The tropical Indian Ocean is a net sink for the carbon dioxide (CO$_{2}$) in the atmosphere and phytoplankton production plays a crucial role in CO$_{2}$ fixation and determines the direction of CO$_{2}$ flux at the sea-to-air interface. In order to assess the influence of phytoplankton composition and primary production on pCO$_{2}$ 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 pCO$_{2}$ was significantly correlated with salinity due to the discharge of low pCO$_{2}$ water by major rivers to the Bay of Bengal (BoB). The stronger negative correlation observed between pCO$_{2}$ and major phytoplankton marker pigments, net primary production and oxygen saturation levels suggesting significant influence of biological processes on pCO$_{2}$ levels in the Indian Ocean. This study indicates that pCO$_{2}$ levels are strongly modulated by biological processes than hitherto hypothesized as solubility pump in the Indian Ocean.

$\bf{Highlights}$

$\bullet$ Surface pCO$_{2}$ levels are undersaturated in the Indian Ocean compared to atmosphere, except Arabian Sea.

$\bullet$ Oligotrophic conditions prevailed in the entire tropical Indian Ocean.

$\bullet$ Picophytoplankton (cyanobacteria) is the dominant phytoplankton in the Indian Ocean.

$\bullet$ Significant relation between phytoplankton groups and pCO$_{2}$ indicates strong biological control on surface pCO$_{2}$.