If you see a bright blue glow in coastal ocean waters at night, it could be Noctiluca scintillans. Also known as sea sparkle, these bioluminescent plankton float under the surface and flash brightly when disturbed, possibly to scare off or distract predators. Since running your hand through the water, swimming in it, or even boating disturbs the little guys, it’s easy to get them riled up and glowing.
Sea sparkle is made up of critters so tiny that a single drop of water can contain thousands of them. But they’re still fairly big for single-celled organisms, so if you catch some, you can actually see them with a microscope or even a strong magnifying glass.
They typically live in warmer seas, both subtropical and tropical, and are more abundant when it’s warm. They live mostly near coasts, and you’re likelier to find them near the mouths of rivers, especially following heavy rains.
Where can you see sea sparkle for yourself? Here’s a list of five places in America:
• Manasquan Beach, New Jersey
• Mission Bay, San Diego, California
• Torrey Pines Beach, San Diego, California
• Cortez, Florida
• Mosquito Bay, Vieques, Puerto Rico
Sea creatures glow primarily to communicate, defend themselves, and sometimes attract prey. In most parts of the ocean, especially the deeper areas, bioluminescence is the only kind of light ever seen.
Larger glowing denizens of the deep include jellyfish, many types of squid, flashlight fish, hatchetfish, dragonfish, and anglerfish (like the toothy creature in Finding Nemo that has a lantern mounted on its forehead). Other underwater light sources include ribbon worms, copepods, and at least one type of clam.
There are two ways a larger animal can glow, and while some can turn on their own lights, many just activate the bioluminescent plankton they have swallowed!