When color bleeds to white - Bleaching coral reefs

I'm moving, tousled, weightless, my hair streaming in front of my eyes as I try desperately to stabilize myself by lightly swishing my hands, keeping my legs completely still. Hand flapping is a movement that comes naturally to me; I've seen the home videos from childhood of an excited bald child waving her hands around in a flurry of activity. This time, however, I'm not simply excited. I'm also kind of wary, because I'm staring at a fiery red branch of coral, and the ocean waves are pushing me ever closer and closer to this bizarre animal that, if I touch it, will burn like fire for the rest of the day. I would kick my legs, but I would crush the unassuming coral beneath me. I'll find out later while I was dodging the infamous fire coral that one of my friends, enamored with a feather duster worm, ended up waving her hand inches from the nose of a nurse shark she didn't even see hiding beneath the reef. Nurse sharks aren't aggressive, but it just goes to show there is always more going on in a reef than you know.
When I think back on my days swimming in Belize, I am constantly pulled between wonder and anxiety. It's anxiety for how close I came to slamming into the delicate animals I was trying to observe, anxiety over the number of dead corals I saw, pale white brain corals wedged between red fire corals or more demure greens, and especially anxiety over the future. While through my eyes seeing the reef for the first time was magical, all I had to do was glance at my professor's faces when they didn't know I was looking, their eyes turned down, and hear them whisper, "It's changed." The reef was not doing as well as in past years. It was evident to anyone who had already been there or had eyes keen enough to see the coral skeletons left over, covered in algae, that the reef was not thriving as it once had. I resolved then that I would one day seek out what had evaded me: a magnificent specimen of coral reefs. I would see the Great Barrier Reef. Little did I know that within a year, the Great Barrier Reef would experience one of its most severe bleaching events in history, followed by another that is underway as I write this. While the Great Barrier Reef is by far the most famous reef, its death throws heard around the world and described in a number of influential news sources, the Great Barrier Reef does not perish alone.

One of my favorite fish at the New England Aquarium. The mandarinfish lives in the living coral exhibit where it can frequently takes cover in the crevices as curious visitors search for this painted beauty.

There are a number of problems facing coral reefs today, including vibrio (a bacteria that causes disease), sedimentation, crown-of-thorns starfish, and even an overgrowth of algae, but what we see at work in the Great Barrier reef and in other areas is perhaps one of the most dramatic threats. In order to understand coral bleaching, you must first understand the structure of coral. There is an old-timey question old jokester uncle figures say, which goes, when presented with something new, "Is it an animal, vegetable, or mineral?" In the unique case of hard corals, the answer is all three. Coral is a small animal, shaped rather like a sea anemone. It's outside is fleshy and soft, vulnerable, but for the fact that it has the incredible ability of building a limestone protective skeleton around its delicate frame. When you look at a branch of coral, you are actually looking at something rather like an apartment building that many corals have built, each small porous hole in the limestone structure a separate apartment for each tiny organism. Once established, however, these organisms cannot stray far. They can open up and reach tiny finger-like structures outside of their limestone castles, searching for food particles that float close enough to fall into their grasp. This, however, does not satiate hungry corals. In addition, corals line their fleshy translucent tissues with cells of algae. As the algae are exposed to sunlight, they photosynthesize and make food for the hungry corals, providing most of the energy that the corals need. Without these algal helpers, corals eventually die. I first learned the name of these vital little algae in the aquarium, gaining countless hours of amusement watching children stumble over the name as I talked to them about coral in the kids corner. They are called zooxanthellae (zoo-zan-thel-ee).

The healthy colors of a coral reef, with butterflyfish

It is the seemingly irrational, self-mutilating action of expunging zooxanthellae that characterizes coral bleaching. Scientists, after countless hours of studying bleaching corals, know what causes bleaching, but have yet to explain what practical purpose the corals' banishing of the algae may serve. What is evident is that corals bleach when they get stressed. Corals, despite being covered in stone, are very delicate. They require just the right amount of sunlight, very particular temperatures, and clean water. When it gets too warm or too cold, or the sunlight is too direct, or there is pollution, the corals get stressed, becoming a fluorescent color, a warning of what is to come. Soon after, the coral spits the algae out of its body. Since the algae is what gives coral its color, the coral is left a ghostly, skeletal white, as if it has been doused in bleach. After expelling the algae, coral have a short time to take up new algae, but if the coral remains stressed, it will simply die, the only thing left the white limestone structure it built for protection. Reefs are sometimes capable of surviving bleaching events; A coral reef may be able to bounce back from a bleaching event after about a decade given the right conditions. If bleaching occurs too frequently, however, corals cannot regenerate. This is why, with two years of bleaching in a row, scientists are in mourning and obituaries for the Great Barrier Reef have been circling the internet.

A bleached coral in front, with healthy non-bleached corals behind

When a coral dies, it does not die alone. A coral reef is a thriving community. While the coral provides the structure, a number of animals build their homes out of what the coral has provided. Sea urchins graze on the algae that grows in the limestone, small fish hide in the crevices of coral to escape predators, some sharks swim around the outside of the reefs, other sharks hide beneath coral crevices, giant hermit crab scavenge along the sea floor, and sea anemones attach themselves to old coral skeletons while anemonefish start families in their tentacles. When a reef dies, it is the underwater equivalent of the death of a city. In short, it is a natural tragedy.
As the climate warms and weather patterns become more extreme, we have seen more coral bleaching, and pristine reefs are few and far between. While it is tempting to lament the destruction of one of the greatest natural wonders of the world, I'm not ready to give up on a future where immersing yourself in an ocean brings you to underwater communities you could hardly imagine. There are a number of things that we can do in this moment:

• Climate change and warming are linked to carbon emissions. Do what you can to limit yours. If it's safe, ride your bike. Take public transportation. Carpool. Buy a fuel efficient car. Eat a few meatless meals. Limiting how much meat you eat has a significant impact on your carbon emissions.
• Be careful what you put on your lawn. While you may live miles and miles from the coast, water running off from your lawn will mix with other water, underground or in rivers, and this water has a tendency to find its way to the ocean. Chemical fertilizers and pesticides are notorious for throwing the ocean out of balance, sometimes by causing large blooms of algae, other times by simply increasing pollution.
• Spread the word about what is happening to the coral reefs. If you are lucky enough to get the opportunity, volunteer at a local aquarium or environmental organization. If you can, invest in organizations that are dedicated to protecting the reefs and investigating ways that we can help them survive.
• If you get to travel someplace where you can see coral, make sure you are following local guidelines to keep coral safe. Kicking coral, stirring up bottom sediment with your flippers, and even wearing certain kinds of sunscreen, when multiplied over many tourists, can stress coral. Make sure that the hotels and restaurants you go to are making sustainable choices by reducing their pollution impacts and offering sustainable seafood.
• Look at your elected officials' history of protecting environment and climate. Hold them accountable for the laws they support and the impact we are having on Earth. What we do in America doesn't just impact our country. The carbon emissions we have released have contributed to the warming that is killing the Great Barrier Reef. Understand that inaction in arresting climate change is the same as complicity in the destruction of one of the most beautiful and diverse ecosystems on the planet.

All hope is not lost. There are some resilient reefs that have shown less damage than other reefs. We know because of history that organisms are capable of adapting to a changing planet if given time. Meanwhile, all we can do as we attempt to reduce our carbon emissions is to limit the other stresses we put on reefs, like pollution and overfishing, in order to give them time to adjust. I, for one, hope that in the future, I will be able to once again submerge my face in sea water and see before me not the skeletons of once great underwater kingdoms, but a brilliant swirl of reds, yellows, and greens as nurse sharks lie like carpets under the tapestries of coral and curious fish swim to my goggles to stare at their own reflections, blissfully unaware of the fate they escaped.