富营养化山仔水库沉积物微囊藻复苏的受控因子

山仔水库作为福建省福州市重要的饮用水水源地之一,从2000年起每年都周期性爆发蓝藻门微囊藻属(Microcystis)水华现象,特别是在温暖的季节。对于这个富营养化水库,是否在沉积物中存在蓝藻门微囊藻的"种源"？假设山仔水库底泥中存在蓝藻门微囊藻休眠体,一定的环境条件能够促进蓝藻门微囊藻的复苏。研究于2009年12月采集水库大坝断面5根柱状沉积物,采用正交试验的方法,模拟了温度、光照、pH值、营养盐、物理扰动和浮游动物(膨大肾形虫)等环境因子对山仔水库沉积物中蓝藻门微囊藻的复苏响应。结果表明,底泥中存在着一定数量的底栖动物和硅藻、蓝藻和绿藻等微藻,从实验结束后沉积物中微囊藻数量的减少和上覆水体中微囊藻数量的增加,可以判断在适宜的环境条件下,蓝藻门微囊藻能够复苏并上浮到上覆水体中。正交实验显著性分析表明,温度是沉积物蓝藻门微囊藻复苏的重要影响因子,光照次之,上覆水体的pH值、营养盐、物理扰动和浮游动物干扰对沉积物蓝藻门微囊藻的复苏影响作用不显著,升温有利于沉积物中微囊藻的复苏。

Factors regulating recruitment of Microcystis from the sediments of the eutrophic Shanzai Reservoir

Shanzai reservoir is one of the drinking water sources to provide 0.23 million people living in Fuzhou City, Fujian province, China. There has excessive blue-green algae growth in this reservoir from 2000 especially in the warmer seasons. Many species of algae can live on sediments during conditions unsuitable for growth. This is true for most blue-green algae, some of which develop as surface water blooms, such as Anabaena and Aphanizomenon produce akinetes forming seed banks which can survive on sediments of water bodies for overwintering. Although the toxic blue-green algae Microcystis does not produce any specialized dormant cells like akinetes, it is reported that Microcystis colonies can accumulate on the sediments during autumn and winter in a vegetative state. We have addressed the question of whether the sediment provides the inoculum for Microcystis population in the eutrophic Shanzai reservoir. Our hypotheses were that if any factor might enhance recruitment of Microcystis from the sediment. Five core samples were collected from the sediment on December 2009 in the dam section of Shanzai reservoir. We examined the recruitment responses of Microcystis to the culture conditions including temperature, light intensity, pH, nutrient, physical disturbance and zooplankton in the sediment of the Shanzai Reservoir. Many kinds of Zoobenthos and algae could be found in the sediment. The main algae included Cyanobacteria, Diatom and Chlorophyta etc. The result of orthogonal experiment showed that temperature was the most important regulating factor for the Microcystis recruitment from sediments, the increased temperature would promote the recruitment of Microcystis, the second one is the light intensity. The effects of the overlying water pH, nutrient, physical disturbance and zooplankton on the recruitment of Microcystis from sediments were not obvious. Reinvasion was quantified by the diminution of benthic Microcystis abundance, and moreover, by the increase of Microcystis in the water column. Our results from the laboratory experiment suggest that the Microcystis in the sediment could recruit and float up to the water surface which support our hypothesis that the sediment is the important seed banks and provide the inocula for Microcystis blooms in Shazai Reservoir and temperature was the most significant environmental factor regulating the recruitment of Microcystis from the sediment. The results would provide a scientific reference for controlling Microcystis bloom in the Shanzai reservoir.