Primary producers in ocean food chains are organisms that convert light energy into chemical energy through photosynthesis. Cyanobacteria, also known as blue-green algae, are photosynthetic bacteria found in oceans. Diatoms are a major group of algae, specifically phytoplankton, that are crucial primary producers in marine environments. Copepods are zooplankton that consume phytoplankton, and foraminifera are protozoa, some of which can be photosynthetic but are generally consumers or detritivores in the marine food web.