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At least 991 records · Page 55Linked to original sources

USGS2014

An experimental investigation of chemical communication in the polar bear

The polar bear ( U rsus maritimus ), with its wide-ranging movements, solitary existence and seasonal reproduction, is expected to favor chemosignaling over other communication modalities. However, the topography of its Arctic sea ice habitat is generally lacking in stationary vertical substrates routinely used for targeted scent marking in other bears. These environmental constraints may have shaped a marking strategy, unique to polar bears, for widely dispersed continuous dissemination of scent via foot pads. To investigate the role of chemical communication, pedal scents were collected from free-ranging polar bears of different sex and reproductive classes captured on spring sea ice in the Beaufort and Chukchi seas, and presented in a controlled fashion to 26 bears in zoos. Results from behavioral bioassays indicated that bears, especially females, were more likely to approach conspecific scent during the spring than the fall. Male flehmen behavior, indicative of chemosignal delivery to the vomeronasal organ, differentiated scent donor by sex and reproductive condition. Histologic examination of pedal skin collected from two females indicated prominent and profuse apocrine glands in association with large compound hair follicles, suggesting that they may produce scents that function as chemosignals. These results suggest that pedal scent, regardless of origin, conveys information to conspecifics that may facilitate social and reproductive behavior, and that chemical communication in this species has been adaptively shaped by environmental constraints of its habitat. However, continuously distributed scent signals necessary for breeding behavior may prove less effective if current and future environmental conditions cause disruption of scent trails due to increased fracturing of sea ice.

Journal of Zoology↗

USGS2017

Mangrove species' responses to winter air temperature extremes in China

The global distribution and diversity of mangrove forests is greatly influenced by the frequency and intensity of winter air temperature extremes. However, our understanding of how different mangrove species respond to winter temperature extremes has been lacking because extreme freezing and chilling events are, by definition, relatively uncommon and also difficult to replicate experimentally. In this study, we investigated species-specific variation in mangrove responses to winter temperature extremes in China. In 10 sites that span a latitudinal gradient, we quantified species-specific damage and recovery following a chilling event, for mangrove species within and outside of their natural range (i.e., native and non-native species, respectively). To characterize plant stress, we measured tree defoliation and chlorophyll fluorescence approximately one month following the chilling event. To quantify recovery, we measured chlorophyll fluorescence approximately nine months after the chilling event. Our results show high variation in the geographic- and species-specific responses of mangroves to winter temperature extremes. While many species were sensitive to the chilling temperatures (e.g., Bruguiera sexangula and species in the Sonneratia and Rhizophora genera), the temperatures during this event were not cold enough to affect certain species (e.g., Kandelia obovata , Aegiceras corniculatum , Avicennia marina, and Bruguiera gymnorrhiza ). As expected, non-native species were less tolerant of winter temperature extremes than native species. Interestingly, tidal inundation modulated the effects of chilling. In comparison with other temperature-controlled mangrove range limits across the world, the mangrove range limit in China is unique due to the combination of the following three factors: (1) Mangrove species diversity is comparatively high; (2) winter air temperature extremes, rather than means, are particularly intense and play an important ecological role; and (3) due to afforestation and restoration efforts, several species of non-native mangroves have been introduced beyond their natural range limits. Hence, from a global perspective, mangroves in China provide valuable opportunities to advance understanding of the effects of freezing and chilling temperatures on mangroves. Within the context of climate change, our findings provide a foundation for better understanding and preparing for mangrove species-specific responses to future changes in the duration and intensity of winter temperature extremes.

Ecosphere↗

USGS2026

Dynamics and evolution of the Kı̄lauea lower East Rift Zone 2018 fissure 8 lava flow and implications for multiphase magma properties

The 2018 Kı̄lauea lower East Rift Zone (KLERZ) eruption was one of the most voluminous eruptions on the Island of Hawai’i in the past 200 years, leading to major disruption and destroying over 700 homes and structures. The majority of the erupted magma was emitted as a lava flow from Ahu’ailā’au (fissure 8), which was active from late May to early August. To better understand the evolution of long-lived channelized lava flows, we examined the evolution of velocity, texture, and inferred rheology of the fissure 8 lava in space and time. We quantified lava flow surface velocities using particle image velocimetry in more than 200 aerial videos that span the lava flow duration and length. Velocity measurements were analyzed together with vesicularity and crystallinity measurements from 9 co-located post-eruptive field samples to understand the textural evolution of this flow and its impact on lava rheology and flow velocity. The fissure 8 flow was highly vesicular, with 79%–88% vesicularity at the vent, decreasing to 16%–26% vesicularity 12.5 km from the vent. The volume fraction occupied by crystals 50 in size increased from 6% at the vent to about 18% at 12.5 km downstream. We find that the effective flow viscosity increased at a quadratic rate with distance. Using experimentally determined liquid viscosity and applying established models to account for the effect of crystals and bubbles, we attribute this increase primarily to textural evolution driven initially by the near-vent loss of deformable bubbles and later by cooling and crystal growth. We demonstrate the importance of accounting for the evolution of vesicularity and the role of vesicles by showing that utilizing this capability in the open-source thermo-rheological lava flow propagation model PyFLOWGO allows for more accurate predictions of the observed flow velocities. Our modeling results suggest that small bubbles behaving rigidly are required to simulate the observed flow length, speed, and viscosities. Flow velocities of the fissure 8 lava also varied with time, driven by near-daily collapse events of the summit caldera. Temporal velocity changes were characterized by a period of steep acceleration, with the volumetric flux peaking around 4 h after a caldera collapse, followed by a period of gradual deceleration lasting up to 40 h or until the next collapse event. We use this temporal behavior to estimate the compressibility of the magma inside the plumbing system between the summit reservoir and the lower East Rift Zone. Overall, quantifying the spatial and temporal evolution of the KLERZ eruption provides information about magma and lava properties that can inform predictive modeling and hazard assessment during an eruption.

Hawaii↗

USGS2003

Sex differences in the thermoregulation and evaporative water loss of a heterothermic bat, Lasiurus cinereus, during its spring migration

This study quantifies sex differences in thermoregulation and water loss of a small (20-35 g) insectivorous heterothermic mammal, the hoary bat Lasiurus cinereus , during its spring migration. We measured body temperature, metabolic rate and evaporative water loss, and calculated wet thermal conductance, for bats exposed to air temperatures ranging from 0 to 40°C for periods of 2-5 h. Pregnant females maintained normothermic body temperatures (35.7±0.7°C; mean ± s.e.m. ) independent of air temperature. In contrast, males became torpid during the majority (68%) of exposures to air temperatures <25°C. The thermal neutral zone (TNZ) ranged between approximately 30°C and 34°C in both sexes and, within the TNZ, females had lower mass-specific metabolic rates (6.1±0.2 mW g -1 ) than males (9.0±0.9 mW g -1 ). Wet thermal conductance values in torpid bats (0.7±0.5 mW g -1 deg. -1 ) were lower than those of normothermic individuals (1.1±0.3 mW g -1 deg. -1 ). Mass-specific rates of evaporative water loss in males were consistently higher than in females at most air temperatures and rates of water loss in torpid bats were 63±6% of normothermic values. These results suggest that male and pregnant female L. cinereus employ different thermoregulatory strategies during their spring migration. Females defend normothermic body temperatures, presumably to expedite embryonic growth, while males use torpor, presumably to minimize energy and water deficits. These variable thermoregulatory strategies may reflect continental differences in the summer distribution of the sexes.

Journal of Experimental Biology↗

USGS1974

Seismotectonic map of the Eastern United States

The purpose of a seismotectonic map is to describe the distribution of historic seismic activity in relation to geologic structures and tectonic provinces and to identify structures or regions that are characterized by consistent relations between seismic activity and structural features. An experimental study to test the feasibility of preparing such a map and its usefulness in evaluating earthquake hazards was initiated jointly by the U.S. Geological Survey and the former Seismology Division of the National Oceanic and Atmospheric Administration; financial support was provided by the U.S. Atomic Energy Commission. It was hoped that the study would develop evidence for the existence of tectonic regions or structural provinces that are useful in defining parameters of seismic hazard in relation to engineered structures. As with many experiments, this one did not produce the results envisioned at the outset, but it did result, we think, in assembling seismic and structural data useful in evaluating the distribution and origin of earthquakes in the eastern part of the United States and in delimiting areas of relative seismic activity.

Miscellaneous Field Studies Map↗

USGS2011

Summary report of responses of key resources to the 2000 Low Steady Summer Flow experiment, along the Colorado River downstream from Glen Canyon Dam, Arizona

In the spring and summer of 2000, a series of steady discharges of water from Glen Canyon Dam on the Colorado River were used to evaluate the effects of aquatic habitat stability and water temperatures on native fish growth and survival, with a special focus on the endangered humpback chub (Gila cypha), downstream from the dam in Grand Canyon. The steady releases were bracketed by peak powerplant releases in late-May and early-September. The duration and volume of releases from the dam varied between spring and summer. The intent of the experimental hydrograph was to mimic predam river discharge patterns by including a high, steady discharge in the spring and a low, steady discharge in the summer. The hydrologic experiment was called the Low Steady Summer Flow (LSSF) experiment because steady discharges of 226 m3/s dominated the hydrograph for 4 months from June through September 2000. The experimental hydrograph was developed in response to one of the U.S. Fish and Wildlife Service's Recommended and Prudent Alternatives (RPA) in its Biological Opinion of the Operation of Glen Canyon Dam Final Environmental Impact Statement. The RPA focused on the hypothesis that seasonally adjusted steady flows were dam operations that might benefit humpback chub more than the Record of Decision operations, known as Modified Low Fluctuating Flow (MLFF) operations. Condensed timelines between planning and implementation (2 months) of the experiment and the time required for logistics, purchasing, and contracting resulted in limited data collection during the high-release part of the experiment that occurred in spring. The LSSF experiment is the longest planned hydrograph that departed from the MLFF operations since Record of Decision operations began in 1996. As part of the experiment, several studies focused on the responses of physical properties related to environments that young-of-year (YOY) native fish might occupy (for example, measuring mainstem and shoreline water temperature, and quantifying useable shorelines). The part of the hydrograph that included a habitat maintenance flow (a 4-day spike at a powerplant capacity of 877 m3/s) and sustained high releases in April and May (averaging 509 m3/s) resulted in sediment export to Lake Mead, the reservoir downstream from Glen Canyon Dam, which is outside the study area. Some mid-elevation sandbar building (between 566 and 877 m3/s stage elevations) occurred from existing sediment deposits rather than from sediment inputs from tributaries during the previous winter. Low releases in the summer combined with low tributary sediment inputs resulted in minor sediment accumulation in the study area. The September habitat maintenance flow reworked accumulated sediment and resulted in increases in the area of some backwaters. The mainstem water temperatures in the reach near the Little Colorado River during the LSSF experiment varied little from previous years. Mainstem water temperatures in western Grand Canyon average 17 to 20 degrees C. During the LSSF, backwaters warmed more than other shoreline environments during the day, but most backwaters returned to mainstem water temperatures overnight. Shoreline surface water temperatures from river mile (RM) 30 to 72 varied between 9 and 28 degrees C in the middle of the day in July. These temperatures are within the optimal temperature range for humpback chub growth and spawning, which is between 15 and 24 degrees C. How surface water temperatures transfer to subsurface water temperatures is unknown. Data collection associated with the response of fish to the 2000 LSSF hydrograph focused on fish growth and abundance along the Colorado River in Grand Canyon. The target resource, humpback chub and other native fishes, did not respond in a strongly positive or strongly negative manner to the LSSF hydrograph during the sampling period, which extended from June to September 2000. In 2000, the mean total length of YOY native fishes was similar to the mean

Arizona↗

USGS2020

Continuous nitrate monitoring in groundwater and potential contribution to surface-water nitrogen loads in Mason County, Illinois

Illinois has some of the most productive farmland in the country. The use of fertilizers to improve crop production has increased, which has resulted in an increase in the concentration of nitrogen in many streams and aquifers. The U.S. Geological Survey, in cooperation with the Illinois Environmental Protection Agency, is continuously monitoring (one reading every 15 minutes) the concentration of nitrate plus nitrite, as nitrogen, in a groundwater well and assessing the potential contribution to surface-water nitrogen loads. Continuous monitoring of the nitrate concentration allows for the collection of a larger dataset in comparison to periodic or event-based sampling. This fact sheet describes the data collection methods, describes the overall experimental design, and displays data collected for the study. The analysis of continuous data improves understanding of the fate and transport of nitrate.

Illinois↗

USGS1981

Experimental seawater-basalt interaction at 300°C, 500 bars, chemical exchange, secondary mineral formation and implications for the transport of heavy metals

Seawater and NaCl solutions were reacted with basalt (basalt glass and diabase) for several months at 300°C, 500 bars and a water/rock ratio of 10. During reaction, seawater was significantly modified, increasing in Ca, H 2 S, CO 2 . SiO 2 , K. Fe, Mn. Ba, Al and H + , and decreasing in Mg and SO 4 . Basalt glass was completely replaced by smectite, wairakite, anhydrite and hematite, and diabase was partially replaced by mixed layered smectite-chlorite, anhydrite and magnetite (?). Diabase was altered more slowly than basalt glass and the corresponding changes in seawater chemistry were less pronounced. Basalt glass reacted with a 0.45 m NaCl solution resulted in the formation of smectite, albite. truscottite and wairakite. Solutions from this experiment were characterized by a relatively high pH and dominated by Ca for Na exchange reactions. At no point in this experiment were heavy metals solubilized, in contrast to the seawater experiments. This behavior illustrates the fundamental importance of seawater chemistry to heavy-metal solubility; that is, the removal of Mg from seawater generates acidity which maintains heavy metals in solution. Apparently seawater chlorinity is not capable of enhancing heavy-metal solubility by chloride complexing. Seafloor heavy-metal deposits can result from the following: Seawater-basalt interaction at moderate temperature (&sim;-300°C and high effective water/rock ratios; or at relatively high temperatures (&sim;-400°C) and low (e.g.< 10) water/rock ratios.

Geochimica et Cosmochimica Acta↗

USGS2008

Soil texture drives responses of soil respiration to precipitation pulses in the sonoran desert: Implications for climate change

Climate change predictions for the desert southwestern U.S. are for shifts in precipitation patterns. The impacts of climate change may be significant, because desert soil processes are strongly controlled by precipitation inputs ('pulses') via their effect on soil water availability. This study examined the response of soil respiration-an important biological process that affects soil carbon (C) storage-to variation in pulses representative of climate change scenarios for the Sonoran Desert. Because deserts are mosaics of different plant cover types and soil textures-which create patchiness in soil respiration-we examined how these landscape characteristics interact to affect the response of soil respiration to pulses. Pulses were applied to experimental plots of bare and vegetated soil on contrasting soil textures typical of Sonoran Desert grasslands. The data were analyzed within a Bayesian framework to: (1) determine pulse size and antecedent moisture (soil moisture prior to the pulse) effects on soil respiration, (2) quantify soil texture (coarse vs. fine) and cover type (bare vs. vegetated) effects on the response of soil respiration and its components (plant vs. microbial) to pulses, and (3) explore the relationship between long-term variation in pulse regimes and seasonal soil respiration. Regarding objective (1), larger pulses resulted in higher respiration rates, particularly from vegetated fine-textured soil, and dry antecedent conditions amplified respiration responses to pulses (wet antecedent conditions dampened the pulse response). Regarding (2), autotrophic (plant) activity was a significant source (???60%) of respiration and was more sensitive to pulses on coarse- versus fine-textured soils. The sensitivity of heterotrophic (microbial) respiration to pulses was highly dependent on antecedent soil water. Regarding (3), seasonal soil respiration was predicted to increase with both growing season precipitation and mean pulse size (but only for pulses between 7 and 25 mm). Thus, the heterogeneity of the desert landscape and the timing or the number of medium-sized pulses is expected to significantly impact desert soil C loss with climate change. ?? 2008 Springer Science+Business Media, LLC.

Ecosystems↗

USGS2009

The speciation of aqueous zinc(II) bromide solutions to 500 °C and 900 MPa determined using Raman spectroscopy

A Raman spectral study was carried out on 3 solutions of varying concentration and bromide/zinc ratios. Spectra were collected at 11 different temperature-pressure conditions ranging from ambient to 500????C-0.9??GPa. Raman band assignments for zinc(II) bromide species reported in previous studies were used to determine the relative concentrations of ZnBr42-, ZnBr3-, ZnBr2, and ZnBr+ species at various temperatures and pressures. Our results are in close agreement with X-ray absorption spectroscopic (XAS) data, and confirm that the tetrabromo zinc(II) complex, ZnBr42-, is the predominant species up to 500????C in solutions having high Zn concentrations (1??m) and high bromide/zinc molar ratios ([Br]/[Zn] = 8). In agreement with previous solubility and Raman spectroscopic experiments, our measurements indicate that species with a lower number of halide ligands and charge are favored with increasing temperature in dilute solutions, and solutions with low bromide/zinc ratios ([Br]/[Zn] < 2.5). The Raman technique provides an independent experimental means of evaluating the quality of XAS analyses of data obtained from high temperature disordered systems. The combination of these two techniques provides complementary data on speciation and the structure of zinc(II) bromide complexes. The preponderance of the ZnBr42- species in highly saline brines at high temperature is consistent with the predominance of ZnCl42- in chloride-rich brines reported in previous XAS studies. Knowledge of Zn complexing in metal-rich highly saline brines is important for numerical models of ore deposition in high temperature systems such as skarns and porphyry-type deposits. ?? 2008 Elsevier B.V.

Chemical Geology↗

USGS2002

Association of methylmercury with dissolved humic acids

Sorption of methylmercury (MeHg) to three different humic acids was investigated as a function of pH and humic concentration. The extent of sorption did not show a strong pH dependence within the pH range of 5−9. Below pH 5, a decrease in adsorption for all humic samples was observed. The experimental data for equilibrium sorption of MeHg were modeled using a discrete log K spectrum approach with three weakly acidic functional groups. The modeling parameters, which were the equilibrium binding constants and the total binding capacities, represented the data well at all MeHg and humic concentra tions and pH values for a given humic sample. The estimated binding constants for complexes of MeHg with humic acids were similar in magnitude to those of MeHg with thiol-containing compounds, suggesting that binding of MeHg involves the thiol groups of humic acids. The results show that only a small fraction of the reduced sulfur species in humic substances may take part in binding MeHg, but in most natural systems, this subfraction is considerably higher in concentration than ambient MeHg. The model developed here can be incorporated into speciation models to assess the bioavailability of MeHg in the presence of dissolved organic matter and competing ligands such as chloride and sulfide.

Environmental Science & Technology↗

USGS2018

Inhibition of grain boundary sliding creep in fine-grained ice by inter-granular particles: Implications for planetary ice masses

Ice in both terrestrial and planetary settings often contains rock particles. Here we present an experimental investigation of the influence of intergranular particles on the rheological behavior of ice. Experiments were performed on samples fabricated from 10‐μm ice powders +1‐μm graphite or 0.8‐μm alumina particles and subjected to elevated confining pressures. A critical particle fraction, ∼6%, was observed, below which samples behave like pure ice and deform by both grain boundary sliding (GBS) and dislocation creep, and above which GBS creep is impeded. Above this critical fraction, ice grains occur in particle‐free clusters surrounded by bands of particles mixed with fine‐grained ice, resulting in the impedance of GBS in the bands as well as sliding between the ice clusters. Our results imply that South Polar Layered Deposits and midlatitude lobate debris aprons on Mars must contain >94% ice and that the shallow subsurface of Ceres could contain >90% ice.

Geophysical Research Letters↗

USGS2026

Meso-scale pressure reactor demonstrates biostimulation of coal-dependent methanogenesis

Replicating deep subsurface conditions remains a major challenge for advancing subterranean biotechnologies. Microbially enhanced coal bed methane production offers a promising approach to increase biogenic gas recovery from coal seams, yet experimental progress has been limited by the difficulty of simulating in situ conditions. A key question is whether nutrient amendments stimulate coal-dependent methanogenesis or simply convert injected nutrients to methane. Here, we report the use of a large-scale (325 L) reactor to investigate 13 C-labeled microalgae amendments on microbially-enhanced coal bed methane production at in situ pressure. Labeled methane was detected only during the initial stimulation phase, while most of the methane produced over five months originated from the coal. These field-relevant results demonstrate that microalgae can accelerate early methanogenesis and enhance coal-derived methane production over time. This study provides a critical proof-of-concept with broad implications for advancing subsurface biotechnologies toward field-scale deployment.

Communications Earth & Environment↗

USGS2010

The anatomy, taphonomy, taxonomy and systematic affinity of Markuelia: Early Cambrian to Early Ordovician scalidophorans

Markuelia is a vermiform, annulated introvertan animal known as embryonic fossils from the Lower Cambrian to Lower Ordovician. Analysis of an expanded and revised dataset for Introverta shows that the precise position of Markuelia within this clade is dependent on the taxa included. As a result, Markuelia is assigned to the scalidophoran total group to reflect uncertainty as to whether it is a stem-scalidophoran or a stem-priapulid. The taxonomy of the genus is revised to provide an improved taxonomic framework for material assigned to Markuelia. Five species are recognized: M. secunda Val'kov, M. hunanensis Dong and Donoghue, M. lauriei Haug et al., M. spinulifera sp. nov. and M. waloszeki sp. nov. Finally, the preservation of Markuelia is evaluated in the light of both the taphonomy of the fossil embryos themselves and the experimental taphonomy of the priapulid Priapulus caudatus, which has been proposed as both a close relative and an anatomical analogue of Markuelia. ?? The Palaeontological Association.

Palaeontology↗

USGS1987

Phase separation in seafloor geothermal systems: An experimental study of the effects on metal transport

Experimental investigations were carried out by reacting natural and evolved sea-water with crystalline basalt from the Juan de Fuca Ridge in order to study the effects of vapour-liquid phase separation on metal mobilization in sea-floor geothermal systems in which phase separation occurs between the top of a magma chamber (300-500 bar) and the sea-floor (230-250 bar). The geochemical processes produced by a combination of closed-system phase separation and adiabatic expansion under the conditions characterizing the sea-floor geothermal systems resulted in a significant increase in the acidity and concentration of heavy metals in the liquid phase and strikingly high concentrations of metals in the vapour.

American Journal of Science↗

USGS2021

Supporting the development and use of native plant materials for restoration on the Colorado Plateau (Fiscal Year 2020 Report)

A primary focus of the Colorado Plateau Native Plant Program (CPNPP) is to identify and develop appropriate native plant materials (NPMs) for current and future restoration projects. Multiple efforts have characterized the myriad challenges inherent in providing appropriate seed resources to enable effective, widespread restoration and have identified a broad suite of research activities to provide the information necessary to overcome those challenges (e.g., Plant Conservation Alliance 2015; Breed et al. 2018; Winkler et al. 2018). Many of the most complex information needs relate to identifying the appropriate sources of plant species that can successfully establish in dryland environments, like the Colorado Plateau, where precipitation is generally low and highly variable. Providing this information requires synergistic research efforts that build upon insight gained from earlier investigations. The U.S. Geological Survey (USGS) Southwest Biological Science Center’s (SBSC’s) research activities that supported CPNPP in FY20 followed the FY20 Statement of Work to support a research framework that is continually adapting based on the needs of the restoration community and results from previous investigations; the long-term research framework is outlined in the 2019-2023 5-Year Research Strategy (hereafter referred to as the 5-year plan). This research framework provides support for the National Seed Strategy for Rehabilitation and Restoration (Plant Conservation Alliance, 2015), Department of Interior Secretarial Order #3347 ( Conservation Stewardship and Outdoor Recreation ), and Bureau of Land Management Leadership Priority #1 ( Create a conservation stewardship legacy second only to Teddy Roosevelt ). Research activities in FY20 centered on landscape genomics, implementing a common garden experiment near Vernal, UT, conducting experimental treatments using the GRID (Germination for Restoration Information and Decision-making) framework, and collecting seeds and leaf tissues in the field in preparation for future experiments. These activities were supported by five biological science technicians. The SARS-CoV-2 pandemic delayed some aspects of the FY20 workplan, especially for contract laboratory services and the construction of the GRID garden in Flagstaff, AZ. However, goals were largely met, and the overall progress of research remains on track with respect to the 5-year plan. While Dr. Rob Massatti was the only scientist supported by the SBSC-CPNPP agreement in FY20, other scientists, including Drs. John Bradford, Seth Munson, Mike Duniway, Sasha Reed, Matt Jones, and Daniel Winkler, spent a considerable amount of time providing expertise and support for individual projects. Work activities performed in support of each goal are discussed in turn.

Arizona, Colorado, New Mexico, Utah↗

USGS2001

Experimental flood effects on the limnology of Lake Powell Reservoir, southwestern USA

In the spring of 1996, a nine-day test flood from Glen Canyon Dam involved the deepest and largest hypolimnetic withdrawals from the penstocks and the river outlet works (ROW) since 1986, interacting with ongoing hydrodynamic and stratification patterns to enhance freshening of the hypolimnion of Lake Powell reservoir and its tailwaters. Prior to the test flood, a six-year drought had produced a pronounced meromictic hypolimnion that was weakening from high inflow events in 1993 and 1995. Hypoxia, however, had continued to increase in the deepest portions of the reservoir. Over the course of the test flood, 0.893 km 3 were released from the ports located at and below the hypolimnetic chemocline. The increased discharge and mixing resulting from the test flood diminished the volume of this hypoxic and meromictic hypolimnion as far as 100 km uplake. This effect was reinforced by seasonal upwelling of hypolimnetic water at the dam and seasonal hydrologic patterns uplake. The timing and magnitude of the discharge maximized the release of the highest salinity and lowest dissolved oxygen (DO) water that typically occurs near the release structures of the dam annually. Subsequent high inflows and discharges in 1997 continued to freshen the hypolimnion. During the flood, large aerated discharges in the tailwaters briefly increased DO to above saturation but dampened diel fluctuations in pH and DO. Downstream ion concentration levels were elevated during the test flood but resumed an enhanced freshening trend following the lower hydrograph. The results indicate that dam operations, timed with predictable limnological events, can be used to manipulate tailwater and reservoir water quality.

Arizona, Utah↗

USGS2015

Experimental infection of meadow voles ( Microtus pennsylvanicus ) with sheep scrapie

Meadow voles (Microtus pennsylvanicus) are permissive to chronic wasting disease (CWD) infection, but their susceptibility to other transmissible spongiform encephalopathies (TSEs) is poorly characterized. In this initial study, we intracerebrally challenged 6 meadow voles with 2 isolates of sheep scrapie. Three meadow voles acquired a TSE after the scrapie challenge and an extended incubation period. The glycoform profile of proteinase K-resistant prion protein (PrP(res)) in scrapie-sick voles remained similar to the sheep inocula, but differed from that of voles clinically affected by CWD. Vacuolization patterns and disease-associated prion protein (PrP(Sc)) deposition were generally similar in all scrapie-affected voles, except in the hippocampus, where PrP(Sc) staining varied markedly among the animals. Our results demonstrate that meadow voles can acquire a TSE after intracerebral scrapie challenge and that this species could therefore prove useful for characterizing scrapie isolates.

Canadian Journal of Veterinary Research↗