Paleophycology of a high arctic lake near Cape Herschel, Ellesmere Island

Abstract

Fifty-five diatom taxa, representing mostly acidophilous and benthic species (e.g., Pinnularia biceps, Nitzschia bryophila, Navicula variostriata), were identified in a 56 cm long core from a small, deep lake (78°29.5′ N, 76°44.3′ W) in innermost Baird Inlet, Ellesmere Island, Arctic Canada. The size and composition of past algal populations appears to have been controlled by fluctuations in the extent of icefree conditions in the littoral zone. The development of planktonic diatoms may have been precluded by extended ice cover in the pelagic region, although planktonic chrysophytes (exclusive of the Synuraceae) were abundant throughout the lake's 9000 year history. Crysophycean success in this harsh environment is attributed to their versatile nutritional strategies, their motility, and their ability to form a good resting stage. Four fossil zones were delineated. Following the onset of organic sedimentation (~ 9000 years before present (BP)), the diatom flora was dominated by small Fragilaria species (zone 1), comparable to early postglacial communities from temperate lakes. A contemporary analog to this early assemblage was recorded in the surficial sediments of Proteus Lake (78°41.7′ N, 74°23.0′ W), on Pim Island, suggesting that these diatoms reflect slightly alkaline conditions and extended ice cover. As the climate warmed, the assemblage shifted to one dominated by Nitzschia bryophila and Pinnularia biceps (zone 2), followed by an increase in Navicula variostriata (zone 3), indicating that ice cover was at a minimum and that bryophytes were abundant. Climatic deterioration (~ 4000 years BP) coincided with a shift to a diverse assemblage of shallow water diatoms and a marked decline in chrysophyte and diatom populations (zone 4). These data suggest that, in arctic regions, diatoms may provide indirect information of past climates, since temperature is closely associated with habitat availability.