XVI International Botanical Congess

Scaled chrysophytes were used to infer changes in lake water pH, specific conductivity and trophic status in 25 Connecticut lakes over the past 100 years and the changes coorelated with alterations in the surrounding watersheds over the same time period. Significant correlations were observed between chemical conditions inferred from organismal remains in surface sediments and present-day land use practices. Approximately 25% of the lake have significantly increased in specific conductivity and become more eutrophic. Despite the fact that the region receives significant amounts of acidic deposition, and many of the waterbodies are situated in poorly buffered watersheds, none of the lakes have declined in pH. In fact, 20% of the lakes have significantly increased in pH. Those lakes that have experienced the greatest degree of change are those situated in watersheds that have had over 25% conversion to residential land use. Based on our study using scaled chrysophytes it appears that if a minimum of 80% of the watershed is maintained as forests that significant changes in water chemistry will not occur.