CGRG Bibliography of Canadian Geomorphology
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Author : Finkelstein, S.; and Gajewski, K.
Date : 2007.
Title : Contrasting ecological response to climatic warming in arctic lakes with low and high diatom biodiversity.
Publication : ArcticNet 2007 Annual Scientific Meeting. December 11-14, 2007. Collingwood, Ontario.
Issue : Programme.
Page(s) : 16.
Abstract
The protection of biodiversity is an important conservation goal but there remains a lack of information on the functional importance of biodiversity, particularly as this relates to responses to climatic change. As a consequence of the current warming climate, some lakes and ponds in the Arctic are experiencing increases in diatom biodiversity, as well as increases in diatom production and changes in community composition. Since algae form the basis of aquatic food webs, such changes in the structure of algal communities could affect the function of aquatic ecosystems as a whole in the Arctic. Arctic lakes vary in their responses to recent and paleoclimatic changes, with some lakes displaying relatively large increases in algal biodiversity, and more significant changes in community composition, while other lakes show lesser response. It has been hypothesized that biodiversity provides "insurance" in the face of environmental change; thus lakes with more diverse diatom assemblages should display less significant changes in response to warming. Paleolimnological records from two lakes in the Prince of Wales group of islands in the central Canadian Arctic were used to test this hypothesis. The two lakes are separated by approximately 100 km, and experience similar climates, however ecological responses to climatic warming differ significantly between the two lakes. Lake PW03 (73.12° N; 96.68°W) is situated on the coast of Prescott Island, on crystalline rocks of the Canadian Shield, and is relatively acidic. Modern and fossil diatom assemblages in Lake PW03 display higher species richness and evenness than average for Arctic lakes. Lake PW02 (74.07°N; 97.77°W), by contrast, is situated on the carbonate-containing conglomerate of eastern Russell Island, and is more alkaline. Modern and fossil diatom assemblages in Lake PW02 have lower diversity relative to Lake PW03 and are >80% dominated by the Fragilarioid group. In Lake PW03, diatom valve production and biogenic silica concentrations increased since 1850 AD but diatom species richness showed little change. At this site, maximum species richness occurred 2300 years ago. The species composition of diatom communities also showed few changes in recent times. In Lake PW02, diatom valve production, biogenic silica concentrations, species richness and evenness also increased significantly, particularly since 1950 AD. However, at this site, the recent values of production and biodiversity exceed any recorded during the Holocene. The composition of diatom communities also changed notably in Lake PW02 following 1950 AD with a decrease in the proportion of small, benthic Fragilarioid species, and increases in epiphytic taxa. Thus, the magnitude of the community and ecosystem response to climate warming was greater in Lake PW02, which had lower biodiversity prior to 1850 AD, than in higher-diversity PW03. These results suggest that the functional response of aquatic ecosystems in the Arctic may depend on prior biodiversity.
Bibliography of Canadian Geomorphology