Make their own food by extracting compounds from the ocean. photoautotrophs, chemoautotrophs, cyanobacteria

Both photoautotrophs and chemoautotrophs synthesize organic compounds from (inorganic) carbon dioxide, a process known as carbon fixation. Photoautotrophs get the energy to perform these reactions from light. Chemoautotrophs get it from electron donors such as hydrogen sulfide and ammonia. Cyanobacteria, by contrast, convert nitrogen from the atmosphere into ammonia, a process known as nitrogen fixation.