Cd^(2+)胁迫下小球藻(Chlorella vulgaris)对岩溶水HCO_3^-、Ca^(2+)利用研究——以桂林寨底地下河为例

Utilization of karst water HCO_3^-,Ca^(2+)by Chlorella vulgaris under different Cd^(2+)concentrations stress

初级生产者藻类对维持生态系统稳定具有重要的意义。2012年底广西龙江重金属Cd^(2+)污染对其下游水体中水生生物造成了严重的彩响,为了解Cd^(2+)对岩溶水体中藻类碳汇效应的影响,针对广西龙江重金属Cd^(2+)污染,文章通过室内封闭培养体系研究了在0、10、20、40μmol/L不同Cd^(2+)浓度胁迫下,小球藻对岩溶水中游离CO_2、HCO_3和Ca^(2+)的利用情况以及体系中pH和生物量的相应变化。结果表明:当Cd^(2+)浓度在0~10μmol/L时,小球藻对岩溶水中Ca^(2+)和HCO_3^-的利用基本上没有受到影响;当Cd^(2+)浓度在10~40μmol/L时,对小球藻利用Ca^(2+)和HCO_3^-具有一定的抑制作用;当Cd^(2+)浓度高于40μmol/L时,小球藻将不能利用岩溶水中Ca^(2+)和HCO_3^-同时pH漂移实验表明:当Cd^(2+)浓度在0~20μmol/L时,小球藻能同时利用岩溶水中游离CO_2和HCO_3^-进行光合作用;Cd^(2+)浓度为10μmol/L时,体系中藻细胞生物量与空白对照组基本相同;当Cd^(2+)浓度在20~40μmol/L时,小球藻只能利用岩溶水中游离CO_2进行光合作用;当Cd^(2+)浓度为20μmol/L时,藻细胞生物量为空白对照组的一半;当Cd^(2+)浓度为40μmol/L时,小球藻生物量仅为20μmol/L时的一半。

The carbon sink effect of algae is a hot topic in global carbon sink research.At the end of 2012,the Longjiang river cadmium pollution event greatly harmed downstream aquatic life.In order to study the effect of cadmium pollution on the algae carbon sink effect,this experiment explored the HCO3-- and Ca2＋ in karst water used by Chlorella vulgaris cultivated in a closed system under the stress of different Cd2＋ concentrations（0,10,20,40 μmol/L）,as well as changes to pH and the biomass of Chlorella vulgaris in the system.The results indicated that HCO3-- and Ca2＋ utilization by Chlorella vulgaris photosynthesis is essentially unchanged when the Cd2＋ concentration is in the range of 0 μmol/L to 10 μmol/L.When the Cd2＋ concentration is 10—40 μmol/L,the use of HCO3-- and Ca2＋ in karst water by Chlorella vulgaris is inhibited.When the Cd2＋ concentration exceeds 40 μmol/L,Chlorella vulgaris essentially doesn＇tuse the HCO3-- and Ca2＋ in the closed system.Furthermore,pH drift experiments show that when the Cd2＋ concentration is in the 0 μmol/L to 20 μmol/L range,Chlorella vulgaris can simultaneously use the free CO2 and HCO3-- in karst water for photosynthesis.But when the Cd2＋ concentration is between 20 μmol/L and 40 μmol/L,Chlorella vulgaris only uses free CO2 as the carbon source.Therefore,the cadmium pollution in karst aquatic ecosystem has a pronounced impact on the algae carbon sink.