赤潮生物伊姆裸甲藻(Gymnodinium impudicum)毒性和温度适应初步研究

Preliminary study on the toxicity and temperature adaptation of a harmful alga Gymnodinium impudicum

2021年8月26日,我国广东省海门湾海域暴发了一起裸甲藻赤潮,现场藻细胞密度达3.39×10^(3)cells·mL^(−1).本文对该次赤潮肇事种进行了形态学与系统发育学分析,对现场赤潮水样进行了海洋青鳉鱼(Oryzias melastigma)48 h急性生物毒性分析,对赤潮藻纯培养细胞进行了卤虫(Artemia salina)48 h急性生物毒性分析、溶血活性测定以及最佳生长温度研究.结果表明,此次赤潮肇事种为伊姆裸甲藻(Gymnodinium impudicum).急性生物毒性实验结果表明,赤潮海水对海洋青鳉鱼无明显致死效应,海洋青鳉鱼48 h内游动正常,无异常反应.该藻纯培养藻种对卤虫具有一定的致死效应,藻密度4.32×10^(3)cells·mL^(−1)时,48 h卤虫死亡率为35%.溶血活性检测结果表明,该藻溶血活性较低,藻细胞密度为3.66×10^(3)cells·mL^(−1)时,溶血活性百分数为26.7%.实验室纯培养下,该藻对温度适应性较强,在20℃、25℃、30℃下均可生长,最高密度达(2.35—2.54)×10^(4)cells·mL^(−1).25℃时藻细胞比生长速率最高(μmax=0.371);33℃不适宜该藻增殖,此温度下,藻密度长时间维持在(1.40—6.85)×10^(2)cells·mL^(−1).本次赤潮为我国南海海域首次报道伊姆裸甲藻赤潮,该藻的潜在危害及赤潮灾害效应值得进一步关注.

A Gymnodinium sp.-dominated algae bloom occurred on August 26th,2021,in Haimen Bay,Guangdong Province.The maximum cell density was 3.39×10^(3)cells·mL^(−1).We investigated the morphology and phylogeny of the causative species in this study.Acute toxicity study of the bloom samples on marine medaka(Oryzias melastigma)over a 48-hour period was conducted.The hemolytic activity assay,toxicity to Artemia salina,and the optimum growth temperature of the algae were also investigated.The dominant species of this bloom was identified as Gymnodinium impudicum.The bloom sample had no toxic effects on marine medaka,and the O.melastigma survived and swam normally in 48 h.The lethality rate of G.impudicum culture(with a cell density of 4.32×10^(3)cells·mL^(−1))to Artemia salina in 48 h was 35%.The hemolytic activity of G.impudicum culture(with a cell density of 3.66×10^(3)cells·mL^(−1))to rabbit’s erythrocyte was 26.7%.The algae grew well at temperature ranged from 20°C to 30°C,reaching a peak cell density of(2.35—2.54)×10^(4)cells·mL^(−1).The maximum growth rate was recorded at 25°C with aμmax value of 0.371.Gymnodinium impudicum failed to reproduce abundantly at 33°C,and maintained at a low density of(1.40—6.85)×10^(2)cells·mL^(−1).This is the first reported of G.impudicum bloom in the South China Sea.More consideration should be given to G.impudicum for its possible risks and disastrous impacts when blooming.