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Leighton King, Paul MacKeigan, Rebecca Garner, Alex Baud, Beatrix Beisner, Isabelle Domaizon, Irene Gregory-Eaves
Long-term trends in cyanobacteria community composition across a range of human development in six eastern Canadian lakes: analyses of sedimentary DNA
Increased human development since the Industrial Era has led to rising reports of toxic cyanobacterial blooms, which pose significant risks to public health and have detrimental effects on lake ecosystems and water quality. Sedimentary DNA from paleolimnological archives provides valuable insights into community structures by evaluating contemporary data within the context of historical baselines—a perspective rarely available through monitoring data alone. This study investigates changes in phytoplankton and cyanobacteria communities over the past ~150 years across six mesotrophic lakes in Quebec and Ontario across a range of human development. Sediment cores collected in 2017 were analyzed using biogeochemical, pigment, and sedimentary DNA techniques targeting specific cyanobacteria marker genes, including quantitative PCR (qPCR) and 16S rRNA gene sequencing. Results indicate widespread increases in total primary production, with cyanobacteria becoming more dominant relative to other phytoplankton groups. Additionally, sharp increases in toxin-producing cyanobacteria were observed alongside slight declines in non-bloom-forming cyanobacteria. By reconstructing historical cyanobacteria dynamics, this study provides critical insights into their temporal variability and relationships with anthropogenic impacts, including climate, population growth, and watershed development.
