Effects of engineered use of water hyacinths (Eicchornia crassipes) on the zooplankton community in Lake Taihu, China

To evaluate the ecological consequences of engineered use of water hyacinths in Lake Taihu, China, we conducted a systematic survey of the dynamics of the zooplankton community (mainly copepods, cladocerans, and rotifers) inside (INE), around (ARE), and far-outside (FAE) a large-scale enclosure of water hyacinths in Zhushan Bay, Lake Taihu from August to November 2009 and calculated five response variables for the zooplankton community for each area. INE, ARE, and FAE differed little in their zooplankton composition at the genus level: the 16 of 21 identified genera were common and the same 6 zooplankton genera were dominant in all three areas, and only 5 sparse zooplankton genera were not collected from all three areas. The average abundance of each zooplankton faunal group and their annual trends displayed similar patterns in INE, ARE, and FAE. The only significant difference (p < 0.05) detected was between INE and FAE in the average abundance of cladoceran fauna (INE > FAE) and rotifer fauna (INE < FAE). The four diversity indices calculated for each zooplankton faunal group did not differ among INE, ARE, and FAE. These results suggest that the zooplankton community in Lake Taihu is not significantly affected by the engineered use of water hyacinths. Thus, use of Eicchornia crassipes appears to be an ecologically safe biomanipulation measure for purifying polluted water in temperate lakes such as Lake Taihu.