Pyrodinium bahamense, considered the sister taxon to Alexandrium, is a tropical euryhaline dinoflagellate found mainly in the Atlantic ocean. It is found in marine waters that have more than 20 psu of salinity and are warmer than 20 °C (68 °F). The optimal salinity is considered to be around 35 psu. P. bahamense has only been studied closely since the 1990s, since it was difficult to culture in labs for study before then. The difficulty of culturing P. bahamense is explained by its specific nutrition needs. It shows optimal growth and chlorophyll levels when nitrogen levels in its environment are greater than 100 μM. It is believed that nitrogen is an important part of the synthesis of toxins in P. bahamense. P. bahamense displays bioluminescence when agitated, glowing blue.