Rebuilding the coral reefs of Golfo Dulce

Like a mermaid on an underwater picnic, she floats gently in the current as slivers of sunlight reveal a garden of corals in the Golfo Dulce, in southern Costa Rica. Holding a basket filled with round, spiked corals, she collects one last specimen, then begins her ascent. As she breaks the surface, Socorro Avila, a research assistant who grew up on this gulf, joins Joanie Kleypas and Tatiana Villalobos – two more mermaids – and they swim towards the boat that idles nearby.

The three scientists deliver their bounty, passing round, spiked corals into the waiting boat. Handling each piece requires patience — some trail along a clear fishing line, while others twist into woven strands of a rope. As they untangle each precious item, the corals’ branches jostle, tinkling like porcelain dolls colliding. The team board the boat, doff their scuba gear, and head further into the gulf — one step closer to understanding these mysterious species.

For three years, this team that goes by the name of Raising Coral Costa Rica has been snapping off coral pieces from existing reefs to grow them in an underwater nursery. Months later, the team moves the nursery-grown corals and attaches them to skeleton-like structures that once were living, thriving reefs in the Golfo Dulce. Kleypas, a scientist at the National Center for Atmospheric Research in Colorado, has spent 30 years spent studying coral reefs, while Villalobos, along with a handful of other researchers involved in the project, are a part of the University of Costa Rica’s ocean and freshwater science division, or CIMAR.

Illustration credit: Serena Richelle

The team is using tested techniques and experimental ideas to grow coral and revive ancient reefs in the Golfo Dulce, an underwater oasis in the Eastern Tropical Pacific Ocean, where coral reefs have been historically understudied. By contrast, researchers have studied corals of the Caribbean Ocean and the Great Barrier Reef far more extensively. “These corals have been ignored, mainly because they don’t form big, huge reefs,” Kleypas said. But the species in this part of the Pacific support high levels of biodiversity, behaving similarly to the well-studied Caribbean reefs, but with fewer corals overall, she added.

Their findings are helping to restore local ecosystems, and could help researchers who hope to revive reefs in nearby countries. The species of the Golfo Dulce, when compared to a lot of the world’s reefs, may hold extraordinary clues about resilience to changing ocean conditions. Each day, the ocean’s tide ebbs and flows in the gulf, which raises and lowers the temperature, acidity, and salinity regularly. Because these reefs are exposed to constant fluctuations, researchers are curious whether they may be better suited to withstand changing ocean conditions than the corals that live in the ocean, without daily fluctuating conditions.

As the race to save our oceans against a changing climate accelerates around the world, knowing how to rebuild one of its foundational components, coral reefs, may be one way that scientists can help them survive in a warming world.

“Sweet Water” no more

Spanish explorers led by Christopher Columbus landed their ships on the western coast of Costa Rica in the early 1500s. In Spanish, Golfo Dulce translates to “sweet gulf,” but the early explorers in this part of Latin America used the name to refer to sweet, or fresh, water. Four large rivers — Tigre, Rincón, Esquinas and Coto-Colorado — empty into the gulf. This fresh and salty water mixture makes the gulf less salty than the ocean; the Golfo Dulce has a salinity of 28 to 34 parts per thousand, compared to an average of 35 parts per thousand in the ocean.

The gulf spans roughly 500 square miles and reaches more than 650 feet deep, making it one of the world’s few tropical fjords, a long stretch of deep water surrounded by steep shores. With its calm waters and expansive depths, Golfo Dulce is a hotspot for marine wildlife. It is the only known place where both northern and southern humpback whales migrate while calving, new invertebrates are still being discovered, and sharks, turtles and fish use these gentle waters as a temporary and permanent residence throughout the year.

Along the gulf’s shallow coastline, and on the sloping bottoms below, lie patches of ancient coral reefs — some dating back thousands of years. Decades ago, these reefs were nearly decimated by agricultural development. Chiquita Banana, part of the larger United Fruit Company, moved to the area in 1937 and began building its headquarters, as well as banana plantations. This heavily altered the tropical jungle, and dirt filled the rivers and gulf in unprecedented amounts. Development in the area continued when banana plantations were converted to plots for palm oil in the 1980s. A study between 1992 and 1996 revealed that live coral coverage on one reef in the gulf, in playa Sándalo, decreased from 29 to 17%, due to elevated amounts of erosion.

“I spent my childhood here. I did my homework, fished and swam,” said Jorge Largaespada Amador. Now 53, Amador moved to Playa Blanca, a small town on the gulf, when he was six. He recounted swimming with red snapper and sharks as they hunted nearby in the reefs.

“The reefs were alive, now they’re dead,” he said.

Today, much of the land surrounding Golfo Dulce is protected as a national park or refuge, but only a small portion of the water is included. “About 10 percent of Piedras Blancas National Park, around 14,000 hectares total, extends into the gulf,” said Geinier Barquero Vanegas, a park ranger with MINAE SINAC, the division of the national government that manages conversation areas. In 2010, the Golfo Dulce was declared an Área Marina para la Pesca Responsable, making it the largest responsible fishing area in Central America. This declaration prevents commercial fishing boats from entering the Golfo Dulce, offering marine life in the gulf a chance to rebuild and flourish.

“Los corales,” the corals

Most of the world’s reefs, including those in the Golfo Dulce, grow in shallow, tropical waters near the equator. In total, these reefs cover 284,300 square kilometers, or less than 1%, of the seafloor — and the reefs in this gulf represent a small fraction of the already thin sliver. But coral reefs build the foundation of marine ecosystems — they support over 25% of ocean life. Coral, using minerals from the seawater, build a structure for countless organisms to live. In the Golfo Dulce, little coral crabs are common tenants in the branches of the reefs, and schools of fish move through the reefs every day. Larger marine animals, like spotted eagle rays and nurse sharks, use these areas as nursery and hunting grounds.

Like New York City, filled with industrial buildings and people keeping the lights on, a coral reef is made up of animals that build the structures and algae that live inside. The algae, known as zooxanthellae, use sunlight to produce the majority of the energy needed to power the underwater cities, and the coral provides a safe haven.

When ocean conditions change, such as when water temperatures rise uncharacteristically or water clarity decreases, the two organisms that work together to build a reef fall out of sync. This off-balanced relationship causes the colorful, energy-producing organism to flee the reef, leaving behind a colorless, “bleached” coral skeleton with no substantial way of producing its own energy.

Over time, as runoff in Golfo Dulce accelerated, the corals were covered with sediment and sunlight was blocked. The algae weren’t able to produce enough energy and the corals eventually began to die. And ocean warming trends of recent history have only accelerated coral bleaching events in Golfo Dulce, and around the world.

During a massive global 2015-2016 coral bleaching event, 75% of the Golfo Dulce’s coral cover declined. But the Raising Coral research team was surprised when corals started to recover only two years later. “We got excited that they came back relatively quickly … they’re so tough,” Kleypas said. Filled with more than an inkling of hope from these hardy corals, the team is working towards establishing a process for coral restoration in the Eastern Tropical Pacific Ocean and genetic testing to define what’s behind this resilience.

Coral species as a whole have become increasingly threatened and researchers don’t know if these complex underwater communities can survive into the next century. Although we can’t necessarily halt climate change or human pressures altogether, there may be ways to lessen the impacts on coral reefs. If done right, coral reef restoration may be a way to produce climate-tolerant corals. In a world where haphazard restoration projects are springing up overnight, this team’s approach to restoration and the unique environment in Costa Rica may serve as a model for researchers racing to rebuild the world’s coral reefs.

The team

When Joanie Kleypas was introduced to the eastern tropical Pacific waters of Costa Rica, she learned about ancient reefs that had been decimated by runoff. “I had to see them for myself,” she said. Kleypas was inspired and used funds from an award in 2011 to begin experimenting with ways to help the corals grow again. “This part of Costa Rica has a history of ecological conservation — the water quality was improving and people were starting to care about the Golfo Dulce,” Kleypas said.

Tatiana Villalobos, who grew up in the northern Alajuela Province in Costa Rica, was embarking on graduate studies at the University of Costa Rica when a mutual friend introduced her to Kleypas in 2016. Villalobos had experienced the shock of seeing a bleached coral reef in her teenage years, and knew that she had to do something to help. Together, they began a project that combined their passion for coral reefs and ties to southern Costa Rica.

The two researchers and their teammate, José Andrés Marín Moraga, who focuses on restoration in Costa Rica’s North Pacific coast, set off to the United States in 2016, to learn how to grow coral species from David Vaughan, then director of the Mote Marine Lab in Florida. Vaughan has pioneered a technique called “microfragmentation,” now used to grow corals around the world. A form of asexual reproduction, microfragmentation creates an exact genetic copy of an individual coral without female or male sex cells combining. It works by breaking off a small piece of living coral and growing it in optimal marine conditions: a steady flow of nutrients and plenty of sunlight. After spending 6 to 10 months in the nursery, the coral fragment grows as a clone of the organism from which it was harvested.

After learning the technique, Kleypas and Villalobos came back to Costa Rica. The team of Raising Coral now includes experts in coral reef ecology, social science, business, and local expertise. Avila, a lifelong resident of the land surrounding the Golfo Dulce, joined the team to help tend to the underwater nurseries each month. Finding people who grew up near these waters, who know them best and have a mutual interest in its health, was a major priority for Villalobos and Kleypas.

Before starting any work in the Golfo Dulce, Villalobos spoke with the local communities who rely on the health of the gulf. She met and interviewed nearly 200 residents, probing their knowledge of coral reefs. “It was really interesting, and at times, very frustrating,” she says. She learned that some of the local fishermen thought that the bleached corals, a brighter white color, were healthy and well, when in reality, healthy coral species of the eastern tropical Pacific have a dull, neutral coloring.

“We really needed to do our homework before we started this project,” Kleypas says. They surveyed all of the reef structures — investigating water quality, proximity to development, and ability to provide larvae to other reef structures. Ultimately, they identified two different sites, both on underwater slopes not far from the shore, that seemed most promising for restoration.

In 2017, the Raising Coral team built an underwater nursery in a shallow, calm section of the Golfo Dulce with PVC pipes, ropes, clear fishing line and empty plastic jugs used as buoys. They tied small bits of coral harvested from the gulf to the PVC structures, creating structures that looked like underwater Christmas trees with coral ornaments floating in the current.

Illustration credit: Sami Chang

In the beginning, things didn’t go well: about 80% of the corals growing in the nursery didn’t survive. “It was scary; we were learning as we went,” says Villalobos. Now, things have changed, after three years of trial and error, over 1,500 new coral reef pieces have grown in their nursery — some as large as a basketball. These are harvested months later and then transported and attached to deadened reef structures.

The researchers visit the newly planted corals each month, recording their growth progress and overall health. So far, about 200 corals have been planted, and of those, 70 to 80 percent appear healthy and growing. Kleypas points out that restoring coral reefs takes time, and that only if the restored reefs survive changing ocean conditions can the restoration be considered successful.

The coral garden

On a recent January afternoon, the team tends to its underwater garden. Villalobos and Avila use a toothbrush to carefully clean the PVC pipes, brushing away algae. Kleypas hovers in the water over a structure that resembles a raised garden bed attached to the bottom of the seafloor with ropes running its length. She is using small, sharp pliers to break apart a large piece of coral and attach each smaller piece into an unraveled section of rope. While the exact reasoning is still unknown, these newer, experimental rope gardens are producing bigger, healthier coral fragments than expected. “There’s something about the rope that they really like,” she said later. “The corals from this line nursery have been growing so fast!”

A long few days lay ahead for Avila and the team of researchers who must clean the underwater nursery, harvest and plant the larger corals and string up new, smaller pieces. Everything seems to take longer underwater, and similar to the investment required in restoration work, patience is a virtue. Much about how to get these corals to grow fast and strong enough to survive outside of the nursery remains unknown — their destiny hinges on an eventual understanding of these species and for now, luck.

Restoration projects around the world are taking off, Kleypas said. The amount of research that goes into the execution of some projects, however, seems shockingly stunted. In the 1970s, a non-profit organization dumped two million used car tires off the coast of Fort Lauderdale, Florida, in an effort to attract more marine life to the area. Nearly 40 years later, the area was barren of any new life (or corals) and local authorities were faced with a new problem — how to remove millions of old tires from the bottom of the Atlantic Ocean.

Rebuilding for the future

But something must be done. As ocean temperatures around the world warm as a result of climate change and human development continues nearly unabated, global coral researchers estimate that reefs may not be able to survive without active restoration. “By 2050, estimates predict that nearly all of the reefs will be threatened, with 75% facing high to critical levels,” said Jose M. Eirin-Lopez, a coral scientist at Florida International University. This means that the 500 million or so people who currently depend on reefs for food, protection or tourism income, 30 million of which are the poorest on the planet, will be affected in some way.

Meticulous, stepwise experiments may hold a key to remedy this climate change catastrophe. Villalobos is working with surrounding countries to share what’s worked and what hasn’t, in hope that it can help. El Salvador’s Pacific coast shares many of the same coral species as those found in the Golfo Dulce, and researchers are starting to take advantage of the lessons learned by Raising Coral to begin rebuilding their own reefs. Active, organized restoration is still in its planning stages, but Johanna Segovia, an associate researcher involved in coral reef management in El Salvador, sees the work of Raising Coral as pioneering and an example to follow.

Drifting into the sunset

As the boat engine roar subsides, we glide through the calm waters of the Golfo Dulce and the boat drifts to a stop near a large, once-thriving reef. The coastline is filled with jungle: trees, vines, an occasional set of scarlet macaws and a glimpse of dark volcanic sand. It’s time to give Avila’s recently-harvested corals a new home.

Villalobos, Kleypas, and Avila slip into the water and begin working to attach the new corals to the ancient reef structure. They hammer a large nail into a section of the reef and use a plastic zip tie to attach each coral ornament to its stake. Even underwater, the distinct tinkling sound of a hammer hitting a nail can be heard. The corals grown in the pieces of rope are left in the twining and attached at either end to the reef structure, swaying like a clothesline in the ocean current.

A symphony of cicadas blares from the shores as the sun begins to set and the Raising Coral crew wraps up their day in the field. The mood oscillates between excitement of what’s ahead and a calm quiet. It was a productive day.

“It’s exhausting but we’re rewarded with the fact that the corals want to grow,” Kleypas said. “As long as they don’t give up, we won’t.”

© Ashleigh Papp / UC Santa Cruz Science Communication Program