||Description: Toxic marine dinoflagellate (Karenia brevis). Karenia brevis (previously known as Gymnodinium breve and Ptychodiscus brevis) is a marine dinoflagellate (microalga) that causes an algal bloom known as toxic red tide (red tide bloom). Dinoflagellates are microscopic, unicellular, flagellated, often photosynthetic protists (algae). K. brevis is a gymnodinioid dinoflagellate with an equatorial groove or girdle containing one flagellum (undulating flagellum) and a second flagellum that trails behind the cell. This dinoflagellate produces a toxin called brevetoxin, which affects the central nervous system of fish. People can become ill with neurotoxic shellfish poisoning (NSP) when they eat shellfish that have accumulated brevetoxin and can also experience respiratory irritation (coughing, sneezing, and tearing) when a red tide bloom is present close to shore. K. brevis has come to be known as the Florida gulf coast red tide organism, it has been implicated in blooms on Florida?s east coast. It has also been implicated in red tide blooms in Louisiana, Texas, Mississippi, Mexico, and the Carolinas.