Phytoplankton composition and abundance in the floating treatment wetlands (FTWs) system of Lake Maninjau, Indonesia

Abstract

Algae blooms have been recorded several times in Lake Maninjau and recently in April 2018. Floating treatment wetlands (FTWs) system was installed in June 2018 in Lake Maninjau as one of the methods to reduce the risk of eutrophication in this lake. The study is to reveal the characteristics of phytoplankton composition and abundance including environmental conditions in the FTWs system in Lake Maninjau. TP concentrations tend to decrease due to nutrient dynamics such as the dilution effect of precipitation which shifting the dominant of phytoplankton composition during observation. There were two different groups separating phytoplankton composition between the inside and outside of the FTWs system. The dominant species of Aphanizomenongracile and Synedra ulnawere related to high conductivity and the TP concentration while Oscillatoriaformosa was related to the high temperature. Phytoplankton abundanceon the inside of FTWsdecreased over time compared to the outside of FTWs, while chlorophyll-a fluctuated with the average value of 6.79 µg.L−1 on the inside of FTWs and 9.54 µg.L−1 on the outside of FTWs. This study suggests that the FTWs could potentially reduce the chlorophyll-a thereby minimizing the risk of eutrophication in a tropical lake.