Effect of two macrophyte species on phytoplankton growth and water quality in a eutrophic pond

To evaluate the ecological restoration effect of floating and submerged macrophytes on phytoplankton inhibition and water quality improvement, an enclosure experiment was undertaken in situ including Hydrilla verticillata mono enclosure, Eichhornia crassipes mono enclosure, and H. verticillata plus E. crassipes mixed enclosure. Concentrations of total nitrogen, ammonia nitrogen, nitrate nitrogen and total phosphorus were significantly lower in the vegetated enclosures than those in the control enclosure. Eichhorniacrassipes mono enclosure had significantly lower concentrations of ammonia nitrogen and nitrate nitrogen compared to the mixed enclosure. Purification ability was higher for faster growing macrophytes. The density and biomass of the phytoplankton in the plant enclosures were lower than those in the control enclosure, while the values in the mixed enclosures were significantly higher than those in the mono enclosures. Chlorophyta were the dominant algae in all the enclosures. Pyrrophyta and Cryptophyta were the co-dominant algae in the control enclosure. Therefore, macrophytes had a significantly inhibitory effect on phytoplankton, with the mono enclosures showing a stronger inhibitory effect compared to the mixed enclosures.