Diving for data: What this oceanographer is learning from coral reefs
Drive a mere 777 miles north of Perth, take a dive beneath the waves, and you’ll find the Ningaloo Reef – the world’s largest fringing reef, stretching 162 miles along Western Australia’s coastline. While the reef is best known for its whale sharks and tropical fish, it’s the 250 species of corals that draw oceanographer Thomas DeCarlo to its waters.
Dives to remote reefs may not be a day-to-day experience, but they are one of the more exciting aspects of DeCarlo’s work as a postdoctoral research fellow at the ARC Centre of Excellence for Coral Reef Studies at The University of Western Australia.
“[As an oceanographer] you get to go to places where you aren’t even allowed to go as a tourist,” DeCarlo said. “So they are completely undisturbed, really beautiful reefs. [Visiting] is a once in a lifetime opportunity.”
And it’s hard work too: scuba diving for science isn’t the same as a leisurely swim.
“Usually we have two or three dives planned,” DeCarlo said, describing his outing to the Ningaloo Reef. “Sometimes it would just be as simple as taking photographs—several hundred photographs—so we can look at what corals are there. Other times we're using an underwater drill, and we're actually drilling into the reef to get coral samples. It's pretty intense diving, and then afterward you're always labeling your samples, trying to write notes [and] keep track of everything.”
A central New York native, DeCarlo didn’t envision a future underwater when he began college—he initially chose to attend the University of San Diego for its business program.
“It was all set to go,” DeCarlo recalled. “Before I actually showed up, I was like ‘I don't want to wear a suit and tie and be in a cubicle.’ I just looked through their list of majors and saw marine science. So I was like, ‘Well, I love the ocean. Let's give that a try.”
For DeCarlo, trading in cubicles for corals was an exercise in adventure that would take him across the globe. He recently received his doctorate from the Woods Hole Oceanographic Institution through MIT’s joint program in oceanography, applied ocean science and engineering. In his current role, working under the Australian Research Council, he’s part of an institution that boasts the world’s highest concentration of coral reef scientists. Now, the reefs accomplish both personal and academic goals.
“Corals are the world’s most diverse marine ecosystems and comprise an industry worth an estimated $172 billion. And yet we know hardly anything about them—except that they’re dying.”
“It's personal in that I like the coral reefs and diving, and more intellectual in that we actually really need to do this work, and it's really important,” DeCarlo said.
Corals are the world’s most diverse marine ecosystems and comprise an industry worth an estimated $172 billion. And yet, DeCarlo explained, we know hardly anything about them—except that they’re dying. Two years ago, DeCarlo visited a remote Pacific reef nearly 2,000 miles away from civilization, and discovered it had bleached completely.
On his upcoming dive, DeCarlo will revisit the Great Barrier Reef to collect core samples from living colonies. The precarious state of the reef’s health has raised questions about whether coral bleaching is beginning to occur even without a phenomenon like an El Niño. Last year’s El Niño caused a severe bleaching event; the bleaching occurred again this year, though sans a climate phenomenon, killing over 20 percent of the reef.
“If this starts happening even when there’s not an El Niño, they’re really in trouble,” DeCarlo said. “I want to quantify if other bleaching events have happened in the past. When [corals] bleach or when they're stressed from high temperature, they make distinct high-density bands. We CT scan or X-ray the corals, and we can see these bands clearly.”
“You never know when your science might be very relevant for a policy, or may be used in a lawsuit, or someone will take a very keen and direct interest…”
After the coral cores are collected, DeCarlo will resume a more typical routine: working with a laser-microscope system to study the structure of coral skeletons and quantify their components.
“Based on how the laser light is reflected, we can essentially tell the pH of the fluid that the coral made the skeleton from,” DeCarlo said. Proving that lasers could show these pH levels was the subject of DeCarlo’s last paper.
The data from DeCarlo’s laser study of coral skeletons is part of a worldwide pool of geochemistry data about coral reefs. Together, the data can reveal temperatures ranging from the past 200 years to the past millennium.
“[People] all around the world collect similar types of data, and we really need to be able to share this in a consistent way. There are databases where people upload their data, but I think it needs to go to the next step of making codes available so the whole process can be transparent…[to] make everything globally consistent.”
Some datasets, like the laser data for DeCarlo’s current coral skeletons, can be difficult for other scientists to interpret on their own. The norm has been to summarize the data and present only a few illustrative numbers. Unfortunately, this habit makes repeating experiments difficult.
“There's huge value [in] making everything transparent,” DeCarlo said. “You never know when your science might be very relevant for a policy, or may be used in a lawsuit, or someone will take a very keen and direct interest, and if things aren't traceable, it's very hard to understand what was shown.”
“It’s really only going to work if people want their science to be transparent,” DeCarlo added. “Hopefully there can be kind of a cultural change toward open science and seeing its value.”
As we continue to ask questions of what our impact has been on the planet, it’s likely we’ll get some of those answers from corals. The data’s there, waiting in the algorithms and the reefs: it’s a matter of bringing researchers across the world together.
DeCarlo’s hopes for coral science in particular aren’t too different: ideally, he’d see a worldwide concerted effort to understand bleaching events and what they spell for the future.