Characterization of high arctic stream diatom assemblages from Cornwallis Island, Nunavut, Canada

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Abstract
Distinct diatom assemblages often characterize stream habitats, providing the potential to reconstruct past precipitation, snowmelt, and streamflow levels in high arctic watersheds by analyzing fossil assemblages preserved in downstream lake sediments. Diatom assemblages were studied from seven streams and two rivers surrounding Lake Sophia, Cornwallis Island, Nunavut, Canada (75°06' N, 93°36' W). A total of 64 diatom taxa were identified from epilithic and epiphytic assemblages in these lotic habitats. Of these, certain diatom taxa exhibited clear microhabitat preferences. Hannaea arcus (Ehrenberg) Patrick, Achnanthes minutissima (Kützing) Hustedt, Achnanthes petersenii Hustedt, and Meridion circulare (Greville) Agardh were the most common taxa on epilithic substrates, and as a group made up 61–95% of the diatom epilithon. Achnanthes taxa (mainly A. petersenii and A. minutissima) were the dominant taxa in moss habitats, representing between 45 and 73% of the diatom epiphyton. The relative abundance of H. arcus in epilithic habitats was negatively correlated with water temperature (r2= 0.71, n = 8). Hannaea arcus was found in greater abundances in cool, fast-flowing streams. This apparent correlation may more closely reflect current speed, which is inversely correlated to temperature in these streams. When these streams discharge into lake basins, the characteristic stream diatoms H. arcus and M. circulare are deposited in lakes. These diatom taxa have the potential to infer past streamflows using paleolimnological techniques.Key words: diatoms, arctic, stream, rheophilous, Lake Sophia, Hannaea arcus.