皖河口江豚主要栖息地浮游动物群落结构特征

Zooplankton Community Structure in Main Habitat of Yangtze Finless Porpoise,Confluence of Wanhe River and the Yangtze River

探究皖河口浮游动物群落结构特征及其主要影响因素,可为长江江豚(Neophocaena asiaeorientalis asiaeorientalis)主要栖息地的生境保护与动态评估提供科学依据。2017年12月、2018年4、6、9月对皖河口4个断面的浮游动物密度、生物量和水环境因子进行调查,运用Pearson相关性和冗余(RDA)分析,解析浮游动物与水环境因子之间的关系。结果显示,调查期间共鉴定出浮游动物32属、47种,其中原生动物(20种)占优,轮虫(12种)和枝角类(11种)次之,桡足类(4种)较少。全年共出现优势种6种,主要为原生动物和轮虫,仅出现螺形龟甲轮虫(Keratella cochlearis)一种富营养指示种。皖河口浮游动物年均生物密度和生物量分别为300.18个/L和0.1586 mg/L,季节性差异显著(P<0.05),生物密度以春季最高,冬季最低;生物量以秋季最高,冬季最低。皖河口浮游动物群落总体上呈小型化现象,以食藻原生动物种类群落及喜中营养化轮虫群落结构为主。Shannon-Wiener指数(H′)、Margalef指数(D)及Pielou均匀度指数(J)分别为0.53、1.53和0.32。综合营养指数(TLI)显示,皖河口水质良好,处于中营养状态。Pearson相关性表明,溶解氧(DO)、总磷(TP)和叶绿素a(Chl-a)与皖河口浮游动物群落结构变化密切相关;RDA分析表明,氨氮(NH;-N)也是影响皖河口浮游动物群落变化的重要因子。

Wanhe River is a tributary of the Yangtze River in Anhui Province, and the confluence of Wanhe River and the Yangtze River, located in Anqing City, is one of the most important habitats of Yangtze finless porpoise. In this study, we explored the characteristics of zooplankton community structure and its relationship with the environmental factors in the confluence of Wanhe River and the Yangtze River, aiming to providing a scientific basis for the dynamic assessment and conservation research of the Yangtze finless porpoise habitat. The investigation of zooplankton and the water environmental factors was conducted at 4 sampling sections in December 2017, April, June and September 2018.The relationship between zooplankton community structure and water environmental factors was analyzed by Pearson correlation analysis and Redundancy analysis(RDA). A total of 47 zooplankton species were identified, belonging to 32 genera and 4 phyla. The dominant zooplankton taxa was protozoa(20 species),followed by rotifers(12 species), cladocera(11 species) and copepods(4 species). There were 6 dominant species recorded around the year, and only one indicator species(Keratella cochlearis) of eutrophic status occurred. The mean density and biomass of zooplankton in Wanhe River cove were 300.2 ind./L and 0.1586 mg/L, respectively, and presented significantly seasonal difference(P<0.05). The highest density was in spring and the lowest in winter, while the highest biomass was in autumn and the lowest in winter. The zooplankton community in Wanhe River cove was generally miniaturized and dominated by ciliates grazing on phytoplankton and rotifers with the preference of mesotrophic water body. ShannonWiener diversity(H′), Margalef richness(D) and Pielou evenness(J) indices of zooplankton community were 0.53, 1.53 and 0.32, respectively. Comprehensive trophic status index(TLI) showed that the water body of Wanhe River cove was in mesotrophic status and water quality was good. Pearson correlation analysis showed that dissolved oxygen(DO), total phosphorus(TP) and chlorophyll a(Chl-a) were closely related to the changes of zooplankton community structure and RDA results showed that ammonia nitrogen(NH3-N) was also an important factor affecting the community structure of Wanhe River cove.