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Jellyfish glow with the flow in the Gulf of Maine and the Weddell Sea. (David Shale / NPL/ Minden Pictures / Ingo Arndt / Minden Pictures)

Bioluminescence: Light Is Much Better, Down Where It’s Wetter

From tracking a giant squid to decoding jellyfish alarms in the Gulf, a depth-defying scientist plunges under the sea

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The winking dinoflagellate blooms in the Indian River Lagoon on Florida’s east coast can be so bright that schools of fish look etched in turquoise flame. It’s possible to identify the species swimming in the lit-up water: Local residents call this guessing game “reading the fire.”

But there isn’t as much fire to read anymore. Long considered North America’s most diverse estuary, the lagoon may now be dying. Pollution has thinned the dinoflagellate blooms, and the light from thousands of new houses drowns out the remaining brightness. Animals once wreathed in blue fire are ailing, too. Many dolphins are afflicted by a flesh-eating fungus that corrodes their skin; others are infected by viruses and have severely suppressed immune systems. Luxurious sea grass beds grow bald, leaving conch and periwinkle snails without shelter. Mammoth algae blooms stink like rotting eggs. The shellfish industry is in shambles.

These ills are not unique to Florida waters. Two abysmal assessments of the ocean’s overall health—the Pew Ocean Report in 2003 and the U.S. Commission on Ocean Policy’s in 2004—spurred Widder to leave her longtime position as a senior scientist at Florida’s Harbor Branch Oceanographic Institute and start ORCA. “Ever since I did my first dive, I’ve been asking why is there all that light in the ocean and what is it used for,” she says. “More recently, I’ve come around to figuring out what we can use it for.”

Scientists are hotly pursuing applications for bioluminescent technology, particularly in medical research, where they hope it will change how we treat maladies from cataracts to cancer. In 2008, the Nobel Prize in Chemistry honored cell biology advances based on the crystal jellyfish’s green fluorescent protein, a bioluminescent substance that is used to track gene expression in laboratory samples. Widder is focused on the uses of luminous bacteria, which are extremely sensitive to a wide array of environmental pollutants.

One day we tour the lagoon in a little flat-bottomed fishing boat. It’s a dense green world, interrupted here and there by the pastel crags of Floridian architecture. A wisp of an egret wanders the shore and pelicans on top of pilings appear sunk in contemplation. Fingers of mangrove roots protrude from the inky banks. More than 150 miles long, the lagoon is a home to logjams of manatees, a rest stop for migratory birds and a nursery for bull and bonnet sharks. But water that 30 years ago was gin clear now looks more like bourbon.

The sources of pollution here are discouragingly diverse: There’s airborne mercury from China, fertilizer and pesticide runoff from inland citrus and cattle farms, even the grass clippings from local lawns. “There are literally thousands of chemicals being released into our environment and nobody is keeping track of them,” Widder says. So much of the surrounding wetlands have been paved and drained that the lagoon is fast becoming a sink for the land’s poisons. It’s hard to imagine a bright future for the place.

To protect the lagoon, Widder has designed ocean monitors that track currents, rainfall and other variables, mapping where water comes from and where it goes in real time. She wants this network to one day span the world—“the wired ocean.”

Now she’s studying the lagoon’s most polluted parts, which she identifies with the help of bioluminescent life-forms. Wearing yellow kitchen gloves, we shovel gray-green muck from the foot of ORCA’s dock, an area that Widder has never tested before. A lab assistant homogenizes the sample in a paint mixer, then retrieves a vial of freeze-dried bioluminescent bacteria. It’s Vibrio fischeri, the same strain that the fireshooter squid uses for its deep-sea dragon breath. She drops it, along with little drips of the lagoon mud, into a Microtox machine, which monitors the light. We can’t see it with our naked eyes, but the healthy bacteria are glowing at first.

“The light output of bacteria is directly linked to the respiratory chain,” Widder explains. “Anything that interferes with respiration in the bacteria quenches the light.” Interfering substances include pesticides, herbicides, petroleum byproducts and heavy metals, and the more they quench the light, the more toxic they are.

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About Abigail Tucker

A frequent contributor to Smithsonian, Abigail Tucker is writing a book about the house cat.

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