Diatoms and dinoflagellates are both types of phytoplankton that live in oceans throughout the world, but they contain unique physical characteristics that make them easy to distinguish from one another. Diatoms and dinoflagellates fall into the broad category of phytoplankton. These two groups are the most common of all phytoplanktons and have single cells but vary in body size and shape.
Both diatoms and dinoflagellates are classified as eukaryotic single-celled algae. However, dinoflagellates share a common body shape among all species varieties. These cells are characterized by two flagella, which allows them to have some mobility. These cells are also covered by a protective layer, which looks and acts much like a sheet of armor. This protective layer can either be smooth or plated in design. Diatoms, in contrast, may assume several different body shapes. Their physical shapes dictate which group they belong to, centrics or pennates. While a sheath protective layer covers the bodies of dinoflagellates, diatoms are enclosed by silica, which look and function like glass containers. They may form chains or colonies. Dinoflagellates, in contrast, function as individuals and move through their aquatic environments alone. Both cells meet their nutritional needs through photosynthesis and are abundant in ecosystems around the world.