for maintaining positive population growth, and identifies those areas for which important information relevant for conservation is lacking. Directing research efforts toward these aspects of giant gartersnake ecology will likely result in improvements to conserving this unique species while meeting the high demands for water in California.

Open-File Report↗

USGS1982

Evaluation of the river die-away biodegradation test

The reliability of the river die-away (RDA) test for establishing the biodegradability of chemicals was assessed. Reproducibility of biodegradation in the RDA test was analyzed under conditions in which the test is commonly done. Biodegradation results were not reproducible for di-2-ethylexyl phthalate (DEHP) and phthalic acid in replicated RDA tests using Missouri River water. Chemical and biological changes during the RDA tests probably reflected relative laboratory conditions. Initial suspended solids and subsequent DEHP biodegradation were directly related. Interpretation of RDA test results is enhanced by replicating experiments and comparing biodegradation of the test compound with a compound whose degradation properties are known. However, biodegradation measured with the RDA test is too variable and too dependent on laboratory treatment of samples to apply results directly to the aquatic environment.

Journal of the Water Pollution Control Federation↗

USGS1970

About nutria and their control

Wild animals are generally classed as beneficial or pest species, depending on the variable interests of man. Those that provide him with earnings, recreation, or enjoyment are considered beneficial; those that compete with him for food, or ruin his possessions or environment, are quickly dubbed pests. But all men do not have the same interests or the same environment, so many animals attain both a beneficial and a pest status. The wild nutria in the United States is one of these animals with a dual nature. It is most numerous in the Gulf States, particularly in Louisiana and Texas, where the sale of nutria fur and meat in some years is a several-million-dollar industry. Although it is a valuable resource, it sometimes causes so much agricultural damage that it is also classified as a pest. In the late 1950's, nutria damage to sugarcane and rice became so acute that the people of Louisiana and Texas asked the Federal Government for help. Research on the problem was assigned to the Division of Wildlife Research, Bureau of Sport Fisheries and Wildlife, which is responsible, among other things, for developing methods to control damage by wild animals. The Division's Denver Wildlife Research Center established field stations at Houma, Louisiana, and Beaumont, Texas, and in 1963 work was begun under congressional appropriation to fulfill this public request. The goal of the Houma and Beaumont stations was to develop a sound, scientific solution to the problem of controlling nutria damage. IT WAS NOT A PROGRAM OF ERADICATION. Because of the involvement of the fur and meat industry, the beneficial aspects of nutria had to be continuously recognized when potential methods of control were evaluated. Especially sought were workable control procedures that could be readily used by laymen. These would have to be relatively selective for nutria and safe for humans, domestic animals, and other wildlife. In 1967, four years after our studies were begun, we had found methods to solve the current and immediately foreseeable problems of nutria damage. This report presents much of the information we gathered during this four-year period about nutria and how to control them. Because it is meant primarily for the general public, it omits the specific references to the scientific literature that pepper most technical reports, but it does present background information on the history, biology, and behavior of nutria, particularly those in the Gulf Coast Region. The control methods presented, when used as directed, are safe and effective and provide solutions for most situations, including those where people want to alleviate nutria damage without killing the nutria. Though we were pleased with these results, research still continues, directed toward discovering new and better methods of control that will solve any future problem with nutria.

Resource Publication↗

USGS2020

Identifying candidate reference reaches to assess the physical and biological integrity of wadeable streams in different ecoregions and among stream sizes

Efforts to quantify disturbances to aquatic systems often use landscape-level metrics, presumably linked to ecological integrity, but fewer studies have directly linked ecological integrity to instream habitat, and applied these results to unsampled stream reaches throughout a landscape. We developed a flexible, quantitative approach that characterizes stream impairment across a landscape and identifies least-disturbed stream reaches to serve as benchmarks for high quality physical habitat and ecological integrity. Fish and macroinvertebrate community characteristics, reach-level physical habitat and water quality metrics were summarized in 891 wadeable stream reaches across two ecoregions in Missouri, USA. The influence of reach and water-quality characteristics as well as landscape-level variables on 7 fish and 3 macroinvertebrate community biological indicator metrics was then modeled using boosted regression trees (BRTs). On average, reach-level models explained more variance (25 and 27% in the two ecoregions examined) in biotic metrics than landscape-level models (18% and 20%). Abiotic and biotic associations differed among ecoregions and stream sizes, however, reach-level habitat (e.g., bankfull width/depth ratio, channel incision height) and water quality (e.g., dissolved oxygen, total chlorophyll) were consistently top predictors. At the landscape scale, fish richness in the agriculturally dominated ecoregion increased with decreased fragmentation/flow modification, while invertebrate metrics responded to agricultural disturbances. Invertebrate metrics in the forested ecoregion showed community degradation apparent with crop coverage as low as 8-10% of the riparian zone, while urban impairment was best detected using invertebrate indicators of biotic integrity and measures of fish trophic ecology. Relationships among landscape-scale variables and reach characteristics identified as top predictors in BRTs also highlighted potential mechanistic relationships among landscape, habitat, and measures of ecological integrity. Using the results of the landscape-level models, estimates for overall ecological integrity were predicted for over 28,000 stream reaches throughout Missouri, and a total of 1,423 candidate reference reaches were identified. The objective approach to characterizing stream impairment developed in this study offers specific advantages, including a reach and landscape-level evaluation of human disturbance as well as an inductive, multi-metric determination of ecological integrity.

Missouri↗

USGS2026

A weight-of-evidence system for integrating monitoring and environmental indicators to guide biological conservation and resource management of native taxa

Many state and federal environmental management agencies are charged with using data-driven evidence to conserve and restore threatened and endangered species that are adversely impacted by humans. Yet, statistical analyses of available environmental indicator data do not always promote unambiguous, ecologically-meaningful, evidence-based decisions for managing native biota. Here we modified our multi-step quantitative adaptive management framework to identify natural and anthropogenic environmental indicators that maintain or threaten native species. In a proof-of-concept example, we quantified how three native stream fish taxa responded to nine environmental indicators based on three criteria (i.e., statistical significance, ecological relevance, and agreement with expectations). The resulting Weight of Evidence (WoE) integration identified five groups of indicators, clarified ambiguous trends, and identified promising future directions that would not have emerged from examining a single analysis or a single taxon alone. Our evaluation and categorization of environmental indicators established the biological foundation on which multi-disciplinary sustainability rests. Our research contribution demonstrates how following a structured integration framework can lead to novel insights that benefit conservation across organisms and systems even when employing relatively simple analytical techniques. Our results address the following often ignored questions: How do we systematically link together different analytical components of the same larger problems? How do we ecologically integrate similar and dissimilar results across analyses? How can we identify generalities by comparing multiple taxa?

Kansas↗

USGS2014

Modelling non-Euclidean movement and landscape connectivity in highly structured ecological networks

Movement is influenced by landscape structure, configuration and geometry, but measuring distance as perceived by animals poses technical and logistical challenges. Instead, movement is typically measured using Euclidean distance, irrespective of location or landscape structure, or is based on arbitrary cost surfaces. A recently proposed extension of spatial capture-recapture (SCR) models resolves this issue using spatial encounter histories of individuals to calculate least-cost paths (ecological distance: Ecology , 94 , 2013, 287) thereby relaxing the Euclidean assumption. We evaluate the consequences of not accounting for movement heterogeneity when estimating abundance in highly structured landscapes, and demonstrate the value of this approach for estimating biologically realistic space-use patterns and landscape connectivity. We simulated SCR data in a riparian habitat network, using the ecological distance model under a range of scenarios where space-use in and around the landscape was increasingly associated with water (i.e. increasingly less Euclidean). To assess the influence of miscalculating distance on estimates of population size, we compared the results from the ecological and Euclidean distance based models. We then demonstrate that the ecological distance model can be used to estimate home range geometry when space use is not symmetrical. Finally, we provide a method for calculating landscape connectivity based on modelled species-landscape interactions generated from capture-recapture data. Using ecological distance always produced unbiased estimates of abundance. Explicitly modelling the strength of the species-landscape interaction provided a direct measure of landscape connectivity and better characterised true home range geometry. Abundance under the Euclidean distance model was increasingly (negatively) biased as space use was more strongly associated with water and, because home ranges are assumed to be symmetrical, produced poor characterisations of home range geometry and no information about landscape connectivity. The ecological distance SCR model uses spatially indexed capture-recapture data to estimate how activity patterns are influenced by landscape structure. As well as reducing bias in estimates of abundance, this approach provides biologically realistic representations of home range geometry, and direct information about species-landscape interactions. The incorporation of both structural (landscape) and functional (movement) components of connectivity provides a direct measure of species-specific landscape connectivity.

Methods in Ecology and Evolution↗

USGS2019

Evaluating consumptive and nonconsumptive predator effects on prey density using field times series data

Determining the degree to which predation affects prey abundance in natural communities constitutes a key goal of ecological research. Predators can affect prey through both consumptive effects (CEs) and nonconsumptive effects (NCEs), although the contributions of each mechanism to the density of prey populations remain largely hypothetical in most systems. Common statistical methods applied to time series data cannot elucidate the mechanisms responsible for hypothesized predator effects on prey density (e.g., differentiate CEs from NCEs), nor provide parameters for predictive models. State space models (SSMs) applied to time series data offer a way to meet these goals. Here, we employ SSMs to assess effects of an invasive predatory zooplankter, Bythotrephes longimanus, on an important prey species, Daphnia mendotae, in Lake Michigan. We fit mechanistic models in a SSM framework to seasonal time series (1994-2012) using a recently developed, maximum likelihood-based optimization method, iterated filtering, which can overcome challenges in ecological data (e.g. nonlinearities, measurement error, and irregular sampling intervals). Our results indicate that B. longimanus strongly influences D. mendotae dynamics, with mean annual peak densities of B. longimanus observed in Lake Michigan estimated to cause a 61% reduction in D. mendotae population growth rate and a 59% reduction in peak biomass density. Further, the observed B. longimanus effect is most consistent with an NCE via reduced birth rates. The SSM approach also provided estimates for key biological parameters (e.g., demographic rates) and the contribution of dynamic stochasticity and measurement error. Our study therefore provides evidence derived directly from survey data that the invasive zooplankter B. longimanus is affecting zooplankton demographics and offer parameter estimates needed to inform predictive models that explore the effect of B. longimanus under different scenarios such as climate change.

Ecology↗

USGS2005

A direct immunoassay for detecting diatoms in groundwater as an indicator of the direct influence of surface water

Groundwater under the direct influence of surface water (GWUDISW) is of concern in communities where growing public demand on groundwater resources has resulted in increased withdrawals and hydraulic stress near surface water bodies. Under these conditions, contaminants such as methyl-tert butyl ether (MTBE) and biological materials have been detected in domestic wells. Other contaminants and pathogens associated with surface water are not routinely tested for in groundwater-supplied systems. To address the need for methods to easily identify potentially vulnerable supplies, a direct immunoassay for the quantitative detection of diatoms in raw water samples was developed as a measure of surface water influence on groundwater. Cell wall preparations from Nitzschia palea Kützing, a freshwater diatom found throughout North America, were used to produce a polyclonal antibody that was applied in a direct enzyme-linked immunosorbent assay (ELISA) developed to detect the presence of N. palea cell wall components. The direct immunoassay allows detection at 500 cells L −1 , a level similar to diatom concentrations observed in samples of groundwater collected near the test site. This investigation was the first attempt to utilize an ELISA as an indicator of surface water influence on groundwater. Further research is needed to develop more specific diatom-based monoclonal antibodies, determine cross-reactivity, and optimize sample processing and ELISA procedures for development of a standardized method.

Journal of Applied Phycology↗

USGS2015

Preliminary methodology to assess the national and regional impact of U.S. wind energy development on birds and bats

The U.S. Geological Survey has developed a methodology to assess the impacts of wind energy development on wildlife; it is a probabilistic, quantitative assessment methodology that can communicate to decision makers and the public the magnitude of these effects on species populations. The methodology is currently applicable to birds and bats, focuses primarily on the effects of collisions, and can be applied to any species that breeds in, migrates through, or otherwise uses any part of the United States. The methodology is intended to assess species at the national scale and is fundamentally different from existing methods focusing on impacts at individual facilities. Publicly available fatality information, population estimates, species range maps, turbine location data, biological characteristics, and generic population models are used to generate both a ranked list of species based on relative risk as well as quantitative measures of the magnitude of the effect on species' population trend and size. Three metrics are combined to determine direct and indirect relative risk to populations. A generic population model is used to estimate the expected change in population trend and includes additive mortality from collisions with wind turbines. Lastly, the methodology uses observed fatalities and an estimate of potential biological removal to assess the risk of a decline in population size. Data for six bird species have been processed through the entire methodology as a test case, and the results are presented in this report. Components of the methodology are based on simplifying assumptions and require information that, for many species, may be sparse or unreliable. These assumptions are presented in the report and should be carefully considered when using output from the methodology. In addition, this methodology can be used to recommend species for more intensive demographic modeling or highlight those species that may not require any additional protection because effects of wind energy development on their populations are projected to be small.

Scientific Investigations Report↗

USGS2016

Annual grass invasion in sagebrush-steppe: The relative importance of climate, soil properties and biotic interactions

The invasion by winter-annual grasses (AGs) such as Bromus tectorum into sagebrush steppe throughout the western USA is a classic example of a biological invasion with multiple, interacting climate, soil and biotic factors driving the invasion, although few studies have examined all components together. Across a 6000-km 2 area of the northern Great Basin, we conducted a field assessment of 100 climate, soil, and biotic (functional group abundances, diversity) factors at each of 90 sites that spanned an invasion gradient ranging from 0 to 100 % AG cover. We first determined which biotic and abiotic factors had the strongest correlative relationships with AGs and each resident functional group. We then used regression and structural equation modeling to explore how multiple ecological factors interact to influence AG abundance. Among biotic interactions, we observed negative relationships between AGs and biodiversity, perennial grass cover, resident species richness, biological soil crust cover and shrub density, whereas perennial and annual forb cover, tree cover and soil microbial biomass had no direct linkage to AG. Among abiotic factors, AG cover was strongly related to climate (increasing cover with increasing temperature and aridity), but had weak relationships with soil factors. Our structural equation model showed negative effects of perennial grasses and biodiversity on AG cover while integrating the negative effects of warmer climate and positive influence of belowground processes on resident functional groups. Our findings illustrate the relative importance of biotic interactions and climate on invasive abundance, while soil properties appear to have stronger relationships with resident biota than with invasives.

Oregon↗

USGS2002

Acoustic profiles and images of the Palos Verdes margin: Implications concerning deposition from the White's Point outfall

Subbottom profiles and sidescan-sonar images collected on and around the Palos Verdes Shelf show a surficial deposit interpreted to contain effluent from the White's Point diffusers, as well as showing several geologic features that affect the deposit's distribution. The effluent-affected deposit is visible in high-resolution subbottom profiles on the shelf and the adjacent San Pedro basin slope to water depths of 170 m. It has a maximum thickness of 75 cm and was mapped acoustically over an area of 10.8 km2, which encompasses a volume of about 3.2 million m3. The deposit's basal reflector is acoustically distinct over most of the mapped area. implying that the deposit has not been extensively mixed across its base, perhaps being relatively free of reworking since its initial deposition. Nearshore, the basal reflector is weak and fades away toward land, which could result from syndepositional intermixing of coarse native sediment (particularly from the Portuguese Bend landslide) with effluent in the high-energy nearshore zone, or postdepositionally by physical (wave) or biological mixing across the interface. The geometry of the deposit implies that effluent is dispersed primarily in a northwesterly and seaward direction from the diffusers. Dispersal across the shelf break is in some places strongly affected by topography, particularly by submarine canyons. The deposit overlies stratified and unstratified Quaternary sediment, up to 30m thick, that in turn overlies the irregular erosional surface of deformed Miocene bedrock that crops out in places on the shelf and upper basin slope. The effluent-affected deposit rests on potentially unstable landslide deposits on the San Pedro basin slope. The acoustic profiles and side-scan images show evidence for active and inactive vents, probably of hot water and gas, some of which are within the boundary of the effluent-affected sediment deposit and could disrupt it if seepage occurs. ?? 2002 Elsevier Science Ltd. All rights reserved.

Continental Shelf Research↗

USGS2019

Replicated landscape genomics identifies evidence of local adaptation to urbanization in wood frogs

Native species that persist in urban environments may benefit from local adaptation to novel selection factors. We used double-digest restriction-side associated DNA (RAD) sequencing to evaluate shifts in genome-wide genetic diversity and investigate the presence of parallel evolution associated with urban-specific selection factors in wood frogs ( Lithobates sylvaticus ). Our replicated paired study design involved 12 individuals from each of 4 rural and urban populations to improve our confidence that detected signals of selection are indeed associated with urbanization. Genetic diversity measures were less for urban populations; however, the effect size was small, suggesting little biological consequence. Using an F ST outlier approach, we identified 37 of 8344 genotyped single nucleotide polymorphisms with consistent evidence of directional selection across replicates. A genome-wide association study analysis detected modest support for an association between environment type and 12 of the 37 F ST outlier loci. Discriminant analysis of principal components using the 37 F ST outlier loci produced correct reassignment for 87.5% of rural samples and 93.8% of urban samples. Eighteen of the 37 F ST outlier loci mapped to the American bullfrog ( Rana [Lithobates] catesbeiana ) genome, although none were in coding regions. This evidence of parallel evolution to urban environments provides a powerful example of the ability of urban landscapes to direct evolutionary processes.

Maine↗

USGS2016

At the nexus of fire, water and society

The societal risks of water scarcity and water-quality impairment have received considerable attention, evidenced by recent analyses of these topics by the 2030 Water Resources Group, the United Nations and the World Economic Forum. What are the effects of fire on the predicted water scarcity and declines in water quality? Drinking water supplies for humans, the emphasis of this exploration, are derived from several land cover types, including forests, grasslands and peatlands, which are vulnerable to fire. In the last two decades, fires have affected the water supply catchments of Denver (CO) and other southwestern US cities, and four major Australian cities including Sydney, Canberra, Adelaide and Melbourne. In the same time period, several, though not all, national, regional and global water assessments have included fire in evaluations of the risks that affect water supplies. The objective of this discussion is to explore the nexus of fire, water and society with the hope that a more explicit understanding of fire effects on water supplies will encourage the incorporation of fire into future assessments of water supplies, into the pyrogeography conceptual framework and into planning efforts directed at water resiliency.

Philosophical Transactions of the Royal Society B:↗

USGS2002

Geologic map and digital database of the Pinto Mountain 7.5 minute quadrangle, Riverside County, California

The geologic map and digital database of the Pinto Mountain quadrangle are products of a regional geologic mapping effort undertaken in the eastern Transverse Ranges in and around Joshua Tree National Park. This investigation, part of the Southern California Areal Mapping Project (SCAMP), is conducted in cooperation with the California Geologic Survey and the National Park Service. In line with the goals of the National Cooperative Geologic Mapping Program (NCGMP), mapping of the Pinto Mountain and other quadrangles has been directed toward generating a multipurpose digital geologic map database that is applicable to land-related investigations in the earth and biological sciences. This mapping is conducted to further understanding of bedrock geology and surficial processes in the region and to document evidence for seismotectonic activity in the eastern Transverse Ranges. It is also intended to serve as a base layer suitable for ecosystem and mineral resource assessment and for building a hydrogeologic framework for Pinto Basin. Initial investigations span Pinto Basin from the Hexie and Eagle Mountains northward into the Pinto Mountains. Quadrangles mapped include the Conejo Well 7.5-minute quadrangle (Powell, 2001a), the Porcupine Wash 7.5-minute quadrangle (Powell, 2001b), the Pinto Mountain 7.5-minute quadrangle, and the San Bernardino Wash 7.5-minute quadrangle (Powell, 2002). Parts of the Pinto Mountain quadrangle had been mapped previously at a variety of scales (Weir, and Bader, 1963; Hope, 1966, 1969; Jennings, 1967; Powell, 1981, 1993).

California↗

USGS2002

Geologic map and digital database of the San Bernardino Wash 7.5 minute quadrangle, Riverside County, California

The geologic map and digital database of the San Bernardino Wash quadrangle are products of a regional geologic mapping effort undertaken in the eastern Transverse Ranges in and around Joshua Tree National Park. This investigation, part of the Southern California Areal Mapping Project (SCAMP), is conducted in cooperation with the California Geologic Survey and the National Park Service. In line with the goals of the National Cooperative Geologic Mapping Program (NCGMP), mapping of the San Bernardino Wash and other quadrangles has been directed toward generating a multipurpose digital geologic map database that is applicable to land-related investigations in the earth and biological sciences. This mapping is conducted to further understanding of bedrock geology and surficial processes in the region and to document evidence for seismotectonic activity in the eastern Transverse Ranges. It is also intended to serve as a base layer suitable for ecosystem and mineral resource assessment and for building a hydrogeologic framework for Pinto Basin. Initial investigations span Pinto Basin from the Hexie and Eagle Mountains northward into the Pinto Mountains (see fig. 1). Quadrangles mapped include the Conejo Well 7.5-minute quadrangle (Powell, 2001a), the Porcupine Wash 7.5-minute quadrangle (Powell, 2001b), the Pinto Mountain 7.5-minute quadrangle (Powell, 2002), and the San Bernardino Wash 7.5-minute quadrangle. Parts of the San Bernardino Wash quadrangle had been mapped previously at a variety of scales (Weir, and Bader, 1963; Hope, 1966, 1969; Jennings, 1967; Powell, 1981, 1993).

California↗

USGS2020

The impact of lime additions on mercury dynamics in stream chemistry and macroinvertebrates: A comparison of watershed and direct stream addition management strategies

Acid deposition has declined across eastern North America and northern Europe due to reduced emissions of sulfur and nitrogen oxides. Ecosystem recovery has been slow with limited improvement in surface water chemistry. Delayed recovery has encouraged acid-neutralization strategies to accelerate recovery of impaired biological communities. Lime application has been shown to increase pH and dissolved organic carbon (DOC), which could also drive increased mobilization of mercury (Hg) to surface waters. A four-year study was conducted within Honnedaga Lake’s watershed in the Adirondack region of New York to compare the effects of watershed and direct channel lime additions on Hg in stream water and macroinvertebrates. All treatments sharply increased stream pH and DOC concentrations, but large differences in the duration of impacts were apparent. The watershed treatment resulted in multi-year increases in concentrations and loads of total Hg (150%; 390%), DOC (190%; 350%) and nutrients, whereas total Hg and DOC increased for short periods (72–96 h) after channel treatments. No response of Hg in macroinvertebrates was evident following the watershed treatment, but a potential short-term and spatially constrained increase occurred after the channel treatment. Our observations indicate that both treatment approaches mobilize Hg, but that direct channel liming mobilizes considerably less than watershed liming over any period longer than a few days. During the final study year, increased methyl Hg concentrations were observed across reference and treated streams, which may reflect an extended dry period, highlighting that climate variation may also affect Hg dynamics.

New York↗

USGS2014

The response of stream periphyton to Pacific salmon: using a model to understand the role of environmental context

1. In stream ecosystems, Pacific salmon deliver subsidies of marine-derived nutrients and disturb the stream bed during spawning. The net effect of this nutrient subsidy and physical disturbance on biological communities can be hard to predict and is likely to be mediated by environmental conditions. For periphyton, empirical studies have revealed that the magnitude and direction of the response to salmon varies from one location to the next. Salmon appear to increase periphyton biomass and/or production in some contexts (a positive response), but decrease them in others (a negative response). 2. To reconcile these seemingly conflicting results, we constructed a system dynamics model that links periphyton biomass and production to salmon spawning. We used this model to explore how environmental conditions influence the periphyton response to salmon. 3. Our simulations suggest that the periphyton response to salmon is strongly mediated by both background nutrient concentrations and the proportion of the stream bed suitable for spawning. Positive periphyton responses occurred when both background nutrient concentrations were low (nutrient limiting conditions) and when little of the stream bed was suitable for spawning (because the substratum is too coarse). In contrast, negative responses occurred when nutrient concentrations were higher or a larger proportion of the bed was suitable for spawning. 4. Although periphyton biomass generally remained above or below background conditions for several months following spawning, periphyton production returned quickly to background values shortly afterwards. As a result, based upon our simulations, salmon did not greatly increase or decrease overall annual periphyton production. This suggests that any increase in production by fish or invertebrates in response to returning salmon is more likely to occur via direct consumption of salmon carcasses and/or eggs, rather than the indirect effects of greater periphyton production. 5. Overall, our simulations suggest that environmental factors need to be taken into account when considering the effects of spawning salmon on aquatic ecosystems. Our model offers researchers a framework for testing periphyton response to salmon across a range of conditions, which can be used to generate hypotheses, plan field experiments and guide data collection.

Freshwater Biology↗