Green Planet Monitor

Bioluminescent Bays

by Ann Dornfeld

In 2003, the U.S. Navy ended its dominance of the Puerto Rican island of Vieques. The Navy had used the island for training exercises for six decades. In recent years the Navy had faced protests from angry citizens, especially after a stray bomb killed a civilian. The Navy left behind toxic waste sites: munitions dumps and other fouled land that has yet to be cleaned up five years later.

But the U.S. Navy’s presence had a silver lining for the Vieques environment. Because it owned two-thirds of the island and developed only part of that, Vieques now boasts huge tracts of unspoiled land – and a brilliant bioluminescent bay that is considered one of the world’s brightest.

Mosquito Bay is full of plankton that glow when they sense movement. Swimmers find themselves surrounded by a halo of blue light. Lifting an arm out of the water creates a shower of sparkling droplets. It’s not known why the plankton light up. One theory is that they are trying to illuminate passing fish so that predators will eat the fish in favor of the plankton. Other theories are that the plankton glow to communicate, or to look like a bigger creature.

Bioluminescent bays were once common around the world, but urban development and chemical and light pollution have dimmed their glow. These factors are becoming increasingly problematic in Vieques, as people flood the island from mainland Puerto Rico and the United States to build vacation and retirement homes.

Light pollution is currently the biggest threat to the visibility of this bioluminescent bay – and possibly to its health. Some scientists believe light pollution inhibits the effectiveness of bioluminescence as a means of communication between organisms, just as it’s hard to hear a friend talking in a noisy room.

To protect the bay from light pollution, the Vieques Conservation and Historical Trust introduced a municipal ordinance to require Vieques residents and businesses to install shields around their outdoor lights. An unshielded outdoor light can cast its glow for miles – and anyone who has flown in an airplane above a major city at night has witnessed the orange glow that stretches far wider than the city itself.

Long-term goals for Mosquito Bay are to limit development around its shores and mitigate the impact of new buildings. Hotel bookings have gone up three times since the Navy’s departure. To encourage healthy growth, area conservationists are trying to build a strong eco-tourism industry on the island that will put a premium on maintaining the island in its most natural state.

Vieques median income was around US$12,000 in the 2000 census, so conserving Mosquito Bay and the island’s lush hiking trails and remote beaches is not only appealing for locals, but also profitable.