The Dinoflagellates (phylum Dinoflagellata) are also within the kingdom Chromista. Dinoflagellates are mostly marine organisms with relatively few freshwater genera. They are mostly planktonic, single-celled organisms; also some live attached to other algae. Some marine species form harm algal blooms in marine systems, such as Karenia brevis (see Fig. 7.7), associated with Red Tide. Some are also endosymbionts in corals.