“it’S like an underwater disco party, and we are the last ones to join the party,” said marine biologist David Gruber, whose life is dedicated to research on bioluminescent and biofluorescent ocean life.

He is looking into the secret language of colors and patterns in the deep, dark ocean.

Oceans cover nearly three-quarters of the planet, but 80 percent of that is darkness. Light penetrates only about the top 100 meters of an average ocean depth of about 4,000 meters.

“So it’s just the skin of the ocean where the light reaches,” Gruber said.

Using submarines, Gruber and his research team have found creatures deep in the ocean who produce their own light.

“They are transforming the light, like a secret mode of communication,” Gruber said at a recent event marking World Oceans Day tomorrow. “This secret has been going on for millions of years, and we humans are just tuning into this world.”

World Oceans Day is sponsored by the National Geographic Society and La Mer cosmetics, which specializes in products using marine extracts. The theme this year is “healthy oceans, healthy planet.”

Gruber said the glowing marine animals found deep in the sea are incredibly useful to humans. Neurologists are using the fluorescent molecules to illuminate the human brain, and other scientists are now capable of illuminating the inner working of cells, resulting in breakthroughs in cancer and other disease research.

But this underwater treasure trove is in trouble. The ocean depths are fragile and under great stress from humans. Some coral reefs have declined up to 70 percent in recent years as a result of global warming and pollution.

“To me, it’s like huge library,” Gruber said. “These creatures have been writing these books for millions of years, and now we are burning some of the books before they have even been read.”

Gruber’s fascination with the deep started as a surfer.

“I got to know the ocean by riding its waves,” he said. “From that, I learned respect and admiration for the ocean and its great beauty.”

His first encounter with bioluminescent animals was on a coral reef off a five-acre island.

“I was 12 hours a day in the water, and one night we came across this huge blue cloud of bioluminescent animals that were everywhere, all over my arms, in a twinkling display,” said Gruber. “I knew at that point that I would spend my life studying these animals and working to protect them and conserve our oceans.”

Each diving experience, he said, unfolds a unique beauty and unique set of characters.

One of his favorite places for research is Bioluminescent Bay in Puerto Ricco, where one can find a very high density of single-celled bioluminescent animals called dinoflagellates that produce blue light when the waves crash.

In Bermuda, there’s the Bermuda fireworm, or odontosyllis enopla, which uses bioluminescence as a mating display. On full moon nights, about 57 minutes after sunset, the females come up, twirl around releasing blue bioluminescence, and the males come in.

“But when you go deeper in the ocean, fish are bioluminescent,” Gruber said. “Sharks are bioluminescent, squid are bioluminescent, and almost every animal you find below 1,000 meters is capable of producing light.”

Gruber said his roles of explorer and scientist are both based on curiosity.

“Some scientists don’t leave their laboratories very much,” he said, “but I’m curious and I want to go underwater to unexplored places.”

Now Gruber spends more time in the classroom since becoming marine biology professor at City University of New York. He still finds time to spend about three months a year undersea.

On his most recent dive in California, he captured biofluorescent swell sharks, or cephaloscyllium ventriosum, on film for the first time.

“I have gone from being a coral scientist to becoming heavily involved in shark research,” he said.

Sharks are misunderstood by people, said Gruber. There are over 600 species and, contrary to popular thinking, only a few of them are very aggressive.

“Most sharks are very shy, and they have no idea that they have such a bad reputation,” he said.

Taking photos of these glowing creatures of the deep is no easy task. Sometimes it takes Gruber and his team months to get the right photo.

“One, you have to get to the bottom of the ocean; two, you have to control a camera in the dark; and three, you can’t use any lights,” he said.

It’s a bit like standing in a dark room with an iPhone, trying to photograph a moving LED around the room without using the flash.

Gruber has had to build much of the equipment he uses to take the photos.

He recalled an interesting encounter with bioluminescent flashlight fish in the South Pacific, where he and several colleagues traveled to a remote island rarely visited by scuba divers.

They found the bioluminescent flashlight fish in shallow depths there.

“I was with a friend who had a camera and a mirror on it,” Gruber said. “It was a 3D camera, and the fish were seeing themselves for the first time in a mirror. They swarmed around this guy with the mirror.”

He went diving there two nights in a row.

“As far as I know, it was the first time anyone has ever seen such a density of flashlight fish at such a shallow depth,” he said. “Normally, you need submarines, but there they were, right at the surface.”

Gruber said the future of research into glowing underwater creatures is exciting as long as oceans are preserved.

“Each week, if you look at science magazine, there’s usually a scientist who found another creative way to use either bioluminescents or fluorescents,” said Gruber.

Today’s underwater explorers are different from their predecessors.

“The new generation is not about conquering, capturing and showing you are stronger than nature,” he said. “It’s now about understanding and realizing that we are just one species among maybe tens of millions, and we all need each other.”

Gruber said he views marine animals as members of the family who deserve our protection.

“They really don’t interact well with humans,” he said, “so the best thing we can do is leave them alone.”

Coral degradation is serious, he added. He saw it when returning in the Caribbean after 10 years ago. “Now, it’s spreading to places like the Great Barrier Reef,” he said. “The reefs that are the healthiest are those located in places remote from humans.”

He said he hopes education will alert the public to what they risk losing.

“The more you know about it, the more you can do about it,” he said.

About David Gruber

David Gruber, 42, is an associate professor of biology and environmental science at Baruch College at the City University of New York and a research associate at the American Museum of Natural History and Central Caribbean Marine Institute. He was named a National Geographic’s Emerging Explorer in 2014. His research group has deciphered the genomic code of scores of new fluorescent proteins that are being developed as tools to aid in medical research and illuminate biological processes.

Bioluminescence vs Biofluorescence

Bioluminescence is produced by a chemical reaction in living organism, like the glow emitted by the firefly.

Biofluorescence is not produced by a chemical reaction, but rather is a process whereby organisms absorb the light and transform it into different colors.

Preserving the oceans

• Recycle. Don’t throw trash in the sea.

• Do not remove marine animals when scuba diving.

• Do not eat rare species of marine animals.

• Do not buy souvenirs or other products made from marine animals, such as eye glasses with sea-turtle shell frames or necklaces made from shellfish.

• Volunteer for beach clean-up campaigns and support organizations dedicated to ocean preservation.

• Take photos of the sea to share its beauty with more people and raise awareness about the need for conservation.