Picture a tropical paradise and you might conjure something like Heron Island, Australia. Two hours by catamaran from the town of Gladstone, Queensland, the sandy island’s 40 acres are shared by a resort, a scientific research station, and thousands of black noddies, a dusky and talkative seabird that nests in the lime-green pisonia trees each austral spring.
Just beyond the white sand beach, however, is where Heron Island’s true treasure lies—a treasure in danger of melting away. The coral reef at Heron Island lies within the Great Barrier Reef Marine Protected Area, meaning that its 900-some fish species and more than 300 coral species are safeguarded from common reef-killers like overfishing, dynamiting and sediment runoff. But in the last decade, a new adversary has entered the ring: ocean acidification.
Caused by the same carbon dioxide emissions as climate change, this coral-corroding drop in seawater pH may be just as far-reaching as its climate counterpart, and just as hard to study in a laboratory—until now. Stanford researchers have joined Australian scientists on Heron Island to try out a new way of looking at acid-addled corals. And it just might be a big step in the right direction for reef survival.
Ocean acidification expert Richard Feely, of the National Oceanographic and Atmospheric Administration (NOAA), calls it “global warming’s evil twin.” Feely and other scientists fear this growing acidification, which was discovered in 2003, is already dissolving the shells and skeletons of creatures like corals, oysters and starfish. As these fears play out, the loss of coral reefs could mean a big-time loss to people: according to data cited by NOAA, the economic value of coral reefs—from tourism, fisheries, and coastal protection, among other services—is nearly $30 billion per year.
With stakes this high, scientists need the right information to place their bets right—in this case, to focus conservation efforts where they will do the most good. Unfortunately, this information has been hard to come by. Ocean acidification research has been hampered by the difficulty of keeping the experiments realistic. Feely lamented at a 2011 talk at the University of Washington, “Our present understanding [of ocean acidification] is from very simplistic experiments: usually short durations, with single species, under very short incubation periods—usually two weeks, three weeks—and extreme pH changes.“
But researchers from Stanford University, the University of Queensland, and elsewhere have invented a new technique that knocks these shortcomings out—and then some. How? By bringing the lab to the reef.
It’s called the Coral Proto Free Ocean Carbon Enrichment system, or CP-FOCE. The brainchild of project leader David Kline (then at UQ, now at the Scripps Institution of Oceanography) and the Monterey Bay Aquarium Research Institute, CP-FOCE is a mini lab that researchers floated out to the reef and anchored on the sandy bottom. They made three copies of the device for the Heron Island experiment, each with a meter-long, clear plastic chamber, open on the bottom so creatures residing in the sand could interact normally with whatever else was inside.
Lida Teneva, a fifth year Ph.D student at Stanford University, participated in the inaugural deployment of CP-FOCE. Teneva spoke about the device and her coral reef research at Stanford’s School of Earth Sciences annual Research Review in April.
“On shore, we created … acidic water by essentially equilibrating CO2 gas at high concentration with seawater,” explained Teneva. The process mimicked what will happen with the actual ocean as carbon dioxide (CO2) in the atmosphere rises to levels expected by the year 2100. That water was then piped out onto the reef and into CP-FOCE’s chambers, which contained a variety of local reef organisms, like coral and algae.
Because CP-FOCE was on the reef among the natural corals, the organisms in its chambers could be subjected to acidified water without dramatically changing the other conditions they experienced. Traditional laboratory experiments, on the other hand, typically involve yanking corals out of their natural habitat and bathing them in acidified water in tanks onshore. Light levels, biological interactions, temperature, and water currents in the onshore tanks can be different from those found on the reef. This can confound the effects of acidification and leave scientists with fewer answers than they hoped for.
Getting the water currents just right wasn’t simple, though. Even though CP-FOCE’s chambers were open to the sea at both ends, those very openings disrupted the water passing through and caused it to swirl unnaturally. The solution? The openings were each fitted with a screen of parallel tubes called a flow conditioner. The flow conditioner kept the currents flowing across the coral and algae as smooth and natural as possible, explained Stanford environmental engineer Jeffrey Koseff, who lent his fluid mechanics expertise to the design of the system.
The results from the first full 8-month-long experiment with CP-FOCE are still under evaluation, said Teneva. “It was the first time that a lab experiment has been brought out into the field like that and for that long,” she explained—far longer than the over-simplistic experiments Feely described. And so far, the results confirm any coral lover’s worst nightmare: “We basically want to compare what was happening to those corals—and they were losing weight, they were dissolving.”
But all may not be lost. The CP-FOCE study is part of a larger research program to discover how fast different coastal areas are acidifying, what effects that acidification will have, and where in the world the most heat- and acid-resistant corals live. “Some corals are just really robust and can take a lot,” said Teneva—but only if they are protected from more localized damage, like the corals at Heron Island are. Identifying these robust reefs and upping their defenses from other hazards could be the key to keeping corals in the game for a long time.
“They’ve been around since the Jurassic,” she says, “about 200 million years.” They’ll survive ocean acidification, she thinks, but likely in diminished range, health and diversity. “But there will be some strongholds,” Teneva said, “and I want to make sure those are protected.” But scientists will have to help find them all, first. And CP-FOCE looks set to be a crucial tool in that search.
