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Research about Manitoba

Source-linked reports with geographic coverage including Manitoba.

At least 19 recordsLinked to original sources
USGS2025

Methylmercury in subarctic amphibians: Environmental gradients, bioaccumulation, and estimated flux

Rapid warming in polar regions is causing large changes to ecosystems, including altering environmentally available mercury (Hg). Although subarctic freshwater systems have simple vertebrate communities, Hg in amphibians remains unexplored. We measured total Hg (THg) in wetland sediments and methylmercury (MeHg) in multiple life-stages (eggs to adults) of wood frogs ( Rana sylvatica ) and larval boreal chorus frogs ( Pseudacris maculata ) from up to 25 wetlands near Churchill, Manitoba (Canada), during the summers of 2018–2019. We used egg mass counts for wood frogs from 24 wetlands (2015–2019) and per-ovum MeHg concentrations to estimate site-level MeHg flux by metamorphs from wetlands to the terrestrial environment. Total Hg in wetland sediment was unrelated to MeHg concentrations of amphibian larvae, but sediment THg increased with from coastal tundra vegetation to inland boreal forests. Methylmercury concentrations of wood frog eggs (geometric mean = 35.9; range: 6.7–77.9 ng/g dry wt) exceeded previous reports for amphibians, including from sites contaminated by industrial sources of Hg. Methylmercury concentrations of adult wood frogs (298.9 ng/g dry wt) were also higher than that for frogs included in a recent assessment of MeHg in amphibians across the contiguous United States. Within wetlands, MeHg concentrations of wood frog larvae were strongly correlated with MeHg concentrations in eggs earlier in the summer, and concentrations increased with each life stage. We estimate there would have been 1,971.8–3,286.4 ng MeHg exported from wetlands by wood frog metamorphs, which is 3.4–5.6 times more MeHg than inputted by eggs. Collectively, these data provide an initial assessment of Hg concentrations, body burdens, and dynamics in subarctic food webs that are expected to experience large changes from climate warming.

Manitoba↗
USGS2024

Assessing predictions from optimal egg theory for an ectotherm relative to habitat duration

Optimal egg size theory predicts females must balance investment per offspring to maximize fitness based on environmental quality. In wetlands, environmental quality can be duration of water and predator presence. Ectotherms using habitats that dry or contain predators are likely under selection to optimize offspring production. We measured reproductive output of wood frogs ( Rana sylvatica ) in 30 wetlands in Subarctic Canada, where rapid climate changes are accelerating wetland drying. We predicted wetlands with short hydroperiods would have larger ova, smaller clutch sizes, and larger ovum-to-clutch-sizes than wetlands with long hydroperiods or with fish predators. We found partial support for predictions with larger ova in habitats with short hydroperiods and no fish but no evidence of larger clutch sizes in wetlands with fish. Our study implicates changes to wetland hydroperiod as a source of plasticity affecting one aspect of reproductive effort (ovum size) in an ectotherm but not another (clutch size).

Manitoba↗
USGS2024

Polar bear energetic and behavioral strategies on land with implications for surviving the ice-free period

Declining Arctic sea ice is increasing polar bear land use. Polar bears on land are thought to minimize activity to conserve energy. Here, we measure the daily energy expenditure (DEE), diet, behavior, movement, and body composition changes of 20 different polar bears on land over 19–23 days from August to September (2019–2022) in Manitoba, Canada. Polar bears on land exhibited a 5.2-fold range in DEE and 19-fold range in activity, from hibernation-like DEEs to levels approaching active bears on the sea ice, including three individuals that made energetically demanding swims totaling 54–175 km. Bears consumed berries, vegetation, birds, bones, antlers, seal, and beluga. Beyond compensating for elevated DEE, there was little benefit from terrestrial foraging toward prolonging the predicted time to starvation, as 19 of 20 bears lost mass (0.4–1.7 kg•day −1 ). Although polar bears on land exhibit remarkable behavioral plasticity, our findings reinforce the risk of starvation, particularly in subadults, with forecasted increases in the onshore period.

Manitoba↗
USGS2023

A new sturgeon herpesvirus from juvenile Lake Sturgeon Acipenser fulvescens displaying epithelial skin lesions

Herpesvirus infections of sturgeon pose a potential threat to sturgeon culture efforts worldwide. A new epitheliotropic herpesvirus named Acipenser herpesvirus 3 (AciHV-3) was detected in hatchery-reared Lake Sturgeon Acipenser fulvescens displaying skin lesions in central Canada. The growths were discovered in the fall, reached average prevalence levels of 0.2–40% and eventually regressed. No unusual mortality was observed. The cellular changes within the lesions included epithelial hyperplasia and were reminiscent of other herpesvirus infections. The virus was not evident in lesions examined by electron microscopy. Skin tissue homogenates from symptomatic sturgeon produced atypical cytopathic effects on a primary Lake Sturgeon cell line, and next-generation sequence analysis of the DNA samples revealed the presence of an alloherpesvirus. A new genotyping PCR assay targeting the major capsid protein sequence detected AciHV-3 in symptomatic Lake Sturgeon as well as other apparently healthy sturgeon species. Bayesian inference of phylogeny reconstructed with a concatenation of five alloherpesvirus core proteins revealed a new Alloherpesviridae lineage isomorphic with a new genus. The presence of AciHV-3 homologs in cell lines and sturgeon sequence datasets, low sequence divergence among these homologs and branching patterns within the genotyping phylogeny provide preliminary evidence of an endogenous virus lifestyle established in an ancestral sturgeon.

Manitoba↗
USGS2023

Migrating ducks and submersed aquatic vegetation respond positively after invasive common carp (Cyprinus carpio) exclusion from a freshwater coastal marsh

Invasive carp can negatively affect waterbirds through habitat degradation, including removal of submersed aquatic vegetation (SAV). At a freshwater coastal marsh of great ecological and cultural significance, we excluded invasive common carp ( Cyprinus carpio ) with the goal of restoring the marsh to historical conditions to support fall-migrating waterfowl. We used a multi-pronged approach to assess the response of ducks and SAV to carp exclusion by leveraging historical duck and SAV surveys and collecting new data for six years post-exclusion on density and distribution of ducks within the marsh, SAV response, and refueling performance (as indexed by plasma-lipid metabolites) by two species of diving ducks. We found that fall-migrating duck numbers and total SAV extent rebounded to historical levels (1970s). There was a 339% increase in diving duck density and a nearly 400% increase in dabbling duck density between the pre- (i.e., 2000s) and post-exclusion periods. Diving ducks were more likely to be observed associated with SAV within the marsh, whereas dabbling ducks responded to emergent vegetation extent and water levels. Refueling performance was stable post-exclusion, despite increased numbers of ducks using the marsh, indicating that marsh habitat quality was sufficient. Some aspects of the marsh recovery remain in question, including possible shifts in SAV community composition. Overall, the carp exclusion has successfully improved the quality of habitat for migrating ducks.

Manitoba↗
USGS2022

Using physiological conditions to assess current and future habitat use of a Subarctic frog

Species with especially close dependence on the environment to meet physiological requirements, such as ectotherms, are highly susceptible to the impacts of climate change. Climate change is occurring rapidly in the Subarctic and Arctic, but there is limited knowledge on ectotherm physiology in these landscapes. We investigated how environmental conditions and habitat characteristics influence the physiological conditions and habitat use of wood frogs ( Rana sylvatica ) in a Subarctic landscape near Churchill, Manitoba (Canada). We used plaster models to estimate water loss rates and surface body temperatures among different habitat types and at specific locations used by radio-tracked frogs. Water loss ( R 2 = 0.67) and surface temperature ( R 2 = 0.80) of plaster models was similar to that of live frogs. Model-based water loss rates were greater in tundra habitat than in boreal forest and ecotone habitat. Habitat use of wood frogs was strongly tied with available surface moisture and decreased water loss rates that were observed with plaster models. Environmental conditions, such as wind speed and ground temperature, explained 58% and 91% of the variation in water balance and temperature of plaster models. Maintaining physiological conditions may be challenging for semi-aquatic ectotherms in environments vulnerable to future climate change. The ability to predict physiological conditions based on environmental conditions, as demonstrated in our study, can help understand how wildlife will respond to climatic changes.

Manitoba↗
USGS2020

Effects of experimental warming and nutrient enrichment on wetland communities at the Arctic’s edge

Global warming-related changes to freshwater ecosystems in Arctic and Subarctic regions have been magnified by nutrient input from increasing waterfowl populations. To gain insight into how these changes might affect ecosystem function, we conducted a mesocosm experiment in the Subarctic by enriching N and P (1 ×, 10 ×, and 20 × treatments) and increasing mean water temperatures ≤ 3°C. We measured responses of two species of larval amphibians, periphyton, and phytoplankton. Wood frog ( Rana sylvatica ) larvae developed quicker (odds ratio [OR] for 1°C increase = 0.903, 95% CI 0.892–0.912) and were more likely to metamorphose (OR 1.076, 95% CI 0.022–14.73) in warmer waters. Boreal chorus frogs ( Pseudacris maculata ) also developed quicker with warmer temperatures (OR 0.880, 95% CI 0.860–0.900), despite a non-significant trend toward reduced survival (OR 0.853, 95% CI 0.696–1.039). Periphyton and phytoplankton concentrations increased with nutrient additions, as did size of wood frog metamorphs. Periphyton and phytoplankton did not vary with temperature, but periphyton was limited by tadpole abundance. Our results highlight the potential for non-linear responses to ecosystem change, with species-specific consumer and ecosystem responses that depend on the magnitude of changes.

Manitoba↗
USGS2018

Post-breeding movement and habitat use by wood frogs along an Arctic–Subarctic ecotone

By altering essential micro- and macrohabitat conditions for many organisms, climate change is already causing disproportionately greater impacts on Arctic and Subarctic ecosystems. Yet there is a lack of basic information about many species in northern latitudes, including amphibians. We used radio telemetry to study the post-breeding movements and habitat use of wood frogs ( Rana [= Lithobates ] sylvatica ) in the Hudson Bay Lowlands near Churchill, Manitoba, Canada. We tracked fifty-seven frogs (thirty-five males, twenty-two females; mean duration = 16.8 d) from three wetlands during the summers of 2015 and 2016. The three wetlands were representative of the Arctic–Subarctic ecotone, with each wetland surrounded by different proportions of boreal forest and tundra. Our results indicate that at the landscape scale, movement distances increased with temperature, and all frogs spent more time in the tundra habitat than in boreal forests, relative to the availability of each habitat type. At the microhabitat scale (1 m 2 plots), frogs selected areas with greater amounts of standing water, sedge, and shrubs. These results provide information on terrestrial movement patterns and critical habitat data for northern populations of wood frogs in a Subarctic environment, which will aid in understanding how climate change will affect amphibians in this rapidly changing ecosystem.

Manitoba↗
USGS2005

Microhabitat characteristics of Lapland Longspur, Calcarius lapponicus, nests at Cape Churchill, Manitoba

We examined microsite characteristics at 21 Lapland Longspur ( Calcarius lapponicus ) nests and land cover types in which they occurred in Wapusk National Park, Cape Churchill, Manitoba. Nests were located in four of six physiographic-vegetation land-cover types. Regardless of land-cover type, all but one nest was built on a pressure ridge or mound. Nests were built midway between the bottom and top of ridges or mounds with steeper slopes than was randomly available. Longspur nests had a distinctive southwest orientation (P < 0.001). Longspurs selected nest sites that consisted of comparatively greater amounts of shrub species and lesser amounts of moss than were randomly available. Nests were generally well concealed by vegetation (mean = 67.0%) and concealment was negatively associated with amount of graminoid species at the nest (P = 0.0005). Our nesting habitat data may facilitate a better understanding of breeding Lapland Longspur habitat requirements, and potential impacts of habitat degradation by increasing Snow Goose ( Chen caerulescens ) populations in the study area.

Manitoba↗
USGS2002

Fire dynamics and implications for nitrogen cycling in boreal forests

We used a dynamic, long-term mass balance approach to track cumulative carbon (C) and nitrogen (N) losses to fire in boreal Manitoba over the 6500 years since deglaciation. Estimated C losses to decomposition and fire, combined with measurements of N pools in mature and burned forest floors, suggest that loss of N by combustion has likely resulted in a long-term loss that exceeds the amount of N stored in soil today by 2 to 3 times. These estimates imply that biological N fixation rates could be as high as 5 to 10 times atmospheric deposition rates in boreal regions. At the site scale, the amount of N lost is due to N content of fuels, which varies by stand type and fire severity, which in turn vary with climate and fire dynamics. The interplay of fire frequency, fire severity, and N partitioning during regrowth are important for understanding rates and sustainability of nutrient and carbon cycling over millenia and over broad regions.

Manitoba↗
USGS1999

Carbon cycling in boreal wetlands: A comparison of three approaches

Three independent methods were used to measure net ecosystem production (NEP) in four wetlands near Thompson, Manitoba, Canada. The first method calculated NEP by subtracting heterotrophic respiration from net primary productivity, using both measurements and estimates derived from the literature. The second method used radiocarbon data from cores to derive long-term NEP averaged over the past several decades. The third method used direct measurement of NEP combined with a model to fill in for days with no data. The three methods, with their independently derived uncertainties, all show the same magnitude and pattern of NEP variation across four different wetland types. However, direct measurement yielded distinctly lower estimates of NEP in the most productive sites. Highest NEP (31–180 gC m −2 yr −1 ) was observed in the two wetlands with the highest proportion of sedge vegetation. A bog collapse scar and a nutrient-rich fen had NEP values not significantly different from zero. The maximum NEP at sites with intermediate nutrient status is due to slower overall decomposition and is likely associated with greater allocation of production below ground by sedges. The three methods for estimating NEP differ in the effort required, the sources of error, and in the timescale over which they apply. Used in combination, they allow estimation of parameters such as below- ground production and the contribution of heterotrophic decomposition to total soil respiration. Using the radiocarbon method, we also derived estimates of the rate of N accumulation in the four wetland types.

Manitoba↗
USGS1997

Effects of 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), or an extract derived from field-collected cormorant eggs injected into double-crested cormorant (Phalacrocorax auritus) eggs

Double-crested cormorant ( Phalacrocorax auritus ) eggs were injected with either 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126), 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD), or an extract derived from field-collected double-crested cormorant eggs. These compounds were injected into the yolks of cormorant eggs from an isolated colony on Lake Winnipegosis, Manitoba, Canada. Upon hatching, chicks were necropsied. The brain, bursa, heart, liver, and spleen were removed and weighed. An approximate median lethal dose (LD50) of 158 μg/kg egg was determined for PCB 126, which is 69 times greater than the LD50 determined for the chicken ( Gallus domesticus ) in a previous study. A significantly greater mortality occurred at the highest dose of TCDD (4.0 μg/kg egg) when compared to the vehicle control. However, the mortality data did not provide sufficient information for the determination of an LD50. The cormorant egg extract did not adversely affect hatchability. No significant increases were observed in the incidence of developmental abnormalities, including pronounced edema, in any of the treatment groups, nor were there any relevant effects on body and organ weights. Based on the results from this study, the cormorant appears to be considerably less sensitive to polyhalogenated diaromatic hydrocarbons than the chicken, which has been the typical species used for egg injection studies.

Manitoba↗
USGS1997

Paleochemistry of Lakes Agassiz and Manitoba based on ostracodes

The ionic composition and salinity of Lake Manitoba and its late-glacial precursor, Lake Agassiz, changed significantly over the past 11 000 years. The paleochemical record reported here is based on modern analog environments of ostracodes identified in a new 14.5 m core from southern Lake Manitoba. The ionic composition of Lake Manitoba today is dominated by Na + , Cl − , and HC0 3 − , with much less Ca 2+ , Mg 2+ , and K + . Evaporative concentration of modern Lake Manitoba water would lead to greater salinity and the near depletion of Ca 2+ due to continued precipitation of calcite. During periods of highest salinity in the Holocene, however, Lake Manitoba supported Limnocythere staplini . Today this species inhabits waters in which [Ca 2+ ] > [HCO 3 − ], including springs associated with groundwater in Paleozoic bedrock discharging into Lake Winnipegosis (and eventually, after much dilution, into Lake Manitoba). Further complicating the Holocene record are intervals containing Limnocythere friabilis that suggest periodic influxes of dilute water, probably from the Assiniboine River, which bypasses Lake Manitoba today. The variations in Holocene paleochemistry indicated by the ostracode record imply changes in the proportion of overland flow plus precipitation relative to groundwater inputs to Lake Manitoba, independent of changes in evaporation relative to precipitation.

Manitoba↗
USGS1994

Hydrologic control of litter decomposition in seasonally flooded prairie marshes

The effect of seasonal inundation on the decomposition of emergent macrophyte litter ( Scolochloa festucacea ) was examined under experimental flooding regimes in a northern prairie marsh. Stem and leaf litter was subjected to six aboveground inundation treatments (ranging from never flooded to flooded April through October) and two belowground treatments (nonflooded and flooded April to August). Flooding increased the rate of mass loss from litter aboveground but retarded decay belowground. Aboveground, N concentration decreased and subsequently increased earlier in the longer flooded treatments, indicating that flooding decreased the time that litter remained in the leaching and immobilization phases of decay. Belowground, both flooded and nonflooded litter showed an initial rapid loss of N, but concentration and percent of original N remaining were greater in the nonflooded marsh throughout the first year. This suggested that more N was immobilized on litter under the nonflooded, more oxidizing soil conditions. Both N concentration and percent N remaining of belowground litter were greater in the flooded than the nonflooded marsh the second year, suggesting that N immobilization was enhanced after water-level drawdown. These results suggest different mechanisms by which flooding affects decomposition in different wetland environments. On the soil surface where oxygen is readily available, flooding accelerates decomposition by increasing moisture. Belowground, flooding creates anoxic conditions that slow decay. The typical hydrologic pattern in seasonally flooded prairie marshes of spring flooding followed by water-level drawdown in summer may maximize system decomposition rates by allowing rapid decomposition aboveground in standing water and by annually alleviating soil anoxia.

Manitoba↗
USGS1986

Identifying hydraulically conductive fractures with a slow-velocity borehole flowmeter

The U.S. Geological Survey used a recently developed heat-pulse flowmeter to measure very slow borehole axial water velocities in granitic rock at a site near Lac du Bonnet, Manitoba, Canada. The flowmeter was used with other geophysical measurements to locate and identify hydraulically conducting fractures contributing to the very slow vertical water flow in the two boreholes selected for study. The heat-pulse flowmeter has no moving parts and operates on the tag–trace principle. It is an improved version of the flowmeter developed by the Water Research Centre in England in 1975. The U.S. Geological Survey's heat-pulse flowmeter has a flow-measuring range in water of 0.06–6 m/min, and can resolve velocity differences as slow as 0.01 m/min. This is an order of magnitude slower than the stall speed of spinner flowmeters. The flowmeter is 1.16 m long and 44 mm in diameter. It was calibrated in columns of 76 and 152 mm diameter, to correspond to the boreholes studied. The heat-pulse flowmeter system is evaluated, and problems peculiar to the measurement of very slow axial water velocities in boreholes are discussed. Key words : flowmeter, borehole flow, low flow, borehole geophysics.

Manitoba↗