Coral Reef Recovery

Randi Rotjan visited the Phoenix Islands Protected Area (PIPA)—a patch of sea in the middle of the Pacific Ocean—for the first time in 2009, aboard the scientific vessel Nai’a. Marine research in the area had begun to blossom, and scientists on the Nai’a—the word for dolphin in many Polynesian languages—were strategizing. They decided to entrust Rotjan, a young coral reef scientist, with running the entire research program for the region, an area about the size of California.

Rotjan would direct not just reef science but also its interplay with oceanography, deep-sea exploration, and climate change. This was a huge opportunity for Rotjan to expand her own research and guide investigations that could help scientists understand oceans and sea life in new ways. She was the last one to hear about it, however, because she was below deck, seasick.

The crossing to PIPA had been rough, with five days of 20-to-30-foot seas tossing the 92-foot ship and its passengers. “It was the worst passage of my life,” says Les Kaufman, a Boston University College of Arts & Sciences (CAS) professor of biology.

But also one of the best. Back in 2002, PIPA’s coral reefs had been devastated by an unusually hot El Niño, a band of warm water that periodically develops and ripples through the Pacific Ocean. By 2005, live coral coverage had shrunk to a quarter of what it had been a few years before. The reefs had been bleached, meaning the symbiotic algae that live there had vanished. “We thought, oh my God, this is a catastrophe,” says Kaufman.

But by the time of Rotjan’s voyage in 2009, something incredible had happened. The reefs had started to recover.

The team of scientists on board the Nai’a saw opportunity. If these reefs can recover, they thought, maybe others can, too. So they tapped Rotjan, a CAS research assistant professor of biology, to lead an extensive program designed to monitor PIPA’s coral reefs and track their progress alongside fluctuations driven by climate change, such as more intense El Niño events. Rotjan was young but “she had the fire,” says Greg Stone, chief scientist for oceans and executive vice president of Conservation International. “Nothing great happens without enthusiasm.”

Rotjan and her colleagues, who continue this work today, hope the science will help them identify the most critical factors involved in reef damage and reef recovery. But also, this research program marks a more general transformation in ocean science. Marine biologists are no longer just explorers, Jacques Cousteau aspirants searching underwater habitats for exotic life. They have, by necessity, become sea doctors—clinician-scientists with a mission not only to understand the sea but also to diagnose its troubles, which are many and accelerating.

Approximately three-fourths of the planet is aquatic, and if the health of coral reefs is any indicator, marine life is being ravaged by human assaults, both local (in the form of pollution, fishing, and shipping) and global (in the form of climate change). The world needs sea doctors now more than ever, to understand what’s ailing our oceans and to find new ways to protect, nurture, and heal them.

A Blue Planet

The story of coral reef health since 2009 has continued to evolve. About two-thirds of the Great Barrier Reef in Australia has suffered a downturn. In places like Florida and the Caribbean, reefs don’t easily recover from assaults like pollution, fishing, and more intense storms, in part because they never get a break. “Reefs get pounded, and things start to recover, but then they get pounded again and again,” says Rotjan, who is also co-chief scientist for the PIPA Trust.

PIPA, however, tells a different story. Established as a protected area in 2008 by its owner, the island nation of Kiribati, in partnership with the New England Aquarium  and Conservation International, PIPA is the first major marine reserve protected almost completely from direct human influence. “We’re taking away all the diseases except for one, the climate insult, and it turns out these reefs are able to survive,” says Stone. “Right now, the only treatment we have is protection. We haven’t yet come up with remedies or countermeasures, but we’re new at this. We’re learning as we go along.”

Kiribati is so remote that it takes eight days by boat to get there from Hawaii. The country, which is the size of the continental United States, is almost all ocean. It is dotted with islands, each of which is actually a reef-rimmed mountain peak with a base 3,000 to 5,000 meters below on the sea floor, putting these mountains on par with the tallest peaks in the Rockies.

The islands, taken together, add up to about the size of Baltimore. They rise at most three meters above sea level, so sea-level rise is of immediate concern. The people of this country, all 130,000 of them, depend on land for habitation but they depend almost entirely on tuna fishing in their waters for economic viability. “What happens if the sea swallows up all of a country’s land? Do they still own that ocean? Do they still own all that tuna?” says Rotjan.

Pressing questions about the country’s fate led the Kiribati people to protect a substantial portion of their islands and ocean. PIPA has been closed to tuna fishing since 2015, though fishing continues in the rest of Kiribati, which is enormous. Further, PIPA is inhabited by a tiny community of two dozen or so people who have minimal impact on the area. There is no local pollution, no fishing, and no shipping.

The only human impacts on these reefs are global. “No walls can keep out global climate change,” says Rotjan. “If you want to ask what climate change is doing, you have to go to the places where there’s essentially very little else happening. PIPA is one of them.”

Reef Recovery

Since 2009, Rotjan has been monitoring PIPA’s coral reefs. To track their size and composition, in 2012 and again in 2015 aboard the vessel Hanse Explorer, her team took thousands of photos in areas about 20 meters square and stitched those images together to create accurate photo mosaics of different reef sites.

Recent biology graduate Brenna Stallings (CAS’17), who now works in Rotjan’s lab, has been poring over those images for the last several months. Her task involves visually identifying each coral community by genus and, if possible, species. (There are hundreds of different species of coral.) She also loads each image onto a tablet and traces the edges of each coral community with a stylus, creating a record of its exact size, shape, and location.

This information, plus documentation from divers who take detailed notes about coral health on waterproof clipboards, helps create a sort of electronic health record for the reefs. “It’s going to be exciting to see how they’re changing over time,” says Stallings. “We can compare them to figure out which factors are reducing corals, and which are buffering them so they stay healthy even if things are going badly around them.”

Other research involves work by Woods Hole Oceanographic Institution scientist Anne Cohen, who is taking cores of corals from the area and learning about their history using computed-tomography (CT) scans, the same types of scans doctors use to diagnose patients. The scans detect changes in a reef’s skeletal composition, revealing growth rates year by year and giving the scientists a way to track past bleaching events. “These cores allow us to reconstruct climate history in these places and see how reefs have been hit by bleaching events and recovered from them in the past,” says Rotjan.

Now that these monitoring programs are in place, Rotjan and her team of PIPA scientists want to learn more about how coral reefs recover from damage. For instance, baby corals born on faraway islands float on an ocean current to a new location. If that baby lands in a hospitable area, it can take up residence and help repopulate a damaged reef.

To better understand the ocean dynamics that support reef rejuvenation, PIPA research includes efforts to track coral genetics and look for clues about coral ancestry and migration. Rotjan’s team is finding that some reefs act as sources that feed the regeneration of distant reefs, while others act as sinks that take in floating corals. The loss of a reef that sustains several others could cause a rippling downturn, so scientists want to understand the distinction, both in terms of their locations in the ocean environment and their coral biology.

Rotjan’s research has also shown that damaged reefs remain hospitable to repopulation for a long time, essentially for as long as the fish stick around. Fish help keep the reef clear of algae overgrowth. “If the fish keep the lawn mowed, so to speak, the baby corals can settle,” says Rotjan. “But if there’s a tangle of matted macroalgae there, the baby corals don’t stand a chance.”

A Natural Laboratory

Coral reefs protect land from storms. They form three-dimensional underwater cityscapes for animals and plants to live in and around. Their economic value can be measured in terms of tourism. Australia’s Great Barrier Reef alone generates over AU $2 billion (about US $1.6 billion) of income from tourism every year. It also can be measured in terms of sustenance, providing about a third of the world’s protein. “What makes coral reefs special is that you have this incredible complexity attached to a very small area of the planet,” says Rotjan. Reefs make up less than one percent of the earth’s surface and less than two percent of the sea floor.

But reefs, she says, are the “tip of the iceberg.” In PIPA, for example, the sea hides an enormous mountain range that has never been explored.

Rotjan and her team, in collaboration with the US government, got their first glimpse of PIPA’s deep-sea floor in March 2017 aboard the R/V Okeanos Explorer. In summer 2016, the team led their fourth oceanography expedition aboard the Sea Education Association (SEA) student sailing platform, the SSV Robert C. Seamans, and the second deep-sea voyage got underway in October 2017 aboard the R/V Falkor, all in an effort to both explore and find ways to protect and save Earth’s reefs and oceans. “It’s like studying the healing process in any complex disease,” says Kaufman. “From that, you get inspiration and ideas for management and therapy that can make the most of natural resilience.”