Coccolithophores, a calcifying phytoplankton group, are a major component of the oligotrophic ocean. The tropical eastern Indian Ocean (EIO) possesses a complex regional hydrological system that also impacts the global climate. Coccolithophores are a major indicator of these oceanographic and air-sea processes. Understanding coccolithophore population dynamics associated with extreme climate events is significant for predicting future ocean biogeochemical studies, and contributing to the regional and global climatic model. Therefore, we used a consecutive 7 years (2011–2018) dataset of coccolithophore assemblages and their organic carbon biomass from the tropical EIO during the spring premonsoon period to interpret the aforementioned climatic changes. Among the 33 identified species, the ecologically important species Gephyrocapsa oceanica, Emiliania huxleyi, Algirosphaera robusta, Florisphaera profunda, Umbilicosphaera sibogae, and Umbellosphaera irregularis dominated the coccolithophore assemblages. In the EIO, regional environmental factors including high-level eddy kinetic energy, equatorial jets and upwelling lead to the patchy distribution of surface coccolithophores, but no signs of interannual spatial variations were observed. Furthermore, this study revealed that variability in euphotic coccolithophore abundance and diversity indices were correlated with global climate anomalies. The variations in the interannual coccolithophore abundance and estimated coccolithophore organic carbon could be a result of global warming and other climatic variabilities. Particularly, an apparent increase in coccolithophore abundance was observed during El Niño and positive Indian Ocean Dipole (IOD) events due to their favorable thermal regimes. In contrast, the abundance of coccolithophores reduced during La Niña and negative IOD events. Overall, our pilot findings would encourage further studies on coccolithophore responses to regional EIO environments and global climatic anomalies.

球藻浮游生物是钙化的浮游植物群，是贫营养海洋的主要组成部分。热带印度洋东部（EIO）拥有复杂的区域水文系统，也影响着全球气候。球墨镜是这些海洋学和海-气过程的主要指标。了解与极端气候事件有关的球石藻种群动态对预测未来的海洋生物地球化学研究以及为区域和全球气候模型做出贡献具有重要意义。因此，我们使用了连续7年（2011-2018年）的数据，从季风前期的热带EIO收集了球石藻类组合及其有机碳生物量，以解释上述气候变化。在确定的33种物种中，具有生态重要性的物种大洋藻（Gephyrocapsa oceanica），艾美耳草（Emiliania huxleyi），稳健藻藻（Algirosphaerarobusta），深层氏菌（Florisphaera profunda），西伯利亚伞形藻（Umbilicosphaera sibogae）和不规则伞藻（Umbellosphaera regularis）占主导地位的cococolithophore组合。在EIO中，包括高涡动能，赤道射流和上升流在内的区域环境因素导致表面球墨鱼鳞片的分布不规则，但未观察到年际空间变化的迹象。此外，这项研究表明，常绿球石藻丰度和多样性指数的变化与全球气候异常有关。年度球藻石藻丰度和估计的球藻石藻有机碳的变化可能是全球变暖和其他气候变化的结果。特别是，在厄尔尼诺和正印度洋偶极子（IOD）事件期间，由于它们有利的热力状态，观察到的球石藻丰度明显增加。相比之下，拉尼娜（LaNiña）和负IOD事件期间，球果绿体的丰度降低。总体而言，我们的试验结果将鼓励进一步研究球石藻对区域EIO环境和全球气候异常的反应。