Monsoon-driven changes of environmental factors have been reported to be significantly variable and affects the phytoplankton community in tropical waters. This study examined the monsoonal changes of environmental parameters and the coastal phytoplankton community, including potential harmful algal bloom species, in the waters of Kota Kinabalu, Sabah, Malaysia. Bi-weekly observations were conducted from August 2017 to January 2019, covering the Southwest Monsoon (SWM), Northeast Monsoon (NEM), and inter-monsoon periods (IMPs). Sea surface temperature, salinity, and daily average photosynthetic active radiation (PAR) were significantly different between the SWM and the NEM. Total phytoplankton densities were significantly higher in the SWM with median cell densities of 1.12 $\times$ 10⁴ cells L⁻¹ compared to the NEM with 3.98 $\times$ 10³ cells L⁻¹. Nutrient measurements indicated that the waters were mesotrophic, with low phosphate (P) levels (<0.3 $\mathrm{\mu }$M-P on average). N:P ratios were often above the Redfield ratio (16N:1P), while high Si:N (>1) and Si:P ratios (>16Si:1P) indicated that silicate was not limiting, a condition favourable for diatom growth. Phytoplankton dynamics shifted from a dinoflagellate-dominant community (Protoperidinium spp. and Prorocentrum spp.) to a diatom-dominant community (Leptocylindrus spp. and Dactyliosolen spp.) during the NEM, which was preceded by a peak in silicate and nitrate. Later, Chaetoceros spp. became dominant during the second SWM. The presence of intermittent increases in Margalefidinium polykrikoides and Pyrodinium bahamense var. compressum cell densities may trigger future blooms in these waters. Canonical Correspondence Analysis suggests that the dinoflagellate-dominant community was driven by changes in PAR and Si:N while changes in N:P and salinity shaped the diatom-dominant community. The shifts of the phytoplankton community composition in relation to the different monsoonal periods suggests that the monsoons function as environmental drivers which structure the phytoplankton community of this coastal ecosystem.

据报道，季风驱动的环境因素变化显着变化，并影响热带水域的浮游植物群落。这项研究检查了马来西亚沙巴州亚庇水域环境参数的季风变化和沿海浮游植物群落，包括潜在的有害藻华物种。从2017年8月至2019年1月，每两周进行一次观测，涵盖西南季风（SWM），东北季风（NEM）和季风间周期（IMP）。SWM和NEM之间的海面温度，盐度和日平均光合有效辐射（PAR）显着不同。SWM中的总浮游植物密度显着更高，中位细胞密度为1.12$\times$10个⁴格L ^-1，而NEM为3.98$\times$10 ³格L ^-1。营养测定表明水是中营养的，磷酸盐（P）水平低（<0.3$\mathrm{\mu }$平均MP）。N：P比率通常高于Redfield比率（16N：1P），而高Si：N（> 1）和Si：P比率（> 16Si：1P）表明硅酸盐不受限制，这是硅藻生长的有利条件。浮游植物动力学从甲藻主导社区（移位Protoperidinium属和原甲藻属物种）的硅藻主导社区（丹麦细菌和Dactyliosolen所述NEM，这是之前通过在硅酸盐和硝酸盐的峰值期间属）。后来，Chaetoceros spp。在第二个SWM中成为主导。Margalefidinium polykrikoides和Pyrodinium bahamense var中存在间歇性增加。ç ompressum细胞密度可能触发这些水域将来的开花。典范对应分析表明，鞭毛虫主导的群落是由PAR和Si：N的变化驱动的，而N：P和盐度的变化则形成了硅藻优势的群落。浮游植物群落组成相对于不同季风周期的变化表明季风是环境驱动因素，构成了该沿海生态系统的浮游植物群落。