The members of this class of fire algae (Division Pyrrophyta) are the dinoflagellates, a major component of marine algae. Many dinoflagellates have a very strange appearance, and they usually move via two flagella that beat in grooves along their bodies.
These organisms, which are often red in color, can produce strong toxins; they are responsible for the deadly red tides that can kill many fish and other marine organisms. One dinoflagellate, Gessnerium catenellum, often causes red tides on the Pacific coast and Gulf of Mexico. Filter-feeding mollusks such as clams and oysters sometimes become toxic to humans and other animals due to their eating dinoflagellates.
Many species of dinoflagellates are bioluminescent; they produce a faint light when they are disturbed, thus sometimes causing nighttime waves breaking against the shore to be faintly luminous.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.