Of all the creatures living in the ocean, corals are some of the most vulnerable, and like the proverbial canary in a coal mine, they can let us know when conditions are dangerous. Unfortunately, just like the canary, they alert us by dying.
Most of us are familiar with the corals from shallow waters, whether we’ve been scuba diving among the reefs or have just seen colorful photos of them. We know the reefs provide shelter for countless fish and other aquatic organisms, and that they help protect our shores from storm surges and erosion. We also know by now that we’re killing the corals through pollution, overfishing, rising temperatures, and ocean acidification. About half the world’s shallow-water reefs have died in the last three decades.
The corals we see close to the surface are only part of the picture, though. About two-thirds of the world’s corals live in deep water, down 3,000 feet or more, and they, too, support a diverse habitat. The temperature down there is colder (these deep-water species are collectively known as cold-water corals or sometimes as super corals), and the environment is harsh; naturally occurring methane seeps up from crevices in the ocean floor, for example. Although the cold-water corals can usually withstand these conditions, additional stressors, such as the oil from the Deepwater Horizon oil spill in 2010 and—even worse—the chemical dispersants used to break up the oil, have killed many of them.
Researchers at Temple University in Philadelphia are now studying cold-water corals; one particularly hardy species, Lophelia pertusa, is an ideal test subject. In the lab, teams of graduate students tend to the specimens, carefully preparing their tanks and hand-feeding them with pipettes, before introducing various stressors to see what they can tolerate. The students expose the corals to high pH, increased temperatures, oils, and oil-dispersing chemicals one at a time and then in different combinations, recording how quickly—or whether—they recover. “We get really invested in them,” one student says in a recent New York Times article, “and then we kill them.”
They’re killing a few to save the many, however. Their research has several goals. One is to see how we can best protect the corals and the ecosystems they harbor. Ensuring oil platforms are not located directly above reefs would be a start, but that’s impractical in places like the Gulf of Mexico—too many reefs and too many oil rigs—so another strategy is to find less-toxic dispersants to use in case of another spill. Some researchers also advocate identifying the toughest of the Lophelia strains and transplanting them to neighboring reefs, hoping the strongest will survive and spread. An extreme version of this strategy would be to use gene-editing techniques to give more corals the characteristics of the most resilient species, but that’s controversial and not certain to work.
So far, the Temple results show that most of the corals can readily withstand one or perhaps two stressors. But adding pollutants to the already-warmer environment, or an oil spill in waters already polluted by runoff, might prove too much and cause a large-scale die-off, and possibly a cascade effect as the species that depend on the reefs lose their support. For example, in 2016 as much as half the coral in the weakened Great Barrier Reef died during a series of heat waves.
We stopped using canaries as sentinels in underground coal mines more than 30 years ago—just about the same time the oceans’ corals began dying off. Technology replaced the birds; it remains to be seen what we can devise to save the corals.
You can read more about the Temple University research here: www.nyti.ms/2lC2dD2.
