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Bioluminescent Bays Shine Light on Puerto Rico's Resilience

By investigating the response of bioluminescent bays to Hurricane Maria, scientists are finding light in dark places.

ByAllison EckNOVA NextNOVA Next
Bioluminescent Bays Shine Light on Puerto Rico's Resilience

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"Ay, que rico,” whispers Leonor Alicea. “Oh, so delicious.”

Alicea isn’t drinking guava juice or eating crunchy tostones. In Puerto Rico, the phrase is not necessarily related to taste—it implies the sensation of sweetness, or the loveliness of a sight. Instead, she’s relishing the essence of a mangrove tree.

“This is just…” Her words hang in the heavy, damp air as she pats the trunk of the tree, leaving me to infer her reverence for this place, Cabezas de San Juan, a nature reserve home to mangrove trees, a coral reef, and a bioluminescent lagoon. Alicea, a marine biologist and environmental interpreter for the nonprofit organization Para La Naturaleza (which translates to “For Nature”), teaches visitors about the reserve’s history and significance.

The view of Laguna Grande from the lighthouse at Cabezas de San Juan, a nature reserve in Puerto Rico near San Juan.

Especially after Hurricane Maria, which struck Puerto Rico on September 20, 2017, Alicea is on a mission to educate people from all walks of life about the value of listening to nature. “Nature is trying to teach us how to survive,” she says. “Nature is talking, and sometimes we don’t hear it.”

“The mangroves are fighters for us,” she says with a hint of drama as we walk through the reserve. She’s alluding to mangroves’ survival skills. These small shrubs manage to thrive in muddy, salty conditions thanks to a filtration system that keeps out the salt, as well as a root system that holds the mangrove upright—this environment would kill most other plants. Moreover, mangroves’ bud-like “propagules,” which they drop into the water, can float solo for up to a whole year, still viable, looking for their optimal new home. Once they settle, they’ll grow into new mangroves.

But mangroves aren’t just fighters for themselves—they’re fighters for the whole ecosystem. Red mangroves sprout a tangle of roots that release bacteria into the water, providing a critical vitamin to a species of dinoflagellate (Pyrodinium bahamense): a single-celled aquatic phytoplankton that, when agitated, produces resplendent bioluminescence—light produced by chemical reactions in the bodies of living things—in the adjacent lagoon. Dinoflagellates are tiny: 200 to 300 of them could rest atop the head of a pin. The presence of billions of them creates the blue-green glow that you see when you swish your hand through the water.

In the Caribbean, there are a few such bioluminescent bays or lagoons that glow year-round: three in Puerto Rico, one in St. Croix, one in Jamaica, and one in the Cayman Islands. That this combination of unlikely, astounding factors comes together to create a perennial nursery for a diverse community—fish, mollusks, birds, insects, reptiles, and more—is remarkable. Bioluminescent bays are vastly understudied, says Michael Latz, a research biologist at the University of California, San Diego’s Scripps Institution of Oceanography. But they shouldn’t be.

“They’re excellent natural laboratories to look at ecosystem competition, the effect of nutrients, and the impact of environmental conditions,” he says. “Why are they so successful? It’s a scientific mystery. We don’t have the full answer.”

Embedded in the mystery of bioluminescent bays is their extraordinary resilience. Hurricane Maria tore through both Laguna Grande (the bioluminescent lagoon at Cabezas de San Juan) and Mosquito Bay, on the nearby little island of Vieques. But nature varies in its resilience, as people do—as such, Mosquito Bay and Laguna Grande responded differently to Hurricane Maria.

For the famed and touristy Mosquito Bay, named after a legendary pirate ship, “El Mosquito,” Maria was devastating. The heavy wind and rain pushed water out of the bay, lowered the salinity of the water (an unfavorable change for P. bahamense), and decimated the mangroves surrounding the bay. Then, the water went dark. It was as though this tiny ecosystem, like the island, was experiencing its own blackout.

Today, the small island of Vieques is still reeling from year-old wounds, its residents worn and weary despite living in what might seem like paradise. But their bay’s bioluminescence is slowly recovering, arguably more quickly than the island’s electrical system. One year later, it may even be in a better state now than it was before the storm. Meanwhile, Laguna Grande isn’t glowing much at all.

What do these strange and beautiful phenomena have to teach us about the dynamics of tropical ecosystems, and just how resilient are they? Scientists are still on the hunt for answers, but one thing’s certain: It’s hardship that brings to life nature’s capacity to repair and renew.

“Welcome to the window of my office.”

At the highest point of Cabezas de San Juan sits the oldest lighthouse in Puerto Rico. At 132 years old, it’s even older than the lighthouse atop Old San Juan’s popular historic fortress, El Morro.

The lighthouse at Cabezas de San Juan, which stands 210 feet above sea level, has a generator. So after Maria hit, Alicea and her colleagues moved their offices there to direct community efforts—including distribution of supplies like diapers, wipes, and toothpaste to 30 communities. The community work wasn’t a one-time thing: Cabezas de San Juan still checks up on these neighborhoods every three to four months to see how they’re doing. The activities that collectively take place atop this gorgeous sanctuary make the lighthouse a sort of headquarters for all that Cabezas de San Juan represents.

“The office is the reserve,” Alicea tells me. “The lighthouse is my window.”

She displays equal parts sass and tenderness as she shows us around. “C’mon, we’ve got company. Behave yourselves!” she snaps at a pair of fighting roosters outside the lighthouse; just a few minutes later, she is waxing poetic about the value of the reserve’s lagoon.

“The lagoon is a fresh book to read,” she says. “Sometimes you can have bioluminescence when the conditions are not supposed to be good for it. And sometimes you have the good conditions but you don’t have bioluminescence.” Biologists hope to figure out how and why these anomalies occur.

Alicea walks through the mangrove swamp at Laguna Grande.

Alicea herself was drawn to marine biology through storytelling. She recalls seeing a book when she was 12 that depicted a “monster” (really it was a manta ray) hanging out near a mangrove forest. Later in her childhood, she watched a TV show called “Man from Atlantis,” which featured a female marine biologist as one of its protagonists. Alicea fell in love with the idea of giving back to nature the riches she had received. “Nature is always giving, and we are always taking,” she says. “Sometimes we don’t think about how we can pay back nature for all the things it gives us.”

Alicea says that Laguna Grande has about the same number of dinoflagellates floating through its waters now as it did last year before the hurricane, most of the mangroves have bounced back, and the conditions are stable—but the bioluminescence just isn’t the same. “We don’t know why it’s not glowing.”

But Alicea isn’t worried. “It’s an opportunity to learn,” she says. “It’s a kind of shock therapy—sometimes we need this shock to react and then take action.”

Juan González Lagoa, a professor emeritus at University of Puerto Rico, Mayagüez and the “father of bioluminescence,” says that Puerto Rico is in the process of establishing a unified conservation plan for all three bioluminescent bays.

“Bioluminescent bays are very sensitive,” Lagoa says. “We have to take good care.”

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“It’s a beautiful night in Puerto Mosquito.”

While Aristotle was the first to describe bioluminescence in writing, it wasn’t until the late 19th century that the term came into widespread use. And it wasn’t until the mid-20th century that Johns Hopkins University scientists like W.D. McElroy, William Biggley, and Howard Seliger (among others) identified an exact ecosystem model for the formation of bioluminescent phytoplankton blooms in coastal waters. (Seliger, in particular, had been obsessed with light and fireflies since childhood; later in his career, he devised experiments related to color and human memory alongside his work on bioluminescence.)

Their model elucidated the mechanics of just one particular bay—Phosphorescent Bay at Puerto Rico’s La Parguera nature reserve—but scientists agree that in general, there’s a special recipe for making an environment hospitable to glowing dinoflagellates.

First, you need a mangrove forest, the right amount of salt water, a semi-protected area of water, and a particular type of current that “traps” the dinoflagellates. On top of that, some bioluminescent bays have other distinguishing characteristics. For example, what makes Laguna Grande special is that it’s partially protected by the reserve’s coral reef, which acts as a kind of breakwater. That’s what makes it a lagoon as opposed to a bay. Jamaica’s bioluminescent bay is unusual because a fresh water river flows into it. The water in the bay is stratified as a result, with fresh water on top and saltier ocean water underneath it. The dinoflagellates simply avoid the upper, freshwater layer. For each bay, a sudden change in rainfall, salinity, temperature, wind speed, or wind direction could turn out the lights.

“That’s one of the things about bioluminescent bays that is incredible—how many things have to be in sync,” says Mark Martin-Bras, the director of research for the Vieques Conservation and Historical Trust. “If you have the right shape and the right size and the right flow, it just does its magic.”

He uses the word “magic” for a reason—there’s long been superstition related to bioluminescence, which “was one of the world’s special effects,” Martin-Bras says. “Some people considered it evil, as they couldn’t understand it. If you put your hands in the water, look—your hand just becomes a wizard’s hand.” Out on Mosquito Bay with Martin-Bras, I lean over the edge of the small boat and dip my hands into the dark, velvety depths. The dinoflagellates’ blue-green glimmers emerge in a stunning dance that mirrors the night sky as the bay breeze envelops us. The feeling is both serene and otherworldly—bewitching, even.

On the island of Vieques, the absence of light pollution post-Maria gave conservationists like Martin a chance to capture bioluminescence in the bay more readily. He and his colleagues want to introduce covered amber lights that will replace other downed sources of light, and that will be angled away from the bay, from sea turtle areas, and other sensitive regions of nocturnal flora and fauna.

“People come to the bioluminescent bay and they’re like, ‘Oh, this is beautiful, but the sky is beautiful, too…I don’t know where to look,’” Martin-Bras says. “It’s a combination that gives [you] a better perspective of the world and the universe—from the microscopic to the universal.”

Martin-Bras recalls feeling similarly when he was eight and his father and uncle took him to see the bay. “It was magic,” he says.

Now, as research director on the island, Martin-Bras is focused on jotting down his observations and taking detailed samples of the water to determine temperature, salinity, turbidity, pH, and more. Over the course of an hour or so, he takes us to a several locations in the bay, including a real-time monitoring station equipped with telemetry that the United States Geological Survey installed in 2014. The 90-milliliter samples at each site are mixed with formaldehyde, which kills and preserves the phytoplankton so that Martin-Bras and his teammates can count them—as well as compare various aspects of water quality to other time periods.

The behavior and size of phytoplankton blooms can tell scientists a lot about the condition of an ecosystem. For example, a bloom of toxic phytoplankton near a chicken farm might suggest there is some anthropogenic (human-caused) activity at bay. Or unusual amounts of phytoplankton could help us understand the relationship between ocean acidification and biodiversity.

The prevailing characteristic of year-round bioluminescence in coastal bays is that one species of dinoflagellate, P. bahamense, dominates. Ecologically, Latz says, this is very unusual—and it’s a rule that holds true even after large-scale disturbances like hurricanes.

If storms become stronger, that could push bioluminescent bays past a tipping point.

After storm events, biologists and conservationists see an increase in phytoplankton communities based on observed chlorophyll levels. But that increase is due to the sudden proliferation of other phytoplankton and a simultaneous decrease in P. bahamense. Later, the system restores itself to equilibrium—to typical conditions in which it’s dominated by P. bahamense.

“It’s incredibly interesting that this single-celled, extremely delicate microscopic plankton is able to dominate at incredible levels and stay that way,” Martin-Bras says. Scientists don’t yet know why P. bahamense is so paramount, nor why faster-growing phytoplankton don’t out-compete it.

If there’s an increase in frequency of storms, though, or if storms become stronger—factors that could be influenced by climate change—that might push the P. bahamense-dominated stable community past a tipping point.

“Then you may have a regime shift where other organisms become dominant and then it doesn’t restore itself,” Latz says. Scientists don’t yet know what the tipping point is for bioluminescent bays; to know the answer would mean witnessing the difference between light and dark—between resilience and death.

On this particular night in Mosquito Bay, at first, the light show is a bit more modest. Hurricane Beryl, which deteriorated into a tropical storm, had just passed through.

But just before we reach the monitoring station, the boat slows and the operator, Carlos, turns off the engine. Crests of radiant bluish silver surround us and the shadows of tarpon fish glide beneath the water’s surface. “When the wind blows, you are able to see what would be foam or movement transform into blue magic,” Martin-Bras says. He notes that there are probably something like 75,000 dinoflagellates per liter in the water at this moment. Despite Beryl, this corner of the bay is glowing incredibly.

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“We have to learn from nature.”

As it becomes clearer that bioluminescent bays could be beacons of light for researchers, many are lobbying for more detailed studies of how severe storms affect them.

Latz and his colleagues have unpublished results showing the importance of wind speed and direction as an environmental factor affecting bioluminescent bays; further studies will address the impact of Hurricane Maria, as well. One of the studies looked at Mosquito Bay over four months and determined that during storm events, if the wind shifted radically, then the bay saw changes in dinoflagellate populations—and, in turn, bioluminescence. In addition, this change was reversible within a week. In general, too, “wind can generate turbulence, which is known to affect population growth because it interferes with the process of cell division,” Latz says.

On the island of St. Croix (part of the U.S. Virgin Islands), there’s another bioluminescent bay that Latz studied. It’s called Salt River Bay, and it was formed after a failed hotel complex project was abandoned 60 years ago; in the intervening decades, what remained of the artificial marina transformed into a bioluminescent bay. In a six-month study at this bay, Latz’s team found that wind speed was an important factor in regulating bioluminescence. Currently, Salt River Bay is doing well—Maria actually washed sediment out of its clogged entrance, which gave the bioluminescence a boost. Sargassum, as it turns out, also impairs bioluminescence—and Laguna Grande has been dealing with a perplexing sargassum situation.

"Mangrove swamps are kind of like immortal forests," Alicea says as she guides us through the reserve. "They are used to hurricanes."

Although it’s hard to uncouple these factors from other measurements like salinity and rainfall, the studies do signify a step in the right direction.

Rising sea levels pose a threat that conservation efforts may not be able to solve. Lagoa notes that in Vieques, Mosquito Bay sits side-by-side with Ferro Bay, a deep bay with a very strong pattern of circulation. “With a rise in sea levels, we may see them connect eventually,” Lagoa says. If that happens, Lagoa says the pattern of circulation in the bay will change and “that will be the end of it. That I know.”

In some ways, the response of bioluminescent bays to Hurricane Maria shows us that the climate change problem is not just one of warming temperatures—it’s a problem of nonlinearity, a problem of refereeing when the direction of things is unclear but beauty is stable, unwavering. How do we come together as a team to maintain a home that is always changing—that always needs repairs—when we’re fractured and broken ourselves?

“That’s the hand we’ve been dealt,” Martin-Bras sighs, looking over the twinkling bay. “That you can go through life without being a nature person. That you could sacrifice this.” He pauses. “Instead of adjusting to life, I saw that we were just trampling through it.”

Back at Laguna Grande, Alicea agrees. “People forget to live with nature, and not far from it,” she says. “If we destroy just one thing in this spot, we are going to have consequences on the other side of the island. Everything is connected.”

Photo credits: Michael Rivera, Phil Hart / CC BY-NC-SA 4.0

Funding for this reporting is provided by the Ives Family Fund.

Funding for NOVA Next is provided by the Eleanor and Howard Morgan Family Foundation.

Major funding for NOVA is provided by the David H. Koch Fund for Science, the Corporation for Public Broadcasting, and PBS viewers. Additional funding is provided by the NOVA Science Trust.