Bioluminescence has become an important tool in the laboratory, with the glowing components of jellyfish and fireflies applied to help scientists visualize and manipulate cells that don’t normally produce light. I’ve toyed with neurons expressing green fluorescent protein (taken from the jellyfish Aequorea victoria under the microscope, and have caught a few lightning bugs in my day. But until last week, I’d never swam in bioluminescence, or seen it sparkling down my arm like I had dipped my hands in stars. It was, um, pretty cool.
My opportunity to swim with the bioluminescents occurred on the island of Vieques, 8 miles off the coast of Puerto Rico. Formerly the site of a U.S. Navy base and controversial bomb testing, the isolated island remains largely undeveloped and undisturbed, with long, empty beaches and diverse wildlife. That has made Vieques a popular site for eco-tourism, and the “Bio Bay” is considered one of the island’s top attractions. Though there are other bioluminescent bodies of water around the world, many of them have found their glow dampened by both light pollution and regular pollution – in some cases, the ironic result of gas-powered boats used for tours of the waters.
But the single-celled dinoflagellates, called Pyrodinium bahamense, of Vieques’ Mosquito Bay have continued to flourish, thanks to the bay’s remote location and careful handling by the local tour operators. My wife and I opted for the pollution-free electric pontoon boat ride from a company called Island Adventures, founded by a former science teacher and the first company to offer Bio Bay tours on Vieques. Unlike the kayak rides also offered for tours of the bay, the boat ride included the opportunity for swimming in the bioluminescence, an opportunity we could not pass up.
One of the intriguing qualities of Vieques is the odd mix of environments nestled against each other on the island: one bay would be humid and still, while walking 10 minutes to the next bay would find a dry and breezy environment. Mosquito Bay is still another micro-climate, surrounded by mangroves and connected to the ocean by only a small opening. That combination creates the perfect swimming pool for Pyrodinium bahamense, which feast on vitamin B12 from leaves dropped by the surrounding plants and grow to concentrations of 700,000 per gallon. When disturbed, the plankton spark a glow through a reaction of the chemical luciferin and the enzyme luciferase – the same elements used by University of Chicago scientists to monitor pancreatic beta cell regeneration in diabetic mice.
Surprisingly, the scientific literature on Pyrodinium bahamense is pretty sparse – scientists have isolated and genetically transferred luciferin to a wide range of organisms, but the natural purpose of the plankton’s glow remains a mystery. A 1969 paper studied Pyrodinium and two other species of bioluminescent microorganisms in the laboratory and in nature, finding that P. bahamense can produce a glow up to 4,000 times it’s size. But the authors conclude, “there does not appear to be any selective advantage to the bioluminescence of dinoflagellates.” A different variety of P. bahamense has also been implicated in cases of puffer fish poisoning in Florida and elsewhere, through the production of a chemical called saxitoxin which blocks sodium ion channels. The variety found in Mosquito Bay are thought to be nontoxic – or at least I hope.
Just getting to the bay, which involved a loud, crazy ride through thick vegetation on a rickety old school bus that had to carefully navigate the unpaved, pothole-ridden “road,” was quite the experience. And swimming in a pitch-black bay (during a short window when the full moon was behind thick clouds) was a bit on the frightening side. But producing hazy-blue clouds of light with every movement of one’s limbs quickly changed fear to wonder, as did the strangely discrete points of light that the dinoflagellates produced while dripping off my hands. The tour guide called it “one of the best ways to directly experience nature,” and I had to agree – even when my wife was stung by a jellyfish, an even more direct experience. Immersing one’s self in biology for a tangible, wondrous few minutes is an unforgettable, almost indescribable reminder of the natural, microscopic world ever present around us…even if it occasionally bites back.