Associations between microbiome composition and microcystin levels in the 2018 Lake Erie HABs Grab

Annual cyanobacterial harmful algal blooms (cHABs) threaten the well-being of western Lake Erie and the surrounding region. To resolve an entire bloom at unprecedently high spatial resolution, researchers coordinated a single-day survey of the Western Lake Erie cHAB (‘HABs Grab’; August 9, 2018). Amplicon sequencing of the V4 region of the 16S rRNA gene was performed on 100 samples to determine how the microbial community varied spatially and in relation to environmental conditions within the bloom. While wide variation in community alpha diversity was observed in and out of the bloom, out-of-bloom communities had higher average evenness. Despite Microcystaceae being the dominant cyanobacterial family, Nostocaceae, Synechococcaceae and Pseudanabaenaceae were present in the bloom as well, while diatoms (mainly Aulacoseira) and cryptomonads (Teleaulax) were abundant both in and out of bloom. Common bloom-associated heterotrophic bacterial groups Flavobacteriia (Cryomorphaceae, Flavobacteriaceae), Planctomycetia (Planctomycetaceae), and Sphingobacteriia (Chitinophagaceae, Saprospiraceae) vary throughout the dataset, in association with nutrient concentrations, algal groups and toxin detections. Environmental and biotic drivers of toxin-producing cyanobacteria are explored to improve our understanding of how the interplay between algae and their microbiomes contributes to bloom composition and toxin production in Lake Erie.