Kapillesh Balasubramaniam MSc, Smol Lab Assessing the impacts of emerging anthropogenic stressors on lakes within the Rideau Canal system: A paleolimnological re-assessment Earlier diatom-based paleolimnological studies were conducted on a suite of diverse lakes (i.e., Lower Rideau L., Big Rideau L., Otter L., Upper Rideau L., Indian L., L. Opinicon) within the Rideau Canal system ~25-30 years ago and provided important information regarding the ecological impacts of canal construction (1827-1832). Following these early paleolimnological studies, the same lakes are now facing the potential impacts of newly emerging environmental stressors, particularly accelerated climate warming. Here, I revisited the same suite of lakes by conducting a series of paleolimnological analyses, focusing on recent changes in diatom assemblage composition, to assess the potential ecological impacts of newly emerging environmental stressors. Despite the substantial environmental impacts associated with canal construction, the highest rate of diatom compositional change across the suite of lakes only took place in the past ~25-30 years, which coincided mainly with an increase in planktonic diatom taxa. This recent shift in assemblage composition could not be explained by nutrient enrichment, as total phosphorus (TP) concentrations, measured since the 1980s, have significantly declined across the study lakes. The continued increase of planktonic taxa across the study lakes suggests the impact invasive zebra (ca. 1990) mussels in the Rideau Canal region appeared to have only been modest. Rather, these recent changes in diatom assemblage composition were strongly related to increasing regional air temperatures, as the conditions associated with warmer temperatures (i.e., longer, and stronger periods of thermal stratification, alterations to water-column mixing regimes, reduced ice cover duration) provide favorable conditions for extensive planktonic diatom growth. Lakes within the Rideau Canal system are changing rapidly in ecologically significant ways and will likely continue to do so as temperatures continue to rise.
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