汾河太原段轮虫多样性及群落结构的动态变化

调查汾河太原段轮虫群落结构的时空变化，探讨轮虫群落结构动态变化规律及其与环境理化因子的关系，为汾河太原段浮游动物动态预测和多样性保护提供必要信息，从生态系统的角度客观评价水质污染状况与水体富营养化程度。在汾河太原段设置采样点7个，于2014年3-12月对轮虫和水体理化指标进行逐月调查。共检出轮虫98种，隶属3目21科33属。全年优势种是长肢多肢轮虫（Polyarthra dolichoptera）和螺形龟甲轮虫（Keratella cochlearis）。调查期间月均检出轮虫28种，轮虫丰度变化范围为153 ~ 1 440 个/L，生物量为0.08～0.89 mg/L；种类数、丰度和生物量均表现为枯水季较低，丰水季最高。群落结构相似性分析表明不同营养状态水体之间差异显著，轮虫丰度、生物量、Shannon-Wiener 多样性指数和Pielou均匀度指数均存在明显差异；中等营养条件的指示种为卵形无柄轮虫（Ascomorpha ovalis）和单趾狭甲轮虫（Colurella unicauda），指示轻度富营养的指示种为柔软龟甲轮虫（Keratella delicata），中等富营养水体的指示种则为臂尾轮属的种类。冗余分析结果显示环境变量对轮虫群落结构变异的解释率为 41.3%，水温、叶绿素a 、溶解氧、总氮等因子是影响轮虫时空分布的主要因素。轮虫群落结构特征可以指示水体的营养状态。

Dynamic Changes in Rotifer Diversity and Community Structure in the Taiyuan Section of Fenhe River

Fenhe River is an important tributary of the Yellow River and the primary river in Taiyuan City. However, over exploitation of underground water and discharge of urban domestic sewage have resulted in a water level decline and eutrophication of Fenhe River. In this study, we investigated the community structure of rotifers in the Taiyuan section of Fenhe River, focusing on species composition, spatiotemporal distribution and biodiversity of the rotifer community. Redundancy analysis was used to explore the effects of environmental factors on changes in rotifer community structure. The aim of the study was to provide necessary information for dynamic zooplankton forecasting and diversity conservation in the Taiyuan section and to evaluate the pollution and eutrophication status from an ecosystem perspective. From March to December 2014, monthly investigations of the rotifer community and water quality was carried out at 7 sampling sites in the Taiyuan section: Site 1, Fenhe Reservoir outlet; Sites 2-4, abundant aquatic vegetation and little human disturbance; Sites 5-6, slow water flow; Site 7, heavily polluted. A total of 98 rotifer species from 33 genera, 21 families and 3 orders were identified, and two species dominated year round, Polyarthra dolichoptera and Keratella chochlearis. During the investigation, rotifer species diversity among the sampling sites was high due to the heterogeneity of the aquatic environment among sites. The monthly average species number was 28, and the ranges of rotifer abundance and biomass were 153-1 440 ind/L and 0.08-0.89 mg/L. Species richness, abundance and biomass of the rotifer community all presented clear seasonal differences, with maximum values during flood season (June-July), and minimum values in dry season (December). Analysis of similarities (ANOSIM) shows that community structure varied significantly among sampling sites and rotifer abundance, biomass, Shannon-Wiener diversity index and Pielou evenness index varied significantly with trophic level. The rotifer abundance at mesotrophic Sites 1-4 was 200-310 ind/L and 1 000-2 100 ind/L at eutrophic Sites 5-7. The Pielou evenness and Shannon-Wiener diversity indices decreased dramatically from mesotrophic Sites 1-4 to eutrophic Sites 5-7. Indicator species scores (IndVal analysis) show that Ascomorpha ovalis and Colurella unicauda are indicators of mesotrophic water, Keratella delicata and K. cochlearis are indicators of slightly eutrophic water, and Brachionus species indicate moderately eutrophic water. According to redundancy analysis (RDA), environmental variables explained 41.3% of the variation in community structure and water temperature, chlorophyll-a, dissolved oxygen, transparency and total nitrogen were the primary factors affecting the spatial and temporal distribution of the rotifer community. Rotifer community structure was shown to be a reliable indicator of trophic status in the Taiyuan section of Fenhe River.