The dinoflagellates are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata[5] and are usually considered algae. Dinoflagellates are mostly marine plankton, but they also are common in freshwater habitats. Their populations vary with sea surface temperature, salinity, and depth. Many dinoflagellates are photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey .[6][7]