Rebecca Garner

Concordia University
eDNA reconstructions of preindustrial and contemporary micro-eukaryotic diversity from Canadian lake sediments

Rebecca Garner, Irene Gregory-Eaves, David Walsh

Canada stewards a substantial percentage of Earth's lakes. These lakes serve as habitat to a vast diversity of microbial eukaryotes and are impacted by a host of anthropogenic pressures. To explain current day distributions of micro-eukaryotes in Canadian lakes, this study asks how and where these communities have changed in response to human stressors. Work to date has focused on studying particularly well-preserved groups (e.g. diatoms) and typically at a regional scale. Here, we develop the nascent paleogenetics approach to reconstruct whole micro-eukaryotic communities from DNA preserved in preindustrial-age lake sediments and compare these with their contemporary counterparts. To reconstruct these assemblages, we sequenced metagenomes as well as taxonomically informative but short 18S rRNA gene amplicons from preindustrial and surface lake sediments collected across Canada. This project is part of the LakePulse Network, which sampled randomly selected lakes representing a range of surface area and human impact classes in each core Canadian ecozone. Our goal is to explore the potential and limitations of paleogenetics, especially as it pertains to the discovery of DNA-based indicators of lake health. This first-ever landscape scale study shines a light on the broad and often undescribed diversity of lacustrine micro-eukaryotes, their integral roles in lake food webs and biogeochemical cycles, and their responses to nearly 150 years of industrial-age impact.