Coupled landscape-lake evolution in High Arctic Canada

Abstract

We profiled five ice-covered lakes and two ice-covered fiords of Ellesmere Island at the northern limit of High Arctic Canada to examine their environmental characteristics, and to evaluate the long-term limnological consequences of changes in their surrounding landscape through time (landscape evolution). All of the ecosystems showed strong patterns of thermal, chemical, and biological stratification with subsurface temperature maxima from 0.75 to 12.15 °C; conductivities up to 98.1 mS cm–1 (twice that of seawater) in some bottom waters; pronounced gradients in nitrogen, phosphorus, pH, dissolved inorganic and organic carbon, manganese, iron, and oxygen; and stratified photo synthetic communities. These ecosystems form an inferred chronosequence that reflects different steps of landscape evolution including marine embayments open to the sea, inlets blocked by thick sea ice (Disraeli Fiord, Taconite Inlet), perennially ice-capped, saline lakes isolated from the sea by isostatic uplift (Lakes A, C1, C2), and isolated lakes that lose their ice cover in summer. The latter are subject to entrainment of saline water into their upper water column by wind-induced mixing (Lake Romulus; Lake A in 2000), or complete flushing of their basins by dilute snowmelt (Lake C3 and Char Lake, which lies 650 km to the south of the Ellesmere lakes region). This chronosequence illustrates how changes in geomorphology and other landscape properties may influence the limnology of coastal, high-latitude lakes, and it provides a framework to explore the potential impacts of climate change.

Seasonal Dynamics of Nutrient Loading and Chlorophyll A in a Northern Prairies Reservoir, Saskatchewan, Canada

“…This is approximately 6-times greater than Chl-a measured in June (0.95 μg Chl-a/L), which indicates a significant increase in phytoplankton biomass. In general, Chl-a concentrations measured in surface water from Lake Diefenbaker were comparable to those reported in other lakes (0.22-7.09 μg Chl-a/L) in Canada [29][30][31][32]. However, compared to other freshwater systems in which massive cyanobacteria blooms occurred (the associated Chl-a concentrations were more than 100-times greater than those recorded during this study; up to 830 μg Chl-a/L; [21]), Chl-a concentrations in Lake Diefenbaker measured during the 2008 sampling season were low.…”

The chemical development of a hypersaline coastal basin in the High Arctic

“…3). Unlike most saline lakes (Van Hove et al 2006) that exhibit steadily increasing salinity profiles, the hypolimnion lacks a diffusion profile and is constant at 56. The upper portion of the hypolimnion is moderately warm and oxic, whereas below 15 m, the temperature cools to 22.2uC.…”

“…If evaporation or ablation is high, water bodies will become hypersaline, as salts are concentrated. Alternatively, if freshwater inputs are high, the influx of freshwater will eventually flush relict saltwater from the basin (Gallagher et al 1989;Van Hove et al 2006). Although the former has been suggested to explain the salinity of some Antarctic lakes (Burton 1981), in the Arctic, evaporative enrichment is minor during the short summer season, and ice ablation rates are low because of snow cover for at least 8 months of the year.…”

“…In the Canadian Arctic, chemical and stratigraphic analyses of sediment cores reveal that many coastal lakes were initially marine basins before coastal emergence (Retelle 1986;King 1991). In certain systems, the transition from marine to lacustrine sediments appears to have been quite abrupt ), yet at least 12 lakes have been discovered that have remained saline or become hypersaline (Ludlam 1996;Van Hove et al 2006). What remain unclear are the different evolutionary processes that control the salinity of coastal polar lakes.…”

“…In polar regions, numerous coastal lakes have been discovered that contain marine-derived water at depth (Burton 1981;Gibson 1999;Van Hove et al 2006). Understanding the formation and evolution of these saline lakes is important for forecasting future changes in lake processes on the basis of watershed hydrological balances; predicting changes associated with future sea-level rise and coastal inundation processes; and understanding biological productivity and the aquatic organisms that are critically dependent on the osmotic strength of their surrounding water (Schallenberg et al 2003).…”