Award: OCE-1735783

This project addressed how coccolithophore and diatom production in Subantarctic Mode Water (SAMW) in the Southern Ocean conditions water mass ocean biogeochemical properties (i.e, inorganic nutrients, alkalinity and dissolved inorganic carbon, carbon dioxide, primary and coccolithophore production and iron) and whether the balance between production by these two groups of marine phytoplankton impacts their growth at low latitudes. Subantarctic Mode Water (SAMW) is a major water mass of the Southern Ocean (SO) which is subducted equatorward in all three SO sectors, with the strongest formation in the Indian Ocean. Our synthesis of data from the Indian Ocean and Pacific Ocean cruises in the Southern Ocean including the following: (1) there was observable drawdown of both dissolved inorganic carbon, DIC and total alkalinity, TA in regions with higher coccolithophore biomass; (2) the drawdown of DIC and TA was accompanied by significant primary production such that the relative drawdown of DIC and TA was close to 1:1. As such, the combination of primary production and calcification reduced pCO2 in the areas of higher coccolithophore biomass and increased the air-sea CO2 gradient. In the Pacific Ocean, the drawdown of DIC and TA in regions associated with coccolithophore was not sufficient to produce a neutral or source region of efflux of CO2. Last Modified: 12/20/2023 Submitted by: NicholasRBates