换水率和营养水平对太湖流域横山水库硅藻水华的影响

Combined effects of water exchange rate and nutrient on diatom proliferation in Hengshan Reservoir,Taihu Basin

为探讨水文过程对水库硅藻异常增殖的影响,对江苏宜兴横山水库的硅藻生消过程中浮游植物、水质、降水、水位、气温等指标进行观测研究.结果表明,横山水库硅藻年际生物量波动很大,9月出现明显的异常增殖,总生物量达到14.27 mg/L,硅藻的优势属为针杆藻(Synedra)、小环藻(Cyclotella)、曲壳藻(Achnanthes)和直链藻(Melosira),以针杆藻的优势度最高;浮游植物生物量与营养盐浓度关系不明显,与总氮浓度甚至呈负相关,但小环藻生物量与水体溶解性磷浓度呈正相关;水库的换水率与浮游植物生物量、硅藻的异常增殖过程和营养盐浓度水平均密切关联,总氮、溶解性磷浓度与水库换水率呈正相关,而硅藻生物量与水库换水率呈指数负相关.数值拟合分析显示硅藻生物量可以用换水率和磷浓度推算而得.研究表明,对于中营养水平的水库,硅藻生物量变化可能受水文过程与水质条件共同控制,在水库的硅藻水华防控中,既要加强营养盐水平的严格控制,也需考虑水文过程的调控手段.

Phytoplankton, water quality and water level in Hengshan Reservoir of Taihu Basin were studied with the meteorological indexes, in order to analyze the influence of hydrological process on diatom proliferation in the reservoir. The results reveal that the annual diatom biomass shows the significant fluctuations. The diatom proliferation in September is considerably high with the bio- mass of 14.27 mg/L. Genera of the dominant diatom are Synedra, Cyclotella, Achnanthes and Melosira, among which Synedra shows the highest abundance of dominance. Correlation of phytoplankton biomass with nutrients is weak and with the total nitrogen is even negative. Cyclotella biomass is positive related with soluble phosphorus. The water exchange rate in Hengshan Reservoir shows the strong controlling effect on algae biomass, diatom proliferation and nutrient level. Both total nitrogen and soluble phos- phorus show the negative correlation with water exchange rate. The simulation analysis indicates that diatom biomass in Hengshan Reservoir is affected by the joint effects of hydrology and water quality. With the purpose of preventing and controlling diatom bloom in reservoirs, the management should pay an emphasis on both nutrient reduction and water residence time regulation.