Research Feature: Trouble in Paradise

Todd LaJeunesse peering into tidepool

A dozen rusty fishing boats rock gently on the surface of the shimmering, aquamarine water. Their wood has splintered and their paint has peeled from years of exposure. I scan the horizon, looking for the research vessel that will carry us out to the reef, but I see nothing that seems suitable for an expedition.

Just as I conclude that our boat has not arrived, two men with dark tans and round bellies approach across the white sand, mutter something in Portuguese to our Brazilian colleague, and set about gathering up our things. I watch, apprehensively, as they hoist crates of expensive scientific equipment onto their heads and wade out into the ocean. They head for a rickety vessel adorned with a sun-faded painting of Saint Peter, the patron saint of fisherman.

I am on the beach in João Pessoa, the capital city of Paraiba state in northeast Brazil, in the company of Todd LaJeunesse, an assistant professor of biology at Penn State, and Bill Fitt, a professor of biology at the University of Georgia. We’re here not for sun and fun, like most of the pale-skinned tourists lounging nearby, but to investigate the ecology and evolution of corals and the symbiotic algae, known as Symbiodinium, that inhabit their cells. The two Americans and their Brazilian colleague, Cristiane Francisca da Costa, are part of an international, World-Bank-funded team that is studying the impacts of environmental stresses on coral reefs around the world.

Coral reefs are diverse ecosystems paralleled only by tropical rainforests in the number of species they support. A healthy reef can harbor millions of organisms, from hair-like strands of cyanobacteria woven into soft mats to barrel-shaped sponges—little smokestacks that purify rather than pollute. Reefs are home to parrotfish that pluck algae with curved beaks and violet-tinged lobsters that scavenge dead animals from the ocean floor. They are visited by giant sea turtles that glide gracefully among coral heads and sleek reef sharks that feast on colorful fish. The hub for all this diversity is the corals and their Symbiodinium, which together provide residents and visitors alike with habitat and food.

Thriving reefs are important to human economies as well. They support fisheries, control coastline erosion, provide tourism opportunities, and serve as a potential source for medically important compounds we don’t even know about yet. In fact, the United Nations estimates the annual value of just one square kilometer of coral reef at some $600,000.

Barrage of threats

These underwater sanctuaries have long suffered from a barrage of threats, including pollution, disease, and overfishing. Their most devastating environmental stressor, however, may turn out to be global warming. Corals rely on their photosynthetic partners to convert sunlight into food, but when temperatures rise, the colorful algae die, leaving coral to starve. Known as bleaching, this phenomenon can lead to the collapse of entire underwater ecosystems. Slight increases in ocean temperature, as little as 2 to 3 degrees Fahrenheit, can kill vast swathes of reef.

LaJeunesse and Fitt are investigating the possibility that certain coral-algal partnerships can withstand the effects of global warming. So far, their search has taken them to reefs off the coasts of Mexico, Thailand, Zanzibar, Australia, Hawaii, and Barbados, among other exotic places. “Our data show that different geographic regions are home to unique combinations of host and symbiont,” says LaJeunesse. “Each of these combinations may respond differently to stresses.” In the eastern Pacific, for example, he has found that a coral in the genus Pocillopora teamed with a particular Symbiodinium can withstand higher temperatures than the same Pocillopora when it associates with another species of algae. Here in João Pessoa, the team will investigate coral-algal symbioses in a region that, so far, has been relatively unaffected by global warming. Regional ocean currents have prevented the local waters from heating up, LaJeunesse explains. “This site will serve as an important benchmark we can compare to other sites that have been affected.”

Brazil’s reefs are special for another reason, too: They contain several species of coral, including a rare, bluish-green branching coral called Mussismilia hartti, that are not found anywhere else in the world. “The reason Brazil has so many endemic species,” says Fitt, “is that the outflow of the Amazon River has prevented the exchange of genes between corals here in the southwestern Atlantic and those in the Caribbean. The Isthmus of Panama further isolates the Atlantic reefs from the Pacific.”

Brazil’s unique corals may in turn harbor unique species of algae. “There are two basic types of Symbiodinium,” explains LaJeunesse. “The ones we call specialists associate only with certain species of coral host. Generalists are less picky. Some of Brazil’s endemic corals may contain algal specialists that are unknown to science.”

Out to sea

LaJeunesse and LaCosta

I wade out to our modest-looking research vessel and begin to climb up a thin-railed ladder when a calloused hand reaches down, grabs my arm and gently pulls me out of the water. The hand belongs to Iran, the boat’s owner. A local fisherman, he has been hired for the day to take us to two reefs where we will collect samples of as many species of coral as we can find.

Iran yanks the throttle and the boat’s engine sputters to a start. Instead of a steering wheel, he uses a long, smooth tree branch to guide the rudder. As we head out to sea, the high-rise hotels and condominiums that line João Pessoa’s beaches become smaller and smaller in the distance.

Located at the easternmost tip of the Americas, João Pessoa is one of Brazil’s oldest cities, founded by the Portuguese in 1585. Although it is larger than Pittsburgh, with about 672,000 residents, its numerous parks and nature preserves earned it a designation as “the second greenest city in the world” by the United Nations in 1992. Even with all the green space, however, local residents have noticed dramatic changes in recent years. “When I was a boy, there were only two tall buildings in João Pessoa,” says Iran. “Now there are dozens.”

I am pleased to find that he speaks English, since my repertoire of Portuguese words is limited to olà (“hello”) and obrigada (“thank you”). Before we get far, I ask him about Internet stories I have read claiming the waters off this point are known for shark attacks. Iran dramatically points to a large scar on his left elbow. “There are many dangerous sharks in these waters,” he says gravely, but he can’t suppress a following giggle. I think he is pulling my leg.

As we make our way to the reef, about half a mile offshore, the three biologists discuss their plan for collecting small samples from individual coral colonies. LaJeunesse and Fitt have been working together since Todd signed on as a postdoctoral researcher in Bill’s lab at the University of Georgia back in 2000. However, the two have known each other for even longer. Both did their graduate work at the University of California, Santa Barbara, under the supervision of renowned marine biologist Bob Trench. Although Fitt is 20 years LaJeunesse’s senior, the two crossed paths during Fitt’s return visits to his alma mater while LaJeunesse was a student. Francisca da Costa, in turn, studied with one of Fitt’s former colleagues. Now a professor of biology at the Universidade Federal de Campina Grande, she is a well-known expert on Brazil’s corals. Her knowledge of local species is a valuable complement to the Americans’ expertise in coral-algal interactions.

A Rare Find

“The first site we are going to has a relatively high diversity of corals,” Francisca da Costa informs us. The spiral curls of her coffee-brown hair whip around as the boat cuts through the wind. “We should be able to find at least eight species there, four of which are endemic to Brazil.”

When we arrive at the site, the water is gray and murky. Heedless of the sharks that may be lurking, the scientists squeeze themselves into tight-fitting wetsuits, strap on flippers and air tanks, and step out, one by one, over the edge of the boat. From the rail, I hand them sacks of gear: hammers and tiny chisels for breaking samples, plastic collection bags, and underwater cameras. Then they disappear beneath the surface.

In a few minutes, I decide to check things out for myself—not diving but snorkeling. Even through the mask, the turbidity prevents me from seeing anything at a distance, but up close I make out some chestnut-colored coral heads—masses of genetically identical polyps—and a small school of butterfly fish, white with golden stripes. I also find a sea hare, a slug-like, fluorescent-yellow animal with stubby antennae.

Eventually, I return to the boat, and shortly thereafter I see big bubbles breaking on the water’s surface as the biologists ascend. Floating a few feet from the boat, they gently hand me their sacks of tools. Then they toss dozens of clear plastic bags onto the boat’s slippery deck, each bag containing two-inch fragments of pink and brown corals.

“I found Mussismilia hartti!” exclaims Francisca da Costa as she climbs onto the boat. She reaches for a towel. “No one has looked at its Symbiodinium,” she continues excitedly. We all gather round to peek at the specimen in her palm. Its lovely blue-green shade makes it look like a small bouquet of flowers. From its base sprout several stalks of calcium carbonate, the hard, non-living substance that corals secrete as they grow. At the end of each stalk sits a plump coral polyp, its tiny tentacles radiating outward like the petals on a flower.

Underwater colossus

We soon push on to our next site, a few miles to the southeast. The water here is much clearer. We’re farther from the mouth of the Paraiba River, Francisca da Costa explains, and as a result there is much less sediment. The plan this time is to sample corals around the edge of the reef, about 12 feet below the surface, and then to swim over the top of the reef, which lies just a few feet underwater. Small changes in depth can significantly influence the composition of a coral community, LaJeunesse explains.

From the boat, the reef looks like a colossal creature crouched at the bottom of the sea. And it is a colossal creature, in a way. Most corals reproduce by cloning themselves until they have formed sizable colonies, or heads. In healthy ecosystems, these colonies become enmeshed with those of other species, eventually forming dense reef patches, some of which are so large they can be seen from space.

The view from below the water, however, is entirely different—a sunny underwater paradise. Tiny black fish with purple faces dart in and out of the reef’s crevices; electric-blue tangs skirt the reef’s edge; and goby fish with their protruding eyes attempt to blend in with the sand and rocks.

As I snorkel, I see bits of colorful coral here and there, but most of the reef is smothered by lush, green leaves with long, feathery tips. Fitt, swimming nearby, pauses to tell me that this is a green algae. “Its presence here indicates nutrients, maybe from the sugar cane fields along the Paraiba,” he says, treading water. “These algae are a problem—they tend to suffocate the corals underneath. They prevent the Symbiodinium from getting the sunlight they need to make food.”

Returning to the boat, I wait for the biologists to finish their work, and Iran begins to regale me with tales of his life on the sea. Soon enough the divers return, and I can see from LaJeunesse’s face that he’s disappointed. “We didn’t find anything new,” he says simply, as he climbs over the side. Fitt, behind him, is more sanguine. “We did get replicate samples,” he pipes. “The lack of new species might mean we’ve thoroughly sampled all the host species in this immediate area.”

Food for Thought

Bill Fitt collecting samples

Later that evening, we stop for dinner at a traditional restaurant near the beach in João Pessoa. Waiters dressed in the brightly colored costumes of former slaves bring out carafes of pineapple juice and fish-ball appetizers. Next come platters of sizzling goat meat and beef steaks garnished with grilled onions. There are bowls of rice, mashed potatoes, fried bananas, and pinto beans mixed with celery, onion and ground manioc, a Brazilian staple. For dessert, we are presented with a traditional cake, bolo de rolo, made up of alternating layers of soft dough and guava jelly.

Full and happy, we head to the university to process the day’s samples. They must be handled quickly, LaJeunesse explains, before the DNA degrades and becomes useless. When we enter Francisca da Costa’s lab, five of her undergraduate and graduate students are there to greet us. The hour is late, but they are eager to learn some new techniques.

With a hammer and chisel, Todd breaks the coral fragments into tiny pieces and places them into finger-sized plastic vials, each containing a liquid salt preservative that will protect the organisms until he is ready to analyze them. Back in his lab at University Park, he explains, he will extract DNA from the Symbiodinium samples and then use a ribosomal fingerprinting technique to rapidly identify their species. The assay separates fragments of DNA based on their sizes, and the resulting pattern is unique to particular species.

Although this technique has been used for many years to identify certain microbes, LaJeunesse was the first to expand its application to Symbiodinium. As a graduate student, he explains, he studied a type of sea anemone that associates with Symbiodinium, but was unable to identify algal species with the available techniques. A friend who had been using ribosomal fingerprinting to identify bacteria suggested he try it. After many months of adjustments, LaJeunesse was able to tailor the method to his needs. Now the application is widely used by coral biologists.

Once he has identified the species of Symbiodinium he has collected, LaJeunesse tells the students, he will use commercial software to construct a phylogenetic tree that depicts the evolutionary relationships between the different species of both coral and algae. “This will help us predict how specific symbioses will respond to climate change,” he says.

Using a different set of samples, Fitt then shows the group how to dry and weigh the coral fragments so as to accurately determine their biomasses, the amount of living tissue they contain. “The thicker the corals’ living tissue is, the more Symbiodinium they contain, and the healthier they are,” he says. Fitt is particularly interested in measuring biomasses in Brazil because he has observed loss of biomass among certain Caribbean species, a condition he attributes to heat stress. “The corals here are not known to have experienced bleaching, but I want to be sure,” he explains.

New Clues

Two weeks later, back in University Park, LaJeunesse’s carefully packaged samples arrive in the mail. He calls me as soon as he’s finished analyzing the first subset, and sounds so eager to share that I immediately head for the lab.

“I’ve discovered some really interesting things,” he says excitedly, as I look for a place to hang my coat. “Remember how we expected Mussismilia harttii to harbor a new symbiont? What I found is that it contains a species indistinguishable from one that lives in the Caribbean! This means there may be some gene flow across the Amazon River boundary.” He describes how he will employ population genetic markers—tools that look for variation among genes in populations—to test this new hypothesis. If he finds that the Mussismilia’s genes are similar to those of the Caribbean species, then he can be sure that gene flow is occurring. But if the genes differ significantly, then the two organisms likely have been separated for thousands of years and have evolved into different species.

Another coral species, Siderasterea stellata, he reports, is capable of harboring any of three different symbionts, a previously unseen variability that may be advantageous in terms of natural selection. It will take several months to analyze the rest of his samples, LaJeunesse acknowledges. Still, he’s already eager to return to Brazil to investigate some of the country’s other reefs, especially those farther from land. One of these, the Abrolhos Bank, is considered to be among the world’s most unique.

“Our ultimate goal is to continue to collaborate with Francisca da Costa on a nation-wide survey,” he says. Such a survey will help LaJeunesse and his colleagues understand the specifity of host-symbiont relationships—how geography and environment influence it and how it changes over time. The data will also serve as an important baseline for tracking host-symbiont communities.

“Corals have experienced major alterations in climate in the past, but they have never faced the rapid changes that are occurring today,” says LaJeunesse. “Understanding the basic biology will help us predict the extent to which these sensitive creatures will respond to unprecedented change."