Comparison Study Of Community Structure Of Metazoan Zooplankton Between Inside And Outside Of Bio-manipulation Area And Engineering Demonstration Area In Lake Gehu.

Lake Gehu, is located in the upstream of Taihu River on the west side of Changzhou and Wuxi City, which is a shallow lake occupy an important position in southern Jiangsu area, the average depth of less than 2 metre. It is not only provide drinking water for the residents of nearby towns, but also bring huge economic benefits for people as an important aquaculture base. With the increasing of aquatic breeding and irrational development water quality of Lake Gehu become more eutrophication. Many scholars believe that the use of filter-feeding stocking silver carp, bighead carp non-classical biological methods can be directly manipulated algae control algae outbreaks, thereby improving water quality, some scholars believe that the implementation of environmental or ecological dredging project can significantly improve the pollution situation quickly. From July 2013 to June 2014, comparative experiment was carried out to study the community structure of meta-zooplankton in three regions of Lake Gehu. The three regions include engineering demonstration area, inside and outside of bio-manipulation pen. Using freshwater plankton survey method to study the relationship between species composition, dominance, standing crop, species diversity of meta-zooplankton and water quality parameters. Provide basic information and scientific basis for improving Lake Gehu eutrophication and ecological networks around the high-income farming. The main results are as follows:1. A total of 92 species of meta-zooplankton were collected and identified from Lake Gehu, belonging to 26 families and 45 genera, which 75 species were identified from inside of bio-manipulation area, 79 species were identified from outside of bio-manipulation area and 71 species were identified from engineering demonstration area.Percentage of rotifers and copepods accounted metazoan zooplankton total density are: inside of bio-manipulation area(94.7%, 2.6%)> outside of bio-manipulation area(94.2%, 2.3%)> engineering demonstration area(89.9%, 1.9%), cladoceras: inside of bio-manipulation area(2.7%) < outside of bio-manipulation area(3.5%) <engineering demonstration area(8.2%); rotifers as a percentage of the total biomass of metazoan zooplankton is: outside of bio-manipulation area(32.4%)> f inside of bio-manipulation area(33.3%)> engineering demonstration area(26.3%); copepods: inside of bio-manipulation area(28.2%)> outside of bio-manipulation area(16.6%)> engineering demonstration area(12.3%); cladoceras: inside of bio-manipulation area(39.4%) < outside of bio-manipulation area(50.1%) <engineering demonstration area(61.3%). While rotifers in three regions of biological density of about 90% of the total, but because of its wet weight compared with copepods and cladocers many small, so little percentage of biomass.2. A total of 51 species of rotifers were identified, belonging to 22 genera and 14 families, of which, 38 species of inside of bio-manipulation area, 44 species of outside of bio-manipulation area, 39 species of engineering demonstration area. Dominant species throughout the year were: Brachionus angularis, Polyarthra trigla, Keratella valga, Polyarthra dolichoptera and Filinia longiseta and so on. The rotifer species of three regions similar medium, including pollution indicating species respectively as 29, 35 and 32. Analysis of variance of existing amount of rotifers showed that there were significant differences or extremely significant difference between any two of three regions, and the standing crop of: engineering demonstration area [density(1216 ± 330) ind ? L-1, biomass(1.589 ± 0.328) mg ? L-1]> outside of bio-manipulation area [density(939 ± 220) ind ? L-1, biomass(0.991 ± 0.316) mg ? L-1]> inside of bio-manipulation area [density(428 ± 96) ind ? L-1, biomass(0.364 ± 0.100) mg ? L-1]. The value of diversity index H ’: outside of bio-manipulation area > engineering demonstration area > inside of bio-manipulation area; value of diversity index J: inside of bio-manipulation area > engineering demonstration area > outside of bio-manipulation area; value of diversity index D: engineering demonstration area> outside of bio-manipulation area > inside of bio-manipulation area. The results of Canonical correspondence analysis(CCA) showed that water temperature(T), dissolved oxygen(DO), permanganate index(CODMn), total nitrogen(TN) and total phosphorus(TP) were the main environmental variables affecting the community structure of rotifer.3. Atotal of 22 species of cladocera were identified, belonging to 11 genera and 6 families, of which, 19 species of inside of bio-manipulation area, 18 species of outside of bio-manipulation area, 16 species of engineering demonstration area. Dominant species throughout the year were: Bosmina longirostris, B. fatalis, Ceriodaphnia cornuta, Moina rectirostris, Diaphanosoma excisum, D. leuchtenbergianum and Moina micrura and so on. The species of cladocera in three regions are similar between inside and outside of bio-manipulation area, extremely similar between inside of bio-manipulation area and engineering demonstration area, outside of bio-manipulation area and engineering demonstration area.The largest number of species of cladoceras appeared in summer and in autumn the situation were opposited. LSD from multiple comparison showed that extremely significantly difference of standing crop of cladoceras were found between inside of bio-manipulation area and engineering demonstration area, outside of bio-manipulation area and engineering demonstration area. The standing crop of copepods are: engineering demonstration area [density(121.5 ± 16.7) ind ? L-1, biomass(4.214 ± 0.930)mg ? L-1]> outside of bio-manipulation area [density(38.7 ± 20.6) ind ? L-1, biomass(1.642 ± 0.926) mg ? L-1]> inside of bio-manipulation area [density(12.3 ± 1.4) ind ? L-1, biomass(0.456 ± 0.034) mg ? L-1]. The values of diversity index H ’, J and D are: engineering demonstration area < outside of bio-manipulation area < inside of bio-manipulation area. The results of redundancy analysis(RDA) showed that the water temperature, permanganate index, dissolved oxygen, transparency and chlorophyll a were the main environmental variables affecting the community structure of cladoceras.4. A total of 19 species of copepods were identified, belonging to 12 genera and 6 families, of which, 18 species of inside of bio-manipulation area, 17 species of outside of bio-manipulation area, 16 species of engineering demonstration area. Dominant species throughout the year were: Microcyclops varicans, Eucyclops serrulatus, Mesocyclops leuckarti, Sinocalanus dorrii, Limnoithona tetraspina, Schmackeria forbesi and Thermocyclops brevifurcatus and so on. The species of copepods in three regions are extremely similar, the largest number of species of copepods appeared in summer and in autumn the situation were opposited. LSD from multiple comparison showed that significantly difference of copepods biological density was only found between inside of bio-manipulation area and engineering demonstration area(P = 0.025 <0.05); extremely significant difference of biomass was found between inside of bio-manipulation area and engineering demonstration area(P = 0.003 < 0.01), significant difference of biomass was found between outside of bio-manipulation area and engineering demonstration area(P = 0.040 <0.05).The standing crop of copepods are: engineering demonstration area [density((28.7 ± 9.2) ind ? L-1, biomass(0.819 ± 0.113) mg ? L-1]> outside of bio-manipulation area [density(24.9 ± 7.4) ind ? L-1, biomass(0.542 ± 0.188) mg ? L-1]> inside of bio-manipulation area [density(11.6 ± 3.1) ind ? L-1, biomass( 0.317 ± 0.051) mg ? L-1].The values of diversity index H ’ and J are: outside of bio-manipulation area > inside of bio-manipulation area > engineering demonstration area, within the value of D : inside of bio-manipulation area > outside of bio-manipulation area > engineering demonstration area. The results of redundancy analysis(RDA) showed that the water temperature, permanganate index, dissolved oxygen, transparency and chlorophyll a were the main environmental variables affecting the community structure of copepods.The density of the total annual standing crop of metazoan zooplankton are: inside of bio-manipulation area(4972.1 ± 7922.7) ind ? L-1 < outside of bio-manipulation area(10970.2 ± 17345.3) ind ? L-1 <engineering demonstration area(14885.3 ± 21899.1) ind ? L-1, the annual average: inside of bio-manipulation area(150.6 ± 240.2) ind ? L-1 < outside of bio-manipulation area(334.2 ± 524.1) ind ? L-1 <engineering demonstration area(455.3 ± 660.3) ind ? L-1, the total annual biomass are: inside of bio-manipulation area(12.379 ± 2.068) ind ? L-1 < outside of bio-manipulation area(32.787 ± 16.401) ind ? L-1 <engineering demonstration area(66.449 ± 50.171) ind ? L-1, the annual average: inside of bio-manipulation area(0.379 ± 0.071) ind ? L-1 < outside of bio-manipulation area(1.059 ± 0.551) ind ? L-1 < engineering demonstration area(2.207 ± 1.779.) ind ? L-1. Whether it is the total of annual standing crop or annual average of standing crop of metazoan zooplankton are: inside of bio-manipulation area < outside of bio-manipulation area < engineering demonstration areas.The results of experiment showed that the use of silver and bighead carp control algae and dredging works would caused metazoan zooplankton species become small. Because of silver and bighead loved to predate metazoan zooplankton, so the standing crop of metazoan zooplankton become smaller in inside of bio-manipulation area. The standing crop of engineering demonstration area were very high indicated that dredging project benefited to the survival and rebuilding of metazoan zooplankton ecosystems.