Cyanotoxin Encoding Genes as a Powerful Marker to Predict Cyanotoxin Production during Cyanobacterial Harmful Algal Blooms: A Confirmation Study in an Inland Freshwater Lake

Harmful algal blooms due to excessive growth of cyanobacteria frequently occur in inland freshwater lakes and significantly threaten water resources and public health. William H. Harsha Lake (Ohio, USA) has a history of serious algal blooms. To deeply understand the bacterial (especially cyanobacterial) community succession during the 2016 algal bloom in this lake, we I) sampled lake water from two sites [Harsha Buoy (BUOY) and East Fork Lake Surface (EFLS)] in this lake from April to November and II) sequenced bacterial 16S rRNA genes in the lake water samples via Illumina MiSeq. The cyanobacterial community was stable at the phylum level. Proteobacteria, Cyanobacteria, Bacteroidetes, Actinobacteria, Planctomycetes, Verrucomicrobia, and Chloroflexi (approximate descending order of relative abundance) were the dominant phyla for both sampling sites. The cyanobacterial community structure at the genus level dynamically changed substantially over the bloom. Dolichospermum, Synechococcus, Pseudanabaena, Prochlorothrix, Planktothrix, and Microcystis were the dominant genera for both sampling sites. Microcystis and Planktothrix as the major microcystin producers thrived in June and July, producing a high concentration of microcystins.