Abundance and structure of phytoplankton in Lake Chitgar during 2017-19 and comparison with previous studies

This study focused on phytoplankton structure and compared with previously study at the 5 stations between 2017 and 2019 in the Chitgar Lake. This study identified 37 phytoplankton taxa comprised of Diatoms (12 genus), Chlorophyta (10 genus), Cyanophyta (8 genus), dinoflagellates (3 genus), chrysophytes (1 genus) and Euglenophyta (3 genus) in the lake. The finding showed, the Diatom abundance dominate (average of 8700000 ± 7900000 cells.l-1) in the lake. The annual average phytoplankton abundance was calculated as 13400000, with the maximum value recorded in March 2018 (23000000 ± 8500000 cell. l-1). The results showed that the abundance of phytoplankton increased (more than 5-fold). Chlorophyll a, 0.5 μg / L was recorded in this study, which was 5 times more than in 2013-14. Phacus, Trachelomonas and Euglena genera from Euglenophyta phylum were first observed in lake, the presence of Euglenophyta indicating increased lake contamination trend. The abundance and species diversity of green-blue algae decreased after release of silver carp in the lake in June 2019. The abundance of Oscillatoria increased from 800,000 cell. l-1 in September 2018 to 200,000 cell. l-1 in June 2019. The decrease in cyanophyta abundance has prevented the unpleasant odor and prevented the increase of insects in the environment around the lake, preventing aquatic mortality and increasing trend of tourists.