All living organisms require nutrients for growth. Nitrogen is of particular importance because it limits primary production in much of the open ocean (i.e. constrains biomass becauseit is in lowest supply relative to the needs of the cell). Steven's research aims to investigate the competition for nitrogen between autotrophs and heterotrophs and to see how this competition affects the biological pump and sequestration of organic matter in the deep ocean. This information could also elucidate some of the major planktonic drivers of the nitrogen cycle in the ocean.