三种大型绿藻光合能力的差异及其在珊瑚养殖中的应用

Photosynthetic capacity of three common species of macroalgae and the application in coral aquarium

利用水下饱和脉冲调制叶绿素荧光仪（Diving-PAM）测定了珊瑚养殖水处理中3种常见大型海藻石莼（Ulva lactuca）、条浒苔（Enteromorpha clathrata）和羽状蕨藻（Caulerpa mexicana）光能转化效率（Fv/Fm）,快速光曲线（RLC）相关参数和非光化学淬灭（NPQ）。结果表明：石莼和条浒苔的Fv/Fm分别为0.808±0.004和0.816±0.009,显著高于羽状蕨藻。最大相对电子传递速率rETRmax（17.52±2.92和19.59±4.43μmol e·m^-2·s^-1、半饱和光强Ik（53.41±8.18和59.71±13.52μmol photons·m^-2·s^-1）也明显高于羽状蕨藻（rETRmax和Ik分别为13.72±5.41μmol e·m^-2·s^-132.67±14.06μmol photons·m^-2·s^-1,表明石莼和条浒苔有着比羽状蕨藻更高的光合能力和对强光的耐受能力,光保护能力更强;羽状蕨藻较高的RLC初始斜率α表明其在弱光下拥有更强的光捕获能力,弱光下光合效率更高;随光照的增强（0-373μmol photons·m^-2·s^-1,羽状蕨藻NPQ的增幅有限（0-0.2）,最大值仅为条浒苔和石莼的38.1%和62.5%,表明这种藻类更容易受到强光的抑制。因此,在珊瑚养殖的水处理中,可以根据不同的光照选择适宜的藻种或藻种组合并根据光梯度进行布局,反之也可以根据藻种来选择合适的光源,以达到最佳的处理效率。

This study investigated the difference of photosynthetic capacity in three macroalgae species（ Ulva lactuca,Enteromorpha clathrata,and Caulerpa mexicana） commonly used for nutrient removal in coral aquariums. The photochemical efficiency（ Fv/Fm）,parameters relevant to rapid light curve（ RLC） and non-photochemical quenching（ NPQ） in the macroalgae were measured by underwater saturation pulse modulated chlorophyll fluorometer（ Diving-PAM）. The results showed that Fv/Fmwas 0. 808 ± 0. 004 for U. lactuca and 0. 816 ± 0. 009 for E. clathrata,which were higher than that for C. mexicana. Higher maximum relative electron transfer rates（ rETRmax）（ 17.52 ±2.92 and 19.59 ±4.43 μmol e·m^-2·s^-1 and half-starved value of light intensities（ Ik）（ 53.41 ±8.18 and 59.71 ±13.52 μmol photons·m^-2·s^-1 were observed in U. lactuca and E. clathrata than that in C. mexicana（ 13. 72 ± 5. 41 μmol e·m^-2·s^-1or rETRmaxand 32. 67 ± 14. 06 μmol photons·m^-2·s^-1or Ik）,indicating that U. lactuca and E.clathrata have stronger photosynthetic capacities,photo-protection capacities and tolerance to higher intense light than C. mexicana. A significantly lower RLC initial slope α in C. mexicana implied that this algal species has a higher photosynthetic capacity under weak light condition.With increasing the light intensity（ 0- 373 μmol photons·m^-2·s^-1,however,C. mexicana had a limited increase of NPQ（ 0- 0. 2）,the maximum of which was equivalent to 38. 1% of that in U. lactuca and 62. 5% of that in E. clathrata. These results indicate that the photosynthesis of E. clathrata may be more easily limited by intense light. Our study suggests that the selection of algal species for nutrient removal in a coral aquarium should be adapted to the light intensity.Single species or the combination of different species of macroalgae can be selected according to the illumination of the coral aquarium in order to maximize the efficiency of nutrient removal.