Under the Sea, Most Animals Shine On

A lobate ctenophore displaying bioluminescence.

BIOLUMINESCENCE AMONG ANIMALS IN THE SEA is generally seen as an exotic phenomenon found only in selected creatures like squids and deep sea anglerfishes. But a study by scientists at the Monterey Bay Aquarium Research Institute has found that three-quarters of marine animals generate their own light.

ACROSS THE BOARD  And bioluminescence wasn’t limited to just fishes and squids. It was found in animals as diverse as sea jellies, worms, snails and krill and shrimps. While 76 percent of all marine animals observed were capable of bioluminescence, it was especially prevalent among sea jellies: 97 percent of Cniderians exhibited the bioluminescent capability.

The study found that the bioluminescence trait was consistent in animals at all levels of the water column, from the surface to deep sea  bottoms. It’s also true that much of undersea creatures’ bioluminescence is faint, enough to signal to other animals but not easy for human eyes or many cameras to detect. And many can turn it on and off.

SEVENTEEN YEARS   For their study, Quantification of bioluminescence from the surface to the deep sea demonstrates its predominance as an ecological trait, published in the journal Scientific Reports earlier this year, the scientists reviewed more than 350,000 observations taken over 17 years of remotely operated vehicle surveys off the California Coast.

Science writer Stephanie Pappas discussed the topic in more detail in Shining Sea: 75 percent of Ocean’s Animals Glow, published by the online publication Live Science.