Cyanobacteria bloom in tropical reservoir

Blooms of the cyanobacterium Microcystis can be a major hazard in recreational lakes, drinking water reservoirs and protected wetland areas. The microcystins produced by them are of major concern in water management. Thus there is a need to investigate what triggers the toxin production of Microcystis spp.. The effect of light plays a significant role in the growth of Microcystis spp. as well as affecting the toxin production. A series of experiments were performed and among them a control experiment was set up and normal white light was used as the light source. In addition, the effect of different coloured light was experimented using green, red and blue translucent films to block out all other wavelengths of light. The light intensity of the coloured lights was also varied to determine the relationship between coloured lights intensity and toxin production. The light-dark cycle was also involved to stimulate the toxin concentration per unit cell. All experiments underwent similar conditions and same set of tests (toxin, optical density and chlorophyll-a). The toxin concentration per unit chlorophyll is observed to be higher in experiments involving high coloured light intensity. The samples under the influence of light-dark cycle produced less microcystins and showed little effect to trigger toxin production. The generality of this finding deserves further investigation with the usage of appropriate light meter to control the desired light intensity and a more sensitive toxin test to determine the accuracy of the concentration of the toxin produced.Bachelor of Engineering (Environmental Engineering