In coastal regions, the primary source of flow-agitated bioluminescence is dinoflagellates. These single-celled organisms are common members of the plankton—tiny marine plants, animals or bacteria that float on or near the ocean’s surface. Bioluminescent dinoflagellates range in size from about 30 µm to 1 mm, and are found in all the world’s oceans. In some areas, such as the so-called bioluminescent bays of Puerto Rico, their concentrations are so high that they produce breathtaking bioluminescent displays throughout the year.

Laboratory experiments have provided insight into the role that dinoflagellate bioluminescence plays in marine ecology. Dinoflagellate flashes decrease the grazing rate of their predators by disrupting their feeding behavior and thus reducing the number of dinoflagellates consumed. Dinoflagellate bioluminescence is also thought to act as a “burglar alarm” to attract a secondary predator that threatens to eat the primary predator. When handled by a predator, the dinoflagellate cell is triggered to flash by the imparted mechanical stress.

Dinoflagellate bioluminescence is also stimulated by fluid forces caused by waves, surge and the flow boundaries of moving animals and objects. The cellular signaling pathway that triggers bioluminescence is complex and only partially understood, but the luminescent chemistry is ultimately caused by a drop in pH due to an influx of protons within the cell. The time from stimulus to light emission is less than 20 ms, making it one of the most rapid cellular processes known. Each dinoflagellate cell can produce more than one flash, which lasts on the order of 100 ms. However, the bioluminescence capacity of a cell is depleted once all its available luciferin has been oxidized.

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