A palaeoenvironmental study of Fairfax Lake,a small lake situated in the rocky mountain foothills of west-central Alberta

Fairfax Lake is a small, oligotrophic to mesotrophic headwater lake situated in the Foothills of the Rocky Mountains of west-central Alberta (Latitude 52° 58 N; Longitude 116° 34 W). Through acquisition of a sediment core, and analyses of the diatoms, chrysophyte stomatocysts, pollen and sedimentary pigments, including myxoxanthophyll and oscillaxanthin, a palaeoenvironmental history of the lake has been determined. The sedimentary record spans ca. 13 200 years. An open tree-less vegetation existed in the region ca. 13 200–ca. 11 600 years BP. Maximum oscillaxanthin and myxoxanthophyll concentrations, hence the largest blue-green algal populations, occurred during the same interval. With increasing temperature pioneering parkland vegetation appeared ca. 11 600 years BP but was replaced ca. 10 100 years BP by spruce forest. Pine appeared ca. 7800 years BP and this marked the development of the present day montane boreal forest. Diatoms were not found until ca. 11 255 years BP. Benthic taxa dominated but by ca. 10 100 years BP planktonic taxa had become more prominent. Lake levels are interpreted as having risen, and the lake water was probably more transparent. Maximum chlorophyll and total carotenoid concentrations occur ca. 11 255 to ca. 7000 years BP corresponding to the warm early to mid-Holocene period. Lake nutrient levels appear to have been higher prior to ca. 7000 years BP, and the lake has changed from being eutrophic during the early Holocene to its present status as an oligotrophic to mesotrophic lake. Subtle hydrological changes have also occurred in the catchment as water levels do not appear to have remained constant.