Calculating growth rate of water hyacinth pollution wise (in relation to trophic state)

Abstract

This study was carried out with respect to calculating growth rate of water hyacinth in relation to the trophic state of the water body. 50 water hyacinth plants about 10 from each lake were taken. The concentrations of phosphorous, nitrogen, potassium and calcium were determined. Biochemical oxygen demand and dissolved oxygen were also determined. Various growth aspects like total number of leaves were counted, root and petiole length were recorded, leaf area was plotted to obtain surface area. Growth Index was calculated based on fresh weight of the plant was chosen to study the growth of water hyacinth with respect to pollution levels of the 5 lakes. Growth Index was calculated using the equation GI = (A / M) ------- where M = Mean fresh weight of 530 water hyacinth plants collected from 5 lakes. A = Mean fresh weight of 10 water hyacinth plants collected from a particular lake in a particular month. A correlation of GI to pollution status of lakes was made and a correlation of lake water constituents with growth parameters of water hyacinth was done: The fresh mean weight of water hyacinth plants collected over 12 months period was distinctly higher for polluted Lakes when compared to less polluted lakes. Mean petiole length of plants collected from Yelahanka, Nagavara and Hebbal Lakes (polluted) were greater as compared to those collected from Jakkur and Doddabommsandra Lakes (less polluted). TSI based on TP was 88.28 for Nagavara lake which was Hypereutrophic and eutrophic for Jakkur lake where TP was 69.81. GI of water hyacinth plants showed a correlation coefficient of +0.62 to TP. This study concludes that higher the pollution level of the lake, higher would be the growth rate of water hyacinth. Polluted lakes had strong and sturdy petioles and more GI compared to less polluted lakes. TP versus GI, showed a good positive person's correlation coefficient. TP the limiting nutrient has significant impact on the pollution level