GROWTH-RESPONSE OF THE CYANOBACTERIUM MICROCYSTIS-AERUGINOSA TO HERBICIDES AND PESTICIDES

Growth response of the planktonic cyanobacterium Microcystis aeruginos a to various concentrations of the herbicides and pesticides viz. CuSO 4, DCMU (analytical grade Diuron), Karmex (commercial grade Diuron), 2 ,4-D, Fernoxone, BHC and bleaching powder (CCH) was studied in laborat ory culture. The organism was sensitive to very low concentrations of CuSO4, DCMU and Karmex. Lethal concentration of Karmex and CuSO4 were found to be O.1 mu g.ml(-1) and 5.0 mu g ml(-1) respectively. The cyan obacterium could tolerate the other chemicals tested up to a concentra tion of over 500 mu g.ml(-1). On culturing the organism in the CuSO4 c ontaining media, toxic effect of the chemical was reduced to a signifi cant extent. This indicated that CuSO4 was accumulated or detoxified i n the Microcystis cells. Toxic effect of Karmex on the organism was no t reduced under similar experimental conditions.