The use of limnological, phycological, and paleolimnological techniques to assess environmental change in the Canadian Arctic islands.

摘要

Environmental change in the Canadian Arctic islands was assessed using three interrelated approaches: limnological, phycological, and paleolimnological analyses. Limnological analyses of lakes and ponds on Axel Heiberg and Victoria islands revealed that, while many sites were typically nutrient-poor and slightly alkaline, they are more limnologically diverse than previous arctic surveys have suggested. Extremely low levels of nutrients and dissolved organic matter (a natural screen for ultraviolet radiation) in some of these sites makes these aquatic ecosystems particularly sensitive to changes associated with global warming and ultraviolet radiation penetration.; Diatom analyses from lakes and ponds on Victoria Island revealed marked differences in assemblages among sites, despite relatively similar limnological characteristics. Analyses of diatom assemblages from sediment, rock, and moss substrates showed that certain taxa exhibited strong habitat preferences. A comparison with three similar diatom surveys previously conducted in the Canadian Arctic, showed that diatom species diversity decreased with progressively cooler conditions.; The response of a high arctic lake (Meretta Lake, Cornwallis Island) to decreased eutrophication following the effects of nearly 50 years of raw sewage input was assessed using phycological and paleolimnological approaches. An annual diatom-based monitoring approach, representing the longest, continuous algal-monitoring program in the High Arctic, revealed that diatom assemblages in moss and rock habitats were tracking changes in the lake's nutrient levels. Analyses of the uppermost sediments of a sediment core revealed the presence of fossil diatom assemblages representative of pre-impact conditions, indicating that the paleolimnological record can also track decreased nutrient inputs, and that no significant lags existed in these largely ice-covered lakes.; A paleolimnological analysis of Char Lake, on Cornwallis Island, revealed that even small changes in climate can induce an ecological response in a deep, often ice-covered high arctic lake. The location of Char Lake within a few kilometres of a high arctic weather station allowed the comparison of the fossil diatom record to instrumental climate over the last ∼50 years. An increase in species diversity was observed that was consistent with the timing of recent climate changes, as opposed to other stressors such as catchment disturbances or atmospheric deposition. (Abstract shortened by UMI.)