Effects of Water Hyacinth on Zooplankton Community and Some Species’ Genetic Structure
|School||Nanjing Normal University|
|Keywords||water hyacinth zooplankton engineered use ecological effect Daphnia pulex Sinocalanus dorrii microsatellite marker genetic structure|
Lake Taihu is a typical large, shallow lake located in delta of River Changjiang. In recent years, as a result of the discharges of urban sewage and industrial wastewater from nearby cities, nutrients of lake water have becoming more and more and its eutrophic level was also raising year by year. In order to reduce the excessive nutrients of lake water and drop its eutrophic level, water hyacinth has been planted as an effective biomanipulation measure in waters where eutrophic level was high. We established large-scale enclosures to restrict water hyacinth because they could reproducted rapidly and floated freely. This engineered use of water hyacinth was the first time in lake Taihu, it purified the polluted water while avoiding the excessive growth of water hyacinth. Growth of water hyacinth and improving of water quality may affected the aquatic ecosystem of lake Taihu to some extent. Zooplankton is an important class of organisms in keeping the balance of aquatic ecosystems, its population dynamics could reflect the variations of lake’s ecosystems. In this research, we studied the effects of engineered use of water hyacinth on the aquatic ecosystem of lake Taihu through investigating the population dynamics of zooplanktons. Meanwhile, we analysised the population genetic structure of Daphnia pulex and Sinocalanus dorrii with microsatellite markers. The main results are as follows:1、There were totally 22 genera of zooplanktons were identified from all the samples collected from 33 sampling sites, among which 7 genera were found to belong to cladoceran,5 genera to copepod and 10 genera to rotifer, and their distributions among INE, ARE and FAE were very similar. The dominant genera of all three zooplankton faunas were congruously the same in three areas. The mean abundance of three zooplankton faunas gave some different performance in three areas, with the cladoceran faunas’ and copepod faunas’ in INE and ARE significantly (p<0.05) and to some extent respectively higher than that in FAE and rotifer faunas’ in INE significantly lower (p<0.05) than that in FAE and ARE. Trends of each zooplankton fauna’s mean abundance in three areas showed the similar patterns. The diversity indices of each zooplankton fauna also gave a very similar performance among the three areas.2、The population genetic structure of Daphnia pulex in the three areas was analyzed using 8 microsatellite markers. The results showed that the number of alleles had a similar distribution in all microsatellite loci and the gene heterozygosity showed no significant difference among the three areas (p>0.05). All loci’s polymorphic information content (PIC) was>0.5, which showed that they were all highly polymorphic loci. There was also no significant difference among the three areas. It was certified that linkage disequilibrium (LD) was not identified between any pairs of loci (p>0.05), Dp321 was found departed from Hardy-Weinberg equilibrium (HWE) (p<0.05), Dp50 and Dp616 were found departed from HWE significantly (p<0.001). Viewed from the mean level of genetic diversity, the populations in INE and ARE were slightly higher than that in FAE. The genetic similarity coefficient among the three populations was high and standard genetic distance (Ds) was low and the Ds between INE and ARE was lowest.3、Five microsatellite markers which were got through FIASCO were used to analyze the population genetic structure of Sinocalanus dorrii in INE, ARE and FAE. The results showed that the number of allele in the three populations was similar, gene heterozygosity was high, polymorphic information content (PIC) was>0.5 which indicated that the 5 loci were all highly polymorphic loci. There was no significant difference on genetic diversity among the three populations (p>0.05). It was certified that linkage disequilibrium (LD) was not identified between any pairs of loci (P>0.05), TCl52 departed from HWE significantly (p<0.001). The population’s mean level of genetic diversity in INE and ARE was slightly higher than that in FAE. The genetic similarity coefficient (I) among the three populations was high and standard genetic distance (Ds) was low and the Ds between INE and ARE was lowest.Main conclusions:1) The engineered use of water hyacinth did not alter the community structure, richness, diversity and dynamics of the zooplankton significantly.2) The analytical results on the genetic structure and genetic diversity of Daphnia pulex and Sinocalanus dorrii with microsatellite marker indicate that the engineered use of water hyacinth did not alter the dominant population’s genetic structure of zooplanktons significantly, either not cause significantly genetic differentiation.3) The research results on community structure and genetic structure of zooplankton both indicate that the engineered use of water hyacinth can’t lead any severe ecological effect to the lake’s ecosystem. It is an ecologically safe measure. This biomanipulation measure shows a great application potential in fighting the water pollution in temperate lakes like Lake Taihu.