太湖蓝藻的时空变化规律及治理方法

利用2009─2012年丰水期和平水期的生物调查获取的环境和生物数据，研究太湖蓝藻的时空分布规律，分析蓝藻分布与其他物理、化学和生物因子（如温度、酸碱性、有机物和营养盐含量、浮游植物与浮游动物密度等）的相关关系。结果表明：太湖水质基本上超出V类地表水指标，主要的超标因子是总氮。总氮在丰水期和平水期的质量浓度分别为3.05 mg·L-1和1.65 mg·L-1，总氮在丰水期质量浓度降低的主要原因可能是丰水期蓝藻迅速生长，吸收了大量的营养盐。蓝藻仍是太湖浮游植物的优势种。2009─2012年太湖蓝藻的密度随年份无明显变化，但随季节和区域存在显著差异：丰水期蓝藻密度均值为4.87×10^7cell·L-1，明显高于平水期蓝藻密度（1.51×10^6 cell·L-1）；太湖东部采样点蓝藻密度明显低于其他湖区。影响蓝藻的非生物因素包括温度、酸碱度和营养盐，高温、偏碱性和高营养盐含量都会增加蓝藻的密度。蓝藻与其他浮游植物和大型水生植物之间存在竞争关系，蓝藻密度增加促进了枝角类的生长。推荐利用机械打捞和大型水生植物修复方法，因为这2种方法可在降低蓝藻密度的同时去除水体中的有机物和营养盐，可以从根本上降低太湖蓝藻水华的风险。增加其他藻类和枝角类控制蓝藻水华方法可行性较差：1）蓝藻暴发时期其它藻类对能量和营养的竞争能力弱于蓝藻，难以抑制蓝藻的生长；2）在太湖中增加枝角类可能降低现有蓝藻的密度，但建立完整的食物链体系降低富营养化程度，防范生物调控中可能存在的生态风险（如其他藻类水华等）较困难。

The temporal and spatial distribution pattern of cyanobacteria and its control method in Taihu Lake

The environmental and biological data observed during the wet seasons and normal seasons in 2009-1012 have been used for the research of the temporal and spatial distribution of cyanobacteria, as well as the analysis of the relationship between the cyanobacteria distribution and the physical, chemical and biological parameters, such as water temperature, pH value, the concentration of organic pollutants and nutrients, and the density of the phytoplankton and zooplankton. Results showed that the water quality of Taihu Lake exceeded the V class of National Standard for Groundwater Environmental Quality, and the main element exceeding the standard was nitrogen. The concentrations of the total nitrogen in Taihu Lake in wet season and normal season were 3.05 mg＆#183;L-1 and 1.65 mg＆#183;L-1, and the main reason of the lower nitrogen concentration in wet season was probably that cyanobacteria grew fast and absorbed a great quantity of nutrients in this period of time. The cyanobacteria were still the dominated species of the phytoplankton in the sampling sites. There was no significant annual change of the density of cyanobacteria during the year of 2009─2012, while the density of cyanobacteria in different seasons and different sites were varied：the average density of cyanobacteria in the wet seasons （4.87＆#215;107 cell＆#183;L-1） was significantly higher than in the normal seasons （1.51＆#215;106 cell＆#183;L-1）, and the density of cyanobacteria in the sampling sites of the Eastern Taihu Lake was significantly lower than the other parts. Abiotic factors including temperature, pH value and the concentration of nutrients could influence the density of cyanobacteria. Higher temperature, pH value and higher concentration of nutrients could increase the density of cyanobacteria. Competition between the growth of cyanobacteria and other primary producers （phytoplanktons and macrophytes） had been observed, and the increase of cyanobacteria density stimulated the growth of the cladocera. The mechanical removal technique and phytoremediation were recommended in this research, for they could reduce the risk of the cyanobacterial bloom in Taihu Lake by reducing the density of cyanobacteria and the concentration of nutrients. However, controlling the bloom of cyanobacteria through increasing the density of other phytoplankton and cladocera was infeasible, for the following reasons：1）the other phytoplankton has lower competitive power than cyanobacteria in absorbing energy and nutrients, which could not inhibit the growth of cyanobacteria;2）the increase of the density of cladocera could probably reduce the density of cyanobacteria in Taihu Lake, but it is hard to complete food chain system to decrease the eutrophication of the lake and prevent the potential ecological risk （e.g. bloom of other angles） in the process of the bio-regulation of the lake.