Cecil Lake British Columbia: a paleolimnological analysis of natural and anthropogenic environmental change
LE3 .A278 2019
Bachelor of Science
Earth & Environmental Sciences
Lake sediment archives are an established tool for examining environmental change over time. Cecil Lake is a productive shallow lake located in the Peace River Region of northeastern British Columbia and supports a variety of waterbirds, including a significant northern breeding population of eared grebes (Podiceps nigricollis). Over 2% of the Canadian population of eared grebes breed at Cecil Lake; this species is iconic and may be an indicator of ecosystem health. The Cecil Lake watershed was primarily well-forested muskeg when the surrounding area was first homesteaded in 1928. As of 2018, ~80% of the landscape has been developed by the agricultural and energy sectors. Consequently, Cecil Lake represents an opportunity to examine the effects of this development on a northern lake. The bulk geochemistry of the lake sediment archive at Cecil Lake was investigated to decouple natural and anthropogenic impacts over time. Water samples were collected for limnological assessment. Three sediment cores were collected in July 2018 using a gravity corer. A 30 cm core was extruded at a 0.5cm scale to determine stratigraphic variations in bulk geochemistry (metals, δ15 N, δ15C, Total C, N). X-ray fluorescence analysis was used to determine metal concentrations at different depths in the core. Total lead data suggested the recovery of a greater than 100-year record. A distinct zone of change, estimated to have occurred 1920-1940, was characterized by increasing calcium, and manganese, as well as decreased titanium, potassium, and iron. This period was also characterized by increased %C, δ13C, and %N and a steadily increasing trend in the δ15N ratio. Strontium, zinc, and iron data showed increased variability from ~1940 onwards. Collectively these data indicate three distinct zones: background conditions, a strong response to initial clearing and development, and increased environmental fluctuations associated with resultant water level variability and nutrient input changes. 210Pb analysis of the core will provide stronger temporal control allowing for the accurate correlation of historic events to the sediment archive. In the future this record will be coupled with ecological data to better understand the vulnerability of habitat in northern lakes to environmental changes.
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