Effects of different irradiation intensity on the growth and absorption properties of <i>Microcystis aeruginosa</i> and <i>Scenedesmus obliqnus</i>

Abstract

在不同的光照强度下,测定了铜绿微囊藻、斜生栅藻在不同生长期的藻细胞密度、粒径、叶绿素a浓度、浮游植物吸收系数以及比吸收系数.单因素方差分析表明,在整个培养周期中,光照强度对铜绿微囊藻及斜生栅藻的藻细胞密度、叶绿素a浓度以及440、675 nm处吸收系数均有着显著的影响.两种藻在光照强度为50μmol/(m²·s)条件下,藻细胞密度、叶绿素a浓度及吸收系数值相对最大.相关性分析表明:藻类特征波段440、675 nm吸收系数与叶绿素a浓度、藻细胞密度在不同光照条件下都存在着显著的正相关性,其中叶绿素a浓度与藻类吸收系数存在着幂函数的关系,而线性关系能更好的说明藻细胞密度与吸收系数之间的关系.在不同光照强度及培养时期,藻类比吸收系数在一定的范围内波动,随光强增加比吸收系数呈上升趋势.铜绿微囊藻440、675 nm处比吸收系数与叶绿素a浓度呈显著的负相关关系,而斜生栅藻比吸收系数与叶绿素a浓度之间无显著相关,体现了不同藻类由于色素组成及比例差异其色素包裹效应也各不相同.对不同光照强度下的铜绿微囊藻及斜生栅藻进行400~700 nm波段积分,得到了两者在5、50及100μmol/(m²·s)不同种光强下的平均比吸收系数分别为0.0144、0.0134、0.0160,0.0086、0.0088、0.0105 m²/(mg Chl.a),铜绿微囊藻比吸收系数明显大于斜生栅藻.;Cell number, cell size, chlorophyll-a (Chl.a) concentration, absorption and specific absorption coefficients of Microcystis aeruginosa and Scenedesmus obliqnus were determined in the different culture times at three different irradiation intensities. Oneway analysis of variance showed that irradiation intensity had great significant effects on cell number, Chl.a concentration and phytoplankton absorption coefficients at 440 nm a_ph (440), 675 nm a_ph (675) in the entire experimental period. The largest values of these parameters were recorded in the light condition with 50 μmol/(m²·s). Phytoplankton needs optimal growth irradiation intensity because over-low or high light density could have negative effects on the growth rate of phytoplankton. Correlation analysis showed that there were significant positive correlations between a_ph (440), a_ph (675) and Chl.a concentration under three different irradiation intensities for M. aeruginosa and S. obliqnus. Power correlation could be best used to describe the correlations between a_ph (440), a_ph (675) and Chl.a concentration, while the linear correlation could be used to explain the relationships between a_ph (440), a_ph (675) and cell number. Meanwhile the specific absorption coefficients of M. aeruginosa and S. obliqnus fluctuated within small range in different irradiation intensities at different experimental periods, and increased with increasing irradiation intensity. A significant negative relationship was found between M. aeruginosa specific absorption coefficients at 440 nm, 675 nm and Chl.a concentration. However, the specific absorption coefficients of S. obliqnus had no relationship with Chl.a concentration mainly due to the composition and proportion of pigments and package effects. The average specific absorption coefficient integrated over the range of PAR (400-700 nm) of M. aeruginosa and S. obliqnus at three irradiation intensities of 5, 50, 100 μmol/(m²·s) are 0.0144, 0.0134, 0.0160 and 0.0086, 0.0088, 0.0105 m²/(mg Chl.a), respectively. The specific absorption coefficients of M. aeruginosa were significantly higher than those of S. obliqnus mainly due to the algae cell size of M. aeruginosa, 3.14 ± 0.43 μm, twice smaller than that of S. obliqnus, 7.24 ± 0.79 μm.