大渡河河口浮游植物群落时空分布及其与环境因子的关系

Spatio-temporal Distribution of the Phytoplankton Community in Dadu River near Angu Reservoir and Its Relationship with Environmental Factors

为了探究安谷水电站建成后浮游植物群落的时空分布及其与环境因子的关系,于2015年5月至2016年9月,在大渡河河口设置8个采样断面,开展浮游植物野外调查。结果表明,调查区域共采集到浮游植物7门、49属、138种,主要由硅藻(种类数占71.02%)、绿藻(15.95%)、蓝藻(9.42%)、裸藻(1.45%)组成。大渡河河口主河道浮游植物种类数较高,特别是安谷水电站坝下断面最高。调查河段浮游植物密度为31.20×104~66.69×104个/L,其组成以硅藻为主,秋季浮游植物密度高于春季。大渡河主河道各样点浮游植物密度水平分布变化大,安谷水电站库区和坝下样点密度显著高于调查河段的其他样点。对比安谷水库蓄水前后,浮游植物种类的季节分布无明显差异,而密度的季节分布则差异明显;浮游植物群落的空间分布发生了显著变化,特别是安谷水电站库区和坝下浮游植物种类和密度明显增加。Person相关性分析显示,影响浮游植物密度的主要因子是水温、流速、透明度,与氮、磷元素的浓度则未显出相关性;RDA分析表明,水温、溶解氧、流速、透明度、总氮是影响浮游植物组成的主要因素。安谷水电站的建设使得水体理化指标及水文情势分布因素发生改变,对浮游植物群落的时空分布造成了直接影响,特别是电站库区和坝下,浮游植物的种类和密度变化明显。

Phytoplankton community structure and distribution are closely related to water environmental factors.In this study,we studied the spatial distribution and seasonal variation of the phytoplankton community above and below Angu hydropower project on the Dadu River and analyzed the response of the phytoplankton community to changes in the water environment.The aim of the study was to provide basic biological data for water ecosystem restoration in Dadu River and a technical reference for evaluating predictions of phytoplankton community dynamics in other similar reservoirs.In May and October of 2015,and April and September of 2016,phytoplankton sampling was carried out at eight sites in Dadu River and its tributaries and water quality parameters were determined.Sites 1-4were in the main channel,with Sites 1-2above the dam and Sites 3-4below the dam,and Sites 5-8were tributary sites.A total of 138phytoplankton species belonging to 49genera and 7phyla were identified.Bacillariophyta was the dominant phytoplankton species(71.02%),followed by Chlorophyta(15.95%),Cyanophyta(9.42%)and Euglenophyta(1.45%).The highest species richness was found in the main channel of Dadu River,especially the transect below the dam.The range of phytoplankton density was 31.20×104-66.69×104 ind/L,dominated by diatoms.Phytoplankton density in autumn was higher than that in spring.Spatially,phytoplankton density varied significantly in the main channel of Dadu River.The densities in Angu Reservoir and below the dam were significantly higher than at other sampling sites.Before and after impoundment of Angu Reservoir,seasonal differences in species richness were not significant,but seasonal differences in density were significant.Spatial differences in phytoplankton community structure were significant and phytoplankton density increased sharply in the reservoir and channel below the dam.Pearson analysis showed that phytoplankton density was significantly correlated with water temperature,flow velocity and transparency.Correlation of density with nitrogen and phosphorus were not significant.Redundancy analysis(RDA)indicates that water temperature,dissolved oxygen,flow velocity,transparency and total nitrogen were the primary factors affecting phytoplankton community composition.In summary,changes in the physicochemistry and hydrology of Dadu River caused by construction of Angu hydropower station directly affected the spatial and temporal distributions of the phytoplankton community,particularly in the reservoir and river below the dam where species composition and phytoplankton density changed significantly.