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White J.,University of Waterloo | Hall R.,University of Waterloo | Wolfe B.,Wilfrid Laurier University | Light E.,Wilfrid Laurier University | And 2 more authors.
Arctic, Antarctic, and Alpine Research | Year: 2014

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 water-chemistry 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.

Eichel K.,University of Waterloo | MacRae M.,University of Waterloo | Hall R.,University of Waterloo | Fishback L.,Churchill Northern Studies Center | Wolfe B.,Wilfrid Laurier University
Arctic, Antarctic, and Alpine Research | Year: 2014

Climate warming is anticipated to affect high-latitude regions, including abundant ponds of the Hudson Bay Lowlands (HBL). However, it remains unclear if associated increased frequency of nutrient pulses will be rapidly consumed by aquatic biota and sediment or lead to a rise in pond-water nutrient concentrations. Here, we performed a nutrient-amendment experiment to examine short-term (‰72 h) nutrient uptake and identify the consumers of the added nutrients (planktonic vs. benthic communities). Microcosms (1 L) with and without sediment were experimentally amended with inorganic nitrogen (nitrate, ammonium) with and without phosphate. Amended nitrate and ammonium concentrations remained high in microcosms without sediments, and phytoplankton biomass did not change relative to the un-amended control. However, phosphate concentration declined significantly in microcosms without sediment, resulting in significant increase of phytoplankton biomass after 72 h. In the presence of sediment, amended nutrients were rapidly removed from the water, stimulating benthic algal biomass when phosphate was co-amended with ammonium or nitrate. Phytoplankton biomass was significantly elevated in microcosms with sediment compared to those without sediment, regardless of whether nutrients were amended or not, indicating that sediment and associated benthic biofilm stimulate phytoplankton growth, likely via supply of nutrients to the overlying water column. A key outcome of the experiment is that pulsed nutrients were taken up rapidly and primarily by the benthic community. Findings suggest that shallow ponds in the HBL are capable of rapidly consuming pulsed nutrient supplies, as may occur due to hydroclimatic events, climate warming and other disturbances.

Wolfe B.B.,Wilfrid Laurier University | Light E.M.,Wilfrid Laurier University | MacRae M.L.,University of Waterloo | Hall R.I.,University of Waterloo | And 5 more authors.
Geophysical Research Letters | Year: 2011

The hydrological fate of shallow tundra lakes and ponds under conditions of continued warming remains uncertain, but has important implications for wildlife habitat and biogeochemical cycling. Observations of unprecedented pond desiccation, in particular, signify catastrophic loss of aquatic habitat in some Arctic locations. Shallow tundra ponds are a ubiquitous feature in the western Hudson Bay Lowlands (HBL), a region that has undergone intense warming over the past ∼50years. But it remains unknown how hydrological processes in these ponds have responded. Here, we use cellulose-inferred pond water oxygen isotope records from sediment cores, informed by monitoring of modern pond water isotope compositions during the 2009 and 2010 ice-free seasons, to reconstruct hydrological conditions of four shallow tundra ponds in the western HBL over the past three centuries. Following an interval of relative hydrological stability during the early part of the records, results reveal widely differing hydrological responses to 20th century climate change among the study sites, which is largely dependent on hydrological connectivity of the basins within their respective surrounding peatlands. These findings suggest the 20th century has been characterized by an increasingly dynamic landscape that has variably influenced surface water balance-a factor that is likely to play a key role in determining the future water balance of ponds in this region. Copyright 2011 by the American Geophysical Union.

Davenport J.M.,University of Montana | Seiwert P.A.,University of Central Arkansas | Fishback L.A.,Churchill Northern Studies Center | Cash W.B.,University of Central Arkansas
Canadian Journal of Zoology | Year: 2013

Fish can have strong predatory impacts on aquatic food webs. Indeed, fish are known to have strong effects on amphibians, with some species being excluded from communities where fish are present. Most research with amphibians and fish has focused on lower latitudes and very little is known of amphibian-fish interactions at higher latitudes. Therefore, we conducted an enclosure experiment in a subarctic natural wetland to examine the predatory effects of two species of fish, brook sticklebacks (Culaea inconstans (Cuvier, 1829)) and ninespine sticklebacks (Pungitius pungitius (L., 1758)), on the survival and growth of Wood Frogs (Lithobates sylvaticus (LeConte, 1825)). We found no significant difference in survival and size at metamorphosis among the two fish species treatments and fish-free treatments. We found that individuals from fish-free treatments metamorphosed earlier than those from either fish species present treatment. Our work suggests that stickleback fish predation may not have a major impact on Wood Frog tadpole survival and growth in a subarctic wetland. Sticklebacks may still have an impact on earlier developmental stages of Wood Frogs. This work begins to fill an important gap in potential factors that may impact larval amphibian survival and growth at higher latitudes.

Sanei H.,Geological Survey of Canada | Outridge P.M.,Geological Survey of Canada | Goodarzi F.,Geological Survey of Canada | Wang F.,University of Manitoba | And 3 more authors.
Atmospheric Environment | Year: 2010

This paper reports mercury (Hg) concentrations and fluxes in precipitation that was collected from 2006 to 2008 at three sites in Canada: sub-Arctic boreal forest, sub-Arctic coast, and southern Alberta, using cold-adapted precipitation collectors which operated reliably at temperatures below -30 °C during the study. The southern Alberta site (Crossfield) may be influenced by Calgary urban air, whereas the sub-Arctic coastal (Churchill, Manitoba) and boreal forest (Fort Vermilion, Alberta) sites are in more remote northern areas. Annual mean Hg concentrations in precipitation (5.0-9.2 ng L-1) at the study sites were in the lower half of the range reported for southern Canada and the USA by the Mercury Deposition Network (MDN). But owing to typically low precipitation rates, gross wet Hg fluxes (0.54-2.0 μg m-2 yr-1) were among the lowest reported by MDN, with Crossfield having about twice the flux in 2007 of the other two sites. Flux was significantly correlated with precipitation, and thus was highest in summer (June-August) and lowest during winter, a pattern typical of other temperate continental locations. There was no evidence of higher wet Hg fluxes or concentrations in springtime at Churchill where atmospheric mercury depletion events (AMDEs) occur. Measured gross deposition fluxes at the study locations were ∼2-8 times lower than estimated by GEOS-Chem and GRAHM atmospheric models. The largest discrepancy occurred for Churchill, which raises the question of how well Hg deposition from AMDEs is described by current models. Better agreement between measurements and models was obtained from MDN stations in Alberta and Alaska, where wet Hg fluxes were 2-10 times higher than the study sites either because of power plant emissions (Alberta), or because of high precipitation rates (Alaska). Crown Copyright © 2010.

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