Abstract

Seven strains of cyanobacteria from Tri An Reservoir, a drinking water reservoir for millions of people in Southern Vietnam, were isolated, cultivated, identified and described. They originated from the species Microcystis aeruginosa, M. botrys, M. wesenbergii, Anabaena circinalis, A. smithii, Aphanizomenon aphanizomenoides and Cylindrospermopsis raciborskii. Microcystin (MC) content in the cultures and two scum samples from Tri An Reservoir were determined by high performance liquid chromatography. Four variants of MC, MC-LR, MC-RR, MC-LA, MC-LY and one un-determined variant were detected in the scum samples but none were found in the cultures. The two variants MC-LA and MC-LY were recorded for the first time for Vietnam. Total MC concentrations in the two scum samples were 0.45 and 0.64 mg g-1 dried weight, respectively. The genus Microcystis in Tri An Reservoir was assumed to be a MC producer as the other possible MC producing species A. circinalis was usually detected in lower quantities.