The goal of the project is to further the Fellows et al. 2007 model, which introduced Darwinian selection and self-assembly among algae in an ocean model. The overall framework will now include an explicit carbon model, a diverse set of potentially limiting nutrients, flexible nutrient quotas, a set of schematic (but poorly described) transformations of these nutrients, and improved scaling and tradeoff relationships. Specifically, the project will: (i) Explicitly couple the ecological scheme to the carbon cycle components of the MIT ocean model. (ii) Introduce an representation of heterotrophic microbes and the respiration of organic matter. (iii) Perform simulations of interannual variability of marine ecosystem and carbon cycle, driven by ocean circulation state estimates from the ECCO project (Estimating the Climate and Circulation of the Oceans), and which will be tested against observed data. (iv) Perform sensitivity studies which explore response of the modeled ecosystem and carbon cycle to significant changes in climate (both warming and cooling) in both quasi-equilibrium and transient approaches. In summary, a new “self-assembling” model of marine microbial communities will be developed and analyzed as a tool for simulations and sensitivity studies of the changing marine carbon cycle.