The effect of pure microcystin (microcystin-RR) from Microcystis aeroginosa (Kützing, 1846) on the survival of Daphnia magna (Straus, 1820) and determination of its lethal concentration (LC50-96h)

This study was carried out to investigate the effect of Microcystin-RR (MC-RR) extracted from Microcystis aeroginosa microalgae on Daphnia magna and determine the lethal concentration of this toxin (LC50-96h). Twenty-one Daphnia magna were exposed to concentrations of 0.5, 2, 10, 20 and 50 μg.ml-1 of MC-RR Microcystin in each replicate, and the daphnia survival for 24 to 96 hours was calculated. One treatment was considered as control (no toxin), each treatment had 3 replications. According to the results of this study, microcystin (MC-RR) had a lethal effect on Daphnia magna, so that even at a low concentration (concentration of 0.5), about 38% of mortality was observed, and none of the Daphnia magna had the ability to survive at 2 μg.ml-1 of pure MC-RR Microcystin for 96 hours. This ability decreased by increasing the concentration of poison, so that at the concentration of 10 μg.ml-1 of Microcystin, on the second day and at concentrations of 20 and 50 μg.ml-1 of poison, all daphnia were dead on the first day. The results of this study showed that in the concentration of 1.75 μg.ml-1 MC-RR Microcystin, during 96 hours, 99 percent of daphnia were died.