光照强度对伪鱼腥藻生长及光合活性的影响

为研究光照强度对一种常见淡水水华蓝藻伪鱼腥藻(Pseudanabaena sp.)生长及光合活性的影响,根据自然界光照强度范围,设计5个光照强度梯度,采用实验室纯培养方法,开展为期16 d的实验研究.实验过程中对伪鱼腥藻的生物量水平、叶绿素荧光参数和关键色素比例进行跟踪监测,结果发现,在500～2 500 lx,伪鱼腥藻的最适生长光照强度为1 500 lx,其比增长速率从高到低排列为1 500 lx,1 000 lx,2 000 lx,2 500 lx,500 lx.伪鱼腥藻的光合活性受光照强度影响显著,培养一段时间后,伪鱼腥藻的光合速率和光能利用效率与光照强度显著负相关,第11天相关系数分别为-0.939(P0.05)和-0.978(P0.01),半饱和光强与光照强度显著正相关,第11天相关系数为0.976(P0.01).伪鱼腥藻属于低光照强度耐受型蓝藻,且具备自身调节机制应对光照不足或光照过强,易于在光照不足或光强波动较大的水体中占据优势,其暴发相对不易受水深和光强的限制,不宜采用垂向扰动或遮光的抑藻措施对其进行控制.上述发现为地表水体中伪鱼腥藻的预测和控制提供了理论基础.

Influence of light intensity on growth and photosynthesis activity of Pseudanabaena sp.

To investigate the impact of light intensity on the growth and photosynthesis activity of Pseudanabaena sp., which is a common species in freshwater cyanobacteria blooms, five light intensity gradients were designed according to the natural light intensity range. Experiments were conducted by pure culture and lasted for 16 days, during which biomass, chlorophyll fluorescence parameters, and the pigment composition of Pseudanabaena sp. were tracked. Results indicated that the optimum light intensity for Pseudanabaena sp. growth was 1 500 lx during 500-2 500 lx. The sequence of the special growth rate of Pseudanabaena sp. from high to low was 1 500 lx, 1 000 lx, 2 000 lx, 2 500 lx, and 500 lx. The photosynthesis activity of Pseudanabaena sp. was significantly correlated with light intensity. After a period of culturing, the photosynthetic rate and the light use efficiency of Pseudanabaena sp. had obvious negative correlation with light intensity, and on the 11th day the correlation coefficients were -0.939 (P<0.05) and -0.978 (P<0.01), respectively. Half light saturation had significant correlation with light intensity, and the coefficient was 0.976 (P>0.01) on the 11th day. Pseudanabaena sp. belongs to low light intensity tolerant cyanobacteria and has self-regulation mechanism that can deal with insufficient or excessive light. It requires relatively low light intensity compared with other algae species and is easy to dominate in water with low or fluctuant light intensity. Outbreaks of Pseudanabaena sp. are relatively unrestricted by water depth and light intensity, so it is not suitable to use vertical disturbance and shading technology for the control of Pseudanabaena sp. Results of this study can contribute to the prediction and control of Pseudanabaena sp. in surface waters.