苏皖交界河网区后生浮游动物群落结构及其影响因子分析

Characterization of Zooplankton Community Structure and Environmental Factors in the Qingyi/Guxi River Network

鉴于长江中下游河网水流条件复杂,河流生境变化导致的浮游动物群落结构特异性,于2012年10月(平水期)和12月(枯水期)在长江下游江苏和安徽交界处的河网区布设6个采样点,进行轮虫和甲壳动物采样调查,并检测NH+4-N、NO-2-N、TN、TP、CODMn和Chl.a含量等水环境指标。结果表明,河网区共检出轮虫31种,优势种包括螺旋龟甲轮虫(Keratella cochlearis)和疣毛轮虫(Synchaeta sp.)等;枝角类14种,优势种为象鼻溞(Bosmina sp.);桡足类20种,优势种为跨立小剑水蚤(Microcyclops varicans)、中华窄腹剑水蚤(Limnoithona sinensis)和温剑水蚤(Thermocyclops sp.)。轮虫密度最高,平均为350.69个/L,其次为桡足类3.44个/L,枝角类最少,仅0.15个/L。轮虫和甲壳动物的季节变化规律不同,平水期的轮虫种类多于枯水期,枝角类和桡足类则相反,浮游动物的密度变化规律也类似。CCA分析表明,氮、磷、CODMn和Chl.a共同影响了浮游动物的群落结构与分布,枯水期轮虫密度与枝角类和桡足类密度均显著正相关(P<0.01),叶绿素a与3类浮游动物密度也显著正相关(P<0.05)。受长江汛后水文条件的影响,河网区浮游动物群落组成及优势种变化有其特定规律,轮虫与甲壳动物的种间关系也对其种类和密度的季节变化造成影响,而食物限制则是枯水期种群竞争的重要因素。

Qingyi River and Guxi River, located in the border area of Jiangsu Province and Anhui Province, con-nect the Yangtze River and Shijiu Lake.These rivers, along with the Qingshan River, Yunliang River and other small connector streams, form a complex river network in the lower reaches of the Yangtze River.The hydrology in the network is complex, influenced by the Yangtze River and regulation of impounded waters, and this is reflected in the zooplankton community structure.Rotifer and crustacean populations were investigated in 2012 during the normal （ October） and dry （ December） seasons at six sample sites in the river network.The species composition of zooplankton and variations in the standing stock were determined and the inter-specific relationship of the zooplank-ton populations and the relationship of the zooplankton community to environmental factors were discussed.The re-sults provide basic data to support continued study of the zooplankton community and manage zooplankton succes-sion in the river network.Samples for qualitative analysis of rotifers were collected with a No.25 plankton net and fixed with 5%formalin.For quantitative analysis, 2 L water composite samples were collected by mixing water from the surface, middle and bottom layers at each sample site and fixing with Lugol′s solution.Crustacean samples for qualitative analysis were collected with a No.13 plankton net.Crustacean samples for quantitative analysis were collected by filtering 20 L of water through a No.25 plankton net and fixing with 5%formalin.Zooplankton in all samples were classified and identified in the laboratory.The water quality parameters, NH4＋-N, NO2--N, TN, TP, CODMn , Chl.a,were determined according to Water and Wastewater Monitoring Analysis Methods.In total, 31 spe-cies of Rotifera （ dominant species： Keratella cochlearis and Synchaeta sp.） , 14 species of Cladocera （ dominant species：Bosmina sp.） and 20 species of Copepoda （ dominant species：Microcyclops varicans, Limnoithona sinensis and Thermocyclops sp.） were identified.Rotifera density was the highest （ average value, 350.69 ind/L） , followed by Copepoda （3.44 ind/L） and Cladocera （0.15 ind/L）.Seasonal variation of species richness and population density of rotifers was different than that for crustaceans.For rotifers, species richness and population density were higher in normal season than in dry season, while species richness and population density for crustaceans displayed the opposite patterns.Canonical correspondence analysis （ CCA） indicates that the zooplankton community struc-ture and distribution are influenced by nitrogen, phosphorus, CODMn and Chl.a.During dry season, there is a sig-nificant positive correlation between the population densities of Rotifera, Cladocera and Copepoda （P〈0.01） and the density of all three populations with Chl.a（P〈0.05）.In conclusion, zooplankton community structure and the succession of dominant species in the river network follows specific patterns determined by the hydrological condi-tion after flood （ high flow ） season and the inter-specific relationship of rotifers and crustaceans.During dry sea-son, the restricted food supply is a primary factor in the competition among zooplankton populations.