Paleolimnological assessment of environmental changes occurring on Pim Island, Nunavut, High Arctic Canada
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Despite the documented sensitivity of polar environments, long-term monitoring data are especially sparse in these regions. Diatom-based paleolimnology has contributed significantly to understanding the response of Arctic lakes to climate change, but most studies have been conducted in regions with relatively high lakewater buffering capacity. As such, Pim Island (Nunavut, Canada) is a region of limnological interest because, due to the local geology, its surface waters are of relatively lower pH and previous research suggests that such softwater lakes may be especially responsive to climate fluctuations and therefore provide the best paleoclimate records. This thesis has two separate but related chapters, as well as an exploratory study included in appendix. First, a novel approach using visible-near-infrared spectroscopy (VNIRS) was used to infer lakewater dissolved organic carbon (DOC), from a 160-lake calibration set from the Canadian Arctic. Historically sound and similar trends were reconstructed when compared against a Canadian diatom-based DOC and Swedish VNIRS-based total organic carbon (TOC) model on Arctic Holocene sediment records. Second, a diatom and spectroscopically-based multi-proxy approach was utilized on Holocene sedimentary records from two lakes on Pim Island to assess long-term environmental change from this region. Benthic and epiphytic diatom taxa dominated the pre-19th century assemblages, although marked shifts in dominant species were recorded during the mid-Holocene. The mid-Holocene diatom assemblages underwent an abrupt ecological shift from alkaliphilous Fragilaria sensu lato to slightly acidophilous Achnanthes and Navicula. The post-19th century was characterized by an increase in the planktonic species (Cyclotella radiosa), indicating marked lakeice reductions. Third, the limnological properties and modern diatom assemblages of ponds and lakes surveyed from 1979 to 2009 on Pim Island were examined as part of an exploratory study. The ponds and lakes displayed typical characteristics observed in high Arctic lacustrine environments (i.e. oligotrophic, very dilute) but with overall relatively low alkalinity. Poorly-buffered sites had diatom assemblages that were distinct from well-buffered lakes elsewhere in the High Arctic. Our findings contribute to an improved understanding of the interactions between local environments and limnological changes, and also provide insight on the biological responses of lakes to Holocene environmental change and allow us to compare responses to those in more alkaline sites.