Analysing the effect of water hyacinth ( Eichhornia crassipes ) invasion on water quality and trophic state of Lake Tana

The spread of invasive species, such as water hyacinth, has a serious impact on biodiversity, ecosystem services and the productivity of aquatic ecosystems. This study aims to study the invasion of water hyacinth has influenced physical and chemical water qualities, as well as the trophic state of Lake Tana. A total of 27 samples were collected and analysed following the procedures outlined in the methodology. The trophic state was determined using phosphorus and chlorophyll-a concentrations to evaluate the impact of the water hyacinth on the lake's trophic condition. The results indicate that the physical quality of the lake was significantly affected by the water hyacinth invasion (p < 0.005). Similarly, the chemical quality of the lake showed a significant deterioration due to the invasion (p < 0.05). The trophic state differed markedly, with the lake being classified as oligotrophic in the invaded areas (TSI-TP, 23.17–31.64) and in non-invaded areas (TSI-TP, 2.31–24.39). However, in terms of chlorophyll-a content, the lake's trophic state ranged from mesotrophic to eutrophic in both invaded (TSI-Chl, 59.34–63.36) and non-invaded (TSI-Chl, 19.72–54.76) zones. The findings suggest that the invasion of water hyacinth has significantly impacted the physical, chemical and trophic states of Lake Tana.