A red tide of the dinoflagellate Alexandrium leei occurred at the beginning of April 2017 in Nomi Bay, Japan, killing aquacultured fishes, such as red sea breams and great amberjacks. This was the first known reported case of an ichthyotoxic red tide of A. leei in Japan, so we collected basic information about this dinoflagellate in the field and laboratory. Wild and cultured A. leei cells from Japan had similar morphological characteristics to cells from foreign waters, and phylogenetic analysis revealed that the Japanese isolate belonged to a northeast Asian group. Meteorological data from 2014 to 2018 showed that precipitation was lowest and the duration of bright sunshine was longest during January–May 2017 than in any other year. Field studies further showed that the water temperature during the red tide was $\sim$18 °C and the salinity and dissolved inorganic nitrogen concentrations during January–May were higher in 2017 than in any other year from 2014 to 2018. A strain of A. leei that was cultured at 10–25 °C grew at photosynthetic photon flux densities $>$15–$30\mathrm{\mu }$mol photons ${\mathrm{m}}^{-2}$ ${\mathrm{s}}^{-1}$, exhibiting a maximum growth rate at 150 $\mathrm{\mu }$mol photons ${\mathrm{m}}^{-2}$ ${\mathrm{s}}^{-1}$ at 20 °C. Toxicity bioassays showed that most red sea breams showed signs of death within 2 h of exposure to cell suspensions containing $>$3 $\times$ 10³ cells ${\mathrm{ml}}^{-1}$ of A. leei in both the logarithmic (log) and stationary phases of growth, rotifers died in a cell suspension containing $<$3 $\times$ 10³ cells ${\mathrm{ml}}^{-1}$, with log-phase cells exhibiting higher toxicity than stationary-phase cells, and haemolytic activity increased in a cell concentration-dependent manner during the log phase of growth to reach $<$90% at 5 $\times$ 10³ cells ${\mathrm{ml}}^{-1}$. The present study indicates that A. leei may affect fishes and other organisms in Japanese coastal waters.

甲鞭毛亚历山大藻雷的红潮于2017年4月初在日本能美湾发生，杀死了红鲷鱼和大great鱼等水产养殖鱼类。这是日本第一个已知的雷氏梭菌鱼腥红潮病例，因此我们在野外和实验室收集了有关该鞭毛藻的基本信息。野生和养殖雷伊来自日本的细胞具有与来自国外水域的细胞相似的形态特征，并且系统发育分析表明日本分离物属于东北亚群。2014年至2018年的气象数据显示，2017年1月至5月的降雨量最低，而晴天的持续时间最长。现场研究进一步表明，赤潮期间的水温为$〜$2017年1月至5月的盐度和溶解无机氮浓度为18°C，比2014年至2018年的任何其他年份都高。在10-25°C下培养的李氏曲霉菌株在光合光子通量密度下生长$>$15 –$30\mathrm{\mu }$摩尔光子 ${\mathrm{米}}^{-2}$ ${\mathrm{s}}^{-\mathrm{1个}}$，最大增长率为150 $\mathrm{\mu }$摩尔光子 ${\mathrm{米}}^{-2}$ ${\mathrm{s}}^{-\mathrm{1个}}$在20°C下。毒性生物测定表明，大多数红鲷鱼暴露于含有$>$3 $\times$ 10 ³ 格 ${\mathrm{毫升}}^{-\mathrm{1个}}$的A. leei在对数（LOG）两者和生长的固定相，轮虫在细胞悬浮液中含有死$<$3 $\times$ 10 ³ 格 ${\mathrm{毫升}}^{-\mathrm{1个}}$，对数期细胞显示出比固定期细胞更高的毒性，并且在达到对数生长期时，溶血活性以细胞浓度依赖性方式增加 $<$5分时90％ $\times$ 10 ³ 格 ${\mathrm{毫升}}^{-\mathrm{1个}}$。目前的研究表明，雷伊曲霉可能会影响日本沿海水域的鱼类和其他生物。