Detection of Microcystin-Producing Cyanobacteria in Finnish Lakes with Genus-Specific Microcystin Synthetase Gene E (mcyE) PCR and Associations with Environmental Factors

We studied the frequency and composition of potential microcystin (MC)producers in 70 Finnish lakes with general and genus-specific microcystin synthetase gene E (mcyE) PCR. Potential MC-producing Microcystis, Planktothrixand Anabaena spp. existed in 70%, 63%, and 37% of the lake samples, respectively. Approximately two-thirds of the lake samples contained one or two potential MC producers, while all three genera existed in 24% of the samples. In oligotrophic lakes, the occurrence ofonly one MC producer was most common. The combination ofMicrocystis and Planktothrix was slightly moreprevalent than others in mesotrophic lakes, and the cooccurrence of allthree MC producers was most widespread in both eutrophic andhypertrophic lakes. The proportion of the three-producer lakesincreased with the trophic status of the lakes. In correlationanalysis, the presence of multiple MC-producing genera was associatedwith higher cyanobacterial and phytoplankton biomass, pH, chlorophylla, total nitrogen, and MC concentrations. Total nitrogen, pH,and the surface area of the lake predicted the occurrence probabilityof mcyE genes, whereas total phosphorus alone accounted for MCconcentrations in the samples by logistic and linear regressionanalyses. In conclusion, the results suggested that eutrophicationincreased the cooccurrence of potentially MC-producing cyanobacterialgenera, raising the risk of toxic-bloomformation.