Interrelationship between water hyacinth and the new water weed in Lake Victoria, Homabay County

Abstract

Lake Victoria is facing an extinction threat from the rising pollution levels. It has been a sink to excessive nutrients and untreated effluent that has led to fish die-offs, algal blooms and the spread of ferocious invasive waterweeds. These invasive weeds cause economic losses estimated to be 0.3% GDP. This study aimed to determine comparative development, uptake and accumulation level of nutrients in water hyacinth and the “Superweed” as well as eutrophication level in the lake. The study was conducted during period of attack by the “Superweed” in Homabay County. Dominant macrophytes were “Superweed” and hyacinth occurring in mixed population or hyacinth sole population. Sites had very low transparency with elevated turbidity (3034-231 NTU) with pH values being slightly acidic (4.54-6.90). The primary eutrophic elements TN (11- 5 mg/L) and P (1.84-0.13 mg/L) were in concentrations higher than minimum allowed pollution standards (N<5mg/L and P<0.005 to 0.020 mg/L) an indication of eutrophication. The study recorded no heavy metal the region. A direct correlation was recorded between nutrient loading rate and nutrient content of macrophytes with TN, P and K being significantly different from each other (P≤0.05). Significantly higher TN, P and K, turbidity and Low pH was recorded in hyacinth sole population (p=0.05). It would therefore be recommended to use the “Superweed” as an animal feed and as soil organic amendments. In-lake management actions such as alum treatments should be applied however they require further studies.