To investigate the water purification effects of different floatingbed systems and their influences on aquatic organisms

floating-bed systems vegetated with Vetiveria zizanioides

Iris pseudacorus

Apium graveolens or their combinations respectively were constructed

6 species of phytoplankton as well as zebrafish (Danio rerio) were also added to the systems. The results showed that the three plant species could all grow well in the floating-bed. The growth of Vetiveria zizanioides and Iris pseudacorus were better than Apium graveolens. All floatingbed systems could prevent the increase of chemical oxygen demand (COD

Mn

) in water. However

no significant difference was observed among different floating-bed systems. Floating-bed systems could also remove the nitrogen and phosphorus nutrients in the water effectively

with V. zizanioides  having the best effect. In general

putting Danio rerio into the systems improved the water purification efficiency to some extent. Floating-beds cultivated with V. zizanioides significantly inhibited the growth of phytoplankton

while the inhibition effects of floating-beds vegetated with other plants were relatively lower or not significant. On the other side

the sensitivity of different phytoplankton species to floating-bed systems was different. The growth of D. rerio was significantly stimulated by floating-beds cultivated with V. zizanioides or I. pseudacorus

with V. zizanioides being more effective. Overall

V. zizanioides might be an excellent candidate for floating-bed cultivation in water purification and bloom prevention

while I. pseudacorus might be used in water purification of urban landscapes.