重金属离子胁迫对赤潮微藻的急性毒性

重金属污染和赤潮都是较为突出的海洋环境问题,为给相关研究提供基础试验数据,在实验室条件下研究了Cu2+、Cd2+、Zn2对米氏凯伦藻和微小原甲藻的急性毒性效应.通过2种藻的EC50(半数抑制浓度)比较了其敏感性差异,分析了不同浓度重金属胁迫对微藻的影响；同时,利用TEM(transmission electronic microscopy,透射电镜技术)和FCM(flow cytometry,流式细胞术)研究了重金属Cu2+的急性毒性胁迫在亚细胞水平上对米氏凯伦藻的损伤.其中,Cu2+、Cd2+、Zn2+对微小原甲藻的48 h EC50和96 h EC50分别为0.514和0.276 mg/L、0.835和1.215 mg/L及4.376和7.976 mg/L;对米氏凯伦藻的48 h EC50和96 h EC50分别为1.881和1.881 mg/L、5.405和6.268 mg/L及13.134和18.732 mg/L.结果表明:2种微藻的种群相对增长率随着胁迫浓度的增加而下降,3种重金属离子的毒性表现出Cu2+＞Cd2+＞Zn2+的趋势,微小原甲藻对重金属胁迫更敏感；Cu2+胁迫可使米氏凯伦藻细胞体积增大,内容物复杂程度增高,但叶绿素a的MFI(mean fluorescence intensity,平均荧光强度)的变化不明显；Cu2+胁迫对藻膜结构的损伤较明显,但对线粒体及叶绿体的结构影响不明显.

Acute Toxic Effects of Heavy Metal Ions on Growth of Marine Bloom-Forming Microalgae

The acute toxic effects of Cu2+,Cd2+ and Zn2+ on growth of the marine microalga Karenia mikimotoi and Prorocentrum minimum were investigated.The sensitivity differences of the two alga were estimated,and the effects of different concentrations of heavy metals on growth of the bloom-forming microalga were analyzed.Moreover,a further study on toxicity of Cu2+ to K.mikimotoi at the sub-cellular level was conducted using the techniques of transmission electron microscope(TEM) and flow cytometry(FCM).The 48 h EC50/96 h EC50 of Cu2+,Cd2+ and Zn2+ stresses on P.minimum were 0.514 and 0.276 mg/L,0.835 and 1.215 mg/L,4.376 and 7.976 mg/L,respectively.The stresses on K.mikimotoi were 1.881 and 1.881 mg/L,5.405 and 6.268 mg/L,13.134 and 18.732 mg/L,respectively.The results showed that: 1) The relative growth rate of both populations of the two marine microalga decreased gradually with the increasing concentrations of the heavy metals,and the sensitivity was Cu2+ > Cd2+ > Zn2+ according to the 48 h EC50 and 96 h EC50.P.minimum was more sensitive to the stress.2) Results of FCM analysis showed that Cu2+ exposure significantly increased the cell volume and the complexity of the cell contents of K.mikimotoi,but it did not affect the mean fluorescence intensity(MFI) of chlorophylls a as compared to the control without Cu2+ stress.3) When exposed to Cu2+ stress,the ultrastructure of the membrane system of K.mikimotoi was obviously damaged,while the structure of mitochondria and chloroplast showed little changes by TEM analysis.