The Impact of Water Hyacinth (Eichhornia crassipes) on Composition and Abundance of Macrophytes and Phytoplanktons, and on Water Quality in Lake Abaya, Southern Ethiopia

Abstract

The impact of water hyacinth (Eichhornia crassipes) on macrophytes, phytoplankton and some physicochemical parameters of water was studied in south western part of Lake Abaya in Gamo Gofa Zone, SNNPRS of Ethiopia. The study was made in two cases in which one with water hyacinth (Eichhornia crassipes) infested and the other with non-infested sites each one consisting of 30 plots. Macrophyte plant samples were collected, dried (using herbarium techniques) and identified (using Ethiopian flora). For phytoplankton studies, two liters of water sample were collected under sterile condition, filtered with 10µm pore size membrane filter, preserved with luglose solution and plankton identification was carried out using inverted microscope. The results showed that water hyacinth negatively affect the abundance of macrophytes by reducing 20% and changing the community into nearly monotypic. However, some macrophytes species from Poaceae and Cyperaceae family were observed to share the same niche with the alien plant. The results also indicated that water hyacinth affect phytoplankton abundance and distribution. Cyanophyceae, Bacillariophyceae and some Chlorophyceae were observed co-existing with the alien species whereas most Chlorophycaea and Dinophyceae were excluded from the niche. The less frequently occurrence of the nuisance Microcyst in infested sites might be contributed to some beneficial impact of the plant. The ANOVA result showed that except salinity there is significant variation of water quality measurements among groups (sites). The Pearson’s correlation analyses also showed that water hyacinth negatively correlated with turbidity, chl-a, DO, Salinity, conductivity and TSS, and positively correlated with TDS and pH of the water. In addition, multivariate correspondence analyses of discrimination measures showed that the alien plant discriminate some of water quality parameters like TDS, DO, TSS and Turbidity more than other macrophytes do. Water hyacinth has the potential to alter the floristic composition, abundance and diversity of plants of the wetland ecosystem. The spreading of the water hyacinth has to be checked and halted before it cause irreversible distraction on the ecosystem