LAKEWIDE SAMPLING REVEALS HOW CIRCULATION PATTERNS STRUCTURE MICROBIAL COMMUNITIES IN LAKE ONTARIO

Microbial communities perform essential biogeochemical processes within the Great Lakes, but previous microbial studies have lacked the spatial resolution to make lake-wide inferences. This gap prevents estimation of the spatial and environmental drivers of microbial community structure. Here, we collected >140 microbial DNA samples across Lake Ontario from 16 sites, at three depths, and between two seasonal collection times. Using a combination of 16S rDNA gene sequencing, flow cytometry, and water quality data, we analyzed the environmental determinants of microbial abundance and composition in Lake Ontario. Taxonomic richness was highest in shallow samples in September, but communities were dominated by a few, highly abundant species. While all samples featured Alphaproteobacteriota LD12, Actinobacteriota acI, and Verrucomicrobiota, shallow May samples were defined by a dominance in Bacteroidota, shallow September samples by Cyanobacteria like Synechococcus, and deep (> 30 m) samples by Chloroflexi and Planctomycetota. Coabundance analysis revealed that potential upwelling zones along the southern shore in September produce highly diverse microbial communities. Further, functional analysis revealed these areas are hot-spots for nitrogen cycling which coincide with a decrease in cyanobacterial abundance coupled with a relative increase in Microcystis and Pseudanabaena. These data enhance our ability to predict the spatial and seasonal distribution of biogeochemical processes and the underlying microbial interactions which determine such processes.

Primary Presenter: Augustus Pendleton, Cornell University (arp277@cornell.edu)

Authors:

Marian Schmidt, Cornell University  (marschmi@cornell.edu)