Whether it's the winter dance of the Northern Lights or the summertime glow of fireflies, displays of natural light fascinate us humans. Bioluminescence is the source of many such light shows in the wild—especially in the ocean.
Similar to when you crack a glow stick and shake it up, numerous marine animals, plants and microbes emit bioluminescent light through a chemical reaction. While the light is beautiful, the goal isn't aesthetic; rather, bioluminescence helps the organism that produces it evade predators, feed or reproduce.
Seen in person, bioluminescence is breathtaking. Here are some ways you can catch sight of life lighting up the ocean:
Bioluminescence is readily visible in scores of microscopic marine organisms, including many of the thousands of dinoflagellate species found throughout the world’s oceans. A slight movement can trigger the bioluminescence in these tiny one-celled plankton, making for spectacular shows as they light up a wave crashing onto the shore or the wake of a boat speeding through the dark.
Why the small creatures light up is still not entirely clear. Bioluminescence can serve a variety of purposes, such as signaling predators to stay away or beckoning mates to come closer. The light can also serve as a tool for those too tiny to defend themselves: When they light up, the microorganisms attract attention in what marine biologist Edith Widder calls a “bioluminescent burglar alarm”. Scientists believe that dinoflagellates may be hoping the fierce glow will scare off predators or attract bigger predators that will eat their pursuers.
The bioluminescence of one species in particular, Lingulodinium polyedrum—known for causing red tides and lighting up the Southern California coast—has its own circadian rhythm, producing more reactions at night than during the day. The chemicals and proteins within L. polyedrum are destroyed on a daily basis and regenerated for their nighttime light show—like the one seen here in a long-exposure photograph. Red tides are unpredictable, though, so if you're hoping to catch a glimpse of the sparkling scene in the wild, you might want to book a trip to Mosquito Bay, off the island of Vieques in Puerto Rico. The glowing waters can be traversed by kayak in the dark, and although in recent years the bioluminescence there has dimmed, it is still a sight worth seeing.
Learn more about bioluminescence from the Smithsonian Ocean Portal.