Source water inputs and catchment characteristics regulate limnological conditions of shallow subarctic lakes (Old Crow Flats, Yukon, Canada)

Abstract

Climate variations exert rapid and strong control on the hydrology of shallow lake-rich subarctic landscapes, but knowledge of the associated effects on limnological conditions remains limited. Based on analysis of water isotope compositions and water chemistry at 56 lakes across Old Crow Flats (Yukon), a large thermokarst landscape, we assess if differences in source water inputs (snowmelt versus rainfall) affect limnological conditions during the ice-free season of 2007 and explore influences of catchment features. Results demonstrate that lakes with snowmelt-dominated source waters, situated in catchments that support tall shrub and woodland vegetation, possess significantly higher (p < 0.05) nutrient (N, P, SiO2) and dissolved organic carbon concentrations than lakes with rainfall-dominated source waters. Conversely, rainfall-dominated lakes, located in catchments dominated by dwarf shrubs and sparse vegetation, have significantly higher concentrations of major ions (Mg2+, Na+, SO42−) and pH. These limnological differences persisted throughout the ice-free season. We suggest that interaction of snowmelt with organic-rich detritus raises nutrient concentrations in snowmelt-dominated lakes and that evaporative-concentration, shoreline erosion and possibly rainfall runoff are processes that raise the ionic content of lakes with rainfall-dominated source waters. Knowledge of these relations improves the ability to anticipate limnological responses to ongoing and future climate and hydrological change in Arctic and subarctic regions.

Biotic responses to multiple aquatic and terrestrial gradients in shallow subarctic lakes (Old Crow Flats, Yukon, Canada)

“…Previous analyses of lakes sampled across OCF have demonstrated strong relations amongst catchment features, water balance, and limnology (Turner et al 2010(Turner et al , 2014Balasubramaniam et al 2015). Water balances of lakes are influenced mainly by snowmelt, rainfall, and evaporation, whose relative roles are associated with catchment features (Turner et al 2010(Turner et al , 2014.…”

“…Recent research demonstrates that variation of lake water chemistry is driven by inter-related gradients of catchment characteristics and hydrology (Stewart and Lamoureux 2011;Herzschuh et al 2013;Balasubramaniam et al 2015), which are strongly associated with climate conditions. For example, warming is increasing the density of shrub vegetation, which traps more snow (Pomeroy et al 2006).…”

“…Elevated frequency and intensity of rainfall events sufficiently large to exceed soil moisture deficits leads to greater hydrologic connectivity (Bowling et al 2003;Woo and Guan 2006) and delivery of catchment-derived solutes to lakes (Herzschuh et al 2013). Higher rates of lake evaporation, when not offset by the diluting effects of precipitation (Turner et al 2010(Turner et al , 2014, are associated with increased concentration of ions in lake water during the ice-free season (Corcoran et al 2008;Balasubramaniam et al 2015). Clearly, the complex interplay among catchment characteristics and hydrology, as driven by climate, influences water chemistry of northern lakes.…”

“…For example, Turner et al (2014) demonstrated that water balances of lakes with abundant tall shrubs and trees in the catchment, which entrap wind redistributed snow, tend to be dominated by snowmelt, whereas lakes situated in catchments dominated by sparsely vegetated tundra possess water balances dominated by rainfall inputs. An investigation of water chemistry in the same lake set by Balasubramaniam et al (2015) found that lakes dominated by snowmelt inputs possess higher concentrations of nutrients (nitrogen and phosphorus) and DOC than lakes dominated by rainfall inputs, likely due to enhanced interaction of snowmelt with organic matter in densely vegetated catchments. These snowmelt-dominated lakes are often situated closer to the fringe of OCF where they experience enhanced hydrologic connectivity to the surrounding hill slopes (Turner et al 2014;Balasubramaniam et al 2015).…”

“…An investigation of water chemistry in the same lake set by Balasubramaniam et al (2015) found that lakes dominated by snowmelt inputs possess higher concentrations of nutrients (nitrogen and phosphorus) and DOC than lakes dominated by rainfall inputs, likely due to enhanced interaction of snowmelt with organic matter in densely vegetated catchments. These snowmelt-dominated lakes are often situated closer to the fringe of OCF where they experience enhanced hydrologic connectivity to the surrounding hill slopes (Turner et al 2014;Balasubramaniam et al 2015). Balasubramaniam et al (2015) found that lakes dominated by rainfall inputs possess relatively higher conductivity, alkalinity, and ion content than lakes dominated by snowmelt inputs.…”