在不同蓄水位下三峡库区春季水华特征及趋势分析

基于2004—2015年三峡库区支流春季水华的监测数据, 开展了三峡库区不同蓄水位下春季水华特征及趋势分析。 结果表明: 总共有26条支流发生春季水华, 香溪河为水华发生概率最高的支流。水华藻类优势种主要是硅藻和甲藻, 甲藻水华出现的概率随着蓄水位的增加而增加, 但是在持续几年175 m蓄水之后, 甲藻水华出现的频率下降, 硅藻水华出现的频率增加。在175 m蓄水之前, 水华发生期藻类密度、叶绿素a含量及水体营养盐水平相对较低, 此后都有了较高的提升, 但是在持续几年175 m蓄水之后, 藻类密度、叶绿素a浓度以及营养盐浓度都有下降趋势。对藻密度及叶绿素a含量与主要环境因子进行主成分分析(Principal components analysis)发现, 藻密度和叶绿素a与总磷、总氮、高锰酸盐指数聚类一簇, 藻密度、叶绿素a浓度与总磷、溶解氧、高锰酸盐指数显著正相关。在蓄水之后, 三峡库区支流营养水平有所增加, 随着蓄水位的增加, 三峡库区支流断面的平均流速降低, 在合适的温度下, 三峡库区支流水华易发生。

CHARACTERISTICS OF SPRING ALGAL BLOOMS UNDER DIFFERENT IMPOUNDED LEVELS IN TRIBUTARIES OF THE THREE GORGES RESERVOIR

This study analyzed the characteristics of algal blooms based on the spring algal blooms data collected from the tributaries of Three Gorges Reservoir from 2004 to 2015. Results showed that the algal blooms had occurred in 26 tributaries of Three Gorges Reservoir (TGR) with the highest rate in Xiangxi River. The dominant species of the algal blooms were Bacillariophyta and Dinophyta. The probability of Dinoflagellate blooms increased correspondently with the increased impounded level, but the occurrence rate of Diatom blooms increased after several years while reserving water level was up to 175 m. The concentrations of algae density, chlorophyll a and trophic state were low when the reservoir water level was below 175 meters, and then increased sharply when the reservoir water level raised to 175 meters with a trend of gradual decrease after years of reservoir impounding to 175 meters. The principal components analysis (PCA) showed that the algae density, chlorophyll a concentration, total phosphorus (TP), total nitrogen (TN) and permanganate index were classified into the same cluster. Algal density and chlorophyll a concentration were significantly positively correlated with TP, dissolved oxygen, permanganate index and pH. With the impounded level of Three Gorges Reservoir, the mean flow velocity of the tributaries decreased, which might result in the algal blooms at the tributaries of Three Gorges Reservoir under proper temperatures.