Water hyacinth (Eichhornia crassipes) affects the composition and abundance of zooplankton in the littoral region of Koka Reservoir, Ethiopia

Water hyacinth,Eichhornia crassipes(Martius) Solms 1883, is a rampant invasive aquatic plant that is recognised as one of the ten worst weeds in the world. Its appearance in Koka Reservoir was reported in 1965 and since then it has become a major threat to the aquatic ecosystem. Despite numerous limnological studies on Koka Reservoir, the effects of water hyacinth on zooplankton has not been addressed previously. To assess this, samples were collected from three weed-infested and three non-infested sites from March to July 2018. The zooplankton community living, which was constituted of 38 species, was dominated by Rotifers, followed by copepods and cladocerans at both sites. The variations in the abundance of zooplankton and species richness (d) 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 the composition and abundance of zooplankton. Therefore, continuous follow-up, such as physical removal of the weed and constructing buffer zone and designing sustainable management strategies, have to be addressed.