Dimethyl sulfide (DMS) is a biogenic organosulfur compound which contributes strongly to marine aerosol mass and the determination of cloud condensation nuclei over the remote oceans. DMS concentrations are directly controlled by marine ecosystems. Various marine mircoorganisms play different roles in the DMS production. Changes in phytoplankton production and community composition can alter the production and distributions of DMS. Observation based estimates showed significant changes in phytoplankton biomass in the last few decades; and climate models also project a reduced marine primary production and shifts in the plankton community structure in the future climate. Here we investigate the contribution of individual phytoplankton functional groups to the DMS production and fluxes to the atmosphere using the improved marine ecosystem-biogeochemical module of the Community Earth System Model (CESM). We will examine the impacts of shifts in phytoplankton community composition on DMS distributions in a RCP climate scenario. We will show changes in the DMS flux due to individual phytoplankton groups, and the subsequent impacts on cloud radiative forcing.