Phytoplankton composition and the occurrence of cyanobacterial bloom in Lake Maninjau, Indonesia

Abstract Algae blooms have been recorded in Lake Maninjau in November 2000, October 2011 and recently on April 2018. These blooms were indicated by green scum formation on the lake surface with a very high chlorophyll-a concentration, as high as > 100 µg-L. We determined the characteristics of phytoplankton composition and abundance including environmental conditions during cyanobacterial blooms and non-cyanobacterial blooms in Lake Maninjau. During cyanobacterial blooms, phytoplankton were dominated by Microcystis aeruginosa with a maximum abundance of 24,320 x 103 individual L-1 (94.4 % of the total assemblage). While during the non-blooming period, cyanobacteria species were more diverse, represented by Cylindrospermopsis raciborskii, Anabaea affinis, Aphanizomeon sp, Planktolyngbya sp. and Chroococcus sp. Diatom (Synedra ulna) generally occurred in all conditions, however, desmids (green algae) disappeared during cyanobacteria blooms. It is highlighted that the occurrence of Microcystis blooms can be related to total phosphorous dynamics in the lake.