Study On Zooplankton Community Structures In The Wetland Restoration Area Of Lianghe Gulf, Taihu Lake

Lianghe gulf is located in the southwest corner of the Taihu Lakeand Northwest of Gonghu Lake with the surface area of256hectare,an average depth is1.8m, maximum depth3.5m, miximum depth0.6m.Taihu Lake (Lianghe gulf—Dasi Kong) artificial wetland restorationproject which is carried out by the municipal government of Wuxi,Bureau of Taihu Lake, Department of Water Resources in JiangsuProvince is the first implementation of key projects of Water Resourcesand an ecosystem restoration wetlands demonstration project, and ithas important ecological and social significance.Through surveying and monitoring the community structure of themicrocystis and zooplankton in the artificial wetland restoration area,The paper studyed the community structure of zooplankton and therelationship between zooplankton and microcystis so as to analyze thedistribution feature in different time and place in the artificial wetlandrestoration project and the relationship between microcystis andzooplankton community structure in the project area. This study bearsimportant guiding significance in controlling eutrophic lake in the future.It lays a biological foundation for water protection and tourismdevelopment in the future. The main results are listed as follows:1. There are56species of zooplankton were identified from Lianghegulf of Taihu Lake from March,2010to February,2011, which belong to30genera of16families. There are40species of Rotifera, belong to17genera of6families, which accounted for71%; There are5species ofCopepoda, belong to5genera of4families, which accounted for9%;11species of Cladocerca, belong to8genera of6families, whichaccounted for20%.2. There are5dominant species of zooplankton in Lianghe gulf:2 species of Rotifera: Polyarthra sp., Brachionus angularis.2species ofCladocerca: Bosmina longirostris、Ceriodaphnia cornuta. Nauplii is theonly dominant group of Copepoda. Bosmina longirostris is th first edominant species.3. The annual zooplankton mean density was860ind/L, rotifers:328ind/L, accounting for38.2%; copepods:133ind/L, accounting for15.5%;Cladocera:398ind/L, accounting for46.3%. The regional distribution:The zooplankton density in the center of lake was788ind/L; theminimum was688ind/L in periphery areas;846ind/L in mesocosm area;1003ind/L in the western area of the artificial Wetland RestorationProject;911ind/L in the east area. The monthly zooplankton meandensity of the whole area ranged from55to2314ind/L. The seasonaldistribution density was high in summer and autumn, low in the winterand spring. The maximum zooplankton density (3642ind/L) presented inthe enclosed area in the middle of September,2010. The minimumdensity (35ind/L) presented in the outer area in March,2010. Thezooplankton average annual monthly biomass was3.63mg/L. Thecenter lake was highest:4.34mg/L; The lowest was3.00mg/L in outerareas;4.23mg/L in the enclosed area;3.61mg/L in the western area ofthe artificial wetland restoration project;3.26mg/L in the east of there.The monthly mean biomass ranged from0.08to15.03mg/L, Themonthly maximum value (29.14mg/L) presented in the enclosed areain mid-September2010, and the minimum value was only0.04mg/L inthe center of lake in May2010.4. The microcystis group appeared from June to October,2010inthe Lianghe gulf. The monthly highest density of microcystis cell (893.89×106cell/L) appeared in July2010, the lowest was55.42×106cell/L inOctober. The average monthly microcystis density of enclosed areahighest was up to697.82×106cell/L, and was up to1134.97×106cell/L inenclosed area in July2010; the minimum value was448.95×106cell/L in the western area of the artificial wetland restoration project.5. The zooplankton community structure of Lianghe gulf waseffected by artificial wetland restoration project in the summer andautumn, especially by the engineering physical collection and aquaticplants biological purification of water bodies, but not obvious in springand winter. The study indicated that the excessive density ofmicrocystis significantly inhibited the survival of the zooplankton,especially the large zooplankton significantly. So the microcystissignificantly reduced the body and biodiversity of zooplankton. In theearly and late outbreak microcystis, appropriate density of microcystisincreased the density and diversity of zooplankton significantly.6. The value of Shannon-wiener index(H) in Lianghe gulf of TaihuLake fluctuated between0.83and2.48.The index(H) ranged from1.58to1.94in the different areas, the annual average index was1.76. As awhole area, the diversity index(H) was high from June to October2010,and lower in the spring and winter. It has different spatial and temporalin different areas in summer and autumn months. The regional averagediversity index(H) in engineering repair area was significantly higherthan others, which was lowest in the lake area and lower in theenclosed area. Upon the evaluation of biological diversity index, thewater quality of Lianghe gulf could be regarded heavy eutrophication,but the engineering repair area is relativelybetter than the other regions.