Quantitative estimates of recent environmental changes in the Canadian High Arctic inferred from diatoms in lake and pond sediments |
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| Authors: | Antoniades Dermot Douglas Marianne S V Smol John P |
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| Institution: | (1) Department of Geology, University of Toronto, 22 Russell St., M5S 3B1 Toronto, ON, Canada;(2) Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen s University, K7L 3N6 Kingston, ON, Canada |
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| Abstract: | Diatoms were examined in three lacustrine sediment records from Alert, northern Ellesmere Island, and from Isachsen, Ellef Ringnes Island. Diatom assemblages changed markedly since the mid-19th century following relatively stable community composition that spanned centuries to millennia. Three different assemblages, primarily composed of Fragilaria pinnata, Diadesmis spp., or Pinnularia spp., dominated the pre-1850 period at the three sites, but were replaced with different, more diverse assemblages in recent sediments. These species shifts occurred in the mid- to late-19th century in the Isachsen sites, and in the mid- to late-20th century in our Alert site. This difference in timing appears to be a result of the different sensitivities of lakes and ponds to environmental change, rather than of site-specific chemical properties. Reconstructions of pH using diatom inference models indicated increases from 0.5 to 0.8 pH units at these sites over this period of assemblage change. The diatom-inferred pH record from Alert showed agreement with measured climate data from Alert over the last  30 years. These marked community changes suggest that these sensitive high arctic sites have recently crossed important ecological thresholds due to environmental change, most likely related to recent warming. |
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| Keywords: | Arctic Climate Diatoms Ellef Ringnes Island Ellesmere Island Environmental change Limnology pH Proxies |
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