越冬浮游植物光合作用活性的原位研究

In situ study on the photochemical vitality of overwintering phytoplankton

水体中浮游植物在越冬期间数量少,关于湖泊中越冬浮游植物如蓝藻、绿藻、硅藻等浮游植物的光合作用活性情况少见报道．本实验通过Phyto-PAM(Pulse Amplitude Modulation)对最大光量子产量F_v/F_m(可变荧光和最大荧光之比)和快速光曲线的测定,结合显微镜镜检结果,并在室内进行了硫酸铜处理以及鲁哥氏液处理实验,对太湖、巢湖和玄武湖处于越冬期间的浮游植物进行了原位光合作用活性的研究．显微镜镜检结果表明太湖和玄武湖水体中以绿藻和硅藻为主,而蓝藻很少,巢湖水体中有大量蓝藻、绿藻和硅藻,Phyto-PAM在对玄武湖和太湖水样原位测定时未检测出蓝藻,而绿藻和硅藻有光合作用活性,其F_v/F_m在0．5左右;对巢湖的水体检测到的蓝藻、绿藻、硅藻都具有光合作用活性,其中绿藻和硅藻的Fv／Fm在0 5左右．蓝藻的n／Fm在0．3左右:用硫酸铜处理实验在巢湖水样中发现水体仅有硅藻活性(F_v/F_m下降至0．2左右),而用鲁哥氏液处理后无任何藻类光合作用活性,上述实验结果表明,即使处于越冬期间,以较多数量出观在水体中的蓝藻、绿藻和硅藻仍然具有较高的光合作用活性．

Photochemical vitality of overwintering phytoplankton including cyanobacteria chlorophyta and bacillariophyta was not known because of the general small blomass. In present study, Phyto-PAM （ Pulse Amplitude Modulation） was applied to measure Fv/Fm （ratio of variable to maximal fluorescence） and rapid light curves of phyto- plankton to study the photochemical vitality in situ of overwintering phytoplankton sampled from LakeTaihu, Lake Chaohu and Lake Xuanwu. Both microscopic determination of cyanobacteria, chlorophyta and bacillariophyta and treatment of copper sulfate and Lugol＇ s solution to water samples were performed. The results from microscopy determination showed that there were ehlorophyta and baeillariophyta but without eyanobaeteria in Lake Taihu and Lake Xuanwu. However, a large amount of cyanophyta was detected in Lake Chaohu besides chlorophyta and bacillariophyta. Fv/Fm and rapid light curves from Phyto-PAM showed that there was no photochemical vitality of cyanobacteria in Lake Taihu and Lake Xuanwu but presented with photochemical vitality of chlorophyta and bacillariophyta （ Fv/Fm was about 0. 5 ）. In Lake Chaohu, all the three kinds of phytoplankton showed photochemical vitality （ Fv/Fm was about 0. 5 in chlorophyta and bacillariophyta; Fv/Fm was about 0. 3 in cyanophyta）. Samples treated with copper sulfate only showed the bacillariophyta photochemical vitality, while even this disappeared when treated with Lugol＇s solution. The results from Phyto-PAM combined with chemical treatment experiments suggested that the photochemical vitality of phytoplankton was still active in overwintering period.