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What is it that sometimes glows green in the water and on the sand at night on the beach?

Gareth McGrath

Martin Posey, head of the marine biology department at the University of North Carolina Wilmington, said two organisms that can create their own light source, dubbed bioluminescence, are often seen in local waters.

The larger of the two is the comb jelly, which doesn’t sting. The bioluminescence, caused by the beating of the cilla along the organism’s comb rows, can give off a shimmering effect as the jellyfish moves through the water.

Like many marine organisms, the jelly “flashes” when it’s disturbed.

The other bioluminescent critter, which is much smaller, is the microscopic phytoplankton.

Posey said the plants, which are found in large numbers together, produce the greenish light when the water is disturbed, such as if you run your arm or an object through it.

Also known as dinoflagellates, the simple organisms are commonly found during warm weather months in back marsh areas.

The phytoplankton, which also are harmless to humans and form an important cog in the marine food chain, also often wash up on shore, sometimes giving a sparkly look to the beach.

Scientists have determined that organisms, ranging in size up to squid and fish, use bioluminescence for a variety of tasks. They include communication, evading predators and attracting prey.

User-contributed question by:
Katrina Pacek

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