Cyst formation plays an important role in the resistance of dinoflagellates to adverse environments, and cyst germination is considered one of the causes of harmful algal blooms (HABs). Among the methods for mitigating HABs, modified clay (MC) is considered a promising strategy because of its high efficiency and low environmental impacts. The typical HAB species Alexandrium pacificum was focused on in this study to clarify the effects of MC on cyst formation and germination. The results showed that more than 90% of the vegetative cells were removed under the 0.6 g/L MC treatment. The vegetative cell density was monitored over 90 d and increased slightly to the peak at 10 d after the cell removal experiment, but persistent growth was not observed. The amount of cysts was maximal at 20 d after removal, however, most of the cysts were temporary cysts that subsequently disappeared. After 80 d, all the remaining cysts were resting ones. The total density of resting cysts was higher under MC concentrations of 0.2 and 0.4 g/L and lower under concentrations of 0.6, 0.8 and 1.0 g/L compared with that in the control. The total formation rate of resting cysts was 29.6% in the control group, and the lowest formation rate in the experimental groups was 15.5% at 0.6 g/L MC. The total germination rate of resting cyst decreased as the MC concentration increased, and approximately 68.0% of the resting cysts in the control group germinated successfully, whereas the addition of MC reduced the germination rate to as low as 12.4%. Our results indicated that the application of appropriate MC concentrations may provide an effective mitigation strategy for A. pacificum blooms because it does not leave more residual cysts, which can act as “seeds” for the initiation of HABs.

囊肿的形成在对鞭毛藻对不利环境的抵抗中起着重要作用，囊肿的萌发被认为是有害藻华（HABs）的原因之一。在减轻HAB的方法中，改性粘土（MC）因其高效和低环境影响而被认为是一种有前途的策略。典型的HAB物种Alexandrium pacificum在本研究中的重点是阐明MC对囊肿形成和萌发的影响。结果表明，在0.6 g / L MC处理下，超过90％的营养细胞被去除。在去除细胞的实验后的90 d内对营养细胞的密度进行了监测，并在10 d时略有增加，达到了峰值，但未观察到持续的生长。去除后20 d囊肿最大，但是大多数囊肿是暂时性囊肿，随后消失。80 d后，所有剩余的囊肿均为静息囊肿。与对照组相比，静息囊肿的总密度在MC浓度为0.2和0.4 g / L时较高，而在0.6、0.8和1.0 g / L的浓度下较低。对照组静息囊肿的总形成率为29.6％，在0.6 g / L MC下，实验组的最低形成率为15.5％。静息囊肿的总发芽率随MC浓度的增加而降低，对照组中约68.0％的静息囊肿成功发芽，而添加MC使发芽率低至12.4％。我们的结果表明，适当的MC浓度的应用可能为以下人群提供有效的缓解策略太平洋开花，因为它不会留下更多的残留囊肿，而这些囊肿可以作为引发HABs的“种子”。