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USGS2013

MODIS phenology image service ArcMap toolbox

Seasonal change is important to consider when managing conservation areas at landscape scales. The study of such patterns throughout the year is referred to as phenology. Recurring life-cycle events that are initiated and driven by environmental factors include animal migration and plant flowering. Phenological events capture public attention, such as fall color change in deciduous forests, the first flowering in spring, and for those with allergies, the start of the pollen season. These events can affect our daily lives, provide clues to help understand and manage ecosystems, and provide evidence of how climate variability can affect the natural cycle of plants and animals. Phenological observations can be gathered at a range of scales, from plots smaller than an acre to landscapes of hundreds to thousands of acres. Linking these observations to diverse disciplines such as evolutionary biology or climate sciences can help further research in species and ecosystem responses to climate change scenarios at appropriate scales. A cooperative study between the National Park Service (NPS), the U.S. Geological Survey (USGS), and the National Aeronautics and Space Administration (NASA) has been exploring how satellite information can be used to summarize phenological patterns observed at the park or landscape scale and how those summaries can be presented to both park managers and visitors. This study specifically addressed seasonal changes in plants, including the onset of growth, photosynthesis in the spring, and the senescence of deciduous vegetation in the fall. The primary objective of the work is to demonstrate that seasonality even in protected areas changes considerably across years. A major challenge is to decouple natural variability from possible trends—directional change that can lead to a permanent and radically different ecosystem state. Trends can be either a gradual degradation of the landscape (often from external influences) or steady improvement (by implementing long-term conservation plans). In either case, it is important to first grasp the magnitude of natural variation so that it is not confused with actual trends. This work used existing and freely available remote sensing data, specifically the NASA-funded 250-meter (m) spatial resolution land-surface phenology product for North America. This product is calculated from an annual record of vegetation health observed by NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The land-surface phenology product is, in essence, a method to summarize all the observations throughout a year into a few key, ecologically relevant “metrics”.

Open-File Report↗

USGS2019

A mosaic of estuarine habitat types with prey resources from multiple environmental strata supports a diversified foraging portfolio for juvenile Chinook salmon

Estuaries provide vital nursery habitat for threatened Chinook salmon (Oncorhynchus tshawytscha) by promoting an ecological portfolio effect, whereby multiple habitat types and environmental strata maximize foraging opportunities for out-migrating salmon by varying the abundance and composition of prey through space and time. To study this portfolio effect, we evaluated the foraging capacity of five estuarine habitat types within the Nisqually River Delta (Puget Sound, Washington, USA). Within each habitat, we sampled invertebrate prey resources from the terrestrial, aquatic, benthic, and epifaunal strata and compared them to juvenile salmon diets from corresponding sampling events. We found that the emergent salt marsh supplied twice as much aquatic prey biomass as any other habitat (720–5523 mg/m3), followed by the mudflat (246–2543 mg/m3) and eelgrass (Zostera marina; 141–2694 mg/m3) habitats. Despite some evidence for selectivity, juvenile salmon diets exhibited substantial compositional overlap, especially when compared to among-habitat differences in available prey resources. Fish that were captured in salt marsh, mudflat, and eelgrass consumed aquatic crustaceans such as mysids, while fish captured upriver in forested and transitional marshes ate a higher proportion of adult and larval insects. The availability and consumption of greater quantities of energy-poor crustaceans in the salt marsh and lower quantities of energy-rich insects upriver highlights a quantity-for-quality tradeoff among estuarine habitats. Our findings indicate that the timing, productivity, and diversity of prey across multiple habitat types and environmental strata determine an estuary’s capacity to support foraging for multiple life history strategies, size classes, and cohorts of juvenile salmon.

Washington↗

USGS2008

Accumulation of environmental contaminants in wood duck (Aix sponsa) eggs, with emphasis on polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans

We measured polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), organochlorine pesticides, and mercury in wood duck (Aix sponsa) eggs collected near a North Carolina (USA) bleached kraft paper mill. Samples were taken a decade after the mill stopped using molecular chlorine. Using avian toxic equivalency factors, 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity equivalent (TEQ) concentrations were 1-30 pg/g fresh wet weight in eggs (n = 48) collected near the mill in 2002-2005 and were significantly higher than those from a reference site (<1 pg/g) 25 km away. Geometric mean wood duck egg TEQs (6 pg/g) were one-fifth those measured at this site prior to the cessation of molecular chlorine bleaching. Concentrations of mercury in wood duck eggs from nests of the Roanoke River sites ranged from 0.01 to 0.14 ??g/g (geometric mean, 0.04 ??g/g) and were significantly higher than those from the reference site, where concentrations did not exceed 0.04 ??g/g (geometric mean, 0.02 ??g/g). All concentrations were lower than those associated with adverse effects in birds. The congener profiles, lack of contamination in reference site eggs, and decline in contaminant concentrations after process changes at the mill provide strong evidence that mill discharges influenced contamination of local wood duck eggs. Collectively, the results indicate that the wood duck is an effective sentinel of the spatial and temporal extent of PCDD, PCDF, and mercury contamination. ?? 2008 US Government.

Archives of Environmental Contamination and Toxico↗

USGS2019

Estimating offsets for avian displacement effects of anthropogenic impacts

Biodiversity offsetting, or compensatory mitigation, is increasingly being used in temperate grassland ecosystems to compensate for unavoidable environmental damage from anthropogenic developments such as transportation infrastructure, urbanization, and energy development. Pursuit of energy independence in the United States will expand domestic energy production. Concurrent with this increased growth is increased disruption to wildlife habitats, including avian displacement from suitable breeding habitat. Recent studies at energy-extraction and -generation facilities have provided evidence for behavioral avoidance and thus reduced use of habitat by breeding waterfowl and grassland birds in the vicinity of energy infrastructure. To quantify and compensate for this loss in value of avian breeding habitat, it is necessary to determine a biologically-based currency so that the sufficiency of offsets in terms of biological equivalent value can be obtained. We describe a method for quantifying the amount of habitat needed to provide equivalent biological value for avifauna displaced by energy and transportation infrastructure, based on the ability to define five metrics: impact distance, impact area, pre-impact density, percent displacement, and offset density. We calculate percent displacement values for breeding waterfowl and grassland birds and demonstrate the applicability of our avian-impact offset method using examples for wind and oil infrastructure. We also apply our method to an example in which the biological value of the offset habitat is similar to the impacted habitat, based on similarity in habitat type (e.g., native prairie), geographical location, land use, and landscape composition, as well as to an example in which the biological value of the offset habitat is dissimilar to the impacted habitat. We provide a worksheet that informs potential users how to apply our method to their specific developments and a framework for developing decision-support tools aimed at achieving landscape-level conservation goals.

Ecological Applications↗

USGS2011

Geochemical and isotopic study of soils and waters from an Italian contaminated site: Agro Aversano (Campania)

Lead isotope applications have been widely used in recent years in environmental studies conducted on different kinds of sampled media. In the present paper, Pb isotope ratios have been used to determine the sources of metal pollution in soils and waters in the Agro Aversano area. During three different sampling phases, a total of 113 surface soils (5-20. cm), 20 samples from 2 soil profiles (0-1. m), 11 stream waters and 4 groundwaters were collected. Major element concentrations in sampled media have been analyzed by the ICP-MS technique. Surface soils (20 samples), all soil profiles and all waters have been also analyzed for Pb isotope compositions by thermal ionization (TIMS). The geochemical data were assessed using statistic methods and cartographically elaborated in order to have a clear picture of the level of disturbance of the area. Pb isotopic data were studied to discriminate between anthropogenic and geologic sources. Our results show that As (5.6-25.6. mg/kg), Cu (9-677. mg/kg), Pb (22-193. mg/kg), Tl (0.53-3.62. mg/kg), V (26-142. mg/kg) and Zn (34-215. mg//kg) contents in analyzed soils, exceed the intervention limits fixed by the Italian Environmental Law for residential areas in some of the sampled sites, while intervention limit for industrial areas is exceeded only for Cu concentrations. Lead isotopic data, show that there is a high similarity between the ratios measured in the leached soil samples and those deriving from anthropic activities. This similarity with anthropogenic Pb is also evident in the ratios measured in both groundwater and stream water samples. ?? 2010 Elsevier B.V.

Journal of Geochemical Exploration↗

USGS2015

Evaluating abundance and trends in a Hawaiian avian community using state-space analysis

Estimating population abundances and patterns of change over time are important in both ecology and conservation. Trend assessment typically entails fitting a regression to a time series of abundances to estimate population trajectory. However, changes in abundance estimates from year-to-year across time are due to both true variation in population size (process variation) and variation due to imperfect sampling and model fit. State-space models are a relatively new method that can be used to partition the error components and quantify trends based only on process variation. We compare a state-space modelling approach with a more traditional linear regression approach to assess trends in uncorrected raw counts and detection-corrected abundance estimates of forest birds at Hakalau Forest National Wildlife Refuge, Hawai‘i. Most species demonstrated similar trends using either method. In general, evidence for trends using state-space models was less strong than for linear regression, as measured by estimates of precision. However, while the state-space models may sacrifice precision, the expectation is that these estimates provide a better representation of the real world biological processes of interest because they are partitioning process variation (environmental and demographic variation) and observation variation (sampling and model variation). The state-space approach also provides annual estimates of abundance which can be used by managers to set conservation strategies, and can be linked to factors that vary by year, such as climate, to better understand processes that drive population trends.

Hawai'i↗

USGS2007

Immunotoxicity of trenbolone acetate in Japanese quail

Trenbolone acetate is a synthetic androgen that is currently used as a growth promoter in many meat-exporting countries. Despite industry laboratories classifying trenbolone as nonteratogenic, data showed that embryonic exposure to this androgenic chemical altered development of the immune system in Japanese quail. Trenbolone is lipophilic, persistent, and released into the environment in manure used as soil fertilizer. This is the first study to date to assess this chemical's immunotoxic effects in an avian species. A one-time injection of trenbolone into yolks was administered to mimic maternal deposition, and subsequent effects on the development and function of the immune system were determined in chicks and adults. Development of the bursa of Fabricius, an organ responsible for development of the humoral arm of the immune system, was disrupted, as indicated by lower masse, and smaller and fewer follicles at day 1 of hatch. Morphological differences in the bursas persisted in adults, although no differences in either two measures of immune function were observed. Total numbers of circulating leukocytes were reduced and heterophil-lymphocyte ratios were elevated in chicks but not adults. This study shows that trenbolone acetate is teratogenic and immunotoxic in Japanese quail, and provides evidence that the quail immune system may be fairly resilient to embryonic endocrine-disrupting chemical-induced alterations following no further exposure posthatch.

Journal of Toxicology and Environmental Health, Pa↗

USGS2014

Exposure and food web transfer of pharmaceuticals in ospreys (Pandion haliaetus): Predictive model and empirical data

The osprey ( Pandion haliaetus ) is a well-known sentinel of environmental contamination, yet no studies have traced pharmaceuticals through the water–fish–osprey food web. A screening-level exposure assessment was used to evaluate the bioaccumulation potential of 113 pharmaceuticals and metabolites, and an artificial sweetener in this food web. Hypothetical concentrations in water reflecting “wastewater effluent dominated” or “dilution dominated” scenarios were combined with pH-specific bioconcentration factors (BCFs) to predict uptake in fish. Residues in fish and osprey food intake rate were used to calculate the daily intake (DI) of compounds by an adult female osprey. Fourteen pharmaceuticals and a drug metabolite with a BCF greater than 100 and a DI greater than 20 µg/kg were identified as being most likely to exceed the adult human therapeutic dose (HTD). These 15 compounds were also evaluated in a 40 day cumulative dose exposure scenario using first-order kinetics to account for uptake and elimination. Assuming comparable absorption to humans, the half-lives (t 1/2 ) for an adult osprey to reach the HTD within 40 days were calculated. For 3 of these pharmaceuticals, the estimated t 1/2 in ospreys was less than that for humans, and thus an osprey might theoretically reach or exceed the HTD in 3 to 7 days. To complement the exposure model, 24 compounds were quantified in water, fish plasma, and osprey nestling plasma from 7 potentially impaired locations in Chesapeake Bay. Of the 18 analytes detected in water, 8 were found in fish plasma, but only 1 in osprey plasma (the antihypertensive diltiazem). Compared to diltiazem detection rate and concentrations in water (10/12 detects, <method detection limits [MDL]–173 ng/L), there was a lower detection frequency in fish (31/233 detects, <MDL–2400 ng/L); however when present in fish, all values exceeded the maximum diltiazem concentration found in water. Diltiazem was found in all 69 osprey plasma samples (540–8630 ng/L), with 41% of these samples exceeding maximum concentrations found in fish. Diltiazem levels in fish and osprey plasma were below the human therapeutic plasma concentration (30 000 ng/L). Effect thresholds for diltiazem are unknown in ospreys at this time, and there is no evidence to suggest adverse effects. This screening-level exposure model can help identify those compounds that warrant further investigation in high-trophic level species.

Integrated Environmental Assessment and Management↗

USGS2020

Antibiotic resistant bacteria in wildlife: Perspectives on trends, acquisitions and dissemination, data gaps, and future directions

The proliferation of antibiotic resistant bacteria in the environment has potential negative economic and health consequences. Thus, previous investigations have targeted wild animals to understand the occurrence of antibiotic resistance in diverse environmental sources. In this critical review and synthesis, we summarize important concepts learned through the sampling of wildlife for antibiotic resistant indicator bacteria. These concepts are helpful for understanding dissemination of resistance through environmental pathways and helping to guide future research efforts. Our review is comprised of six sections. The first section briefly introduces antibiotic resistance as it pertains to bacteria harbored in environmental sources such as wild animals. Next, we differentiate wildlife from other animals in the context of how diverse taxa provide different information on antibiotic resistance in the environment. In the third section, we identify representative research and seminal works that illustrate important associations between the occurrence of antibiotic resistant bacteria in wildlife and anthropogenic inputs into the environment. For example, we highlight numerous investigations that support the premise that anthropogenic inputs into the environment drive the occurrence of antibiotic resistance in bacteria harbored by free-ranging wildlife. Additionally, we summarize previous research demonstrating foraging as a mechanism by which wildlife may be exposed to anthropogenic antibiotic resistance contamination in the environment. In the fourth section of our review, we summarize molecular evidence for the acquisition and dissemination of resistance among bacteria harbored by wildlife. In the fifth section, we identify what we believe to be important data gaps and potential future directions that other researchers may find useful towards the development of efficient, informative, and impactful investigations of antibiotic resistant bacteria in wildlife. Finally, we conclude our review by highlighting the need to move from surveys that simply identify antibiotic resistant bacteria in wildlife towards hypothesis-driven investigations that: (1) identify point sources of antibiotic resistance; (2) provide information on risk to human and animal health; (3) identify interventions that may interrupt environmentally mediated pathways of antibiotic resistance acquisition/transmission; and (4) evaluate whether management practices are leading to desirable outcomes.

Journal of Wildlife Diseases↗

USGS2016

Perchlorate and selected metals in water and soil within Mount Rushmore National Memorial, South Dakota, 2011–15

Mount Rushmore National Memorial is located in the east-central part of the Black Hills area of South Dakota and is challenged to provide drinking water to about 3 million annual visitors and year-round park personnel. An environmental concern to water resources within Mount Rushmore National Memorial has been the annual aerial fireworks display at the memorial for the Independence Day holiday during 1998–2009. A major concern of park management is the contamination of groundwater and surface water by perchlorate, which is used as an oxidizing agent in firework displays. A study by the U.S. Geological Survey, in cooperation with the National Park Service, was completed to characterize the occurrence of perchlorate and selected metals (constituents commonly associated with fireworks) in groundwater and surface water within and adjacent to Mount Rushmore National Memorial during 2011–15. Concentrations of perchlorate and metals in 106 water samples (collected from 6 groundwater sites and 14 surface-water sites) and 11 soil samples (collected from 11 soil sites) are reported. Within the Mount Rushmore National Memorial boundary, perchlorate concentrations were greatest in the Lafferty Gulch drainage basin, ranging from less than 0.20 to 38 micrograms per liter (μg/L) in groundwater samples and from 2.2 to 54 μg/L in surface-water samples. Sites within the Starling Gulch drainage basin also had some evidence of perchlorate contamination, with concentrations ranging from 0.61 to 19 μg/L. All groundwater and surface-water samples within the unnamed tributary to Grizzly Bear Creek drainage basin and reference sites outside the park boundary had concentrations less than 0.20 μg/L. Perchlorate concentrations in samples collected at the 200-foot-deep production well (Well 1) ranged from 17 to 38 μg/L with a median of 23 μg/L, whereas perchlorate concentrations in samples from the 500-foot-deep production well (Well 2) ranged from 2.1 to 17 μg/L, with a median of 6.1 μg/L. Perchlorate concentrations in samples of the treated groundwater were similar to the concentrations from Well 1, which was the predominant source of the water supply at Mount Rushmore National Memorial during the study period (2011–15). Springflow upstream from the production wells in the West Fork Lafferty Gulch drainage had the greatest perchlorate concentrations, ranging from 21 to 54 μg/L. The groundwater site within Lafferty Gulch drainage basin but downstream from the park boundary also had a perchlorate concentration less than 0.20 μg/L in the one sample collected at the site. Water samples collected at reference sites generally had concentrations of metals within the same range of those sites within the Mount Rushmore National Memorial boundary, presenting little evidence of metal contamination due to anthropogenic factors within the park boundary. Soil samples were collected near most water sampling sites and within the Hall of Records Canyon where fireworks were launched. Perchlorate concentrations in soil were greatest in the West Fork Lafferty Gulch drainage and Hall of Records Canyon, which are topographically higher than the two groundwater wells. The perchlorate concentrations in groundwater and surface water within Lafferty Gulch drainage basin during 2011–15 were greater than the U.S. Environmental Protection Agency’s Interim Drinking Water Health Advisory benchmark of 15 μg/L. The perchlorate concentrations in the Mount Rushmore water supply relative to this benchmark are of concern; however, this health advisory is based on the assumption that consumers are using the supply as their primary water source and currently is not a regulated standard. The groundwater system at West Fork Lafferty Gulch is highly susceptible to contamination by way of recharge and is isolated from downstream movement by an intrusive body acting as a dam, which may explain why a contamination problem is not likely to disappear or disperse, as could happen in larger aquifer systems. The observed deposition of firework debris within Lafferty Gulch drainage basin coupled with the lack of alternative perchlorate sources indicates that past firework displays are the most probable source of perchlorate contamination.

South Dakota↗

USGS2023

No evidence for cottonwood forest decline along a flow-augmented western U.S. river

In contrast to many other arid region rivers, streamflow in the South Platte River is heavily augmented by trans-basin water imports and irrigation return flows. Hydrological changes began in the 1880s, resulting in channel narrowing and the development of a continuous Populus-Salix forest by the mid-twentieth century. We assessed the composition, structure and regeneration status of the riparian forest and identified environmental variables affecting annual Populus deltoides tree growth. We sampled forest structure at four sites in 2015, and conducted dendroecological analysis at seven additional sites in 2019. The riparian forest was dominated by P. deltoides , which occurred at all sites, comprising 79% of total tree basal area and 62% of total tree density. Age structure data indicated ongoing though episodic recruitment of P. deltoides , at least over the past ~130 years. We tested 14 linear mixed effects models to describe the effect of climate and streamflow on individual tree growth (modeled as the log of BAI, n = 237 trees). The most parsimonious model selected with AICc explained 28.6% of BAI variability, and included hydrology and climate factors during the growing season (i.e., June–August streamflow, June–July PDSI), some aspects of off-season (i.e., previous November and March) streamflow, along with tree age and study site effects. The riparian forest developed in response to, and has been maintained by, current climate conditions and water management regimes. It may be negatively affected by future climate change and increased urban water demand in the basin.

Colorado↗

USGS2023

Patterns of water use by raptors in the southern Great Plains

There is a paucity of data evaluating water use by raptors. Although raptors are believed to satisfy their water requirements through metabolic processes, they are known to experience reduced reproductive success during periods of drought, and there is evidence of water being important for site occupancy in arid landscapes. Several raptor species have a seasonal or year-round presence in west Texas, a drought-prone, semi-arid region of the Southern Great Plains. We examined species-specific timing of free water use by common raptors in this region, and examined environmental conditions associated with water use. We collected 4549 camera trap-days of data across 4 yr at ten human-made water sources placed for cattle. We recorded 14 species of raptors among the 1177 detections of raptors visiting water sources; of these, 1084 raptors (92.1%) perched at tanks, and 93 (7.1%) flew by tanks. Of the raptors that perched at tanks, 63.5% drank and 20.8% both bathed and drank. Barn Owls ( Tyto alba ; 35.6%), Swainson's Hawks ( Buteo swainsoni ; 32.0%), and Northern Harriers ( Circus hudsonius ; 21.0%) were the predominate species detected. Visits by Northern Harriers and Swainson's Hawks increased with increasing temperature and decreasing precipitation. Visits by Barn Owls increased with increasing drought severity. Further, detections per 100 trap-days increased substantively across our 4-yr study period during which the region experienced one of the worst droughts on record. Although our data do not demonstrate these raptors require free water, they do reveal an increasing use of free water in relation to hotter and drier conditions. How this influences survival and reproduction remains unknown, but may become a pressing question because current climate models predict the study area will experience increases in heat and decreases in precipitation.

Journal of Raptor Research↗

USGS2024

Environmental DNA (eDNA) surveillance of the federally threatened Slender Chub (Erimystax cahni) in the Clinch River and Powell River

The slender chub ( Erimystax cahni ) is a federally threatened fish native to and geographically restricted to eastern North America. More specifically, the Powell, Clinch, and lower Holston Rivers in Tennessee were historical collection areas. Habitat degradation from multiple sources, including surface mining, agriculture, dams, and urbanization, is associated with the decline of this species - an obligate inhabitant of gravel shoals in large rivers. As of 1964, only 15 voucher specimens were known and no living specimens were documented for decades. A federal recovery plan and Species Status Assessment were developed to determine if slender chub still exists and could be restored. Given the lack of recent observations using conventional sampling to search for its presence, we used environmental DNA sampling to determine their potential presence. Our specific objectives were to (1) develop a quantitative polymerase chain reaction (qPCR) assay aimed at species-specific detection and (2) sample historically known areas of collection. We sampled 43 sites in the Clinch and Powell Rivers. For the first time in almost two decades, we provide evidence for the continued existence of a putatively extinct species. We detected evidence of E. cahni in both the Clinch and Powell Rivers, but only at a few sites. We cannot confirm the presence of E. cahni , and positive eDNA matches could be attributed to amplification from a hybrid. Our results do indicate slender chub DNA perseveres in the Clinch and Powell Rivers and can inform resource agencies of localities to pursue on-the-ground searches for the slender chub with conventional methods (e.g., snorkeling) and potential restoration and recovery sites.

Tennessee, Virginia↗

USGS2024

A hierarchical model for eDNA fate and transport dynamics accommodating low concentration samples

Environmental DNA (eDNA) sampling is an increasingly important tool for answering ecological questions and informing aquatic species management; however, several factors currently limit the reliability of ecological inference from eDNA sampling. Two particular challenges are (1) determining species source location(s) and (2) accurately and precisely measuring low concentration eDNA samples in the presence of multiple sources of ecological and measurement variability. The recently introduced eDNA Integrating Transport and Hydrology (eDITH) model provides a framework for relating eDNA measurements to source locations in riverine networks, but little empirical work has been done to test and refine model assumptions or accommodate low concentration samples, that can be systematically undermeasured. To better understand eDNA fate and transport dynamics and our ability to reliably quantify low concentration samples, we developed a hierarchical model and used it to evaluate a fate and transport experiment. Our model addresses several low concentration challenges by modeling the number of copies in each PCR replicate as a latent variable with a count distribution and conditioning detection and quantification on replicate copy number. We provide evidence that the eDNA removal rate declined through time, estimating that over 80% of eDNA was removed over the first 10 m, traversed in 41 s. After this initial period of rapid decay, eDNA decayed slowly with consistent detection through our farthest site 1 km from the release location, traversed in 67.8 min. Our model further allowed us to detect extra-Poisson variation in the allocation of copies to replicates. We extended our hierarchical model to accommodate a continuous effect of inhibitors and used our model to provide evidence for the inhibitor hypothesis and explore the potential implications. While our model is not a panacea for all challenges faced when quantifying low-concentration eDNA samples, it provides a framework for a more complete accounting of uncertainty.

Environmental and Ecological Statistics↗

USGS1987

Fate and movement of azaarenes and their anaerobic biotransformation products in an aquifer contaminated by wood-treatment chemicals

Infiltration of wastes containing creosote and pentachlorophenol from surface impoundments at an abandoned wood-treatment facility near Pensacola, Florida, resulted in contamination of the underlying sand and gravel aquifer. Pond sludges and sediments near the source were contaminated with 2- to 5-ring azaarenes having log Kow values of from 2.0 to 5.6. However, the ground water contained only azaarenes and their oxygenated and methylated derivatives having log Kow values of less than 3.5. These compounds also were present in coal tar-contaminated ground water at a site near St. Louis Park, Minnesota. Laboratory anaerobic degradation studies and on-site observations indicated that oxygenated azaarenes probably were biotransformation products of reactions mediated by indigenous microbial populations. Microbial N-methylation, C-methylation and O-methylation reactions are reported here for the first time. In the presence of nutrients and carbon sources such as acetate and propionate, all azaarenes studied were either partially or completely degraded. Evidence for the microbial degradation of azaarenes in ground water from anaerobic zones is presented. Oxygenated azaarenes were relatively more water-soluble, mobile and persistent in hydrogeologic environments.

Minnesota, Florida↗

USGS2018

Fire and grazing influence site resistance to Bromus tectorum through their effects on shrub, bunchgrass and biocrust communities in the Great Basin (USA)

Shrubs, bunchgrasses and biological soil crusts (biocrusts) are believed to contribute to site resistance to plant invasions in the presence of cattle grazing. Although fire is a concomitant disturbance with grazing, little is known regarding their combined impacts on invasion resistance. We are the first to date to test the idea that biotic communities mediate the effects of disturbance on site resistance. We assessed cover of Bromus tectorum , shrubs, native bunchgrasses, lichens and mosses in 99 burned and unburned plots located on similar soils where fires occurred between 12 and 23 years before sampling. Structural equation modeling was used to test hypothesized relationships between environmental and disturbance characteristics, the biotic community and resistance to B. tectorum cover. Characteristics of fire and grazing did not directly relate to cover of B. tectorum. Relationships were mediated through shrub, bunchgrass and biocrust communities. Increased site resistance following fire was associated with higher bunchgrass cover and recovery of bunchgrasses and mosses with time since fire. Evidence of grazing was more pronounced on burned sites and was positively correlated with the cover of B. tectorum , indicating an interaction between fire and grazing that decreases site resistance. Lichen cover showed a weak, negative relationship with cover of B. tectorum . Fire reduced near-term site resistance to B. tectorum on actively grazed rangelands. Independent of fire, grazing impacts resulted in reduced site resistance to B. tectorum , suggesting that grazing management that enhances plant and biocrust communities will also enhance site resistance.

Great Basin↗

USGS2023

Understanding drivers of mercury in lake trout (Salvelinus namaycush), a top-predator fish in southwest Alaska's parklands

Mercury (Hg) is a widespread element and persistent pollutant, harmful to fish, wildlife, and humans in its organic, methylated form. The risk of Hg contamination is driven by factors that regulate Hg loading, methylation, bioaccumulation, and biomagnification. In remote locations, with infrequent access and limited data, understanding the relative importance of these factors can pose a challenge. Here, we assessed Hg concentrations in an apex predator fish species, lake trout (Salvelinus namaycush), collected from 14 lakes spanning two National Parks in southwest Alaska, U.S.A. We then examined factors associated with the variation in fish Hg concentrations using a Bayesian hierarchical model. We found that total Hg concentrations in water were consistently low among lakes (0.11–0.50 ng L− 1). Conversely, total Hg concentrations in lake trout spanned a thirty-fold range (101–3046 ng g− 1 dry weight), with median values at 7 lakes exceeding Alaska’s human consumption threshold. Model results showed that fish age and, to a lesser extent, body condition best explained variation in Hg concentration among fish within a lake, with Hg elevated in older, thinner lake trout. Other factors, including plankton methyl Hg content, fish species richness, volcano proximity, and glacier loss, best explained variation in lake trout Hg concentration among lakes. Collectively, these results provide evidence that multiple, hierarchically nested factors control fish Hg levels in these lakes.

Alaska↗

USGS2020

Are environmental DNA methods ready for aquatic invasive species management?

Multiple studies have demonstrated environmental (e)DNA detections of rare, invasive species. However, invasive species managers struggle with using eDNA results because detections might not indicate species presence. We evaluated if eDNA methods have matured to a point where they can be widely applied to aquatic invasive species management. We found that eDNA methods meet legal standards for being admissible as evidence in most courts, suggesting that eDNA method reliability is not the problem. Rather, we suggest that the interface between results and management needs attention since there are few tools for integrating uncertainty into decision-making. Solutions include decision support trees based on molecular best practices that integrate the temporal and spatial trends in eDNA positives relative to human risk tolerance.

Trends in Ecology and Evolution↗