Sensitivity of tropical freshwater microalgae (Mesotaenium sp., Chlorococcum sp. and Scenedesmus sp.) to environmentally relevant concentrations of hexavalent chromium (Cr⁶⁺) and cadmium (Cd²⁺) was compared individually in three growth media viz. Bold’s Basal Medium (BBM), Test Medium 1 (TM1) and Test Medium 2 (TM2) based on fluorescence reduction. Free metal content of growth media was determined by Visual MINTEQ (version 3.1). After 24 h, relative fluorescence of microalgae in the three media decreased with increased metal concentration showing a concentration dependent graded toxicity response. All microalgae were more sensitive to the metals when grown in TM1, when compared, more sensitive to Cr⁶⁺ than Cd²⁺. Metal speciation indicated that TM1 and TM2 media have higher percentage of bioavailable Cd²⁺ than BBM, and chromium was present mainly as CrO₄²⁻ and HCrO₄⁻. The results suggest that the TM1 medium is more suitable under short term exposure of microalgae to metals in environmental monitoring.

在三种生长培养基中分别比较了热带淡水微藻（中叶藻，绿球藻和风光藻）对环境相关浓度的六价铬（Cr ⁶⁺）和镉（Cd ²⁺）的敏感性。基于荧光还原的Bold基础培养基（BBM），测试培养基1（TM1）和测试培养基2（TM2）。通过Visual MINTEQ（版本3.1）确定生长培养基中的游离金属含量。24小时后，三种金属中微藻的相对荧光随金属浓度的增加而降低，显示出浓度依赖性的分级毒性反应。与之相比，在TM1中生长时，所有微藻对金属均较敏感，对Cr较敏感比Cd ^2+高6+。金属形态表明，TM1和TM2介质具有生物可利用镉更高百分比²⁺比BBM，和铬为主要存在以CrO ₄ ^2-和HCRO ₄ ^- 。结果表明，TM1培养基更适合在环境监测中将微藻短期暴露于金属下使用。