Abstract

The tropical Indian Ocean is a net sink for the carbon dioxide (CO₂) in the atmosphere and phytoplankton production plays a crucial role in CO₂ fixation and determines the direction of CO₂ flux at the sea-to-air interface. In order to assess the influence of phytoplankton composition and primary production on pCO₂ levels in the Indian Ocean, sampling was conducted at 25 stations during the spring intermonsoon period under the auspices of the Indian GEOTRACES program. The pCO₂ was significantly correlated with salinity due to the discharge of low pCO₂ water by major rivers to the Bay of Bengal (BoB). The stronger negative correlation observed between pCO₂ and major phytoplankton marker pigments, net primary production and oxygen saturation levels suggesting significant influence of biological processes on pCO₂ levels in the Indian Ocean. This study indicates that pCO₂ levels are strongly modulated by biological processes than hitherto hypothesized as solubility pump in the Indian Ocean.

Research highlights

• Surface pCO2 levels are undersaturated in the Indian Ocean compared to atmosphere, except Arabian Sea.

• Oligotrophic conditions prevailed in the entire tropical Indian Ocean.

• Picophytoplankton (cyanobacteria) is the dominant phytoplankton in the Indian Ocean.

• 4.Significant relation between phytoplankton groups and pCO2 indicates strong biological control on surface pCO2.

中文翻译：

---

印度洋浮游植物色素成分和初级生产对pCO 2水平的影响

摘要

热带印度洋是大气中二氧化碳（CO ₂）的净汇，浮游植物的产生在CO ₂固定中起着至关重要的作用，并决定了海空界面处CO _2的通量方向。为了评估印度洋中浮游植物组成和初级生产对pCO ₂水平的影响，在印度季风期的春季季风期期间，在25个台站进行了采样，这是在印度GEOTRACES计划的主持下进行的。由于主要河流向孟加拉湾（BoB）排放低pCO ₂水，因此pCO ₂与盐度显着相关。在pCO ₂之间观察到较强的负相关性以及主要的浮游植物标志物色素，净初级生产力和氧饱和度水平，表明生物过程对印度洋pCO ₂水平具有重大影响。这项研究表明，pCO _2的水平受到生物过程的强烈调节，远比迄今被认为是印度洋溶解度泵的水平高。

研究重点

• 与印度洋相比，印度洋的地表pCO2含量低于饱和，阿拉伯海除外。

• 整个热带印度洋普遍存在营养不足的状况。

• 浮游植物（蓝藻）是印度洋的主要浮游植物。

• 4.浮游植物基团与pCO2之间的重要关系表明对pCO2的表面有很强的生物学控制作用。