Application of an Effective Microorganism Product as a Cyanobacterial Control and Water Quality Improvement Measure in Putrajaya Lake, Malaysia

Abstract

This study investigated the effects of effective microorganism (EM) in reducing the cyanobacterial density and improving the water quality and phytoplankton diversity. Four thousand litre of EM was sprayed over an area of 0.7 ha in a semi-enclosed area of the Putrajaya Lake. Sampling and analysis of water quality and phytoplankton were carried out at three locations over a period of 50 days. The results of the study showed that EM treatment temporarily reduced the cyanobacterial density from 3909.5 to 2200.9 cells/ml after 18 days, but the density began to increase again soon after. Similarly, mean phytoplankton density showed similar pattern to the cyanobacterial trend of decreasing density after application but started to increase 3 weeks afterwards. Cyanobacteria was the dominant phytoplankton group before and during EM treatment. Cyanobacterial dominance decreased 55.2% after EM application resulting in more balanced phytoplankton assemblages 18 days after treatment before regaining its dominance 3 week after EM application. Nostoc sp. was the main cyanobacterial species before-, during and after EM treatment. Only pH significantly differed after the EM treatment; while, other parameters such as dissolved oxygen, chlorophyll-a, transparency showed no significant changes before and after EM application. This study illustrated that EM application did not provide sustained microalgae reduction nor water quality improvement throughout the experiment.