Divergent Temporal Trends of Mercury in Arctic Char from Paired Lakes Influenced by Climate-Related Drivers.

Climate-driven changes including rising air temperatures, enhanced permafrost degradation, and altered precipitation patterns can have profound effects on contaminants, such as mercury (Hg), in High Arctic lakes. Two physically similar lakes, East Lake and West Lake at the Cape Bounty Arctic Watershed Observatory on Melville Island, Nunavut, Canada are being affected by climate change differently. Both lakes have experienced permafrost degradation in their catchments; however, West Lake has also undergone multiple underwater Mass Movement Events (MMEs; beginning in fall 2008), leading to a sustained 50-fold increase in turbidity.

Snow Deposition and Melting as Drivers of Polychlorinated Biphenyls and Organochlorine Pesticides in Arctic Rivers, Lakes, and Ocean.

Concurrent sampling of freshwater (lakes and rivers), seawater, snow, air, and zooplankton for a range of legacy polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) was undertaken in the Canadian High Arctic during ice-covered, melting, and ice-free conditions. Overall, there was a general trend of higher fluvial PCB/OCP concentrations associated with the spring snow melt (early-mid June), while much lower concentrations were detected during the snow-free season (end of July). In contrast, PCB concentrations in two Arctic lakes (West and East Lakes, Melville Island) and in ocean waters, sharply increased in the ice-free period, likely because of inputs from the ice/snow layer melting and river runoff.

Legacy and Emerging Persistent Organic Pollutants (POPs) in Terrestrial Compartments in the High Arctic: Sorption and Secondary Sources.

Legacy persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and emerging perfluoroalkyl substances (PFASs) were measured in vegetation and soil samples collected at remote lakes in the Canadian High Arctic. Field studies were carried out in 2015 and 2016 to assess concentrations of POPs, study the relevant sorbing phases, and determine whether Arctic soils were sinks or sources of legacy POPs to the atmosphere and to neighboring lakes. The patterns of legacy POPs in vegetation and soils were dominated by low molecular weight PCB congeners along with OCPs, confirming the importance of long-range atmospheric transport.

Long-term deepened snow promotes tundra evergreen shrub growth and summertime ecosystem net CO gain but reduces soil carbon and nutrient pools.

Arctic climate warming will be primarily during winter, resulting in increased snowfall in many regions. Previous tundra research on the impacts of deepened snow has generally been of short duration. Here, we report relatively long-term (7-9 years) effects of experimentally deepened snow on plant community structure, net ecosystem CO exchange (NEE), and soil biogeochemistry in Canadian Low Arctic mesic shrub tundra.

Differences in Riverine and Pond Water Dissolved Organic Matter Composition and Sources in Canadian High Arctic Watersheds Affected by Active Layer Detachments.

Regional warming has caused permafrost thermokarst and disturbances, such as active layer detachments (ALDs), which may alter carbon feedback in Arctic ecosystems. However, it is currently unclear how these disturbances alter DOM biogeochemistry in rivers and ponds in Arctic ecosystems. Water samples from the main river channel, ALD-disturbed/undisturbed tributaries, and disturbed/undisturbed ponds within a catchment in the Canadian High Arctic were collected and analyzed using carbon isotopes and spectroscopic methods.

Diversity, abundance, and potential activity of nitrifying and nitrate-reducing microbial assemblages in a subglacial ecosystem.

Subglacial sediments sampled from beneath Robertson Glacier (RG), Alberta, Canada, were shown to harbor diverse assemblages of potential nitrifiers, nitrate reducers, and diazotrophs, as assessed by amoA, narG, and nifH gene biomarker diversity. Although archaeal amoA genes were detected, they were less abundant and less diverse than bacterial amoA, suggesting that bacteria are the predominant nitrifiers in RG sediments. Maximum nitrification and nitrate reduction rates in microcosms incubated at 4°C were 280 and 18.

Organochlorine pesticide and polychlorinated biphenyl concentrations in snow, snowmelt, and runoff at Bow Lake, Alberta.

We present analyses of the concentrations of organochlorine (OC) contaminants (including organochlorine pesticides and PCBs) in snow, snowmelt, and runoff in glacier and snowmelt fed streams at Bow Lake, Alberta in two contrasting hydrological years (1997 and 1998). The study investigates the variability in OC burdens in snow across the catchment, the elution of OCs from the snowpack, and the relationship between OC concentrations in streams and the annual snowpack. Snowpacks in forested sites were thinner and had lower OC concentrations than snowpacks in open or sparsely vegetated sites.