Temporal Trends in Cyanobacteria Through Paleo-Genetic Analyses

Abstract

With increasing eutrophication and climate change, temperate lakes are experiencing conditions favoring cyanobacterial dominance, leading to toxic blooms. However, the relative importance of these two factors remains unclear, due to a lack of historical records. This thesis analyzed sediment DNA from four lakes in Central Ontario to quantify trends over the past ~ 200 years in bacteria, cyanobacteria, and microcystin toxins through ddPCR of target genes. Climate related variables explained a small amount of variation. However, lakes with more development exhibited significant increases in cyanobacterial dominance, indicating regime shifts not occurring in less developed lakes. These shifts were likely driven by nutrient loading in concert with climate change. Sediment cores were also compared within a single multi-basin lake to determine the effect of depth and morphometry on DNA preservation. Sites of greater depth (20 m +) were more conducive to long-term DNA preservation and sheltered morphometry increased sediment DNA deposition.