POC is generally converted to DIC through heterotrophy and respiration. Three nutritional strategies are seen in dinoflagellates&colon; phototrophy, mixotrophy, and heterotrophy. Many bacteria get their carbon from other organic carbon, called heterotrophy. Thus, the protist exhibits an unusual life cycle of alternating autotrophy and heterotrophy. Marine dinoflagellate species undergo three major trophic modes&colon; autotrophy, mixotrophy and heterotrophy. Historically, many rhizarians were considered animals because of their motility and heterotrophy. Facultative mixotrophs, in which autotrophy or heterotrophy is sufficient for nutrition, are classified as amphitrophic. "Paramecia" live mainly by heterotrophy, feeding on bacteria and other small organisms. Other microbes, living in sediments, may utilise available organic compounds (heterotrophy). They are flagellated eukaryotes that combine photoautotrophy when light is available, and heterotrophy via phagocytosis.