Hudson Bay Lowlands Research Articles

An Exploratory Survey of Summer Water Chemistry and Plankton Communities in Lakes near the Sutton River, Hudson Bay Lowlands, Ontario, Canada

We provide the first assessment of regional water chemistry and plankton (phytoplankton and crustacean zooplankton) for a suite of lakes near the Sutton River region of the north-central Hudson Bay Lowlands (HBL). We use ordination analyses to examine the spatial variation in water chemistry and plankton across lakes, and to explore the factors that may explain this variation. Based on data collected during summer from 2009 to 2011, we found that in addition to geology, water chemistry was strongly influenced by a lake’s proximity to salt water and the degree of permafrost development within its catchment. Phytoplankton composition varied across lakes based on differences in water depth and nutrient concentrations, with non-filamentous cyanobacteria and chlorophytes more common in shallow lakes, and deeper lakes dominated by planktonic diatoms or filamentous cyanophytes. Crustacean zooplankton community composition and richness in the HBL lakes was similar to communities found in Ontario lakes in more temperate regions within the Precambrian Shield. These baseline data provide a foundation upon which future surveys in this climatically sensitive region may be compared.

Observed and Projected Climate Change in the Churchill Region of the Hudson Bay Lowlands and Implications for Pond Sustainability

There is concern over the fate of surface water bodies at high latitudes as a consequence of rising global temperatures. The goal of this study is to characterize climatic change that has occurred in the northern Hudson Bay Lowlands (HBL), Canada, from 1943 to 2009, to determine if this has resulted in a change to pond surface areas and to predict if changes may continue in the future. Climate change and changes to pond volume and size over the past ∼60 years were examined using a combination of field methods/instrumental records (1943–2009), modeling (1953–2009; 1961–2100), and remote sensing/imagery analyses (1947–2008). Results demonstrate that temperatures are warming and breakup dates are earlier, but this has not significantly increased the duration of the open-water period or pond evaporation rates, which can be highly variable from year to year. Annual precipitation, primarily summer rainfall, has increased, lessening the summer moisture deficit and leading to wetter conditions. The observed changes of a smaller summer moisture deficit are predicted to continue in future, although there is less certainty with predictions of future precipitation than there is with predictions of air temperature. Thus, ponds are likely not at risk for drying and instead may be at risk for expansion. Despite the increases in summer rainfall, imagery analysis of 100 ponds shows that pond surface areas have fluctuated over the study period but have not increased in size.

Hydrological Connectivity and Basin Morphometry Influence Seasonal Water-Chemistry Variations in Tundra Ponds of the Northwestern Hudson Bay Lowlands

Due to shallow depth and high surface area—to—volume ratio, ponds of the Hudson Bay Lowlands are vulnerable to climatic and hydrological changes, but relations between hydrological processes and limnological conditions remain unknown. Here, we measured water balance and limnological variables (water chemistry, suspended sediments, chlorophyll-a) at 20 ponds near Churchill (Manitoba) three times during the ice-free season of 2010 to explore relations among hydrological connectivity, basin morphometry, and waterchemistry variations. Using principal components analysis, we identified that the ponds followed one of four distinctive “seasonal water chemistry trajectories” (SWCT1–4). Most of the ponds that lacked apparent hydrologic connectivity displayed SWCT1, characterized by rising alkalinity and ionic content between early June and late July due to evaporative concentration. In contrast, most ponds with apparent hydrological connectivity displayed SWCT2 or SWCT3, characterized by marked changes in suspended sediment and total nitrogen concentrations due to inflow that transferred allochthonous materials from the catchment. Ponds in SWCT2 likely possessed temporary hydrological connections during periods of relatively high water supply and exhibited marked decline of suspended sediment and total nitrogen content when hydrological connection was lost. Most ponds in SWCT3 maintained active hydrological connections during all or most of the ice-free season and possessed relatively high suspended sediment and total nitrogen concentrations throughout the season. Ponds in SWCT4 possessed relatively stable water chemistry due to greater water depth and local features that reduced wind-induced sediment resuspension. We conclude that hydrological connectivity and basin morphometry exert important influence on seasonal pond water-chemistry dynamics.

Peatland Initiation, Carbon Accumulation, and 2 ka Depth in the James Bay Lowland and Adjacent Regions

Peatlands surrounding Hudson and James Bays form the second largest peatland complex in the world and contain major stores of soil carbon (C). This study utilized a transect of eight ombrotrophic peat cores from remote regions of central and northern Ontario to quantify the magnitude and rate of C accumulation since peatland initiation and for the past 2000 calendar years before present (2 ka). These new data were supplemented by 17 millennially resolved chronologies from a literature review covering the Boreal Shield, Hudson Plains, and Taiga Shield bordering Hudson and James Bays. Peatlands initiated in central and northern Ontario by 7.8 ka following deglaciation and isostatic emergence of northern areas to above sea level. Total C accumulated since inception averaged 109.7 ± (std. dev.) 36.2 kg C m-2. Approximately 40% of total soil C has accumulated since 2 ka at an average apparent rate of 20.2 ± 6.9 g C m-2 yr-1. The 2 ka depths correlate significantly and positively with modern gridded climate estimates for mean annual precipitation, mean annual air temperature, growing degree-days > 0 °C, and photosynthetically active radiation integrated over days > 0 °C. There are significantly shallower depths in permafrost peatlands. Vertical peat accumulation was likely constrained by temperature, growing season length, and photosynthetically active radiation over the last 2 ka in the Hudson Bay Lowlands and surrounding regions.

Surface Water and Groundwater Contributions to Streamflow in the James Bay Lowland, Canada

Climate and land-use changes are going to leave an indelible mark on the hydrology and globally significant peatlands of the Hudson Bay Lowlands (HBL), Canada. With forecasts for warmer and drier conditions over the next century, the relative contribution of water from surface and subsurface sources affecting both water quantity and quality will undoubtedly shift. Unfortunately, no empirical data exist for any streams or rivers of the HBL on the relative contributions of surface water and groundwater to streamflow, making assessment of future change difficult. Here we report the first data on sources of water to streams and rivers across a range of catchment sizes in the James Bay Lowland (JBL) ecoregion of the HBL. Solute chemistry was determined for a range of potential end members, end members were identified, and a chemical mixing model approach was used to determine the relative end-member contributions to streamflow across a range of catchment sizes (∼30–2000 km2). The relative contributions of bedrock-derived groundwater to streamflow increased with catchment area from <20 to >40% under dry conditions, and were ∼50% lower under wet conditions across all catchments. Runoff contributions from peatlands were relatively constant over space and time (53–67%), but the fraction of streamflow composed of rain and snowmelt varied dramatically between wet and dry periods, and among catchments. Given the importance of peatland-derived surface waters, future changes in precipitation and temperature could have significant implications for streamflow in the JBL, particularly during summer base-flow conditions. Moreover, the definition of reference catchments for baseline/impact monitoring must be carefully considered, given the potential for variation in hydrochemistry across physiographically similar catchments.

Observational constraints on the distribution, seasonality, and environmental predictors of North American boreal methane emissions

Wetlands comprise the single largest global source of atmospheric methane, but current flux estimates disagree in both magnitude and distribution at the continental scale. This study uses atmospheric methane observations over North America from 2007 to 2008 and a geostatistical inverse model to improve understanding of Canadian methane fluxes and associated biogeochemical models. The results bridge an existing gap between traditional top‐down, inversion studies, which typically emphasize total emission budgets, and biogeochemical models, which usually emphasize environmental processes. The conclusions of this study are threefold. First, the most complete process‐based methane models do not always describe available atmospheric methane observations better than simple models. In this study, a relatively simple model of wetland distribution, soil moisture, and soil temperature outperformed more complex model formulations. Second, we find that wetland methane fluxes have a broader spatial distribution across western Canada and into the northern U.S. than represented in existing flux models. Finally, we calculate total methane budgets for Canada and for the Hudson Bay Lowlands, a large wetland region (50–60°N, 75–96°W). Over these lowlands, we find total methane fluxes of 1.8±0.24 Tg C yr−1, a number in the midrange of previous estimates. Our total Canadian methane budget of 16.0±1.2 Tg C yr−1 is larger than existing inventories, primarily due to high anthropogenic emissions in Alberta. However, methane observations are sparse in western Canada, and additional measurements over Alberta will constrain anthropogenic sources in that province with greater confidence.

Relative importance of hydrological and climatic controls on Holocene paleoenvironments inferred using diatom and pollen records from a lake in the central Hudson Bay Lowlands, Canada

Postglacial paleoenvironmental changes and landscape development in the Hudson Bay Lowlands in subarctic Canada were inferred using sediment properties and diatom and pollen assemblages in the sediments of a lake raised above the surrounding peatlands in an ice-marginal landform. Coarse-grained, inorganic sediments at the base of the Lake AT01 core suggest a high-energy periglacial environment, following isostatic emergence from Hudson Bay around 6840 cal. BP. Initial diatom assemblages dominated by Fragilaria spp., and pollen of Shepherdia canadensis, indicate early successional conditions in a recently deglaciated environment. Around 6200 cal. BP, tychoplanktonic Fragilarioid diatoms are replaced by large benthics. Coincident increases in Equisetum spores, Cyperaceae pollen and sediment organic matter suggest the establishment of a more productive macrophyte-rich shallow lake. While the Holocene Thermal Maximum and subsequent Neoglacial may have contributed to these shifts, pollen and diatom records suggest only subtle responses to Holocene climatic changes. A core chronology inferred from radioisotopes suggests a hiatus in sediment accumulation between 3650 and 200 cal. BP. Peaks in carbonate inferred from loss-on-ignition and increases in bulk density in that section of the core suggest some effect of erosional or thermokarst processes, or the breaching of a sandbar, now a remnant island in the lake, in the drainage of the lake and ensuing hiatus. Sediment accumulation resumed within the past two centuries; diatom assemblages in the uppermost section are characterized initially by benthic diatoms of smaller valve size compared with the pre-hiatus assemblages. More recently, increases in the planktonic diatom Cyclotella stelligera are recorded, signaling significant environmental changes.

The Technology Imperative of the Cree

In this article we discuss how the incorporation of selected technologies (i.e., outboard motor, snowmobile) in Northern Ontario profoundly and irrevocably transformed two Cree nations located in the Hudson Bay Lowlands. We demonstrate how this technological integration has provided two remote First Nations in Canada with the ability to adapt to biophysical and socio-cultural changes, thereby sustaining traditional livelihood and providing food security. Interviews conducted in 2006–2010 with the Weenusk First Nation at Peawanuck, and the Washaho First Nation at Fort Severn are used to contextualize the discussion and answer the following research questions: (a) Are a greater or smaller number of people in these two First Nations engaged in subsistence behaviour today than in the past?; (b) Are these harvesters more or less successful?; and (c) Are levels of subsistence consumption different? The findings indicate that while less people are generally participating in traditional subsistence activities, access to traditional foods due to technology remains, for the time being, the same. The sustainability of these activities on the long-term is examined in the conclusion.

Fire, humans, and climate: modeling distribution dynamics of boreal forest waterbirds

Understanding the effects of landscape change and environmental variability on ecological processes is important for evaluating resource management policies, such as the emulation of natural forest disturbances. We analyzed time series of detection/nondetection data using hierarchical models in a Bayesian multi-model inference framework to decompose the dynamics of species distributions into responses to environmental variability, spatial variation in habitat conditions, and population dynamics and interspecific interactions, while correcting for observation errors and variation in sampling regimes. We modeled distribution dynamics of 14 waterbird species (broadly defined, including wetland and riparian species) using data from two different breeding bird surveys collected in the Boreal Shield ecozone within Ontario, Canada. Temporal variation in species occupancy (2000-2006) was primarily driven by climatic variability. Only two species showed evidence of consistent temporal trends in distribution: Ring-necked Duck (Aythya collaris) decreased, and Red-winged Blackbird (Agelaius phoeniceus) increased. The models had good predictive ability on independent data over time (1997-1999). Spatial variation in species occupancy was strongly related to the distribution of specific land cover types and habitat disturbance: Fire and forest harvesting influenced occupancy more than did roads, settlements, or mines. Bioclimatic and habitat heterogeneity indices and geographic coordinates exerted negligible influence on most species distributions. Estimated habitat suitability indices had good predictive ability on spatially independent data (Hudson Bay Lowlands ecozone). Additionally, we detected effects of interspecific interactions. Species responses to fire and forest harvesting were similar for 13 of 14 species; thus, forest-harvesting practices in Ontario generally appeared to emulate the effects of fire for waterbirds over timescales of 10-20 years. Extrapolating to all 84 waterbird species breeding on the Ontario Boreal Shield, however, suggested that up to 30 species may instead have altered (short-term) distribution dynamics due to forestry practices. Hence, natural disturbances are critical components of the ecology of the boreal forest and forest practices which aim to approximate them may succeed in allowing the maintenance of the associated species, but improved monitoring and modeling of large-scale boreal forest bird distribution dynamics will be necessary to resolve existing uncertainties, especially on less-common species.

A midge-salinity transfer function for inferring sea level change and landscape evolution in the Hudson Bay Lowlands, Manitoba, Canada

We compared water chemistry and environmental data with midge assemblage data, using multivariate analysis to assess the environmental gradients that limit midge (Chironomidae, Chaoboridae and Ceratopogonidae) distributions in the Hudson Bay Lowlands, northeastern Manitoba, Canada. Midge remains, comprising 62 taxa, were obtained from surficial sediments of 63 ponds. Ponds were sampled to maximize the salinity gradient. Specific conductance ranged from 46 to 29,000 μS cm−1. Proximity to the coast was a principal determinant of pond salinity, with ponds closer to Hudson Bay shoreline more saline that those farther away. Multivariate analysis indicated that midge distributions have a significant relationship (\( {\text{r}}_{\text{boot}}^{2} = 0.68 \)) with salinity in the data set. This work will allow paleolimnological inferences of midge community responses to changing sea level (i.e. salinity) via isostatic rebound within the Hudson Bay Lowlands, and will provide essential limnological information to scientists and managers in a region where understanding of aquatic ecosystems is limited. One undescribed midge taxon was dominant in ponds with the highest salinities and may be a key indicator for inferring highly saline environments.

Vulnerability of shallow subarctic lakes to evaporate and desiccate when snowmelt runoff is low

AbstractSnowmelt is a crucial source of water for many shallow subarctic lakes, but climate models predict that snowfall will decrease in some regions, with profound ecological consequences. Here we use lake water isotope data across gradients of terrestrial vegetation cover (open tundra to closed forest) and topographic relief to identify lakes that are vulnerable to desiccation under conditions of low snowmelt runoff in two subarctic landscapes—Old Crow Flats, Yukon, and Hudson Bay Lowlands, Manitoba (Canada). Lakes located in low‐relief, open tundra catchments in both landscapes displayed a systematic, positive offset between directly measured lake water δ18O over multiple sampling campaigns and lake water δ18O inferred from cellulose in recently deposited surface sediments. We attribute this offset to a strong evaporative 18O‐enrichment response to lower‐than‐average snowmelt runoff in recent years. Notably, some lakes underwent near‐complete desiccation during midsummer 2010 following a winter of very low snowfall. Based on the paleolimnological record of one such lake, the extremely dry conditions in 2010 may be unprecedented in the past ~200 years. Findings fuel concerns that a decrease in snowmelt runoff will lead to widespread desiccation of shallow lakes in these landscapes.

Global warming triggers the loss of a key Arctic refugium

We document the rapid transformation of one of the Earth's last remaining Arctic refugia, a change that is being driven by global warming. In stark contrast to the amplified warming observed throughout much of the Arctic, the Hudson Bay Lowlands (HBL) of subarctic Canada has maintained cool temperatures, largely due to the counteracting effects of persistent sea ice. However, since the mid-1990s, climate of the HBL has passed a tipping point, the pace and magnitude of which is exceptional even by Arctic standards, exceeding the range of regional long-term variability. Using high-resolution, palaeolimnological records of algal remains in dated lake sediment cores, we report that, within this short period of intense warming, striking biological changes have occurred in the region's freshwater ecosystems. The delayed and intense warming in this remote region provides a natural observatory for testing ecosystem resilience under a rapidly changing climate, in the absence of direct anthropogenic influences. The environmental repercussions of this climate change are of global significance, influencing the huge store of carbon in the region's extensive peatlands, the world's southern-most polar bear population that depends upon Hudson Bay sea ice and permafrost for survival, and native communities who rely on this landscape for sustenance.

Evidence of Territoriality and Species Interactions from Spatial Point-Pattern Analyses of Subarctic-Nesting Geese

Quantifying spatial patterns of bird nests and nest fate provides insights into processes influencing a species’ distribution. At Cape Churchill, Manitoba, Canada, recent declines in breeding Eastern Prairie Population Canada geese (Branta canadensis interior) has coincided with increasing populations of nesting lesser snow geese (Chen caerulescens caerulescens) and Ross’s geese (Chen rossii). We conducted a spatial analysis of point patterns using Canada goose nest locations and nest fate, and lesser snow goose nest locations at two study areas in northern Manitoba with different densities and temporal durations of sympatric nesting Canada and lesser snow geese. Specifically, we assessed (1) whether Canada geese exhibited territoriality and at what scale and nest density; and (2) whether spatial patterns of Canada goose nest fate were associated with the density of nesting lesser snow geese as predicted by the protective-association hypothesis. Between 2001 and 2007, our data suggest that Canada geese were territorial at the scale of nearest neighbors, but were aggregated when considering overall density of conspecifics at slightly broader spatial scales. The spatial distribution of nest fates indicated that lesser snow goose nest proximity and density likely influence Canada goose nest fate. Our analyses of spatial point patterns suggested that continued changes in the distribution and abundance of breeding lesser snow geese on the Hudson Bay Lowlands may have impacts on the reproductive performance of Canada geese, and subsequently the spatial distribution of Canada goose nests.

The Legacy of Destructive Snow Goose Foraging on Supratidal Marsh Habitat in the Hudson Bay Lowlands

Ecological succession and climate change are pushing tundra as well as Arctic and subarctic lowland plant communities toward increased woody vegetation cover. However, areas along the Hudson Bay Lowlands that are over-grazed by hyper-abundant lesser snow geese are experiencing drastic losses of grass, sedge, and woody cover. We assessed longterm changes in proportional ground cover and habitat patch characteristic at a subarctic supratidal marsh that was largely vacated by breeding snow geese over a decade ago. We found no evidence of habitat recovery. Rather, snow geese leave a legacy on the land that propagates degradation of habitat long after their direct removal of vegetation through foraging. Over a 35 year period, we documented a 46% reduction in graminoid cover and an 84% reduction in shrub cover, which led to smaller and more isolated patches of shrubs that many avian species depend upon for foraging and nesting. Recent experimental goose exclosures suggest that recovery of degraded habitat is possible, but habitat management at a large scale will require drastic reductions in lesser snow goose numbers.

Benthic macroinvertebrate communities in five rivers of the Coastal Hudson Bay Lowland

As a precursor to developing a biomonitoring program for rivers of the Coastal Hudson Bay Lowland, this study characterized and compared the benthic macroinvertebrate communities and water chemistry in 5 remote, previously undescribed, rivers near Fort Severn, Ontario, Canada. The pH of river water ranged from 8.1 to 8.7, total phosphorus from 11 to 26 μg L−1, dissolved organic carbon from 8 to 12 mg L−1, and chloride from 56 to 153 mg L−1. A total of 57 benthic macroinvertebrate taxa were represented, and the 10 most numerically dominant were the Chironominae (26 % of collected individuals), Orthocladiinae (16 %), oligochaetous clitellata (9 %), Hyalellidae (7 %), Hydropsychidae (6 %), Gammaridae (5 %), Elmidae (5 %), Sphaeriidae/Pisidiidae (4 %), Nemata (3 %), and Tanypodinae (3 %). Rivers’ positions in ordinations of chemical and biological datasets were similar, suggesting that water chemistry has a role in structuring riverine benthic communities in the study region. Correlations between water-chemistry or habitat predictors and site-scores in the ordination of benthic macroinvertebrate taxa counts suggested that biological community structure was most associated with river-water pH, nutrient concentrations (e.g., total phosphorus, nitrogenous compounds, dissolved organic carbon, calcium, and silicate), the relative abundance of submerged macrophytes, conductivity (i.e., the concentrations of chloride and various other dissolved ions), and several geomorphological variables (e.g., bank-full river width, current speed, and the size of the dominant inorganic particles in the pavement layer of the streambed). Interest in mineral extraction and other resource-based exploration in Ontario’s Far North is increasing. This study represents a start on baseline characterization for ecological monitoring and cumulative effects assessment that should proceed along with northern development.

Evidence for microbially mediated production of elemental mercury (Hg0) in subarctic lake sediments

The production and fate of Hg0 in lake sediments remains poorly characterized, although it can potentially influence Hg toxicity and mobility. Using slurry incubations, we assessed the effect of nutrients, pH, ionic strength, and tested the role of microbes, on Hg0 production from pristine lake sediments of the Hudson Bay Lowlands in Ontario, Canada. We showed that Hg0 production from oxygenated sediments was low (<1% of the Hg flux to sediments), biogenic, and did not appear to be dependent on the predicted HgII speciation in the slurry. The addition of biologically labile carbon sources and ionic strength, particularly [Na+], had the greatest impact on Hg0 production, increasing it by over 10-fold. These results suggest that under changing conditions, such as increasing temperature or alteration of water chemistry as observed in numerous locations throughout Arctic and subarctic environments, a fraction of sedimentary Hg may be remobilized and available for microbial reduction.

Seasonal dynamics of methane emissions from a subarctic fen in the Hudson Bay Lowlands

Abstract. Ecosystem-scale methane (CH4) flux (FCH4) over a subarctic fen at Churchill, Manitoba, Canada was measured to understand the magnitude of emissions during spring and fall shoulder seasons, and the growing season in relation to physical and biological conditions. FCH4 was measured using eddy covariance with a closed-path analyser in four years (2008–2011). Cumulative measured annual FCH4 (shoulder plus growing seasons) ranged from 3.0 to 9.6 g CH4 m−2 yr−1 among the four study years, with a mean of 6.5 to 7.1 g CH4 m−2 yr−1 depending upon gap-filling method. Soil temperatures to depths of 50 cm and air temperature were highly correlated with FCH4, with near-surface soil temperature at 5 cm most correlated across spring, fall, and the shoulder and growing seasons. The response of FCH4 to soil temperature at the 5 cm depth and air temperature was more than double in spring to that of fall. Emission episodes were generally not observed during spring thaw. Growing season emissions also depended upon soil and air temperatures but the water table also exerted influence, with FCH4 highest when water was 2–13 cm below and lowest when it was at or above the mean peat surface.

Spatio‐temporal features of permafrost thaw projected from long‐term high‐resolution modeling for a region in the Hudson Bay Lowlands in Canada

AbstractAlthough studies agree that climate warming will cause permafrost thaw, projected permafrost conditions differ widely, and most projections use half degree latitude/longitude or coarser spatial resolution. Using a process‐based model, this study projected changes of permafrost from 2010 to 2200 at 30 m by 30 m resolution for a region in the northwest of the Hudson Bay Lowlands in Canada. This long‐term spatially detailed modeling revealed some general features of permafrost dynamics with climate warming. Temporally, permafrost degradation at a site can be divided into five stages: gradual‐thawing stage, increased‐thawing stage, frequent‐talik stage, isothermal‐permafrost stage, and permafrost‐free stage. This study determined the beginning or ends of the stages for each grid cell and mapped the degradation stages in this region. Spatially, permafrost was predicted to become increasingly discontinuous with climate warming. By the end of the 22nd century, only 20% to 65% of the land area in this region will be underlain by permafrost. With the formation of taliks, the maximum summer thaw depth will increase significantly, and near‐surface permafrost will disappear in many areas while permafrost at depth can persist for decades. Thus, the spatial distribution of near‐surface permafrost and permafrost at depth can be very different. This study also shows that climate scenarios, the depth of permafrost considered, spatial resolution and associated ground conditions used for modeling could cause significant differences in permafrost projections.

Glacial and nonglacial events in the eastern James Bay lowlands, Canada

Marine and continental records indicate that the Laurentide Ice Sheet (LIS) was highly dynamic throughout the last glacial cycle, with significant reorganizations of its ice divide system. The extensive depositional record of the Hudson Bay lowlands (HBL) is particularly important for the study of ice sheet dynamics because this region was once located near two important ice domes of the LIS. However, important stratigraphic issues remain in the HBL, notably regarding the chronology of nonglacial units and the direction and extent of the ice-flow events recognized. Here we focus on the northeastern sector of the LIS by documenting the provenance of tills and dating nonglacial deposits in sedimentary sequences east of James Bay. Our investigations indicate that the regional stratigraphy comprises at least five distinct tills and an important unit of glaciolacustrine rhythmites. This glacial sequence lies on massive lacustrine clay and fluvial sand containing abundant organic debris and wood fragments. The ...

Small-scale variability in peatland pore-water biogeochemistry, Hudson Bay Lowland, Canada

The Hudson Bay Lowland (HBL) of northern Ontario, Manitoba and Quebec, Canada is the second largest contiguous peatland complex in the world, currently containing more than half of Canada's soil carbon. Recent concerns about the ecohydrological impacts to these large northern peatlands resulting from climate change and resource extraction have catalyzed a resurgence in scientific research into this ecologically important region. However, the sheer size, heterogeneity and elaborate landscape arrangements of this ecosystem raise important questions concerning representative sampling of environmental media for chemical or physical characterization. To begin to quantify such variability, this study assessed the small-scale spatial (1m) and short temporal (21day) variability of surface pore-water biogeochemistry (pH, dissolved organic carbon, and major ions) in a Sphagnum spp.-dominated, ombrotrophic raised bog, and a Carex spp.-dominated intermediate fen in the HBL. In general, pore-water pH and concentrations of dissolved solutes were similar to previously reported literature values from this region. However, systematic sampling revealed consistent statistically significant differences in pore-water chemistries between the bog and fen peatland types, and large within-site spatiotemporal variability. We found that microtopography in the bog was associated with consistent differences in most biogeochemical variables. Temporal changes in dissolved solute chemistry, particularly base cations (Na+, Ca2+ and Mg2+), were statistically significant in the intermediate fen, likely a result of a dynamic connection between surficial waters and mineral-rich deep groundwater. In both the bog and fen, concentrations of SO42− showed considerable spatial variability, and a significant decrease in concentrations over the study period. The observed variability in peatland pore-water biogeochemistry over such small spatial and temporal scales suggests that under-sampling in northern peatland environments could lead to erroneous conclusions concerning the abundance and distribution of natural elements and pollutants alike.