Bioluminescent organisms can create their own light! There are many weird and wonderful bioluminescent creatures in the ocean. Some emit light as a predatory tactic, like the anglerfish, which has a light-emitting photophore that protrudes from the top of its head. The anglerfish has a symbiotic relationship with bioluminescent bacteria that collect on the photophore and help lure prey towards the fish’s mouth. This is helpful in the darkness of the deep sea where food is scarce and hard to find.
Other organisms use bioluminescence to defend themselves. Dinoflagellates are a type of phytoplankton that flash a blue-green light when they get agitated by waves or predators at nighttime. This light can startle and distract the phytoplankton’s predators, or it can act as a burglar alarm that attracts bigger predators to come to the feeding site. Sperm whales are known to linger around places with lots of these bioluminescent organisms because their glowing alerts the whale that there is prey in the area.
Next time you are by the ocean at nighttime, try splashing around in the water and see if these dinoflagellates will light up for you!