Lacy, blossomed, branching, glowing in neon pink, green, yellow, purple, or orange—coral is a bouquet strewn on the sea floor. Who dives for fish when you can dive to be hypnotized by such beauty? Had I the courage to carry my breath in a tank, I would hang underwater for hours, trying to fathom coral’s mystery.
To be plant, to be animal—we learn those essences. But to be an animal that looks like a plant? To be a living, breathing fossil made up of thousands of tiny animals called polyps? Coral lives in the soundless underwater, surrounded by darting, gliding creatures and able to do nothing but wave from a rock. Coral hunts subtly, eating the plankton that brushes against the pressure-sensitive stinging cells in its tentacles. Built simply, it has a central mouth that takes in food and later excretes its remains.
Confused, one of Aristotle’s pupils first classed coral as a mineral, then as a deep sea plant. Pliny the Elder said the various types of coral were “neither animals nor plants, but are possessed of a third nature.” The Babylonian Talmud called coral an underwater tree. And what confounded all of them was the coral’s responsivity to touch. Finally, in the eighteenth century, William Herschel put coral under his microscope and pointed out the thin cell membranes characteristic of an animal.
By then, superstition had accrued. Ovid thought coral could turn someone to stone because it had emerged from the touch of Medusa. Stare at the Old Masters, and you will see red coral necklacing the baby Jesus. The Chinese find red coral auspicious and associate it with a long life (a bitter irony, given what is now happening to coral itself). Once used as a building stone, coral limestone anchors St. George’s tower at Oxford Castle. African women, both free and enslaved, wore red coral jewelry to honor their shared past. To this day, people in southern Italy give one another horn-shaped charms made of red coral for good luck.
If you do not know this history, coral seems insignificant, mainly because it is so beautiful, like a runway model we assume to be vacuous. Yet coral reefs shelter more than a fourth of the world’s marine species, feeding millions of people. The reefs absorb 97 percent of a wave’s energy, protecting shorelines from storm surges. Chemical compounds from corals could help treat cancer, neurological diseases, arthritis and other forms of inflammation, pain, bone loss, and high blood pressure.
Provided the coral is healthy.
If one of us goes days without food, the blood drains from our face, and we collapse. Without a meal, soon, we will die. Coral’s widespread bleaching signals the same fate.
Those neon colors came not from the coral itself but from its guests, zooxanthellae, an algae whose photosynthesis stains its host. The transaction is straightforward: the zooxanthellae give the coral food, oxygen, and vivid color as their rent payment, trading sustenance for a place to live. But if stressed by heat or toxins, the zooxanthellae will vacate the premises. Once they are gone, the color drains from the coral. It looks like a ghost of itself, pale and still beautiful, its skeleton shining white beneath a translucent covering. But it is dying, because its source of food and oxygen has left.
Every time we break temperature records—which lately is every year—heat stress decimates more coral, breaking down the reefs. They are made of hard coral, which secretes calcium carbonate and builds its own scaffolding. They are extraordinarily durable—as long as the coral lives. But scientists confirm bleaching and death in reefs in the Caribbean, Central America, South America, Mexico, Africa, China, Japan, Southeast Asia, and Florida.
“I was not prepared for what I saw,” Dr. Ian Enochs, head of NOAA’s coral program, told a reporter after a recent visit to reefs in the Florida Keys. “Every single coral I saw was affected—either bleached or severely paled. It is pretty hard to wrap your brain around.”
Greenhouse gases are causing the heat stress, but there are other complications, like the macro algae (more sinister than the zooxanthellae) that bloom from the toxins polluting the ocean water. In desperation, scientists are releasing Caribbean king crabs in the Keys to eat this algae, which is discouraging coral every way it can: by taking up sea-floor space, choking out sunlight, and producing inhospitable chemicals. Lab-raised, voracious as teenage boys but clueless about the real world, the crabs are trained with hand puppets, conditioned to fear predators before they are released.
At the St. Louis Aquarium, I linger outside every tank that includes coral, stunned by the variety. “You can tell the soft-body coral by the way it moves and attaches to the rock,” says a voice over my shoulder. We start to talk, and Louis Rosche confides that he has just interviewed to be the aquarium’s director of education. Now he is staring into the tanks, letting the interview stress subside.
“What got you interested in all this?” I ask. His answer is immediate and lovely: “Nature was my first friend.”
We talk about the fifty-pound chunk of colony coral one of my friends keeps in her living room, a memento from the early Paleozoic era, when what is now Missouri was covered by a shallow sea. We talk about the present day, too: how the unprecedented heat is starting three months earlier than usual, lasting longer, and weakening whatever coral it does not kill altogether. The reefs no longer have enough time to recover before the next heat wave.
The oceans absorb 93 percent of the heat that we create by burning fossil fuels. But now those oceans are warming up 40 percent faster, on average, than scientists predicted they would. If that warming abates, the coral is ready to work its own magic. In milder temperatures, some bleached coral will begin to manufacture its own pigment, achieving the same vivid colors and blocking certain wavelengths of light, making it safe for the light-sensitive zooxanthellae to return.
They need the symbiosis. We do, too, but have not yet mastered that realization.
Read more by Jeannette Cooperman here.