铀对2种小球藻生长和光合作用的影响

Effects of uranium on the growth and photosynthesis of two types of Chlorella vulgaris

【目的】探究铀对藻类生长及光合作用的影响,筛选新的基于光合作用的水体铀污染生态风险评价指标。【方法】采用不同浓度铀(0,0.5,1,5,10,20 mg/L U^(6+))分别处理普通小球藻(Cholorella vulgaris)和黄龙普通小球藻2种来自不同生境的微藻,在处理后的第3,5,7,10,14天进行相对生长速率、光合放氧速率、叶绿素含量和叶绿素荧光动力学参数等指标的测定。【结果】(1)0.5 mg/L低浓度铀处理显著促进2种小球藻的生长和光合作用效率,表现为2种微藻的相对生长速率、光合放氧速率、光系统Ⅱ最大光化学量子产量(F_(v)/F_(m))、实际光化学量子产量[Y(Ⅱ)]、相对电子传递速率(rETR)等叶绿素荧光参数均显著高于对照,而5~20 mg/L高浓度铀处理则显著抑制2种小球藻的生长和光合作用;(2)黄龙普通小球藻比普通小球藻对铀处理更敏感,在1 mg/L处理浓度下生长与光合作用就受到显著抑制,可以作为水体铀污染生物监测的指示生物;(3)回归分析表明,不同浓度铀处理下,叶绿素荧光参数Y(Ⅱ)和rETR的响应速度快于相对生长速率、光合放氧速率、叶绿素含量和F_(v)/F_(m)等指标,可以作为水体铀污染生态风险评价的敏感指标。【结论】铀对小球藻的生长和光合作用表现出低促高抑的浓度效应,且黄龙小球藻对铀污染更敏感,可将黄龙小球藻和叶绿素荧光动力学参数Y(Ⅱ)和rETR结合起来应用于水体铀污染的生态风险评价。

[Objective]In order to explore the impact of uranium on algae growth and photosynthesis,and to screen new ecological risk assessment indicators for uranium pollution in water bodies based on photosynthesis.[Methods]This experiment used different concentrations of uranium(0,0.5,1,5,10,20 mg/L U^(6+))to treat two types of microalgae,chlorella(Chlorella vulgaris)and Huanglong chlorella,from different environments.The relative growth rate,photosynthetic oxygen release rate,chlorophyll content,and chlorophyll fluorescence kinetic parameters were measured on the 3rd,5th,7th,10th,and 14th days after treatment.[Results](1)Low concentration uranium(0.5 mg/L)treatment significantly promoted the growth and photosynthetic efficiency of the two types of microalgae,where the relative growth rate,photosynthetic oxygen release rate,maximum photochemical quantum yield(F_(v)/F_(m))of photosystemⅡ,actual photochemical quantum yield Y(Ⅱ),and relative electron transfer rate(rETR)of the two microalgae were significantly higher than the control.However,high concentration uranium treatment(5-20 mg/L)significantly inhibited the growth and photosynthesis of the two types of chlorella.(2)Huanglong chlorella was more sensitive to uranium treatment than chlorella,and its growth and photosynthesis were significantly inhibited at 1mg/L,and it could be used as an bioindicator for monitoring of uranium pollution in water bodies.(3)Regression analysis showed that under different concentrations of uranium treatment,the response speed of chlorophyll fluorescence parameters Y(Ⅱ)and rETR was faster than the changes in relative growth rate,photosynthetic oxygen release rate,chlorophyll content,and F_(v)/F_(m),which could be used as sensitive indicators for ecological risk assessment of uranium pollution in water bodies.[Conclusion]Uranium exhibits a concentration effect on the growth and photosynthesis of chlorella,where low concentrations promote growth while high concentrations inhibit growth.Huanglong chlorella is more sensitive to uranium pollution.Therefore,the combination of Huanglong chlorella and chlorophyll fluorescence kinetic parameters Y(Ⅱ)and rETR can be applied for the ecological risk assessment of uranium pollution in water bodies.