Mapping of cyanobacteria and potential cyanotoxin producing taxa in large rivers of the United States

Cyanobacteria and cyanotoxin blooms (harmful algal blooms: HABs) are a trending focus of current research due to their increased frequency and impact on freshwater ecosystems, public health, and the economy. Currently, many studies focus on bloom events in lentic environments such as lakes or ponds. Comparatively few studies have explored lotic environments and fewer still have examined the cyanobacterial communities and toxin producers in nonHAB conditions. Here we used a metagenomics-based approach to profile nonHAB microbial communities and cyanobacteria in twelve major US rivers at multiple time points during summer months. Our data show that US rivers possess diverse microbial communities in which cyanobacteria often comprised significant portions, including multiple potential toxin-producing species. Further, we performed deep sequencing of the microcystin E (mycE) gene to understand i) the capacity of these cyanobacteria to produce toxins, ii) the distribution of toxin producing potential across genera and across river location and time, and lastly iii) the spatio-temporal distribution of mycE genotypic diversity. Combined, these data provide a unique perspective on cyanobacteria and toxin producing taxa that exist in large rivers across the US and can be used to better understand the conditions that may precede bloom events in lotic freshwater ecosystems.