Untitled

Abstract

Invasion of aquatic habitats by non-native species is a global environmental challenge with serious ecological, social and economic consequences demanding urgent action. Water hyacinth's (Eichhornia crassipes) appearance in Koka Reservoir was reported in 1965 and has become a threat to the aquatic ecosystem. Even though there were several limnological and fish related studies, the effects of water hyacinth on water quality and phytoplankton composition and abundance in Koka Reservoir have not been addressed. To assess its effect on water quality, composition and abundance of phytoplankton in the reservoir, samples were collected from three weed-infested and three non-infested sites from March to July 2018. The phytoplankton community, which constituted of 62 species, was dominated by Bacillariophyceae followed by Cyanophyceae and Chlorophyceae at both weed-infested and non-infested sites. The variations in the Physico-chemical parameters, abundance and species richness (d) of phytoplankton between the two sites were significant, with higher mean values in the non-infested sites (P<0.05). The existing infestation level of water hyacinth poses a significant effect on water quality, composition, and abundance of phytoplankton. Therefore, continuous monitoring of Physico-chemical and biological water quality parameters and the development of a sustainable management strategy are deemed imperative.