Corals in Peril

Corals in Peril

The Great Barrier Reef can be seen from space, a vast maze of reefs, passages, and coral islands that stretches for 1,400 miles off Australia’s northeastern coast. It’s the world’s largest coral reef ecosystem, home to a staggeringly diverse array of plant and animal life. It’s been declared a World Heritage Site and one of the seven natural wonders of the world. It’s also in serious trouble.

Nearly 90 percent of the Great Barrier Reef is suffering from a condition called coral bleaching. In some parts of the reef, half the corals have died. Bleaching isn’t just happening at the Great Barrier Reef, though; it’s part of an ongoing global bleaching event that’s threatening reefs all over the world.

To learn more about what’s happening, we checked in with Dr. Mark Eakin ’76, a coral reef specialist and the Coordinator of the Coral Reef Watch Program at NOAA—the National Oceanic and Atmospheric Administration. Coral Reef Watch uses satellite data and computer modeling to identify areas where coral reefs might be at risk. “We work not only with scientists, but also with marine resource managers and the general public,” Mark explains. “We work with people all around the world who are concerned about the problem of coral bleaching.”

NOAA announced the current global bleaching event in late 2015, and media around the world have begun to pay attention. Mark estimates that he’s given over a hundred interviews, including appearances on The Diane Rehm Show, Science Friday, and The Today Show. Over the last four months, he says, about 20 percent of his time has been spent discussing coral bleaching in various interviews and articles.

Mark says that to understand the current bleaching event, you first have to understand the unique nature of corals. “It’s like the children’s game 20 Questions,” he says, “where you usually start by asking ‘Animal, vegetable, or mineral?’ The interesting thing about corals is that they’re all three.”

Healthy corals have a symbiotic relationship with the algae that live inside them. These algae turn sunlight into food, providing coral not only with essential nutrients, but also with their beautiful colors. “It’s a symbiotic relationship that benefits both the algae and the coral,” Mark explains. “What’s happening now is that this relationship is breaking down. The corals are being forced to expel their algae—they literally rip their guts out and spit them out into the water.”

After the coral expels its algae, only the white skeleton is left behind, which is why the sick corals are described as bleached. “It looks like what would happen if you took a coral and poured bleach all over it. What you’re looking at is an animal that is still alive, but it’s very sick and has lost its source of food. It’s starving and is more susceptible to disease.”

This global bleaching event is the third that NOAA has documented since 1998, but Mark says that the current event is unprecedented in both scale and impact. “This global bleaching event we’re in is unlike any we’ve seen in the past. This is the longest bleaching event on record and also the most widespread. It’s caused damage in most areas around the world because it’s been such a long event—we’re going into our third season in some areas … We’re talking about an event that’s had devastating impacts on many coral reef ecosystems around the world.”

While the bleaching at the Great Barrier Reef is troubling, Mark says there are other reef systems around the world that are much worse off. “What’s happening at the Great Barrier Reef sounds horrible, but then you hear about some of the other areas, like Christmas Island in the central Pacific. When people were looking at it in April, over 80 percent of their corals had died. That number is just going to go up as injured corals continue to die. Then there’s Jarvis Island, a small US island in the middle of the Pacific, where 90 percent of the corals had died as of May.”

Mark points out that the impact of bleaching extends beyond the reefs themselves, leading to serious human and economic consequences. “You have to remember that a lot of people are dependent on coral reefs for a variety of services that they provide. We’ve got at least a half billion people around the world who are completely dependent on the reefs as their main source of food. The fish in their diet comes from these reefs. When you wipe out these corals, you’re losing all of that.”

Reefs also play an important role in protecting the shoreline from erosion. In many places, the reef’s protection is what allows people to live near the shore. “The reefs are protecting the shoreline from the incoming wave energy,” Mark says, “whether it’s a routine wave or a large storm or a tsunami.”

What’s causing all this? Mark says there are a number of factors, but the most important are rising ocean temperatures and ocean acidification—both related to the buildup of carbon dioxide in the atmosphere. “These corals are seeing sustained high temperatures that they cannot tolerate, and that’s what’s breaking down the coral-algal symbiosis. Additionally, ocean acidification makes it harder for corals and other organisms to build their skeletons and makes it easier for natural forces of erosion to break down those skeletons. It also makes them more susceptible to higher temperatures. It’s essential that we act to protect coral reefs from local stressors, but we also have to deal with the issue of excess CO2 in the atmosphere. If we don’t, then we’re just rearranging the deck chairs on the Titanic.”

Mark has seen some of the devastating effects of coral bleaching firsthand. “It’s not a requirement of my job to get out and dive,” he says, “but I enjoy the opportunity to do so whenever I can. It’s also important to get out and help with documenting the changes that are going on.”

Mark’s love of diving goes back a very long time. In fact, if you look up his senior page in the 1976 Fleur-de-Lis yearbook, you’ll find a picture of him in a scuba mask and snorkel as well a quote from Jacques Cousteau. “I’ve been lucky to have had a chance to go diving in reefs in much of the world,” he says. “I’ve seen some amazing places and I’ve also seen some devastating destruction. Over my 40 years of diving on coral reefs, I’ve sees places that are now nothing like they used to be. It’s heartbreaking to see the damage that’s been caused from a variety of reasons. There are some places I’m just not interested in going back to. I’ve heard enough about how bad it is—I don’t want to see it. I want to keep those memories alive.”

photo courtesy XL Catlin Seaview Survey