Coastal eutrophication is one of the pivotal factors driving occurrence of harmful algal blooms (HABs), whose underlying mechanism remained unclear. To better understand the nutrient regime triggering HABs and their formation process, the phytoplankton composition and its response to varying nitrogen (N) and phosphorus (P), physio-chemical parameters in water and sediment in Johor Strait in March 2019 were analyzed. Surface and sub-surface HABs were observed with the main causative species of Skeletonema, Chaetoceros and Karlodinium. The ecophysiological responses of Skeletonema to the low ambient N/P ratio such as secreting alkaline phosphatase, regulating cell morphology (volume; surface area/volume ratio) might play an important role in dominating the community. Anaerobic sediment iron-bound P release and simultaneous N removal by denitrification and anammox, shaped the stoichiometry of N and P in water column. The decrease of N/P ratio might shift the phytoplankton community into the dominance of HABs causative diatoms and dinoflagellates.

沿海富营养化是导致有害藻华（HABs）发生的关键因素之一，其潜在机制尚不清楚。为了更好地了解触发 HAB 的营养状况及其形成过程，我们分析了 2019 年 3 月柔佛海峡水和沉积物中浮游植物的组成及其对不同氮 (N) 和磷 (P)、理化参数的响应。表面和亚表面 HAB 与主要致病物种Skeletonema、Chaetoceros和Karlodinium一起被观察到。骨骼虫的生态生理反应对于低环境 N/P 比，例如分泌碱性磷酸酶，调节细胞形态（体积；表面积/体积比）可能在支配群落方面发挥重要作用。厌氧沉积物与铁结合的 P 释放和通过反硝化和厌氧氨氧化同时去除 N，塑造了水柱中 N 和 P 的化学计量。N/P 比的降低可能使浮游植物群落转变为 HAB 致病硅藻和甲藻的优势。