The East China Sea (ECS) is the largest marginal sea in the northern western Pacific Ocean. In comparison to various physical studies, little information on the seasonal patterns in community structure of phytoplankton is currently available. Based on high performance liquid chromatography (HPLC) pigment analysis, spatiotemporal variations in phytoplankton community compositions were investigated in the northern ECS. Water temperature and salinity generally decreased toward the western part of the study area but warmer conditions in August led to strong vertical stratification of the water column. In general, major inorganic nutrient concentrations were considerably higher in the western part with a shallow water depth, and consistent with previous results, had no discernable vertical pattern during our observation period except in August. This study also revealed PO4-limited environmental conditions in May and August. The monthly averaged integral chlorophyll-a concentration varied seasonally, highest (35.2 ± 20.22 mg m−2) in May and lowest (5.2 ± 2.54 mg m−2) in February. No distinct vertical differences in phytoplankton community compositions were observed for all the sampling seasons except in August when cyanobacteria predominated in the nutrient-deficient surface layer and diatoms prevailed at deep layer. Canonical correlation analysis results revealed that nutrient distribution and the water temperature were the major drivers of the vertical distribution of phytoplankton communities in August. Spatially, a noticeable difference in phytoplankton community structure between the eastern and western parts was observed in November with diatom domination in the western part and cyanobacteria domination in the eastern part, which were significantly (p < 0.01) correlated with water temperature, salinity, light conditions, and nutrient concentrations. Overall, the two major phytoplankton groups were diatoms (32.0%) and cyanobacteria (20.6%) in the northern ECS and the two groups were negatively correlated, which holds a significant ecological meaning under expected warming ocean conditions.

中文翻译：

---

环境因子驱动的东海北部浮游植物群落时空变化

东海（ECS）是西太平洋北部最大的边缘海。与各种物理研究相比，目前关于浮游植物群落结构季节性模式的信息很少。基于高效液相色谱 (HPLC) 色素分析，研究了北部 ECS 浮游植物群落组成的时空变化。研究区西部的水温和盐度普遍下降，但 8 月的温暖条件导致水柱发生强烈的垂直分层。一般来说，西部浅水区的主要无机养分浓度要高得多，与之前的结果一致，在我们的观察期间，除了 8 月份外，没有可辨别的垂直模式。这项研究还揭示了 5 月和 8 月限制 PO4 的环境条件。月平均积分叶绿素-a 浓度随季节变化，5 月最高 (35.2 ± 20.22 mg m-2)，2 月最低 (5.2 ± 2.54 mg m-2)。浮游植物群落组成的垂直差异在所有采样季节都没有观察到明显的差异，但在 8 月份，此时营养缺乏的表层以蓝藻为主，深层为硅藻。典型相关分析结果表明，养分分布和水温是8月份浮游植物群落垂直分布的主要驱动因素。在空间上，11 月观察到东部和西部浮游植物群落结构存在显着差异，西部以硅藻为主，东部以蓝藻为主，与水温、盐度、光照条件显着 (p < 0.01) 相关，和营养浓度。总体而言，ECS北部的两个主要浮游植物群是硅藻（32.0%）和蓝藻（20.6%），并且这两个群呈负相关，在预期的变暖海洋条件下具有显着的生态意义。