ABSTRACT: -Diatom community dynamics in a Fragilarioid-dominated Holocene paleolimnological record from Russell Island in the central Canadian Arctic Archipelago.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Many diatom records from Arctic lakes are dominated by a single group of benthic taxa: the Fragilarioids. This group can constitute >90% of valves in fossil diatom assemblages. It is often assumed that diatom records dominated by this group offer little in terms of paleoecological information. We present here a whole-Holocene paleolimnological record from a small lake on Russell Island (Lake PW02), in the central Canadian Arctic Archipelago (74°00' N, 97°50' W, 182 m asl). The record is dominated by Fragilarioid types; we examine separately each of nine species or morpho-types within this group to test whether individual Fragilarioid taxa responded differently to Holocene climatic changes. The ratio of the two most common types indicates a higher proportion of Staurosira venter relative to Staurosirella pinnata in the earliest Holocene. By 8300 years ago, S. pinnata rises to an abundance of ~20% and Staurosira construens appears. Fragilaria oldenburgiana declines by 5000 years ago, as two species in the genus Pseudostaurosira begin to increase. Recent sediments deposited over the past 200 years contain the highest numbers of individuals of S. venter and S. pinnata morpho-types with particularly long valves. We conclude that studies done at high taxonomic resolution offer possibilities to extract enhanced paleoecological information from records dominated by Fragilarioid diatoms. The record from Lake PW02, like many others from Arctic lakes with low algal diversity throughout the Holocene, shows pronounced increases in diatom diversity in the most recent sediments.

Bibliography of Canadian Geomorphology