Early in her career, the ocean explorer and scientist Dr. Edie Widder received a phone call from a distraught physicist. The physicist was working on a major project aimed at detecting neutrinos, elusive subatomic particles that can give off faint flashes as they move through water. He and his colleagues needed the darkest place they could get, so they placed their ultra-sensitive light detectors deep in the ocean, beyond the reach of the sun’s rays. But there was a problem. The sensors were detecting a lot of light. A colleague suggested the light could be from animals. ‘Could it be true?’ the physicist asked Dr. Widder, now a world authority on marine bioluminescence. ‘Yes,’ she told him. And then, after a long pause, he followed up: ‘Is there some place in the ocean where there isn’t any bioluminescence?’ ‘Not that I know of,’ Dr. Widder replied.
Like many of us land-lubbers, the physicist had assumed that light-making among ocean creatures is an exotic and rare phenomenon. But that’s wrong. The majority of animals in the ocean — which means the majority of animals on the planet — are capable of making light. From top to bottom, the ocean is absolutely teeming with unforgettably beautiful and extraordinarily diverse light shows made by living things that we’re only beginning to understand. There are deep-sea shrimp that spew glowing mucus like fire-breathing dragons to distract predators. Single-celled algae that glitter en masse as a form of burglar alarm. Crustaceans that put on complex, twinkling courtship displays. Fish that counter-illuminate their bodies to match the water above them for camouflage from creatures looking up from below. Squids that backlight their body tissue in flickering patterns that seem to coordinate group hunting. These are just a few examples of the roughly 75 percent of ocean animals that can make their own light. According to Dr. Widder, there are possibly quadrillions of light-producing fish in our seas.
