Effect of Xenocypris microlepis on feces and microcystis activity from microcystis-dietary silver carp and bighead carp
GUO Yan-min1, GAO Yue-xiang2, ZHANG Yi-min2, SUN Li-wei1, HE Dong2, WU Dan2
1. School of Energy and Environment, Southeast University, Nanjing 210096, China; 2. Nanjing Institute of Environmental Science, Ministry of Environmental Protection, Nanjing 210042, China
Abstract：Effects on the amounts of feces and the activity of microcystis by the introduction of the different combination of Silver carp, bighead carp and Xenocypris microlepis were studied in indoor simulation experiments. During the experiment,three groups were set up:silver carp and bighead carp group, silver carp、bighead carp and Xenocypris microlepis group, blank control group, and the biomass proportion of silver carp and bighead was carp 3:1. The results showed that in both experimental groups, the densities of Microcystis aeruginosa were significantly reduced than blank control group (P<0.01). The feces weight in silver carp and bighead carp group continually increased, however, which of polyculture of Xenocypris microlepis group reached maximum on the 4th day, then declined rapidly, and finally was 16.08% of silver carp and bighead carp group at the end of the experiment. There were no obvious change in algae digestibility in silver carp and bighead carp group, while the algae digestibility of the polyculture of Xenocypris microlepis gruoup appeared rapid growth from 5th day, reached 85.9% at the end of the experiment, which was significantly higher than the silver carp and bighead carp group (P<0.01). The amino acid and nitrogen content in the feces of experimental groups decreased compared with those undigested Microcystis aeruginosa:the decrement in silver carp and bighead carp group were 33.17% and 53.62% and those in polyculture of Xenocypris microlepis were 34.97% and 53.62%, respectively. Furthermore, after Microcystis aeruginosa was digested by fish, chlorophyll fluorescence parameters (except NPQ) was significantly lower than the blank control group (P<0.05), but NPQ was significantly higher than the blank control group (P<0.05). Chlorophyll fluorescence parameters (except NPQ) in silver carp and bighead carp group increased after a brief decreasing. Fv/Fm、Fv/Fo、Yield and qP values in polyculture of Xenocypris microlepis group early rapidly declined at first, tended to be stable after the 11day, and 5days later were significantly lower than that of silver carp and bighead carp group (P<0.01). NPQ in polyculture of Xenocypris microlepis group showed ascendant trend, and then was significantly higher than that of silver carp and bighead carp group after the 7th day (P<0.01).During the feces cultivation, the EPS and Chla of feces in polyculture of Xenocypris microlepis group continually decreased, and until the end of the experiment, they was significantly lower than those of silver carp and bighead carp group (P<0.01).Beside the introduction of silver carp and bighead carp, the polyculture of Xenocypris microlepis could reduce the feces of silver carp and bighead carp by feeding Microcystis aeruginosa and further reduce the activity of the algae in feces therefore, improved the removal effect caused by Microcystis aeruginosa, provided theoretical basis for biomanipulation mode of polyculture of Xenocypris microlepis.
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