不同磷源对砷胁迫下2种绿藻生长的影响

Stress Effects of Arsenate on Two Common Freshwater Green Microalgae under Different Phosphorus Regimes

选取常见淡水绿藻——斜生栅藻和蛋白核小球藻为试验藻种,通过室内培养分析其在不同磷源下(溶解性无机磷(DIP)(本研究选取磷酸氢二钾)、β-甘油磷酸钠(β-P)和腺苷-5’-三磷酸二钠盐(ATP-P))的生长差异及受砷酸盐(As(Ⅴ))的胁迫响应。结果表明,在给定的3种磷源下,2种绿藻经连续7 d培养均能增殖,其中,以叶绿素a(Chl a)得到的2种藻的比生长率较细胞光密度(OD)在3种磷源环境下差异更为显著,蛋白核小球藻在ATP环境下的实际光合产率(Yield)较DIP和β-P相对要低(降低约4.55%)且差异显著(P<0.05),总体上斜生栅藻表现出对β-P更好的适应性,蛋白核小球藻则最适应于DIP环境。As(Ⅴ)胁迫不仅改变了不同磷源环境下藻体Yield与OD和Chl a的相关性,使其由原来的无规则相关转变为显著正相关,进而可较好响应不同磷源环境下As(Ⅴ)的胁迫,并且使2种藻体的Chl a在3种磷源环境下以及蛋白核小球藻的Yield在有机与无机磷间均表现出显著差异;由OD、Chl a和Yield得出的3种磷源环境下As(Ⅴ)对斜生栅藻的96 h半数效应浓度(96 h-EC 50)均表现为β-P>DIP>ATP-P,且以OD得出的96 h-EC 50差异较为显著,分别为2.58×109、4.46×105和1.95×105μg·L-1,蛋白核小球藻为DIP>ATP-P>β-P,以Yield得出的96 h-EC 50差异显著,分别为2.95×109、1.60×106和7.52×104μg·L-1,说明As(Ⅴ)对藻的胁迫因藻种及其对磷的适应性差异而表现不同;藻对磷的较好适应性一定程度上可以缓解其受As(Ⅴ)的胁迫。OD可较好指示A s(Ⅴ)胁迫下斜生栅藻的生长,而Yield可指示As(Ⅴ)胁迫下蛋白核小球藻的生长。研究结果对深入了解不同磷源环境下砷胁迫对淡水藻体的生长影响具有重要科学意义。

The stress effects of arsenate(As(Ⅴ))on algal growth were investigated in two green microalgae Scenedesmus obliquus and Chlorella pyrenoidosa under three different phosphorus substrates including the dissolved inorganic phosphorus(DIP)of orthophosphate,dissolved organic phosphorus(DOP)ofβ-sodium glycerophosphate(β-P)and adenosine triphosphate(ATP-P).Experimental results showed that both of the microalgae in 7 d-culture period could grow well with significant differences in their chlorophyll a(Chl a)under three phosphorus conditions than that of optical density(OD),and actual quantum yield(Yield)of Chlorella pyrenoidosa especially in ATP-P was significantly lower than that of DIP andβ-P(about 4.55%).In contrast,better adaptability was presented for Scenedesmus obliquus inβ-P condition and Chlorella pyrenoidosa in DIP conditions.The correlations were significantly positive between Yield and Chl a(or OD)of the both microalgae under different phosphorus conditions after As(Ⅴ)exposure,indicating the efficient response of these two algae to As(Ⅴ)stress.Meanwhile,the significant differences of Chl a for the both microalgae were observed under different phosphorus conditions,including the Yield of Chlorella pyrenoidosa between DIP and DOP.The 96 h-EC 50 of As(Ⅴ)obtained from OD,Chl a and Yield for the two selected microalgae were consistent under different phosphorus conditions.Specifically,the tolerance of Scenedesmus obliquus to As(Ⅴ)ranked in the order ofβ-P>DIP>ATP-P,with the 96 h-EC 50 obtained from OD of 2.58×109,4.46×105 and 1.95×105μg·L-1 which had significant differences;for Chlorella pyrenoidosa the order was DIP>ATP-P>β-P,with the 96 h-EC 50 from Yield of 2.95×109,1.60×106 and 7.52×104μg·L-1.Suggestively,the stress of As(Ⅴ)on the two selected microalgae were affected by different algal species and their relative adaptabilities to different phosphorus conditions.Specifically,the better adaptability for phosphorus of microalgae could reduce As(Ⅴ)stress.Furthermore,the growth indicator of OD could demonstrate As(Ⅴ)stress well for Scenedesmus obliquus,but it is Yield for Chlorella pyrenoidosa under different phosphorus conditions.Accordingly,our findings will facilitate the comprehensive understanding of As(Ⅴ)effects on freshwater microalgae under different phosphorus conditions.