Laguna Grande Charms, Even as its Glow Dims

By Stacey McKenna

“If baby Nemo gets hungry and he’s from Colorado, he gets the munchies,” the guide explained, pausing for laughs. “And maybe he wants to eat the dinoflagellate. So the dinoflagellate lights up to protect himself.” Thirty of us gathered around our enigmatic marine biologist-cum-entertainer, floating in the middle of Laguna Grande. We had come out on this near-moonless January night to see a show for which Puerto Rico has become known—marine bioluminescence.

The small island nation is home to three of the world’s glowing bodies of water. Laguna Grande, due to its proximity to San Juan, may be the most popular, drawing approximately 50,000 visitors annually. Part of Las Cabezas de San Juan Nature Reserve, this quiet bight in the sea is one of only a handful that glow year-round. But like Vieques Island’s Mosquito Bay and the west coast’s Cabo Rojo, its glow may be decreasing. And while tourism is not entirely to blame, humans have definitely played a role, so Puerto Rico has upped its regulations and preservation efforts. Balancing tourism, economic need and ecological conservation is no easy task, but visitors can help by seeking out locally-owned companies that minimize environmental footprints and educate their guests. Fortunately, such businesses abound at Laguna Grande.

After a brief instructional session, our party launched in an untidy string of tandem kayaks from the port at Las Croabas. As we approached the mouth of the canal, I whispered to my husband, “Psst, let’s slow down, give them some space.” We held back, letting the pair in front of us bounce from one bank to the other, paddles flailing haphazardly. Eventually, they found their way back to the single-file line and we slipped in behind them, quickly ensconced by the mangrove’s dense canopy.

Noctiluca_scintillans © Hans Hillewaert CC BY-SA 4.0

Noctiluca_scintillans © Hans Hillewaert CC BY-SA 4.0

The route—and the wily roots that defined its edges—was visible only by the light-sticks tied to our boats. And although we occasionally encountered other groups, at moments I felt completely alone, surrounded only by eery trees and still black water. “Wow, this is so magical,” I murmured repeatedly, gazing enchantedly at my surrounds before narrowly avoiding collision with a rogue mangrove arm. “Low branch!” I hollered to the kayaks bringing up the rear. “Low branch!” echoed behind me in the night.

According to local lore, 17th century Spanish explorers happened upon Laguna Grande and, fearing the bioluminescence, blocked the canal’s entrance with rocks. As the tale goes, isolation concentrated nutrients, making the little plankton shine brighter. However, geologists offer a different story. Sedimentary data suggest that the pool was completely cut off for several centuries until the mangrove channel formed roughly 300 years ago. Connected to the open ocean and with nutrients from the mangroves, dinoflagellate populations rose. Thus, scientists urge careful maintenance of the winding passage, claiming its importance to Laguna Grande’s luminescence.

After about a half hour of paddling, the canal opened into the sparkling lagoon. With little moonlight to interfere, stars illuminated the sky in blankets of constellations. As we formed a circle, the guides deftly connected our vessels, darkened our light-sticks and offered a brief astronomy tutorial. Once we settled, they launched into their spiel. “It’s January, so the glowing is not so strong right now,” they warned. “For you, if you’re from Minnesota, maybe this weather is nice. But for Puerto Rico, this is winter, the water is cold. And we don’t see as much dinoflagellate activity in cold water. But we will try.”

The guides presented a tarp which we clumsily draped over our chain of kayaks to block out the bright stars and distant city lights. As instructed, 30 hands dipped into the cool water, rotating slowly but firmly. Flashes sprang from fingertips like sparks.

Though the exact reasons for dinoflagellate luminescence aren’t clear, data point to communication and defense mechanisms. Laguna Grande’s bioluminescent microorganisms light up when they feel threatened. But, they probably aren’t telling baby Nemo, “back off, I’m dangerous!” Rather, the glow alerts larger predators—ones who may eat baby Nemo—to his presence.

After several minutes, we lifted our makeshift canopy and dispersed to explore independently with one prohibition: No swimming! Bug spray and sunscreen can harm the organisms. My husband and I nestled in along the shadowed bank and stirred the water with our paddles. As I watched the mostly faint and short-lived luminescence, my mind wandered to a friend who has been visiting Puerto Rico annually for over a decade. Several years ago, he lamented that Vieques Island’s famous Mosquito Bay just isn’t what it used to be. As pleased as I was with my own experience, I wondered just what he saw.

Satisfied with our ability to conjure at least some sparkle, my husband and I sought out our guide to ask questions. “Are we harming the organisms by making them light up?” I asked, ever the animal-lover.

“No,” he assured me. “Not at all.” Before I could follow up, he reached into the water, distracted. When he pulled his hand out, an iridescent creature filled his palm. “Anybody who wants to see something cool, come over here!”

Published: 2/8/2016

Stacey is a freelance writer covering travel, adventure, health and social justice. A longtime vagabond, she lived all over the U.S. as well as in France, Austria, Morocco, and Canada before landing in northern Colorado. If not tramping about the U.S. with her husband and dog, she’s probably avoiding winter in the deserts or tropics.

You can read more of her writing at Stacey McKenna Writes, check out her climbing & travel blog, and follow her on Twitter.