The main objective of this study was to confirm and estimate the algal inhibiting effects of the ethanol and ethyl acetate E. fortunei extracts at concentrations of 500 in some natural water samples collected from Hoan Kiem and Lang Lakes. The results of this work may be useful for controlling the toxic cyanobacterium bloom in natural aquatic ecosystem. | HNUE JOURNAL OF SCIENCE Natural Sciences 2020 Volume 65 Issue 4A pp. 11-20 This paper is available online at http EFFECT OF PLANT EXTRACTS FROM Eupatorium fortunei TURCZ ON THE GROWTH OF PHYTOPLANKTON COMMUNITIES IN NATURAL WATER SAMPLES COLLECTED FROM HOAN KIEM AND LANG LAKES Pham Thanh Nga1 Le Thi Phuong Quynh2 Nguyen Tien Dat3 and Dang Dinh Kim4 1 Hanoi National University of Education 2 Institute of Natural Products Chemistry Vietnam Academy of Science and Technology 3 Center for Research and Technology Transfer Vietnam Academy of Science and Technology 4 Institute of Environmental Technology Vietnam Academy of Science and Technology Abstract. This study presents the inhibited effect of these extracts on the growth of Microcystis and phytoplankton communities in natural water samples collected from Hoan Kiem and Lang Lakes in a 10-day experiment. By using chlorophyll a concentration analysis the ethyl acetate extract at 500 mg L-1 indicated the highest toxicity with inhibition efficiency IE reaching - in Hoan Kiem and Lang s natural water samples respectively following by the CuSO 4-sample at 5 mg L -1 with IE of and and the E-ethanol sample with IE of and . The maximum inhibition of Microcytis growth was observed for the ethyl acetate extract during the experiment. However by cell counting methods the ethanol extracts showed selectively toxic to Microcystis in comparison with other phytoplankton communities in natural water samples collected from both lakes. It had the IE values around - for Microcystis genus which was much higher than those for other species such as green algae and silica algae - . The ethyl acetate extract and CuSO 4-samples did not indicate significant differences in the inhibition effects to the species in the communities with IE from - and - respectively. The results proved that the ethanol extract should be further investigated to use as
