三峡水库运行期间原生动物群落的时空异质性

Spatio-temporal heterogeneity of protozoan communities during the period of Three Gorges Reservoir operation

于2010年10月—2011年6月三峡水库正常运行周期内对库区干流原生动物进行调查,研究其空间分布及水库周期排蓄期间的变化。共检测到原生动物99种,蓄水后纤毛虫有增多的趋势。水库运行的不同阶段优势种不同,大致演变为:砂壳纤毛虫(蓄水期)—非砂壳类纤毛虫(高位运行期间)—有壳肉足虫(低位运行期间)。不同水域优势种也存在差异,从上游到下游特征指示种变化为:有壳肉足虫(变动回水区)—纤毛虫(湖泊区)。结果表明,三峡水库原生动物的分布具有明显的时空异质性(P<0.05),影响原生动物时空分布的主要因素有透明度、温度、电导率和叶绿素a。原生动物平均密度为952.19个/L,平均生物量为8.14μg/L。蓄水期上游现存量高于下游,低位运行期间则低于下游。原生动物Marglef和Shannonn-Weiver多样性指数平均值分别为3.78和2.18,1月份最低,6月份最高。蓄水175 m后上游变动回水区原生动物具有较高的丰度。水库冬蓄夏排的运行模式模糊了河流本身的季节变化,使原生动物的种类和现存量更多的受水库水动力学的影响,使水体理化因子和水文特征呈现明显的时空差异,最终形成原生动物种群的时空异质性分布。

Three Gorges Reservoir was impounded to 175 m for the first time in October 2010,of which the backwater area arrived in Chongqing,and the upstream water retention time extended further and the reaches changed to transitional waters.The heterogenrity of protozoan communities was studied in the main stem of Three Gorges Reservoir during the period of Three Gorges Reservoir normal operation（ October 2010—June 2011）. The spatial variations in community structure and species distribution were observed during reservoir drainage and storage. A total of 99 protozoan species were identified. Of these taxa,ciliates represented an increasing tendency after impoundment. The dominant species differed in operating stages,with the indicator species generally evolved from tintinnids（ impounding period）,ciliates（ high water level period） to testate amoebae（ low water level period）. The dominant species varied in different reservoir areas,while the indicator species testate amoebae（ transition zone） were changed into ciliates（ lake zone） from upstream to downstream. Detrended correspondence analysis（ DCA） and multi-response permutation procedure（ MRPP） analysis showed that protozoan community structures and species distributions showed a clear spatio-temporal heterogeneity in Three Gorges Reservoir. The temporal heterogeneity peaked during impounding stage（ P〈0. 05）. The statistical analysis showed that the spatio-temporal variations in community pattern and species distribution were significantly correlated to environmental variables,especially transparency,temperature,conductivity and chlorophyll a. The average density and biomall of protozoa were 952. 19 ind. / L and 8. 14 g / L,respectively.The standing crops of protozoa in upstream were higher than that in downstream during impounding stage,but lower than that during low water level period. The mean values of Marglef＇ s and Shannon-Weiner diversity indices were 3. 78 and 2. 18,respectively,with minimum value in January and maximum in June. The abundance of protozoa in transition zone was high after 175 m impoundment. It may be due to large amount of organic matter brought by water flow during the first impounding stage. Reservoir operation pattern of ＂drainage in winter and storage in summer＂＂blurs＂seasonal variation of the river.Protozoan species composition and standing crops are mainly affected by reservoir hydrodynamic. Physic-chemical factors and hydrological characteristics showed different spatio-temporal variations,and resulted in the heterogeneity in community pattern and species distribution of protozoa on both temporal and spatial scales.