PERFORMANCE OF SPIODELA POLYRHIZA AND ALTERNANTHERA PHILOXEROIDES IN REDUCING SALINITY AND ALKALINITY AND THEIR EFFECTS ON WATER QUALITY

The experiment was conducted in Daluhu aquaculture site, Gaoqing County, Shandon g Province during August and December, 1998. It was aimed at study on the effect s of applications of aquatic plant Spiodela polyrhiza and Alternanthera philoxer oides on the chemical and hydrobiological factors in brackish-water ponds. Spiod ela polyrhiza and Alternanthera philoxeroides's performance in reducing salinity and alkalinity had also been studied. The results show that Alternanthera philo xeroides had no significant effect on reducing salinity and alkalinity. Spiodela polyrhiza also had no significant effect on reducing salinity, but it was evide nt that Spiodela polyrhiza could reduce alkalinity, lead to increasing pH values and reducing Calcium concentrations. In addition, they were able to reduce the concentrations of nutrients and phytoplankton biomass, but their effects on zoop iankton had not been observed.