苏南水库硅藻群落结构特征及其控制因素

为了解我国东南湿润区丘陵山地型水库硅藻的群落结构特征和控制因素,于2015年6月硅藻水华敏感期对苏南地区18座水库的浮游植物群落结构和水质进行调查,分析了营养盐、水深、库容等因素与硅藻及其它浮游生物的关系.结果表明,硅藻达到轻度水华水平(硅藻细胞含量介于100~1 000万cells·L~(-1))的水库有10座,对供水和景观功能产生明显影响;苏南地区水库普遍处于中营养和富营养水平,总氮浓度普遍偏高,磷及营养状态指数与硅藻生物量的关系密切;苏南地区水库中的浮游植物在数量上以蓝藻门中的席藻为主,在生物量上则以硅藻门、绿藻门和蓝藻门为主,其中硅藻门浮游植物平均占总浮游植物生物量的46.8%,是浮游植物异常增殖的主要门类;硅藻门中,主要是针杆藻、小环藻、曲壳藻和直链藻这4个种属占优,特别是针杆藻和小环藻,平均占硅藻总生物量的51.6%和21.4%;较深的水体,利于硅藻成为主要优势藻门;较大的水库流域库容比和较高总磷水平会导致水库营养水平和叶绿素浓度增加,促进浮游植物从硅藻门向绿藻门、蓝藻门演替,增加藻类危害的风险.因此,对于该地区水库,需要加强流域管理,并且针对水库自身的特点,包括水深、流域库容比等,确定其特定的富营养化控制策略,从而减少硅藻等藻类水华发生的风险,提升水源地水质安全保障能力.

Community Structure Characteristics of Diatom in Reservoirs Located in the South of Jiangsu Province, China and Its Control Factors

In order to understand the community structure characteristics of Bacillariophyta and its controlling factors in reservoirs located in the Southeast, China, in the geographic background of hills landscape and humid climate, 18 reservoirs were investigated in June, 2015, during the period with high risk of diatom bloom, covering water quality, and the community structures of phytoplankton. The correlations between Bacillariophyta and other planktons with nutrients, water depth, storage capacity, etc. were analyzed. The results showed that, 10 reservoirs reached the light extent of diatom bloom (density between 100×10⁴-1000×10⁴ cells·L^-1); reservoirs in this area were generally in mesotrophic or eutrophic state with considerably high total nitrogen concentrations; total phosphorus and trophic level index were both closely correlated with Bacillariophyta biomass. Phormidium in Cyanophyta was the dominating generus among phytoplankton in terms of density; with respect to biomass, Bacillariophyta, Chlorophyta and Cyanophyta were the top three phylum, and Bacillariophyta accounted for 46.8% of the total phytoplankton biomass, becoming the most important one resulting in abnormal propagation of algae; Synedra (51.5%) and Cyclotella (21.4%) were the main dominating genera in Bacillariophyta, together with Achnanthes and Melosira. Deep water was favored by Bacillariophyta to dominate among different phyla. Larger ratio between catchment and reservoir storage capacity, on the other hand, caused the increase of trophic level and chlorophyll, and benefited the shift of dominating phytoplankton from Bacillariophyta to Chlorophyta and Cyanophyta, by which, the risk of algae bloom would be increased. It reveals that to alleviate the risk of algae bloom and protect drinking water resources, catchment management is crucial for the studied reservoirs. And the establishment of nutrient reduction strategies needs to consider the features of each individual reservoir, i.e. water depth, ratio between catchment and capacity.