| Summary: | Thesis (Master, Biology) -- Queen's University, 2009-05-06 17:04:38.302 The study of long-term climatic change in the Arctic, a region both particularly sensitive to the effects of a warming climate and an important driver of global climate, is pertinent to understanding the rates and magnitude of current ecosystem changes. Analyses on geological time frames provide insight into the variability of Arctic climate, allowing a contextualized understanding of recent ecosystem changes that have been documented across the Arctic. Lake CF8, a mid-Arctic lake on Clyde Foreland, Baffin Island, contains a unique sedimentary archive of the present and last two interglacial periods, due to past non-erosive glaciation patterns, providing an opportunity to study interglacial climate trends. Diatom assemblages were analyzed through the organic sediment record of the past three interglacials. Trends in the ontogeny of this lake were revealed: the early, post-glacial environment was dominated by species of the colonial Fragilaria genera, which transitioned into high relative abundances of tychoplanktonic Aulacoseira species. Benthic/periphytic taxa, such as Psammothidium marginulatum, tended to increase in relative abundance in the mid- to late-interglacial periods. The ecological interpretation of this pattern is examined in this study, and suggests that climate drives the succession of the diatom community primarily through indirect effects on lake ice and pH. The extent of ice cover likely plays a large role in the biotic community of this lake; the diatom assemblages within the past ~ 50 years indicate increasing littoral habitat complexity with a peak in Eunotia species and a slightly acidic pH, which is discussed in relation to changing habitat availability associated with decreasing ice cover. In-lake production was examined through the use of spectrally-inferred chlorophyll a trends, which also indicate elevated production in the past ~ 50 years. As climate change becomes an increasingly significant threat to the stability of Arctic ecosystems, interest in paleoclimate records that extend into past, non-anthropogenically mediated warm periods, is increasing. This sediment record extends our understanding of past environmental trends beyond the longest records in this part of the Arctic, the Greenland ice core records, and enhances our understanding of the variability of Arctic climate. M.Sc.
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