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At least 1,009 records · Page 56Linked to original sources
USGS2019

Interspecific aggression among parapatric and sympatric songbirds on a tropical elevational gradient

Interspecific competition is hypothesized to be a strong force that sets species range limits and drives parapatric distributions of closely related species on tropical mountains. Yet, experimental evidence that competition drives spatial segregation of closely related species on elevational gradients is rare. To test whether competition limits elevational ranges of tropical songbirds, we conducted reciprocal playback experiments on 2 pairs of species with adjacent but nonoverlapping (parapatric) distributions and 1 pair of sympatric species. We found asymmetric interspecific aggression in one parapatric pair (Pycnonotidae) and a complete absence of interspecific aggression in the other (Zosteropidae) . We also found asymmetric interspecies aggression in a pair of sympatric flycatchers (Muscicapidae). Our results indicate that interspecific aggression may set range limits in some cases, but it is not a prerequisite for parapatry. Furthermore, the presence of interspecific aggression between co-occurring relatives suggests that while competition may play a role in limiting species distributions, interspecific aggression alone is not sufficient evidence to assert that competition is the primary driver of parapatric distributions.

Behavioral Ecology↗
USGS2019

Addressing barriers to improve biocrust colonization and establishment in dryland restoration

Methods to reduce soil loss and associated loss of ecosystem functions due to land degradation are of particular importance in dryland ecosystems. Biocrusts are communities of cyanobacteria, lichens, and bryophytes that are vulnerable to soil disturbance, but provide vital ecosystem functions when present. Biocrusts stabilize soil, improve hydrologic function, and increase nutrient and carbon inputs. Methods to reestablish biocrust rapidly, when lost from ecosystems, have the potential to restore important dryland ecosystem functions and thereby increase probability of successful rehabilitation. The aim of this study was to identify habitat ameliorations to enhance the success of biocrust inoculation by: (1) reducing physiological stress on biocrusts and increasing resource availability (using shade, soil surface roughening, and watering), and (2) stabilizing mobile soils (using straw borders, three soil tackifiers [soil stabilizers], and a combination of shade, water, roughening, and tackifier). In the Great Basin Desert on the Utah Test and Training Range near Salt Lake City, we applied field‐harvested biocrust material to experimental plots on coarse‐ and fine‐textured soils with the top 2 cm of soil and biocrust removed. Habitat ameliorations were applied with and without biocrust addition. Shade provision increased biocrust cover 50% over controls. Biocrust cover and soil stability were 65% lower in straw border plots relative to controls. Soil tackifiers, alone and in combination with resource augmentation and stress reduction, did not improve cover and stabilization over inoculated controls. We found variability in recovery by time and between soil types. These results suggest plausible strategies to improve success of biocrust inoculation.

Utah↗
USGS2018

Experimental infection of Tadarida brasiliensis with Pseudogymnoascus destructans, the fungus that causes white-nose syndrome

White-nose syndrome (WNS) is causing significant declines in populations of North American hibernating bats, and recent western and southern expansions of the disease have placed additional species at risk. Understanding differences in species susceptibility and identifying management actions to reduce mortality of bats from WNS are top research priorities. However, the use of wild-caught susceptible bats, such as Myotis lucifugus , as model species for WNS research is problematic and places additional pressure on remnant populations. We investigated the feasibility of using Tadarida brasiliensis , a highly abundant species of bat that tolerates captivity, as the basis for an experimental animal model for WNS. Using methods previously established to confirm the etiology of WNS in M. lucifugus , we experimentally infected 11 T. brasiliensis bats with Pseudogymnoascus destructans in the laboratory under conditions that induced hibernation. We detected P. destructans on all 11 experimentally infected bats, 7 of which exhibited localized proliferation of hyphae within the epidermis, dermis, and subcutaneous tissue, similar to invasive cutaneous ascomycosis observed in M. lucifugus bats with WNS. However, the distribution of lesions across wing membranes of T. brasiliensis bats was limited, and only one discrete “cupping erosion,” diagnostic for WNS, was identified. Thus, the rarity of lesions definitive for WNS suggests that T. brasiliensis does not likely represent an appropriate model for studying the pathophysiology of this disease. Nonetheless, the results of this study prompt questions concerning the potential for free-ranging, migratory T. brasiliensis bats to become infected with P. destructans and move the fungal pathogen between roost sites used by species susceptible to WNS.

mSphere↗
USGS2008

Elevated CO 2 enhances biological contributions to elevation change in coastal wetlands by offsetting stressors associated with sea-level rise

1. Sea-level rise, one indirect consequence of increasing atmospheric CO 2 , poses a major challenge to long-term stability of coastal wetlands. An important question is whether direct effects of elevated CO 2 on the capacity of marsh plants to accrete organic material and to maintain surface elevations outweigh indirect negative effects of stressors associated with sea-level rise (salinity and flooding). 2. In this study, we used a mesocosm approach to examine potential direct and indirect effects of atmospheric CO 2 concentration, salinity and flooding on elevation change in a brackish marsh community dominated by a C 3 species, Schoenoplectus americanus, and a C 4 grass, Spartina patens. This experimental design permitted identification of mechanisms and their role in controlling elevation change, and the development of models that can be tested in the field. 3. To test hypotheses related to CO 2 and sea-level rise, we used conventional anova procedures in conjunction with structural equation modelling (SEM). SEM explained 78% of the variability in elevation change and showed the direct, positive effect of S. americanus production on elevation. The SEM indicated that C 3 plant response was influenced by interactive effects between CO 2 and salinity on plant growth, not a direct CO 2 fertilization effect. Elevated CO 2 ameliorated negative effects of salinity on S. americanus and enhanced biomass contribution to elevation. 4. The positive relationship between S. americanus production and elevation change can be explained by shoot-base expansion under elevated CO 2 conditions, which led to vertical soil displacement. While the response of this species may differ under other environmental conditions, shoot-base expansion and the general contribution of C 3 plant production to elevation change may be an important mechanism contributing to soil expansion and elevation gain in other coastal wetlands. 5. Synthesis. Our results revealed previously unrecognized interactions and mechanisms contributing to marsh elevation change, including amelioration of salt stress by elevated CO 2 and the importance of plant production and shoot-base expansion for elevation gain. Identification of biological processes contributing to elevation change is an important first step in developing comprehensive models that permit more accurate predictions of whether coastal marshes will persist with continued sea-level rise or become submerged. ?? 2008 The Authors.

Journal of Ecology↗
USGS2007

A unified equation for calculating methane vapor pressures in the CH4-H2O system with measured Raman shifts

A unified equation has been derived by using all available data for calculating methane vapor pressures with measured Raman shifts of C-H symmetric stretching band (??1) in the vapor phase of sample fluids near room temperature. This equation eliminates discrepancies among the existing data sets and can be applied at any Raman laboratory. Raman shifts of C-H symmetric stretching band of methane in the vapor phase of CH4-H2O mixtures prepared in a high-pressure optical cell were also measured at temperatures between room temperature and 200 ??C, and pressures up to 37 MPa. The results show that the CH4 ??1 band position shifts to higher wavenumber as temperature increases. We also demonstrated that this Raman band shift is a simple function of methane vapor density, and, therefore, when combined with equation of state of methane, methane vapor pressures in the sample fluids at elevated temperatures can be calculated from measured Raman peak positions. This method can be applied to determine the pressure of CH4-bearing systems, such as methane-rich fluid inclusions from sedimentary basins or experimental fluids in hydrothermal diamond-anvil cell or other types of optical cell. ?? 2007 Elsevier Ltd. All rights reserved.

Geochimica et Cosmochimica Acta↗
USGS2015

Trophic ecology of northern pike and their effect on conservation of westslope cutthroat trout.

Westslope Cutthroat Trout Oncorhynchus clarkii lewisi in Coeur d’Alene Lake, Idaho, have declined in recent years; predation by Northern Pike Esox lucius , a nonnative sport fish, is thought to be a causative mechanism. The goal of this study was to describe the seasonal food habits of Northern Pike and determine their influence on Westslope Cutthroat Trout in Coeur d’Alene Lake by using a bioenergetics modeling approach. Fish were sampled monthly from March 2012 to May 2013 using pulsed-DC electrofishing and experimental gillnetting in four bays. Northern Pike catch rates from electrofishing were generally low but increased slightly each season and were highest in the southern portion of the lake; catch rates from gillnetting were approximately 50% higher during the two spring sampling periods compared with the summer and fall. Seasonal growth and food habits of 695 Northern Pike (TL = 16.2–108.0 cm; weight = 24–9,628 g) were analyzed. Diets primarily consisted of kokanee O. nerka , Westslope Cutthroat Trout, and Yellow Perch Perca flavescens . Results of a bioenergetics model estimated that Westslope Cutthroat Trout represented approximately 2–30% of the biomass consumed by age-1–4 Northern Pike. Total Westslope Cutthroat Trout biomass consumed by Northern Pike (2008–2011 year-classes) across all seasons sampled was estimated to be 1,231 kg (95% CI = 723–2,396 kg), and the total number consumed was 5,641 (95% CI = 3,311–10,979). The highest occurrence of Westslope Cutthroat Trout in Northern Pike diets was observed during spring. Thus, reducing Northern Pike predation on Westslope Cutthroat Trout would be one tool worth considering for conserving Westslope Cutthroat Trout populations in Coeur d’Alene Lake.

Idaho↗
USGS2023

Gene expression reveals immune response strategies of naïve Hawaiian honeycreepers experimentally infected with introduced avian malaria

The unprecedented rise in the number of new and emerging infectious diseases in the last quarter century poses direct threats to human and wildlife health. The introduction to the Hawaiian archipelago of Plasmodium relictum and the mosquito vector that transmits the parasite has led to dramatic losses in endemic Hawaiian forest bird species. Understanding how mechanisms of disease immunity to avian malaria may evolve is critical as climate change facilitates increased disease transmission to high elevation habitats where malaria transmission has historically been low and the majority of the remaining extant Hawaiian forest bird species now reside. Here, we compare the transcriptomic profiles of highly susceptible Hawai‘i ‘amakihi ( Chlorodrepanis virens ) experimentally infected with P. relictum to those of uninfected control birds from a naïve high elevation population. We examined changes in gene expression profiles at different stages of infection to provide an in-depth characterization of the molecular pathways contributing to survival or mortality in these birds. We show that the timing and magnitude of the innate and adaptive immune response differed substantially between individuals that survived and those that succumbed to infection, and likely contributed to the observed variation in survival. These results lay the foundation for developing gene-based conservation strategies for Hawaiian honeycreepers by identifying candidate genes and cellular pathways involved in the pathogen response that correlate with a bird’s ability to recover from malaria infection.

Hawaii↗
USGS2017

Suppression of invasive lake trout in an isolated backcountry lake in Glacier National Park

Fisheries managers have implemented suppression programmes to control non-native lake trout, Salvelinus namaycush (Walbaum), in several lakes throughout the western United States. This study determined the feasibility of experimentally suppressing lake trout using gillnets in an isolated backcountry lake in Glacier National Park, Montana, USA, for the conservation of threatened bull trout, Salvelinus confluentus (Suckley). The demographics of the lake trout population during suppression (2009–2013) were described, and those data were used to assess the effects of suppression scenarios on population growth rate ( λ ) using an age-structured population model. Model simulations indicated that the population was growing exponentially ( λ = 1.23, 95% CI: 1.16–1.28) prior to suppression. However, suppression resulted in declining λ (0.61–0.79) for lake trout, which was concomitant with stable bull trout adult abundances. Continued suppression at or above observed exploitation levels is needed to ensure continued population declines.

Fisheries Management and Ecology↗
USGS2004

Selective defecation and selective foraging: Antiparasite behavior in wild ungulates?

Selective defecation and selective foraging are two potential antiparasite behaviors used by grazing ungulates to reduce infection by fecal-oral transmitted parasites. While there is some evidence that domestic species use these strategies, less is known about the occurrence and efficacy of these behaviors in wild ungulates. In this study, I examined whether wild antelope use selective defecation and selective foraging strategies to reduce exposure to gastrointestinal nematode parasites. By quantifying parasite levels in the environment in relation to the defecation patterns of three species, dik-dik (Madoqua kirkii), Grant's gazelle (Gazella granti), and impala (Aepyceros melampus), I found that nematode larval concentrations in pasture were higher in the vicinity of clusters of feces (dung middens) compared to single fecal pellet groups or dung-free areas. In addition, experimental feeding trials in free-ranging dik-dik showed that individuals selectively avoided feeding near concentrations of feces. Given that increased parasite contamination was found in the immediate vicinity of fecal clusters, fecal avoidance could help reduce host consumption of parasites and may therefore be an effective antiparasite behavior for certain species. On the other hand, while the concentration of parasite larvae in the vicinity of middens coupled with host avoidance of these areas during grazing could reduce host contact with parasites, results showing a positive correlation between the number of middens in a habitat and larval abundance at control sites suggest that dung middens might increase and not decrease overall host exposure to parasites. If this is the case, dung midden formation may not be a viable antiparasite strategy.

Ethology↗
USGS2014

Testing ecological tradeoffs of a new tool for removing fine sediment in a spring-fed stream

Excessive fine sediment is a focus of stream restoration work because it can impair the structure and function of streams, but few methods exist for removing sediment in spring-fed streams. We tested a novel method of sediment removal with the potential to have minimal adverse effects on the biological community during the restoration process. The Sand Wand system, a dredgeless vacuum developed by Streamside Technologies, was used to experimentally remove fine sediment from Kackley Springs, a spring creek in southeastern Idaho. We assessed the effects of the Sand Wand on stream physical habitat and macroinvertebrate composition for up to 60 days after the treatment. We documented changes in multiple habitat variables, including stream depth, median particle size, and the frequency of embedded substrate in stream reaches that were treated with the Sand Wand. We also found that macroinvertebrate composition was altered even though common macroinvertebrate metrics changed little after the treatment. Our results suggest that the Sand Wand was effective at removing fine sediments in Kackley Springs and did minimal harm to macroinvertebrate function, but the Sand Wand was not ultimately effective in improving substrate composition to desired conditions. Additional restoration techniques are still needed to decrease the amount of fine sediment.

Ecological Restoration↗
USGS2007

Responses of hydrochemical inorganic ions in the rainfall-runoff processes of the experimental catchments and its significance for tracing

Aimed at the rainfall-runoff tracing using inorganic ions, the experimental study is conducted in the Chuzhou Hydrology Laboratory with special designed experimental catchments, lysimeters, etc. The various runoff components including the surface runoff, interflow from the unsaturated zone and the groundwater flow from saturated zone were monitored hydrometrically. Hydrochemical inorganic ions including Na+, K+, Ca2+, Mg2+, Cl-, SO42-, HCO3- + CO32-, NO3-, F-, NH4-, PO42-, SiO2 and, pH, EC, 18O were measured within a one month period for all processes of rainfall, various runoff components and groundwater within the catchment from 17 boreholes distributed in the Hydrohill Catchment, few soil water samples were also included. The results show that: (a) all the runoff components are distinctly identifiable from both the relationships of Ca2+ versus Cl-/SO42-, EC versus Na+/(Na+ + Ca2+) and, from most inorganic ions individually; (b) the variation of inorganic ions in surface runoff is the biggest than that in other flow components; (c) most ions has its lowermost concentration in rainfall process but it increases as the generation depths of runoff components increased; (d) quantitatively, ion processes of rainfall and groundwater flow display as two end members of that of other runoff components; and (e) the 18O processes of rainfall and runoff components show some correlation with that of inorganic ions. The results also show that the rainfall input is not always the main source of inorganic ions of various runoff outputs due to the process of infiltration and dissolution resulted from the pre-event processes. The amount and sources of Cl- of runoff components with various generation mechanisms challenge the current method of groundwater recharge estimation using Cl-.

Shuikexue Jinzhan/Advances in Water Science↗
USGS2022

Vegetative buffer strips show limited effectiveness for reducing antibiotic transport in surface runoff

Vegetative buffer strips (VBS) have been demonstrated to effectively reduce loads of sediment, nutrients, and herbicides in surface runoff, but their effectiveness for reducing veterinary antibiotic (VA) loads in runoff has not been well documented. The objective of this study was to determine the effectiveness of VBS vegetation and width on surface runoff loads of the VAs sulfamethazine (SMZ) and lincomycin (LIN). Experimental design of the plots (1.5 × 25 m) was a two-way factorial with four vegetation treatments (tall fescue [ Festuca aruninacea Schreb.]; tall fescue with switchgrass [ Panicum virgatum L.] hedge; warm-season native grass mix; and continuous fallow control), and four buffer widths (0, 2, 5, and 9 m). Turkey litter spiked with SMZ and LIN was applied to the source area (upper 7 m) of each plot, and runoff was collected at each width. Runoff was generated with a rotating boom simulator. Results showed VA loads in runoff at the 0-m sampler ranged from 3.8 to 5.9% of applied, and overall VA transport in runoff was predominately in the dissolved phase (90% for SMZ and 99% for LIN). Among vegetation treatments, only tall fescue significantly reduced loads of SMZ and LIN compared with the control, with load reductions of ∼30% for both VAs. Estimated field-scale reductions in VA loads showed that source-to-buffer area ratios (SBARs) of 10:1 to 20:1 reduced VA loads by only 7 to 16%. Overall, the grass VBS tested here were less effective at reducing SMZ and LIN loads in surface runoff than has been previously demonstrated for sediment, nutrients, and herbicides.

Journal of Environmental Quality↗
USGS2004

Pressure changes associated with the ascent and bursting of gas slugs in liquid-filled vertical and inclined conduits

At basaltic volcanoes, the sources of long-period and very-long-period seismicity and acoustic signals are frequently described in terms of fluid dynamic processes, in particular the formation and ascent of gas slugs within the magma column and their bursting at the surface. To investigate pressure changes associated with these processes, two-phase flow experiments have been carried out in vertical and inclined pipes with both single gas slugs and a continuously supplied gas phase. The ascent of individual gas slugs is accompanied by strong dynamic pressure variations resulting from the flow of liquid around the slug. These dynamic transients generate sub-static pressures below the ascending slug in viscosity-controlled systems, and produce super-static pressures when the slug reaches the surface and motion ceases in inertia-dominated systems. Conduit inclination promotes a change of regime from bubbly to slug flow and favours an increase in size and velocity of the slugs at the expense of their frequency of occurrence during continuously supplied two-phase flow. The experimental pressure data support previous theoretical analyses of oscillatory sources in ascending slugs as the slugs approach the surface and burst. Pressure oscillations are also observed during the release of gas slugs and in their wake region.

Journal of Volcanology and Geothermal Research↗
USGS2024

Deformation-induced graphitization and muscovite recrystallization in a ductile fault zone

A suite of slate samples collected along a 2 km transect crossing the Lishan fault in central Taiwan were evaluated to assess the role of ductile deformation in natural graphitization at lower greenschist facies metamorphic conditions. The process of natural aromatization, or graphitization, of an organic precursor is well established as a thermally driven process; however, experimental studies have shown that the energy provided by deformation can substantially reduce the activation energy required for graphitization. This study provides a natural example of deformation-induced graphitization. A strain gradient approaching the Lishan fault was established by scanning electron microscope imaging and X-ray diffraction analysis of phyllosilicates and quartz that showed an increase in the strength of slaty cleavage development via dissolution-precipitation processes. Thermal conditions were constrained to be near isothermal using calcite-dolomite geothermometry. Raman spectroscopic results from carbonaceous material, including D1-full width-at-half-maximum (FWHM), G-FWHM, Raman band separation (RBS), and a lesser-known vibrational mode B 2g -FWHM, showed robust linear trends across the same sampling transect. However, the G-FWHM parameter showed a trend opposite of that expected from thermally driven graphitization. The Raman results are interpreted to reflect a strain-driven reduction in graphite crystallite size (decrease in G-FWHM) but improvement in structural ordering in individual coherent domains. A multiple linear regression with an R 2 value of 0.92 predicts the graphite D1-FWHM values from the XRD-derived ratio of muscovite populations and muscovite microstrain, demonstrating the concomitant recrystallization of silicates and carbonaceous material across the strain gradient, despite the disparate processes accommodating the deformation. This study demonstrates the role of deformation in natural graphitization and provides a new perspective on the use of graphite as a geothermometer in strongly deformed greenschist facies rocks.

Journal of Metamorphic Geology↗
USGS2009

An experimental study of hydromagmatic fragmentation through energetic, non-explosive magma-water mixing

In this paper we report the first experimental investigation of non-explosive hydromagmatic fragmentation during energetic mixing with water. We mix magma and water by two methods: (1) pouring a basaltic melt between two converging water sprays; and (2) jetting basaltic melt at high pressure (3??MPa) through a nozzle into a tank of stagnant water. These experiments involved shear at relative velocities of ~ 5-16??m/s and vigorous mixing for less than a second, providing sufficient time for glassy rinds to grow but insufficient time for clot interiors to cool. In resulting fragments, we examined the gross morphology, which reflects fluid deformation during mixing, and surface textures, which reflect the growth and disruption of glassy rinds. We find major differences in both fragment morphology and surface texture between experiments. Water-spray experiments produced Pele's hair, thin bubble shards, melt droplets, and angular, fracture-bound droplet pieces. Melt-jet experiments produced mostly coarse (> 1??mm diameter), wavy fluidal fragments with broken ends. Fluidal surfaces of fragments produced by water-spray experiments were generally shiny under reflected light and, in microscopic examination, smooth down to micron scale, implying no disruption of glassy rinds, except for (a) rare flaking on Pele's hair that was bent prior to solidification; or (b) cracking and alligator-skin textures on segments of melt balls that had expanded before complete cooling. In contrast, textures of fluidal surfaces on fragments produced by melt-jet experiments are dull in reflected light and, in scanning electron images, exhibit ubiquitous discontinuous skins ("rinds") that are flaked, peeled, or smeared away in stripes. Adhering to these surfaces are flakes, blocks, and blobs of detached material microns to tens of microns in diameter. In the water-spray fragments, we interpret the scarcity of disrupted surface rinds to result from lack of bending after surfaces formed. In the melt-jet fragments, the ubiquity of partially detached rinds and rind debris likely reflects repeated bending, scraping, impact, and other disruption through turbulent velocity fluctuations. When extrapolated to jets of Surtseyan scale, where velocity fluctuations reach tens of meters per second and turbulent mixing persists for tens of seconds, rind disintegration could fragment a large fraction of the erupted material.

Journal of Volcanology and Geothermal Research↗
USGS2020

The freshwater mysid Mysis diluviana (Audzijonyte and Väinölä, 2005) (Mysida: Mysidae) consumes detritus in the presence of Daphnia (Cladocera: Daphniidae)

Freshwater mysids of the Mysis relicta group are omnivorous macroinvertebrates that form an important link between fishes and lower trophic levels in many north temperate to Arctic lakes, where they exhibit diel vertical migration (DVM) to exploit subsurface food-rich layers at night. Benthic food resources have been assumed to be less important for mysid diets than pelagic zooplankton. Studies have nevertheless indicated that mysids consume benthic sedimented detritus, calling this assumption into question. We conducted a food-choice experiment to evaluate the feeding preferences of Mysis diluviana (Audzijonyte & Vainola, 2005) by presenting field-caught specimens in individual foraging arenas with multiple choices of food. Experimental food treatments included a preferred pelagic prey (Daphnia), a presumed less desirable benthic resource (detritus), and a combination of both. We hypothesized that M. diluviana 1) prefers Daphnia over detritus and consumes only Daphnia in combination treatments, and 2) would not consume detritus except when detritus was the only food source available. Contrary to our hypothesis, M. diluviana readily consumed detritus in the presence of Daphnia. M. diluviana unexpectedly consumed more individuals of Daphnia in the presence rather than in the absence of detritus. Our results demonstrate that mysids take advantage of benthic food resources even in the presence of a presumably preferred zooplankton prey, calling to question the long-held assumption that benthic resources are unimportant when considering the trophic role of freshwater mysids of the M. relicta group.

Journal of Crustacean Biology↗
USGS1964

A thermodynamic study of pyrite and pyrrhotite

Through the use of the electrum-tarnish method the following equation has been found to interrelate the composition of pyrrhotite, fugacity of sulfur, and temperature: In this equation f s2 is the fugacity of sulfur relative to the ideal diatomic gas at 1 atm, N is the mol fraction of FeS in pyrrhotite (in the system FeS-S 2 ), and T the absolute temperature. The experimental uncertainty in the equation is 0–003 in N . The activity of FeS ( a FeS ) in pyrrhotite relative to the pure substance at the temperature of consideration follows from the above equation by virtue of the Gibbs-Duhem relation; it is given by: The electrum-tarnish method has permitted us to determine the f s2 vs. T curve for the univariant assemblage pyrrhotite-pyrite-vapor from 743 to 325°C. Our determinations of the composition of pyrrhotite are in excellent agreement with the results of Arnold. The activity of FeS in pyrite-saturated pyrrhotite is very different from unity, a fact that greatly influences the interpretation of some other phase equilibrium studies involving pyrrhotite and their application to sulfide mineral assemblages, but has little effect on the more general calculations of composition of hydrothermal or magmatic fluids. Pressure effects calculated from available volumetric data on the phases are small.

Geochimica et Cosmochimica Acta↗
USGS2011

Evaluation of offshore stocking of Lake Trout in Lake Ontario

Restoration stocking of hatchery-reared lake trout Salvelinus namaycush has occurred in Lake Ontario since 1973. In U.S. waters, fish stocked through 1990 survived well and built a large adult population. Survival of yearlings stocked from shore declined during 1990–1995, and adult numbers fell during 1998–2005. Offshore stocking of lake trout was initiated in the late 1990s in response to its successful mitigation of predation losses to double-crested cormorants Phalacrocorax auritus and the results of earlier studies that suggested it would enhance survival in some cases. The current study was designed to test the relative effectiveness of three stocking methods at a time when poststocking survival for lake trout was quite low and losses due to fish predators was a suspected factor. The stocking methods tested during 2000–2002 included May offshore, May onshore, and June onshore. Visual observations during nearshore stockings and hydroacoustic observations of offshore stockings indicated that release methods were not a direct cause of fish mortality. Experimental stockings were replicated for 3 years at one site in the southwest and for 2 years at one site in the southeast. Offshore releases used a landing craft to transport hatchery trucks from 3 to 6 km offshore out to 55–60-m-deep water. For the southwest site, offshore stocking significantly enhanced poststocking survival. Among the three methods, survival ratios were 1.74 : 1.00 : 1.02 (May offshore : May onshore : June onshore). Although not statistically significant owing to the small samples, the trends were similar for the southeast site, with survival ratios of 1.67 : 1.00 : 0.72. Consistent trends across years and sites indicated that offshore stocking of yearling lake trout during 2000–2002 provided nearly a twofold enhancement in survival; however, this increase does not appear to be great enough to achieve the 12-fold enhancement necessary to return population abundance to restoration targets.

North American Journal of Fisheries Management↗