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Amy Wagner’s team drills a coral sample from the Flower Garden Banks in 2005. Courtesy of Amy Wagner and John Halas
After hours of drilling, they patched up the hole and swam the 6-foot-long core to the surface. Back at the lab, they split open the core samples and x-rayed them. “They’re like trees,” Wagner said. “You can count the tree rings and go back in time. Corals produce these annual bands.”
Every year, the living coral organism lays down a new growth band, using the nutrients and minerals it pulls out of the seawater. Essentially, whatever’s in the seawater makes it into that year’s layer of coral skeleton. “So we have this long record of these little, tiny time capsules that are sort of locking in the ocean chemistry,” Wagner said.
Using a high-tech version of a dentist’s drill, Wagner and her colleague Kristine DeLong, a professor at Louisiana State University, collected a tiny bit of dust from each growth band. Then, like detectives, they analyzed different elements in the dust for clues, looking at the variations in the coral core over time.
Just like humans, corals build their skeletons out of calcium. But sometimes they make mistakes, accidentally grabbing look-alike elements from the seawater. One of those elements is barium, which is often used as a lubricant in offshore oil wells. During the 1970s energy crisis, oil drilling boomed in the Gulf of Mexico. And Wagner and DeLong could see that spike reflected in the barium levels in the coral: When oil prices crashed, production went down, and so did the barium.
There are many other histories scientists can see etched in this coral core. By looking at nitrogen, they can see the rise of fertilizer pollution from the Mississippi River. By looking at radioactive carbon, they can see the rise of nuclear weapons tests during the Cold War.
And the corals even tell the story of how fossil fuels are changing the climate — in the words of one scientist, “recording their own demise.” To see how, it’s important to know that carbon atoms aren’t all exactly the same. They actually come in a few different weights, depending on the number of neutrons in each carbon atom. A carbon atom with seven neutrons is called “heavy carbon,” while an atom with six neutrons is called “light carbon.” Plants prefer to use the light carbon for photosynthesis. So, inside of a plant, the carbon atoms tend to be a little bit lighter than those, say, inside of a volcano.
Fossil fuels come from ancient plants, which are full of light carbon. As fossil fuel emissions rise, the carbon atoms in our atmosphere are slowly getting lighter.
You can see this same trend playing out inside of the corals: The carbon in the coral slowly gets lighter in the band samples as the world burns more fossil fuels. As those fossil fuel emissions warm the climate, they put reefs around the world in danger.
Today, the Flower Garden Banks are still holding on, but they won’t be safe forever. As early as 2040, the Flower Garden Banks could start to see major bleaching events every summer. If we can reduce our emissions at a more reasonable pace, climate models say we might be able to buy an extra 15 to 20 years for the Flower Garden Banks — essentially doubling its window of time. That window would be critical for the sanctuary staff and independent scientists who are working hard to study and protect what might become one of the last coral reefs.
“Going to a place like Flower Gardens, it’s like — these corals, they’re still pretty darn healthy,” said DeLong. “Being able to manage those reefs and take care of them is important, because they may be the last ones we have.”
Recently, scientists at the Flower Garden Banks have started collecting corals from the reef and storing them in an onshore coral lab. The hope is to eventually bank enough coral here in case the worst happens.
“It is a grim prospect,” Johnston said. “It’s better to be proactive and have some things banked versus getting into the situation where all the corals have bleached and died and we have nothing left. It’s my hope that nature can figure things out and things can adapt. I think the problem is that the climate is changing quickly enough that there might not be time.”
The Flower Garden Banks are a product of 10,000 years of slow, steady growth, capturing annual snapshots of our world, in small millimeter-sized chapters. The next few decades will be critical in determining just how much longer this reef will be able to continue its ancient undersea story.
This article originally appeared in Grist at https://grist.org/video/coral-oil-flower-garden-banks-reef-climate-science/.
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