Marine cladocerans are secondary producers in marine neritic ecosystems. To investigate the population dynamics and species-specific habitats of marine cladocerans in the Sea of Japan, marine cladoceran abundance was evaluated in the southern Sea of Japan and the East China Sea-Kuroshio using three mesh-size (0.06, 0.10, and 0.33 mm) plankton nets at several depths (n = 4674) over two decades from 1997 to 2018. We observed seven out of eight species, including Penilia avirostris, Evadne nordmanni, E. spinifera, Pseudevadne tergestina, and Pleopis schmackeri, from > 10% of samples, and Pleopis polyphemoides and Podon leuckartii from < 2% of samples. Abundance and diversity were higher in the Sea of Japan than in the East China Sea-Kuroshio during summer. In the East China Sea-Kuroshio, E. spinifera and Ps. tergestina abundances were high and they were distributed widely; however, other species were rare and were sparsely distributed. These suggested that the environmental conditions in the Sea of Japan are optimal for the reproduction of marine cladocerans because horizontal advective transport of marine cladocerans is not expected from the East China Sea-Kuroshio to the Sea of Japan. The habitats of the five common species in the Sea of Japan were estimated using generalized additive models (GAMs), revealing different optimal temperature ranges. Evadne nordmanni performed optimally under cold water, and the other four performed optimally under warm water. Penilia avirostris, E. spinifera, Ps. tergestina, and Pl. schmackeri coexisted in time and space in the Sea of Japan, although the vertical habitats were potentially different. Based on the estimated habitats, steep and shallow thermocline was responsible for the high marine cladoceran abundance and rich diversity in the southern Sea of Japan during summer.

海洋枝角类动物是海洋侵蚀性生态系统中的次要生产者。为了调查日本海中海洋蓝藻的种群动态和特定物种的栖息地，我们在日本南部海域和东海黑潮中使用三种筛网尺寸（0.06、0.10和0.33 mm）评估了海洋蓝藻的丰度。 ）在几个深度（浮游生物网ñ  = 4674）在1997年的二十年至2018我们观察到十分之七的8种，包括喙avirostris，Evadne nordmanni，具刺E.，Pseudevadne tergestina，和Pleopis schmackeri，从> 10％样品，以及多菌灵和Podon leuckartii来自<2％的样本。夏季，日本海的丰度和多样性高于东海黑潮。在东海黑潮中，E。spinifera和Ps。tergestina丰度高，分布广泛。但是，其他物种很少见，分布稀疏。这些表明日本海的环境条件是繁殖海洋枝角类鱼类的最佳条件，因为预计不会出现从东海黑潮到日本海的水平枝状对流运输。使用广义加性模型（GAM）估算了日本海中五个常见物种的栖息地，揭示了不同的最佳温度范围。伊娃娜·诺德曼尼（Evadne nordmanni）在冷水下表现最佳，而其他四个在温水下表现最佳。喙avirostris，E.具刺，诗篇。tergestina和Pl。schmackeri在日本海中时空共存，尽管垂直栖息地可能有所不同。根据估计的栖息地，夏季期间，陡峭而浅的温跃层是造成日本南部海域海洋蓝藻丰富和多样性丰富的原因。