福建沿海米氏凯伦藻赤潮对皱纹盘鲍的危害原因

The detrimental impacts of Karenia mikimotoi blooms on the abalone Haliotis discus hannai in Fujian Province

针对2012年在福建沿海致鲍鱼大量死亡、造成了巨大经济损失的米氏凯伦藻赤潮,为验证鲍鱼短时间内大量死亡的原因是否来源于米氏凯伦藻自身的毒性效应,本文初步研究了不同环境条件下,分离自赤潮现场的一株米氏凯伦藻（Karenia mikimotoi）对皱纹盘鲍（Haliotis discus hannai）的急性毒性效应。实验过程中,监测了曝气与非曝气条件下,环境因素中氨氮（TAN）、p H、DO的变化。研究发现,曝气条件下,实验体系中DO的变动范围为7.3~7.8 mg/L,p H的变动范围为7.5~8.2,TAN浓度的变动范围为0.0035~0.084 mg/L（能维持贝类正常生存）,此时米氏凯伦藻趋近于赤潮现场藻细胞数量时（3×10~7/L）,鲍鱼48 h死亡率为33.3%,96 h内死亡率达100%,说明此时鲍鱼的急剧死亡是由米氏凯伦藻本身的毒性效应引起的。在非曝气条件下,DO由7.1 mg/L降低至1.8 mg/L,实验体系中p H的变动范围为7.2~8.1,TAN的变动范围为0.007~0.051 mg/L,此时米氏凯伦藻藻细胞数量为3×10~7/L时,鲍鱼16 h内死亡率达100%,说明低氧的环境条件可以导致赤潮对鲍鱼的毒性效应加剧。由此可以推测,赤潮发生时皱纹盘鲍短时间内的大量死亡与米氏凯伦藻本身的毒性效应有关,而低氧等环境条件可以导致毒性效应加剧。

During May and June in 2012 ,Karenia mikimotoi blooms occurred in the coastal sea areas of Fujian Province, which were responsible for massive mortalities of abalones and huge economic losses. However, little is known about whether the mortalities of abalones were associated with the detrimental effects of K. mikimotoi or not. Under laboratory conditions, we investigated the effects of K. mikimotoi on the survival of the abalone Haliotis discus hannai at different environmental conditions. Meanwhile, we also monitored the changes of some main environmental factors in the conditions of aeration and non-aeration, including DO, pH, and total ammonia （ TAN ）. At the aeration condition, DO was in the range of 7.3 - 7.8 mg/L,pH of 7.5 - 8.2,TAN of 0. 0035 - 0. 084 mg/L,which were all suitable for the survival of abalone. At this condition, the mortality rates reached 33.3 % in 48 h,and reached 100% in 96 h when exposed to K. mikimotoi at the cell amounts of 3 × 10^7/L, which indicated that the rapid mortalities of abalones were caused by the detrimental effects of K. mikimotoi. At the non-aeration condition, DO was in the range of 7.1 - 1.8 mg/L,pH of 7.2 -8. 1, TAN of 0. 007 -0. 051 mg/L, the mortality rates reached 100% in 16h when exposed to K. mikimotoi at the cell amounts of 3 × 10^7/L. The results showed that the low oxygen condition made the toxic effects stronger. Therein, we can speculated that the rapid and massive mortalities of abalone during the occurrence of K. mikimotoi bloom were related with the toxic effects of the dinoflagellate K. mikimotoi, furthermore, the low oxygen conditions during blooms may strengthen the effects.