PARENT SESSION
Oral Session #10: Paleoecology. Presiding: S. Hotchkiss.
Monday, August 6, 2001. 8:00 AM to 12:00 PM. Hall of Ideas J.
Using subfossil Chironomidae (Diptera) to determine past and present lake conditions in the Northern Niagara Escarpment Region, Ontario, Canada.
NEILL, KIMBERLEY1, SMOL, JOHN1, 1
ABSTRACT- In 1990, the Niagara Escarpment was declared a World Biosphere Reserve by the United Nations Educational Scientific and Cultural Organization. Since that time there has been considerable interest in determining how anthropogenic activities (e.g. agriculture, aquaculture, cottage development) have impacted lakes within this landscape. Currently, there is a lack of long-term data on the ecological and environmental conditions of lakes within this region. This study uses a "before and after" impact paleoecological assessment approach to determine if anthropogenic disturbances have caused significant changes in lake conditions. Subfossil Chironomidae (Diptera) were analyzed from sediment cores (approximately 40 cm long) taken from 44 lakes in the Northern Niagara Escarpment Region. Limnological characteristics were also collected. These lakes varied in trophic state, depth, and level of anthropogenic activities occurring within their catchments. Two chironomid-based models were developed based on surface sediment chironomid assemblages and recent limnological characteristics. A shallow polymictic lake chironomid-based model was developed to reconstruct lake trophic variables. A second model was also developed to reconstruct dissolved oxygen in deeper, thermally stratified lakes. These models quantitatively determine limnological conditions within lakes based on recent chironomid assemblages. To assess how lake conditions changed with the onset of human disturbances, these models were applied to assemblages preserved in the bottoms (pre-impact sediment) of the sediment cores. This study provides new insights into chironomid-based paleolimnology and the effects of cultural eutrophication on shallow lakes.
KEY WORDS: subfossil chironomids, paleolimnology, shallow lakes, lake management