The composition of the phytoplankton community in Tokyo Bay was analyzed using samples collected monthly at 0 and 5 m depths from 2003 to 2017, along with environmental factors. Three diatom genera—Skeletonema, Thalassiosira, and Pseudo-nitzschia—dominated over the study period. The sum of the three genera accounted for 75% of the total phytoplankton cell density. Skeletonema was the most abundant taxon, of which the cell density reached > 10⁴ cells mL⁻¹. A pattern of seasonal change in the community composition was detected, and the varying compositions were grouped into three seasons: a mixing season (November–February), an early stratified season (March–June), and a late stratified season (July–October). The mixing season was characterized by high nutrient content (dissolved inorganic nitrogen > 30 µM) and low temperature (< 17 °C), and the late stratified season was characterized by high temperature (> 22 °C) and low salinity (< 28 at the surface). In a modified seasonal Mann–Kendall test, we did not find any increasing or decreasing trend of three diatom genera in the analysis for whole months. However, the test applied to each seasonal group revealed a significant increasing trend of Pseudo-nitzschia abundance in the late stratified season at 0 m depth. In contrast, Skeletonema abundance showed a decreasing trend at a 5 m depth in the same season. The succession of the phytoplankton community was more obvious when the yearly trend was analyzed for each season.

利用 2003 年至 2017 年每月在 0 和 5 m 深度采集的样本以及环境因素分析了东京湾浮游植物群落的组成。三个硅藻属——骨条藻属、海藻属和拟菱形藻属——在研究期间占主导地位。三个属的总和占浮游植物细胞密度的75%。骨条藻是最丰富的分类单元，其细胞密度达到>10 ⁴  cells mL ^-1。检测到群落组成的季节变化模式，并将不同的组成分为三个季节：混合季节（11月至2月）、早期分层季节（3月至6月）和晚期分层季节（7月至10月） ）。混合季的特点是高养分含量（溶解无机氮> 30 µM）和低温（< 17 ℃），分层后期的特点是高温（> 22 ℃）和低盐度（< 28 °C）。表面）。在修改后的季节性曼-肯德尔检验中，我们在整个月的分析中没有发现三个硅藻属有任何增加或减少的趋势。然而，对每个季节组进行的测试表明，在分层季节末0米深度处，拟菱形藻的丰度呈显着增加的趋势。相比之下，同一季节5 m 深度的骨条藻丰度呈下降趋势。从各季节的年度趋势分析来看，浮游植物群落的演替更加明显。