东江支流夏季小型浮游动物群落特征研究

Aestival Characteristics of Small Zooplankton Communities in the Main Tributaries of the Dongjiang River

于2010年7月对东江流域主要支流进行调查,共布设79个有效样点,定量鉴定出原生动物和轮虫共计36属,据此研究小型浮游动物群落种类组成特征及其与环境因子的关系,探讨运用小型浮游动物辅助评估河流水环境状况可能性。结果表明:①研究区多数样点内小型浮游动物群落呈现种类少、密度小的特征,在样点内相对密度占绝对优势的种类多,但在样点内相对密度和区域频度均占优势的种类少;②顺流而下,小型浮游动物的种类数、密度、多样性均趋向增大,第一优势种类相对密度趋向降低,优势种类频繁变化,种类组成结构不稳定;③小型浮游动物密度与环境因子关系较为密切,具备成为评估河流水环境状况辅助或备选指标的可能性。

Our goal was to describe the aestival features of small zooplankton communities in the main tributaries of the Dongjiang River and test the possibility of using prominent features derived from the zooplankton community as predictive indicators of water quality. By systematically selecting representative tributaries of the Dongjiang River as case study sites, we randomly sampled small zooplankton （Protozoa and Rotifers） communities along the tributaries in July 2010. The species composition of those zooplankton communities was identified to the genus level, and indices including richness, density, relative density, frequency and diversity were counted. Environmental variables including temperature, dissolved oxygen, electrical conductivity, total phosphorus, total nitrogen, ammonia nitrogen, nitrate nitrogen, permanganate index, and chlorophyll a were also measured. We identified 36 genera, of which 23 belonged to Protozoa and 13 to Rotifers. Those taxa in most cases emerged in low density and low richness in samples. Within a sample, however, often one of the genera was found at a relatively high density, while fewer genera dominated the density and frequency. This implied that small river channels are not suitable for zooplankton growth, whereas diversified habitats resulted in a variety of community composition types. An increased trend from up-to down-stream was found in density, richness and diversity, while at the same time a decreased trend in dominance occurred. Many factors, such as zooplankton origins, available nutrients and flow velocity, could all be influencing the small zooplankton community. Significant correlations between the density of certain special genera and most environmental variables were found, indicating that density might be used as the zooplankton indicator in assessing and monitoring river environmental conditions. On the contrary, the diversity of zooplankton should not be used as a competent indicator in assessment, since there was no significant correlation with most environmental factors. In addition, Vorticella significantly dominated the zooplankton communities both in relative density and in frequency, and should be a focus of future work in this area.