A diverse community constitutes global coccolithophore calcium carbonate stocks

Coccolithophores are key marine phytoplankton contributing to the global ocean carbon cycle through calcium carbonate production. Most studies focus on Gephyrocapsa huxleyi, a globally abundant but lightly calcified species, potentially misrepresenting coccolithophore biogeochemistry. Combining new observations with species-resolved machine learning, we map global distributions and carbon stocks of the most abundant coccolithophore species. We estimate a total inorganic carbon stock of 10.3 [3.8, 20.1] Tg C. G. huxleyi accounts for only ≈ 7.2 % of this stock, while more heavily calcified species, Florisphaera profunda, Calcidiscus leptoporus and Coccolithus pelagicus, dominate. Furthermore, 13 species are required to constrain 80 % of stocks. Our findings demonstrate a diverse community constitutes coccolithophore stocks and that a focus on G. huxleyi misrepresents the role of coccolithophores in the carbon cycle.