Pyrodinium bahamense, considered the sister taxon to Alexandrium, is a tropical photosynthetic euryhaline species of dinoflagellates found mainly in the Atlantic Ocean.

[3] However, regions where large cell densities of Pyrodinium are found are usually shallow and have varied salinities and long water residence times.

The influence of soil-derived selenium on growth suggests that Pyrodinium requires terrestrial nutrients in order to reach bloom-level cell densities.

[6] In addition, there are at least two places in the world where both varieties of Pyrodinium bahamense are found together: the Persian Gulf[7] and coast of Mexico.

Blooms also tend to occur after periods of high rain, suggesting that a terrestrial-sourced nutrient is usually limiting.

[1] On a global scale, blooms seem to be linked to the El Nino Southern Oscillation (ENSO), probably because of changes in precipitation and delivery of terrestrial nutrients.

[8] The bright cobalt blue light produced by these dinoflagellates when they are mechanically disturbed creates a magical effect that draws many tourists to the bays.

Pyrodinium bahamense cells are shaped like ellipsoids and are covered with thick, protective thecal plates that have many small, evenly distributed knobs and trichocyst pores.

These cysts, called Polysphaeridium zoharyi in the paleontological classification system, are similar in both P. bahamense varieties and have tubular processes protruding from the outer layer.