动态调水模式下生态系统重建过程中浮游藻类群落演替及其响应机制—以丹江口水库为例

Due to climate change, economic development and population growth, clean freshwater resources are becoming increasingly scarce globally. Therefore, the ecological security of drinking water quality is increasingly perceived as one of the top global environmental issues. The composition of phytoplankton assemblages in drinking water source reservoirs is regarded as an important factor affecting the safety of water supply in the projects of dynamic eco-hydrological regulation. However, little attention has been given to the response of phytoplankton assemblages to the dynamic eco-hydrological regulations during the reconstruction of the reservoir ecosystems. Based on the strategic demands for China’s regional sustainable development, Danjiangkou Reservoir is built for the water source area of the Middle Route of the South-North Water Diversion Project. The reservoir ecosystem is currently under its reconstructing process after the water level increase for the need of the Middle Route after 2014. In the present study, phytoplankton assemblage is takes as the main research object to carry out under multi-scale in-situ surveys at 16 monitoring sites based on different types of interference (water level fluctuations, water quality, etc.) and laboratory simulation studies in the next four years. Both the traditional optical microscopy method (TOM) and the 16S and 18S rRNA high throughput sequencing method (HTS) are applied to the categorical division of phytoplankton assemblage. The method of phytoplankton functional classification is used for dividing functional groups to understand the structure characteristics, genetic diversity and phylogenetic relationship of phytoplankton assemblages under different disturbance conditions. Combined with the historical data of hydrology, water quality, and phytoplankton assemblages, the pressure strength of the reservoir hydrology on phytoplankton assemblages is also analyzed. Integrating hydrodynamic environmental pressure and population characteristics, such as population decline, expansion, and migration, the succession trend and response mechanism are further discussed under the mode of dynamic eco-hydrological regulation. The results of the present study will expect to present the new and key scientific data for the development of the healthy and safe water ecosystems, and therefore provide a theoretical basis for the water quality of the water source area and ecological security system of similar larger water diversion projects.

水质生态安全是全球最重要的环境问题之一。调水工程中水源藻类群落构成是影响供水安全的重要因素。对于水源水库生态系统重建过程中藻类群落对动态调水的响应关注甚少。本项目以丹江口水库水位升高后水体生态系统重建过程为案例，以入库河口、库区、出水等不同水域浮游藻类群落为主要研究对象进行野外原位多尺度监测及室内模拟研究，采用传统分类法和高通量测序法进行藻类分类，用功能组法对藻类功能群进行划分，掌握不同干扰条件下浮游藻类群落结构、遗传多样性及系统发育关系，结合水文、水质和藻类群落历史数据分析动态调水模式下水库水动力变化对浮游藻类的压力强度。综合水动力的环境压力和浮游藻类对水动力变化的种群衰退或扩增、迁移等响应特征，分析藻类群落的演替过程，揭示动态调水模式下藻类群落演替规律和响应机制。本项目为发展健康安全的生态水利提供新的关键科技数据，为我国类似调水工程的水源水质生态安全保障体系提供理论基础。

水质生态安全是全球最重要的环境问题之一。调水工程中水源藻类群落构成是影响供水安全的重要因素。研究发现丹江口水库不同季节样点间均能较好地聚集在一起，春季与夏季差异不明显，秋季和冬季聚集现象明显。在时间尺度上，水温、pH、Cond、ORP、DO、TOC、COD、TN、TP 和 NH4+ -N 呈现出明显的季节变化特征；在空间尺度上，Cond、SD、CODMn、TN、NO3 --N 和 Chl.a 具有显著的空间差异性。丹江口水库 TLI（∑）值为 37.62，水体水质处于中营养状态，综合营养状态指数（TLI）呈现出春夏季较低，秋冬季较高的现象；从空间尺度分析，TLI（∑）值排序为丹库<汉库<出库口<入库口，冬季丹库库区呈现最小值，夏季入库区呈现最大值。春季 pH 与 浮游植物完整性指数(P-IBI)评分呈负相关，Cond、TN、NO3 --N、TLI（∑）与 P-IBI 评分呈正相关；秋季 TLI（∑）与 P-IBI 评分呈负相关。丹江口水库整体处于健康水平。.研究水体共发现浮游植物 7 门 49 科 100 属 164 种，浮游植物群落演替规律是春季为硅藻-绿藻型，夏季为绿藻-硅藻型，秋季蓝藻型，冬季蓝藻-绿藻-硅藻型；而库湾浮游植物群落变化是春季硅藻-绿藻型，夏季蓝藻-绿藻-硅藻型，秋季蓝藻型，冬季绿藻-硅藻-蓝藻型，与丹库群落演替不完全相同。浮游植物优势种具有时空差异。Shannon-Weiner 多样性指数在时间上呈现秋季>夏季>春季>冬季，在空间上呈现出库口>入库口>汉库>丹库；Margalef 丰富度指数在时间上呈现夏季>春季>秋季>冬季，在空间上呈现入库口>出库口>汉库>丹库，Pielou 均匀度指数在时间上呈现秋季>夏季>春季>冬季，在空间上呈现出库口>入库口>汉库>丹库。.水文因子和营养盐对浮游植物群落多样性产生了一定的影响。水深、pH、TP、Cond、ORP 和水温是影响丹江口水库浮游植物群落演替的驱动因子。.采用高通量测序技术分别对浮游细菌（包括蓝藻）、浮游真核生物（包括硅藻和绿藻等藻类）和浮游真菌进行分析，揭示了中线水源区水生微型生物的多样性。