三亚造礁石珊瑚虫黄藻光合作用效率的日变化规律

Diurnal variations of photosynthetic efficiency of symbiotic algae of reef-building corals in a Sanya fringing reef

对海南三亚鹿回头珊瑚礁礁坪上块状类型的粗糙菊花珊瑚Goniastrea aspera、澄黄滨珊瑚Porites lutea和枝状类型的指状蔷薇珊瑚Montipora digitata的虫黄藻光合作用的有效光量子产量Fv/Fm′(Fv为可变荧光值,Fm′为光适应后的最大荧光值)开展了连续4d的现场监测,旨在了解珊瑚共生虫黄藻光合作用效率的日变化规律。结果表明:1)3种造礁珊瑚虫黄藻的Fv/Fm′与太阳辐射、温度呈现良好的负相关性,即太阳辐射越强、温度越高珊瑚虫黄藻的Fv/Fm′就越低,其中Fv/Fm′与太阳辐射的相关性高于与温度的相关性。2)珊瑚虫黄藻能够利用日照光进行光合作用,但存在一定的阈值,当光合有效辐射强度PAR<250μmol.(m2.s)?1时,珊瑚虫黄藻的有效光量子产量Fv/Fm′随着光强增强而增强,超过这一辐射强度时,珊瑚虫黄藻的Fv/Fm′迅速降低。3)从珊瑚虫黄藻的有效光量子产量Fv/Fm′的日变化看,粗糙菊花珊瑚虫黄藻的日变化幅度最小,澄黄滨珊瑚和指状蔷薇珊瑚的变化幅度接近。

Using pulse amplitude modulated（PAM） chlorophyll fluorescence techniques,the authors monitored the photo-chemical efficiency of symbiotic algae（zooxanthellae） within the tissues of three species of reef-building corals in a Sanya fringing reef,and analyzed their response to diurnal irradiance variations.The results indicate that： 1） Fv/Fm′,an indicator of actual photochemical efficiency,showed clear diurnal variations,with high values occurring in the morning and evening when solar radiation was weak and low values occurring in the noon matching with strong solar radiation.Regression analysis suggests that the Fv/Fm′ values were negatively corelated to both radiation and water temperature,and were more likely adjusted by solar radiation.2）Although sunlight is essential for the photosynthesis of symbiotic algae,a threshold was found between the sunshine intensity and photosynthetic efficiency.When the photosynthetic active radiation（PAR） was lower than 250μmol.（m2.s）？1,the Fv/Fm′ increased with the increasing of PAR;while Fv/Fm′ decreased with the increasing of PAR when PAR was higher than 250μmol.（m2.s）？1.3） Among the three investigated corals,Goniastrea aspera showed smaller amplitude of daily Fv/Fm′ variations than that of Porites lutea and Montipora digitata,which had similar Fv/Fm′ variations to each other.