太湖春季和秋季浮游植物的光合作用活性

Photochemical Activity of Phytoplankton in Taihu Lake in Spring and Autumn

应用Phyto-PAM浮游植物荧光仪对2012年太湖浮游植物群落光合作用活性的时空分布进行测定.结果表明：春季蓝藻、绿藻和硅甲藻的FvFm（最大光量子产量）分别为0.35-0.49、0.34-0.68和0.09-0.56;秋季则分别为0.34-0.53、0.55-0.68和0.28-0.61.春季蓝藻、绿藻和硅甲藻的NPQ（非光化学淬灭）分别为0.012-0.165、0.085-0.201和0.104-0.281,秋季则分别为0.035-0.263、0.052-0.118和0.048-0.301.RLC（快速光响应曲线）的特征参数表明,太湖浮游植物群落光能利用效率和光合作用速率具有显著时空差异.相关分析表明,绿藻和硅甲藻的光合作用活性与环境因子没有显著相关性;而蓝藻的FvFm与RLC的特征参数呈显著正相关,与ρ（Chla）呈显著正相关（P〈0.05,R=0.49）,与SD（透明度）呈极显著负相关（P〈0.01,R=-0.56）,说明太湖蓝藻的光合作用活性与富营养化水平具有一致性.从空间分布来看,草型湖区蓝藻的光合作用活性和ρ（Chla）均显著低于藻型湖区,表明水草能抑制蓝藻的光合作用活性和生长,进而降低蓝藻水华强度.

Lake eutrophication and cyanobacterial blooms are two serious aquatic environmental problems in the world. Taihu Lake is the third largest freshwater lake in China and has suffered from eutrophication since the 1980 s. Currently,it is considered to be hypertrophic.In addition,Taihu Lake has experienced annual cyanobacterial blooms for the last few decades. The phytoplankton assemblages dominated by cyanbacteria in Taihu Lake are attributed to their ecological and physiological advantages over other algae. The spatial and temporal changes of photochemical activity of cyanobacteria,chlorophytes and diatoms/dinoflagellates in Taihu Lake have not previously been reported. In the present study,the temporal and spatial distributions of photochemical activity of phytoplankton in Taihu Lake were investigated using a Phyto-PAM analyzer. The ratio of variable to maximal fluorescence（ Fv/Fm） of cyanobacteria,chlorophytes and diatoms/dinoflagellates in spring varied from 0. 35 to 0. 49,from 0. 34 to 0. 68 and from 0. 09 to 0. 56,respectively,while in autumn the ratio varied from 0. 34 to 0. 53,from 0. 55 to 0. 68 and from 0. 28 to 0. 61,respectively. Non-photochemical quenching（ NPQ） of cyanobacteria,chlorophytes and diatoms/dinoflagellates in spring ranged from 0. 012 to 0. 165,from 0. 085 to 0. 201 and from 0. 104 to0. 281,respectively. In autumn,they ranged from 0. 035 to 0. 263,from 0. 052 to 0. 118,and from 0. 048 to 0. 301,respectively.Characteristic parameters of rapid light response curve（ RLC）suggested that there were temporal and spatial differences in light use efficiency and photosynthesis rate of the phytoplankton.Correlation analysis indicated that there was no significant relationship between photochemical activity of chlorophytes and diatoms/dinoflagellates and environmental factors. However,there was a strong positive relationship between Fv/Fmand RLCparameters for cyanobacteria. The Fv/Fmof cyanobacteria was significantly correlated with chlorophylla（ P 0. 05,R = 0. 49） and transparency（ P 0. 05,R =- 0. 56）,which indicated that the photochemical activity of cyanobacteria was consistent with the eutrophication level in Taihu Lake. Meanwhile,it was also found that photochemical activity of cyanobacteria in grass-dominated sampling locations was much lower than that in algae-dominated sampling locations. The results suggested that water grass can effectively inhibit the photochemical activity of cyanobacteria,and further reduce the intensity of cyanobacterial blooms in Taihu Lake.