Protists—organisms that are found in nearly all aquatic and moist environments—are important to the global carbon cycle. In particular, just the sheer numbers of protists affect the carbon percents. For example, protists living in the open ocean, in algal beds and reefs, and in swamps and marshes—including algae, diatoms, and dinoflagellates— form part of the basis for major food webs in aquatic environments and are one of the greatest contributors to the global carbon cycle. (For more about protists, see the chapter “Bacteria, Viruses, and Protists.”)