Search USGS⌕ Search

SEARCH · Search USGS

Results for “Nature Food”

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

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

At least 271 records · Page 15Linked to original sources
USGS2021

Terrestrial ecological risk analysis via dietary exposure at uranium mine sites in the Grand Canyon watershed (Arizona, USA)

The U.S. Department of the Interior recently included uranium (U) on a list of mineral commodities that are considered critical to economic and national security. The uses of U for commercial and residential energy production, defense applications, medical device technologies, and energy generation for space vehicles and satellites are known, but the environmental impacts of uranium extraction are not always well quantified. We conducted a screening-level ecological risk analysis based on exposure to mining-related elements via diets and incidental soil ingestion for terrestrial biota to provide context to chemical characterization and exposures at breccia pipe U mines in northern Arizona. Relative risks, calculated as hazard quotients (HQs), were generally low for all biological receptor models. Our models screened for risk to omnivores and insectivores (HQs>1) but not herbivores and carnivores. Uranium was not the driver of ecological risk; arsenic, cadmium, copper, and zinc were of concern for biota consuming ground-dwelling invertebrates. Invertebrate species composition should be considered when applying these models to other mining locations or future sampling at the breccia pipe mine sites. Dietary concentration thresholds (DCTs) were also calculated to understand food concentrations that may lead to ecological risk. The DCTs indicated that critical concentrations were not approached in our model scenarios, as evident in the very low HQs for most models. The DCTs may be used by natural resource and land managers as well as mine operators to screen or monitor for potential risk to terrestrial receptors as mine sites are developed and remediated in the future.

Arizona↗
USGS1989

Toxic effects of boron on mallard reproduction

Boron, a naturally occurring trace element generally considered environmentally innocuous, was documented to severely impair mallard reproduction. Boron is leached from irrigated agricultural soils and transported in drainage water that contaminates wetlands. Until now, only the selenium accumulated in aquatic food chains has been documented to pose a toxic hazard to wildlife in drainage water wetlands. Adult mallard ( Anas platyrhynchos ) ducks were fed diets supplemented with 0, 30, 300 or 1,000 ppm boron (fresh weight; diets contained about 10% moisture). The hatching success of fertile eggs was significantly reduced by 1,000 ppm boron, less than one-third the highest boron concentrations found in plants in California's San Joaquin Valley. Hatching weights, duckling survival and duckling weight gain were also reduced by 1,000 ppm boron. Boron concentrations in mallard egg, liver and brain tissues were dose-related. Boron did not affect adult survival or egg fertility. Management of drainage water-contaminated environments must now also consider the adverse effects of boron, as well as the possible interactions of drainage water contaminants.

Environmental Toxicology and Chemistry↗
USGS2017

Land use history and population dynamics of free-standing figs in a maturing forest

Figs ( Ficus sp.) are often considered as keystone resources which strongly influence tropical forest ecosystems. We used long-term tree-census data to track the population dynamics of two abundant free-standing fig species, Ficus insipida and F . yoponensis , on Barro Colorado Island (BCI), a 15.6-km 2 island in Lake Gatún, Panama. Vegetation cover on BCI consists of a mosaic of old growth (>400 years) and maturing (about 90–150 year old) secondary rainforest. Locations and conditions of fig trees have been mapped and monitored on BCI for more than 35 years (1973–2011), with a focus on the Lutz Catchment area (25 ha). The original distribution of the fig trees shortly after the construction of the Panama Canal was derived from an aerial photograph from 1927 and was compared with previous land use and forest status. The distribution of both fig species (~850 trees) is restricted to secondary forest. Of the original 119 trees observed in Lutz Catchment in 1973, >70% of F . insipida and >90% of F . yoponensis had died by 2011. Observations in other areas on BCI support the trend of declining free-standing figs. We interpret the decline of these figs on BCI as a natural process within a maturing tropical lowland forest. Senescence of the fig trees appears to have been accelerated by severe droughts such as the strong El Niño event in the year 1982/83. Because figs form such an important food resource for frugivores, this shift in resource availability is likely to have cascading effects on frugivore populations.

PLoS ONE↗
USGS2020

Seabird‐induced natural mortality of forage fish varies with fish abundance: Evidence from five ecosystems

Forage fish populations often undergo large and rapid fluctuations in abundance. However, most of their predators are buffered against such fluctuations owing to their slower pace of life, which allows them to maintain more stable populations, at least during short periods of food scarcity. In this study, we investigated top‐down processes exerted by seabirds on forage fish stocks in five contrasted marine ecosystems, compiling numerous data sets on seabird counts, diets, energetic needs and prey energy content and abundance. Off Norway, South Africa, Peru, Sweden and Scotland, we found that predation pressure—estimated as the proportion of a fish stock consumed by seabirds—was generally low (median = 1%), but increased sharply at low levels of prey abundance. When prey biomass decreased below 15–18% of its maximum recorded value, predation by seabirds became a source of important additional pressure on prey stocks (~20% of prey biomass is consumed by seabirds). An earlier empirical study advocated for keeping forage stocks from falling below a threshold of 33% of long‐term maximum prey biomass in order to safeguard seabird breeding success, but here we further suggest that a threshold of 18% should be considered as a limit not to be exceeded for the sake of the forage fish themselves, and below which extra cautious management of fisheries may be required. Nevertheless, despite exceptionally high rates of predation on some occasions, predation pressure was not correlated with prey dynamics, suggesting an absence of prey entrapment due to seabirds alone in these five ecosystems.

Fish and Fisheries↗
USGS2016

Trophic dynamics of shrinking Subarctic lakes: naturally eutrophic waters impart resilience to rising nutrient and major ion concentrations

Shrinking lakes were recently observed for several Arctic and Subarctic regions due to increased evaporation and permafrost degradation. Along with lake drawdown, these processes often boost aquatic chemical concentrations, potentially impacting trophic dynamics. In particular, elevated chemical levels may impact primary productivity, which may in turn influence populations of primary and secondary consumers. We examined trophic dynamics of 18 shrinking lakes of the Yukon Flats, Alaska, that had experienced pronounced increases in nutrient (>200 % total nitrogen, >100 % total phosphorus) and ion concentrations (>100 % for four major ions combined) from 1985-1989 to 2010-2012, versus 37 stable lakes with relatively little chemical change over the same period. We found that phytoplankton stocks, as indexed by chlorophyll concentrations, remained unchanged in both shrinking and stable lakes from the 1980s to 2010s. Moving up the trophic ladder, we found significant changes in invertebrate abundance across decades, including decreased abundance of five of six groups examined. However, these decadal losses in invertebrate abundance were not limited to shrinking lakes, occurring in lakes with stable surface areas as well. At the top of the food web, we observed that probabilities of lake occupancy for ten waterbird species, including adults and chicks, remained unchanged from the period 1985-1989 to 2010-2012. Overall, our study lakes displayed a high degree of resilience to multi-trophic cascades caused by rising chemical concentrations. This resilience was likely due to their naturally high fertility, such that further nutrient inputs had little impact on waters already near peak production.

Alaska↗
USGS2024

Intrinsic and environmental drivers of pairwise cohesion in wild Canis social groups

Animals within social groups respond to costs and benefits of sociality by adjusting the proportion of time they spend in close proximity to other individuals in the group (cohesion). Variation in cohesion between individuals, in turn, shapes important group-level processes such as subgroup formation and fission–fusion dynamics. Although critical to animal sociality, a comprehensive understanding of the factors influencing cohesion remains a gap in our knowledge of cooperative behavior in animals. We tracked 574 individuals from six species within the genus Canis in 15 countries on four continents with GPS telemetry to estimate the time that pairs of individuals within social groups spent in close proximity and test hypotheses regarding drivers of cohesion. Pairs of social canids ( Canis spp.) varied widely in the proportion of time they spent together (5%–100%) during seasonal monitoring periods relative to both intrinsic characteristics and environmental conditions. The majority of our data came from three species of wolves (gray wolves, eastern wolves, and red wolves) and coyotes. For these species, cohesion within social groups was greatest between breeding pairs and varied seasonally as the nature of cooperative activities changed relative to annual life history patterns. Across species, wolves were more cohesive than coyotes. For wolves, pairs were less cohesive in larger groups, and when suitable, small prey was present reflecting the constraints of food resources and intragroup competition on social associations. Pair cohesion in wolves declined with increased anthropogenic modification of the landscape and greater climatic variability, underscoring challenges for conserving social top predators in a changing world. We show that pairwise cohesion in social groups varies strongly both within and across Canis species, as individuals respond to changing ecological context defined by resources, competition, and anthropogenic disturbance. Our work highlights that cohesion is a highly plastic component of animal sociality that holds significant promise for elucidating ecological and evolutionary mechanisms underlying cooperative behavior.

Ecology↗
USGS2009

Predicting dietborne metal toxicity from metal influxes

Dietborne metal uptake prevails for many species in nature. However, the links between dietary metal exposure and toxicity are not well understood. Sources of uncertainty include the lack of suitable tracers to quantify exposure for metals such as copper, the difficulty to assess dietary processes such as food ingestion rate, and the complexity to link metal bioaccumulation and effects. We characterized dietborne copper, nickel, and cadmium influxes in a freshwater gastropod exposed to diatoms labeled with enriched stable metal isotopes. Metal influxes in Lymnaea stagnalis correlated linearly with dietborne metal concentrations over a range encompassing most environmental exposures. Dietary Cd and Ni uptake rate constants (k uf ) were, respectively, 3.3 and 2.3 times higher than that for Cu. Detoxification rate constants (k detox ) were similar among metals and appeared 100 times higher than efflux rate constants (k e ). Extremely high Cu concentrations reduced feeding rates, causing the relationship between exposure and influx to deviate from linearity; i.e., Cu uptake rates leveled off between 1500 and 1800 nmol g -1 day -1 . L. stagnalis rapidly takes up Cu, Cd, and Ni from food but detoxifies the accumulated metals, instead of reducing uptake or intensifying excretion. Above a threshold uptake rate, however, the detoxification capabilities of L. stagnalis are overwhelmed.

Environmental Science & Technology↗
USGS2001

Sustainability of coastal resource use in San Quintin, Mexico

San Quintin, Mexico, provides a useful site for integrated analyses of material fluxes and socioeconomic constraints in a geographically isolated system. Natural resource utilization on the land is dominated by groundwater exploitation for cultivation of horticulture crops (primarily tomatoes). Irrigation exceeds water recharge minus export by a factor of 6. Resource utilization in the bay is dominated by oyster culture; food for the oysters is provided by tidal exchange of bay and ocean water. Consideration of oyster respiration and system respiration suggests that the present level of aquaculture is about 40% of the sustainable level. A "physical unsustainability index" (PhUI) was developed to measure the proportional departure of utilization of the most limiting resource for sustainability: 6 on land; 0.4 in the bay. Based on PhUI and measures of economic development, we conclude that aquaculture is more viable than agriculture.

Ambio↗
USGS2012

Context-dependent planktivory: interacting effects of turbidity and predation risk on adaptive foraging

By shaping species interactions, adaptive phenotypic plasticity can profoundly influence ecosystems. Predicting such outcomes has proven difficult, however, owing in part to the dependence of plasticity on the environmental context. Of particular relevance are environmental factors that affect sensory performance in organisms in ways that alter the tradeoffs associated with adaptive phenotypic responses. We explored the influence of turbidity, which simultaneously and differentially affects the sensory performance of consumers at multiple trophic levels, on the indirect effect of a top predator (piscivorous fish) on a basal prey resource (zooplankton) that is mediated through changes in the plastic foraging behavior of an intermediate consumer (zooplanktivorous fish). We first generated theoretical predictions of the adaptive foraging response of a zooplanktivore across wide gradients of turbidity and predation risk by a piscivore. Our model predicted that predation risk can change the negative relationship between intermediate consumer foraging and turbidity into a humped-shaped (unimodal) one in which foraging is low in both clear and highly turbid conditions due to foraging-related risk and visual constraints, respectively. Consequently, the positive trait-mediated indirect effect (TMIE) of the top predator on the basal resource is predicted to peak at low turbidity and decline thereafter until it reaches an asymptote of zero at intermediate turbidity levels (when foraging equals that which is predicted when the top predator is absent). We used field observations and a laboratory experiment to test our model predictions. In support, we found humped-shaped relationships between planktivory and turbidity for several zooplanktivorous fishes from diverse freshwater ecosystems with predation risk. Further, our experiment demonstrated that predation risk reduced zooplanktivory by yellow perch (Perca flavescens) at a low turbidity, but had no effect on consumption at an intermediate turbidity. Together, our theoretical and empirical findings show how the environmental context can govern the strength of TMIEs by influencing consumer sensory performance and how these effects can become realized in nature over wide environmental gradients. Additionally, our hump-shaped foraging curve represents an important departure from the conventional view of turbidity's effect on planktivorous fishes, thus potentially requiring a reconceptualization of turbidity's impact on aquatic food-web interactions.

Ecosphere↗
USGS2013

Progress toward establishing a national assessment of water availability and use

The Omnibus Public Land Management Act of 2009 (Public Law 111-11) was passed into law on March 30, 2009. Subtitle F, also known as the SECURE Water Act, calls for the establishment of a "national water availability and use assessment program" within the U.S. Geological Survey (USGS). A major driver for this recommendation was that national water availability and use have not been comprehensively assessed since 1978. This report fulfills a requirement to report to Congress on progress in implementing the national water availability and use assessment program, also referred to as the National Water Census. The SECURE Water Act authorized \$20 million for each of fiscal years (FY) 2009 through 2023 for assessment of national water availability and use. The first appropriation for this effort was \$4 million in FY 2011, followed by an appropriation of \$6 million in FY 2012. The National Water Census synthesizes and reports information at the regional and national scales, with an emphasis on compiling and reporting the information in a way that is useful to states and others responsible for water management and natural-resource issues. The USGS works with Federal and non-Federal agencies, universities, and other organizations to ensure that the information can be aggregated with other types of water-availability and socioeconomic information, such as data on food and energy production. To maximize the utility of the information, the USGS coordinates the design and development of the effort through the Federal Advisory Committee on Water Information. A National Water Census is a complex undertaking, particularly because there are major gaps in the information needed to conduct such an assessment. To maximize progress, the USGS engaged stakeholders in a discussion of priorities and leveraged existing studies and program activities to enhance efforts toward the development of a National Water Census.

Circular↗
USGS2002

Human impact on the planet: an earth system science perspective and ethical considerations

The modern Earth Narrative, the scientific story of the 4.5 billion-year natural and human history of the Earth, has emerged from the solid foundation of two factual concepts: Deep (or Geologic) Time and Biological Evolution. spread acceptance of the Earth Narrative is critically important as we begin the third millennium, because it provides a clear understanding of the growing impact of human population growth and associated activities on the Earth System, especially the negative impact on Earth?s biosphere. It is important for humans to realize that we are but one of 4,500 species of mammals that exist on Earth and that we are but one species in the estimated 30 to 100 million species that form the complex biosphere. We also need to recognize that all species exist within the physical limits imposed by the geosphere. We are totally dependent on the biosphere for food, oxygen, and other necessities of life. mans are one of the latest results of biological evolution operating over a long period of Geologic Time. We find ourselves on Earth, after 4.5 billion years of Earth history by chance, not by design. Humans have become so successful at modifying their environment that many of the natural limitations on the expansion of populations of our fellow animals have been overcome by technological and cultural innovations. According to Peter Raven, ?Humans, at a current population of 6 billion [expected to nearly double by 2050], are consuming or wasting about 50 percent of the total net biological productivity on land and 50 percent of the available supply of freshwater. The overwhelming and expanding human presence leaves less and less room in the environment for other biota.? st century will be a pivotal time in the fate of Earth?s biosphere. Whereas human modification of the geosphere will slowly recover over time, human changes to the biosphere are a far more consequential matter? extinction of a species is forever! Will humans effectively use our new knowledge of natural and human history to stop further degradation of Earth?s ecosystems and extinction of its biota? The fate of the biosphere, including humanity, depends on a reaffirmation by all humans of all cultures and religions of the global importance of a planet-wide conservation of the Earth?s biotic heritage. For the world?s religions it means elevation of stewardship of the Earth to a moral imperative and a goal of complete preservation of the Earth?s biotic inheritance, one which is based on a Do No Harm ethic.

Open-File Report↗
USGS1995

[Book review] The Eastern Screech Owl: Life History, Ecology and Behavior in the Suburbs and Countryside, by Frederick Gehlback

Review of: Eastern Screech Owl: Life History, Ecology, and Behavior in the Suburbs and Countryside. Frederick R. Gehlbach. Issue 16; Issue 2008 of W. L. Moody Jr. Natural History Series. Texas A&M University Press; 1st edition (November 1994). ISBN: 0890966095. For ornithologists and ecologists alike, Fred Gehlbach's book promises to hold both interest and information value as a comprehensive study of the eastern screech owl (Otus asio hasbroucki). Gehlbach was intrigued with screech owls as a boy and encouraged as an undergraduate by William Hamilton, who underscored that in-depth studies of familiar backyard species can be as fascinating as those in exotic sites. Correspondence with another owl-aficionado, the late H. N. Southern, inspired the author's long-term study of screech owls in a woodland landscape in central Texas and led him to provide nest boxes to enhance his access and sample size. This book is based on observations over a 25-year period-beginning in 1967, with intensive study during an 11-year period (1976-1987) in Texas south of Waco, where Gehlbach teaches at Baylor University. The study represents observations on 659 screech owls, covering several generations of birds and entire lives of many individuals. Gehlbach compares screech owl nesting behavior in a rural versus suburban setting and includes chapters on food supplies and predation tactics; egg-laying, incubation, and parental behavior; vocalizations; and population structure and flux. He discusses why screech owls are widespread across the eastern half of North America and why they succeed among people in suburban environments, where they adapt as easily to mailboxes and porch columns as to natural tree cavities. The book mixes two approaches: on the one hand the dense style of a technical book in which the professional biologist can find information on many aspects of screech owl behavior, life history, and population, including tables, figures, summary statistics, results of statistical comparisons, and experimental tests of hypotheses. On the other hand, each chapter begins with and includes vivid visual images, personal experiences, and thoughtful reflections to draw in the general reader, bridging the interesting topic to the technical details and making the information accessible to a wider audience. The reader is impressed with Dr. Gehlbach's love of his subject, his devotion to long-term study, and his care in presenting the work to his fellow ornithologists, ecologists, and all those interested in wildlife and conservation. It will be a useful reference because of its wealth of information on all aspects of screech owl life history. It is well documented and, in addition to its 10 chapters, includes 10 appendices with information on types of food supplies, bird species that mob screech owls, a daily chronology of nestling development, and a selection of edited field notes to provide background for each chapter. The book is thoroughly referenced and indexed. The Eastern Screech Owl will be read with interest by those with an interest in long-term, in-depth studies and those who love charming stories about remarkable birds with strong personalities and interesting behavior.

Wildlife Review↗
USGS2001

Survival costs of chick rearing in black-legged kittiwakes

1. We tested for costs of chick rearing in the black-legged kittiwake Rissa tridactyla (Linnaeus) by removing entire clutches from 149 of 405 randomly selected nests, in which one or both mates was colour-banded. After the manipulation, we monitored adult nest attendance and body condition at unmanipulated and manipulated nests, and measured the survival and fecundity of these adults the following year. 2. Late in the chick-rearing period, adults from unmanipulated nests (i.e. with chicks) went on significantly longer foraging trips, and were significantly lighter for their size, than adults from manipulated nests (i.e. without chicks). 3. Adults from unmanipulated nests also survived to the following nesting season at a significantly lower rate than those from the manipulated nests (0·898 vs. 0·953), suggesting that attempting to raise chicks can reduce life expectancy by 55%. 4. There was a tendency for adults from nests that were unmanipulated in year one to have lower reproductive success in year two, primarily because of reduced fledging success, and a higher incidence of non-breeding. 5. These findings suggest that mass loss in kittiwakes during chick rearing may not be adaptive. Raising chicks can lead to reproductive costs, and the causal mechanism appears to be a reduction in body condition. 6. We compare our results with previous brood (or clutch) size manipulation experiments that have measured adult body condition, survival and/or future fecundity. Although the empirical evidence suggests that long-lived species are more likely to experience survival costs than short-lived species, we believe the opposite may be true. We suggest that shifting the experimental protocol of cost of reproduction studies from brood enlargements (an approach taken in most prior studies) to brood reductions will provide more accurate quantifications of naturally occurring costs. 7. The cost of reproduction is one mechanism proposed to explain the reduced survival rates reported for kittiwake populations in the North Atlantic relative to those in the North Pacific ocean. Oceanographic data, however, suggest that lower food availability may limit survival of kittiwakes in the North Atlantic where a deeper mixed layer and reduced primary production combine to make conditions less favourable for this seabird during the winter months.

Alaska↗
USGS1986

Effects of supplemental feeding on growth, production, and feeding habits of striped bass in ponds

Production of fingerling striped bass (Morone saxatilis) was increased by feeding fish every hour. In a 42‐d study, survival and production averaged 52.8% and 167.9 kg/hectare (150 lb/acre) in ponds to which feed was delivered hourly and 34.9% and 110.6 kg/hectare (99 lb/acre) in ponds to which feed was delivered only twice a day. Types of food items selected by larvae and fingerlings in treatment and control groups were similar. Cladocerans, adult copepods, and chironomid larvae were the predominant food organisms eaten. Particles of supplemental prepared feed were found in 92% of the fish sampled from treatment ponds and in 89% of those from control ponds. The addition of supplemental feed appeared to enhance rather than to replace the natural diet.

Progressive Fish-Culturist↗
USGS2023

Sea-ice conditions predict polar bear land use around military installations in Alaska

Polar bears ( Ursus maritimus ) are threatened by sea-ice loss due to climate change, which is concurrently opening the Arctic to natural resource extraction and a broader scope of national security responsibilities. Mitigating the risk of human–bear conflicts is an emerging challenge as many polar bears spend longer ice-free summers on land where they have limited access to food and come into more frequent contact with people. We investigated a suite of physical and ecological variables that influence the timing of polar bear arrival on, and departure from, land using remote-sensing data on sea-ice extent and satellite telemetry data from 72 radio-collared adult female polar bears from 1986 to 2015. Analyses encompassed the coastline of the Southern Beaufort Sea north of Alaska, USA, and focused on zones within a 35-km radius (mean daily travel distance of a polar bear) of 5 military installations. Sea ice in the Southern Beaufort Sea retreated approximately 1 month earlier in spring, and reformed 1 month later in fall, in 2015 compared to 1979. In generalized linear mixed models, the most important predictors of polar bear arrival and departure were the dates of sea-ice breakup and formation, respectively, in localized marine areas surrounding each military zone. Region-wide sea-ice conditions also influenced land use, although to a lesser extent. We found that polar bears spent longer periods on land in the military zones compared to outside the zones, which may reflect increased land use in areas with human activity and potential attractants (noting that some military installations were in proximity to other human settlements). Our results demonstrate that the timing of polar bear land use in northern Alaska is influenced by sea-ice conditions on multiple spatial scales. This information can be used to predict and manage the presence of polar bears around military installations and other places of interest.

Alaska↗
USGS2025

Summary of selenium in the lower Gunnison River Basin, Colorado—Information and data gaps

The Cretaceous Mancos Shale is a geologic source of selenium in the lower Gunnison River Basin. Natural weathering processes and human activity mobilize selenium from the Mancos Shale and derived materials, and surface water, groundwater, and sediment all affect the transport of selenium from source areas to receiving streams and biota. Selenium accumulates through the aquatic food chain, and its toxic effects can result in invertebrate mortality and mortality, decreased reproduction, and deformities to fish and birds. The Bureau of Reclamation, in cooperation with the State of Colorado and Gunnison River Basin water users, is implementing a Selenium Management Program to reduce selenium concentrations in the lower Gunnison River Basin of Colorado. Goals of the Selenium Management Program are to (1) achieve compliance with the State of Colorado chronic aquatic-life standard for dissolved selenium (4.6 micrograms per liter) in the Gunnison River near Grand Junction, Colorado; (2) sufficiently improve water-quality conditions to assist in the recovery of endangered species in the Gunnison and Colorado Rivers by reducing selenium concentrations; and (3) support continued water uses in the basin. Many previous studies have contributed to the understanding of selenium in the environment; however, monitoring and research data gaps exist in the lower Gunnison River Basin. The purpose of this report is to summarize information regarding selenium in the lower Gunnison River Basin and describe strategies for scientific research and monitoring to potentially improve understanding of selenium sources; processes affecting the mobilization, transport, and fate of selenium; and the effects of selenium-mitigation projects in the lower Gunnison River Basin. Monitoring and research data gaps discussed in this report include geologic mapping and geochemical source characterization, long-term and ongoing monitoring of the surface-water and groundwater networks, developing and refining statistical models, characterizing selenium on suspended sediment, modeling selenium in the food web, evaluating best management practices, and more.

Colorado↗
USGS2016

Energetic costs of mange in wolves estimated from infrared thermography

Parasites, by definition, extract energy from their hosts and thus affect trophic and food web dynamics even when the parasite may have limited effects on host population size. We studied the energetic costs of mange ( Sarcoptes scabiei ) in wolves ( Canis lupus ) using thermal cameras to estimate heat losses associated with compromised insulation during the winter. We combined the field data of known, naturally infected wolves with data set on captive wolves with shaved patches of fur as a positive control to simulate mange-induced hair loss. We predict that during the winter in Montana, more severe mange infection increases heat loss by around 5.2 to 12 MJ per night (1240 to 2850 kcal, or a 65% to 78% increase) for small and large wolves, respectively accounting for wind effects. To maintain body temperature would require a significant proportion of a healthy wolf's total daily energy demands (18-22 MJ/day). We also predict how these thermal costs may increase in colder climates by comparing our predictions in Bozeman, Montana to those from a place with lower ambient temperatures (Fairbanks, Alaska). Contrary to our expectations, the 14°C differential between these regions was not as important as the potential differences in wind speed. These large increases in energetic demands can be mitigated by either increasing consumption rates or decreasing other energy demands. Data from GPS-collared wolves indicated that healthy wolves move, on average, 17 km per day, which was reduced by 1.5, 1.8 and 6.5 km for light, medium, and severe hair loss. In addition, the wolf with the most hair loss was less active at night and more active during the day, which is the converse of the movement patterns of healthy wolves. At the individual level mange infections create significant energy demands and altered behavioral patterns, this may have cascading effects on prey consumption rates, food web dynamics, predator-prey interactions, and scavenger communities.

Montana↗
USGS1989

Magnification of secondary production by kelp detritus in coastal marine ecosystems

Kelps are highly productive seaweeds found along most temperate latitude coastlines, but the fate and importance of kelp production to nearshore ecosystems are largely unknown. The trophic role of kelp-derived carbon in a wide range of marine organisms was assessed by a natural experiment. Growth rates of benthic suspension feeders were greatly increased in the presence of organic detritus (particulate and dissolved) originating from large benthic seaweeds (kelps). Stable carbon isotope analysis confirmed that kelp-derived carbon is found throughout the nearshore food web.

Science↗