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浮游植物是生活在河流、湖泊、海洋等水体中的一类营光合作用的微型生物,含原核生物(蓝藻)和各种真核生物. 浮游植物群落结构受各种环境因素和污染物的影响,当水体中的氮、磷、硅等营养物质过量时,浮游植物会暴发性增殖形成赤潮(也称藻华)[1]. 赤潮暴发可对渔业、海洋资源、水产养殖、公共健康等造成直接或间接的危害[2]. 赤潮暴发期会造成养殖水体光照、二氧化碳等严重不足,从而破坏水体生态系统. 赤潮消亡时由于微生物分解作用也会造成水体缺氧而引发水生生物的死亡. 同时,一些赤潮种,如亚历山大藻(Alexandrium spp.)可产生毒素并通过食物链在水生生物体内富集或引起鱼类死亡[3].
裸甲藻类是我国近海常见的一类赤潮生物,其中链状裸甲藻(Gymnodinium catenatum)已经在澳大利亚、墨西哥、日本等23个国家引发赤潮[3–4]. 链状裸甲藻可产生麻痹性贝类毒素,2017年我国福建省沿海海域发生了由该藻引起的数十人中毒事件[5]. 伊姆裸甲藻(Gymnodinium impudicum)是裸甲藻属(Gymnodinium)下的另一常见赤潮肇事种,已在埃及、韩国、西班牙等多地暴发赤潮[6–8]. 该种与链状裸甲藻形态极为相近,常发生两种藻鉴定混淆的情况,如发生在帕加西蒂科斯湾(Pagassitikos Gulf)的链状裸甲藻赤潮后经鉴定肇事藻应为伊姆裸甲藻[8],因此推测伊姆裸甲藻赤潮的暴发频数可能因错误鉴定而被低估.
广东省海门湾位于练江流域入海口. 根据2020至2022年海门湾闸桥断面监测站点每月入海河流监测信息显示,该区域过去3年水质污染严重[9] . 2021年8月,广东省海门湾暴发了一起裸甲藻类赤潮,本文对此次赤潮进行了采样,对肇事种进行形态学鉴定与系统发育学分析,并探究了赤潮种的温度适应性、溶血活性和急性生物毒性,以期为我国近海有毒有害赤潮的监测与研究提供参考.
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
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摘要: 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3.39×103 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4.32×103 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3.66×103 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)×104 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)×102 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.Abstract: A Gymnodinium sp.-dominated algae bloom occurred on August 26th, 2021, in Haimen Bay, Guangdong Province. The maximum cell density was 3.39×103 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 4.32×103 cells·mL−1) to Artemia salina in 48 h was 35%. The hemolytic activity of G. impudicum culture (with a cell density of 3.66×103 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)×104 cells·mL−1. The maximum growth rate was recorded at 25 °C with a μmax value of 0.371. Gymnodinium impudicum failed to reproduce abundantly at 33 °C, and maintained at a low density of (1.40—6.85)×102 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.
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