Using Chironomidae (Diptera) assemblage changes to establish past and present lake conditions in the northern Niagara Escarpment region: Application of the top-bottom paleolimnological approach

Since the Niagara Escarpment region was designated as a World Biosphere Reserve by the United Nations Education Scientific and Cultural Organization in 1990, there has been considerable interest in determining how cultural eutrophication has affected lakewater quality variables, such as dissolved oxygen conditions, over the past ∼150 years. Unfortunately, long-term limnological data on dissolved oxygen conditions were unavailable for the lakes throughout the region. However, paleolimnological analyses of subfossil Chironomidae can be used to reconstruct these missing data. In this thesis a “before and after impact” paleolimnological approach was used to develop transfer functions relating recent chironomid assemblages to measured environmental variables, and then using these data to reconstruct past lake conditions (i.e. prior to European settlement).; This study confirmed, through a series of canonical ordinations, that when well-oxygenated polymictic lakes and oxygen-limited thermally stratified lakes were analysed together, end-of-summer, bottom dissolved oxygen concentrations explained a significant amount of chironomid assemblage variation.; Two inference models were developed for end-of-summer bottom dissolved oxygen that included both thermally stratified lakes and polymictic lakes. (Abstract shortened by UMI.)...