CAN WATER HYACINTH (EICHHORNIA CRASSIPES) BE CONTROLLED BY REDUCING NITROGEN AND PHOSPHORUS POLLUTION OF WATER BODIES?

Abstract

Increasing concentration of nutrients in water is regarded as one of the most important external factors responsible for the invasion of the common water hyacinth. In order to test whether nutrient availability limits the growth and spread of this species, we investigated the influence of water nitrogen (N) and phosphorus (P) concentrations on growth using both greenhouse and field experiments. We found that in the greenhouse experiment, only high P concentration (>1.25 mg l -1 ) can significantly increase numbers of ramets and leaves, and N concentration exceeding 62.5 mg l -1 can greatly increase water hyacinth biomass in a tank. In the field experiment, the clonal growth of water hyacinth was not correlated with N and P concentrations in water bodies where the range of N and P concentrations was narrow compared with their range in the greenhouse. This suggests that controlling water hyacinth through minimizing sewage discharging is impractical, the importance of the ability of water hyacinth to grow clonally should be considered.