Non-Redfield Stoichiometry and the Carbon Cycle.

Evidence increasingly suggests that marine phytoplankton deviate substantially from the canonical Redfield ratio. These deviations strongly correlate with environmental and ecological variables such as nutrient levels, temperature, and community composition. We develop a model based on allocations to sub-cellular compartments in order to predict phytoplankton stoichiometry as a function of environmental conditions. As an application of this modeling approach, we study how phytoplankton stoichiometry interacts with environmental changes by coupling our biological model to a simple model of the carbon and phosphorus cycles. Since most models of the Earth's carbon cycle rely on an assumed Redfield ratio for organic matter, we investigate the effect of non-Redfield stoichiometry on the distribution of carbon within the oceans and atmospheres. Focusing on two important scenarios, anthropogenic CO2 release and glacial/interglacial transitions, we find environmental perturbations can have a large impact on stoichiometry and consequently the export of carbon. One potential consequence, predicted by our model, is that nutrient utilization patterns in regions other than the Southern Ocean have a large effect on atmospheric CO2 levels.