The Response of Macrophytes to Nutrients and Implications for the Control of Phytoplankton Blooms in East Taihu Lake, China

Abstract

When macrophytes are growing in the eutrophicated aquatic ecosystem, the vegetation induces important effects to the water quality and phytoplankton concentrations in the water which affected by macroscopic physical, chemical and biological processes and the effects are the results of direct and indirect interactions of the aquatic plants and water body. The interactions between macrophytes, nutrients and phytoplankton blooms were examined in the water and sediments of a shallow, eutrophic and typical East Taihu, China. The importance of macrophytes as a sink for nutrients, and the inhibitory effect of macrophytes on phytoplankton bloom potential were assessed through three different seasons. Luxuriant aquatic plants growth in this system led to decrease available nutrients for phytoplankton and prevented bloom development. Uptake of N and P by aquatic plants accounted for a major portion of the observed N and P loss from the water column and sediments. Luxury uptake of N and P were indicated by high biomass and tissues N and P concentrations, indicating the capacity of macrophytes to act as a nutrient sink in midsummer. Dissolved inorganic N (DIN) and soluble reactive phosphorous (SRP) in water were reduced in midsummer in the presence of macrophytes. The use of macrophytes to reduce the nutrients in water system and thereby inhibit freshwater phytoplankton blooms should be considered as an effective management strategy in shallow eutrophicated lakes. As aquatic macrophytes also develops considerable indirect effects that could have a vital impact than the direct uptake the nutrients into the plant biomass.