Prokaryotic heterotrophs play a key role in marine global carbon fluxes by way of their consumption of dissolved organic matter, respiratory CO2 production and nutrient recycling activities.
Micro-algae transform carbon dioxide (CO2) and nutrients dissolved in the ocean into organic matter and oxygen. This process, photosynthesis, uses sunlight energy. These primary producers then become an energy source for a vital link in the marine food chain, that being herbivorous zooplankton.