each primer set, dissociation curve was run following the real-time PCR, and found no other dsDNA was amplified including primer dimers, contaminating DNA, and PCR product from misannealed primer, except the targeted fragment. Agarose gel electrophoresis of PCR products also demonstrated that only targeted fragment was amplified. The relative quantification of gene expressions among the treatment groups was analyzed by the 22DDCt method [40], where Ct is the cycle number at which the fluorescent signal rises statistically above the background. Microcystin analysis Aliquots (30 mL) were centrifuged to collect the M. aeruginosa bodies. The aliquots were then resuspended in 300 mL of Milli-Q water to extract the microcystins using the boiling water bath method, as described by Metcalf and Codd [41]. The MC content was calculated by a standard curve, which was drafted from standard microcystin-LR (MC-LR) that was purchased from Sigma-Aldrich (CAS number: 101043-37-2, analytical standard). 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