Dinoflagellates

Single celled eukaryotes of the phylum Dinoflagellata, most of them marine and freshwater plankton, many photosynthetic and some mixotrophic, combining photosynthesis with the ingestion of prey. Covers the bloom forming and toxin producing species responsible for red tides and shellfish poisoning alongside the reef dwelling symbionts that live inside corals and other marine animals, identified by their own sourced description rather than by name. Kept as its own subcategory, distinct from the broader microalgae grouping, because dinoflagellates form a single well defined phylum with a distinctive two flagellum swimming structure, not merely a shared small size.