RENEE MONTAGNE, host:
For much of the 20th century, the U.S. Navy used most of the Puerto Rican island of Vieques for target practice. Five years ago, the Navy left the island and left behind a federal superfund site after spending decades dumping toxic waste. And at the same time the presence of the Navy protected the island from development. So Vieques has one of the world's last pristine bioluminescent bays. But that's changing, as Ann Dornfeld reports.
ANN DORNFELD: On a moonless night, an electric boat full of tourists glides across Mosquito Bay. When the boat stops, everyone slips into the water. And from their giggles you'd think they'd found the fountain of youth.
Unidentified Man #1: My feet are glowing.
Unidentified Man #2: (Unintelligible)
DORNFELD: Every time the swimmers move they're trailed by bright blue light. It comes from microscopic plankton in the water that light up when they sense movement. This bay is considered one of the brightest in the world. The tour guide, Mark Martin, works at the Vieques Conservation and Historical Trust. Its mission is to preserve the bay. Martin says there are many reasons why these waters are so bright. One is the shape of the bay makes it hard for the glowing plankton to escape.
Mr. MARK MARTIN (Vieques Conservation and Historical Trust): There are vitamin levels, the nutrient levels, the water temperature, the water quality. It's all kind of perfect for them. And that type of water and that amount of plankton is sort of trapped in there. It can get out, but mostly is stays kind of floating around in a great situation.
DORNFELD: Scientists say bays like this one are rare. Chemicals from boat fuel and pesticide runoff can kill plankton, and bright lights can outshine bioluminescence.
Edie Witter is president of the Ocean Research and Conservation Association. She says this bay is valuable because it helps scientists understand how people affect coastal zones. To gauge how healthy the bay is, scientists just need to measure how bright or dim it is.
Ms. EDIE WITTER (Ocean Research and Conservation Association): And so it is the perfect canary in the coal mine in terms of being able to monitor a very delicately balanced ecosystem and see how humans are impacting it in a variety of different ways.
DORNFELD: Since the Navy left Vieques, vacationers and retirees have flocked to the island. New houses dot the landscape and the number of hotel room bookings tripled to more than 34,000 last year alone. It's a welcome development on an island that has an annual median family income of just $9,000.
Conservationist Mark Martin says ecotourism is important to the island's economy. So he and his colleagues have begun taking local residents out on the bioluminescent bay.
Mr. MARTIN: And it's a best-convincing strategy. If you let them see it, everybody falls in love with it. Nobody doesn't like it, you know. And they kind of get like a pride and an inspiration to say, hey, we've got to protect this. It's the best way.
DORNFELD: A new Vieques law requires people to shield their outdoor lights so the glow doesn't spread beyond their property. But Martin said efforts to create a development buffer zone around the bay haven't been as successful. He says ecotourism could provide the incentive that local government needs to protect Mosquito Bay.
Mr. MARTIN: It's pure magic. One of those things that captures everybody and turns them into little kids.
DORNFELD: And then he hopes turns them into conservationists.
For NPR News, I'm Ann Dornfeld.
Mr. MARTIN: Your bathing suit's going to glow for awhile. Transcript provided by NPR, Copyright NPR.
