UC Irvine

Phytoplankton play a key role in regulating the global carbon cycle by exporting carbon to the deep ocean via the biological pump. The ratio of carbon to nutrients in exported organic matter has long been used to simplify biogeochemical cycles, where a fixed Redfield ratio is assumed. However, these ratios are not truly fixed, and many instances of variation have been observed. Here I aim to illustrate the importance of variable stoichiometry in accurately representing ocean biogeochemical cycling the modern steady state ocean. First, I will highlight the role of variable iron to carbon stoichiometry in coupling of the marine carbon and nitrogen cycles and regulating marine ecosystem response to global changes in atmospheric iron deposition. Second, I will show the impacts of fully variable C:N:P:Fe:Si stoichiometry on biogeochemical cycle interactions and how using a fixed implementation may introduce bias in the interactions between the carbon and nitrogen cycles. Lastly, I will show the roles of individual nutrient variability in driving patterns of nutrient stress and limitation in the modern ocean and how variable stoichiometry plays a role in regulating ocean carbon cycling under nutrient stress.