潮间带大型海藻孔石莼和鼠尾藻对铜胁迫的生理响应

Physiological response of intertidal marine macroalgae Ulva pertusa and Sargassum thunbergii to heavy metal copper stress

以潮间带大型海藻孔石莼(Ulva pertusa)及鼠尾藻(Sargassum thunbergii)为试材,研究了不同Cu^2+浓度(0,0.5,1.0,1.5,2.0mg/L)胁迫下海藻中叶绿素含量、光合特性和ATP酶活性的响应变化。结果表明,随Cu^2+浓度增加,孔石莼及鼠尾藻的光合色素含量、叶绿素荧光参数包括光能利用效率(alpha)、最大相对电子传递速率(rETRm)、半饱和光强(IK)及PSⅡ最大光能转化效率(Fv/Fm)随胁迫浓度升高均呈下降趋势,其中孔石莼Fv/Fm下降幅度更大;2种海藻中Na^+K^+-ATP及Ca^2+Mg2^+-ATP酶活性总体上随Cu^2+浓度的升高亦呈降低趋势,且孔石莼降低幅度尤为显著。这些结果表明,随胁迫程度加剧,孔石莼及鼠尾藻光合作用受抑,代谢酶活性降低,藻体遭受不可逆的严重损伤,处理体现出较明显的剂量效应;二者相比,鼠尾藻相比孔石莼对铜胁迫具更强的耐受性;叶绿素荧光参数Fv/Fm测定结果极其稳定且与胁迫程度相关极显著,可作为海藻生长及生理代谢对重金属耐受性的有效评价指标。

This study analyzed the changes in chlorophyll content, photosynthetic characteristics, and ATPase activity of Ulva pertusa and Sargassum thunbergii under different concentrations of copper (0, 0.5, 1.0, 1.5, 2.0 mg/L). Results showed that the photosynthetic pigment content, light energy utilization efficiency (alpha), the maximum relative electron transport rate (rETRm), semi-light saturation intensity (IK), and PS II maximum energy conversion efficiency (Fv/Fm) of the two species of macroalgae generally decreased with the increase in copper ion concentrations, with a higher decrease in the chlorophyll fluorescence parameters Fv/Fm of U. pertusa. The activities of both Na^+K^+-ATPase and Ca^2+Mg^2+-ATPase declined in the two species of algae with the increase in the copper ion concentration, with a particularly significant decrease being observed in U. pertusa. These results indicate that with the increase in the degree of stress, the photosynthetic rates of U. pertusa and S. thunbergii were inhibited and the activities of metabolic enzymes were reduced. The algae suffered irreversible damage, with apparent dose effects. S. thunbergii was more tolerant to copper stress than U. pertusa. Furthermore, results of the chlorophyll fluorescence parameters Fv/Fm were extremely stable and correlated significantly with the degree of stress, which can be used as an effective evaluation index for assessing the impact of heavy metal exposure on the growth and physiological metabolism of algae.