Organic Time Capsules

By Deborah Malarek for JISAO Magazine

Corals Communicate Changes In Climate And Ocean Chemistry

Sara Sanchez

Maybe it was her childhood in the Midwest that drew JISAO postdoc Sara Sanchez to study the sea. Two trips to the ocean as a kid left her in awe of the vastness of it.

Or maybe it was the summer between her sophomore and junior years at the University of Arizona when she worked as an intern at the National Science Foundation. Sanchez was fascinated by all the projects. “People were saying, ‘Why aren’t you doing research?’ I didn’t know I could!” she says, shrugging.

Whatever it was, after graduating with her PhD in oceanography from Scripps Institution of Oceanography, Sanchez arrived at JISAO prepared to continue her studies of coral paleoclimatology – evaluating how corals have responded to a changing climate from the 1800s to present. “I’m studying already collected data, some of it by me,” she says of doing her studies in an area not known for coral.

In fact, some of the data came from her prior research trip to the Palmyra Atoll – a mostly uninhabited island located about 1,000 miles from Hawaii. Now owned by the Nature Conservancy, it is managed by the Conservancy and the U.S. Fish and Wildlife Service as a site for scientific research and conservation. Its remoteness is its saving grace – allowing for the survival of one of the largest shelf-reefs in the world with more than 150 species of coral.

Sanchez points to a picture she took of a coral there. “That one’s a baby,” she says, adding that the corals add layers over hundreds of years, and drilling through the top straight down to remove a sample allows scientists to measure salinity, temperature, and other markers indicating the conditions years before scientists collected such data. The corals serve as organic time capsules that allow scientists to see what was in the ocean water at the time the layers were growing. “They grow bands like tree rings,” she says.

Asked if the drilling hurts them, Sanchez says, “The only live part is the surface.” She says data can be collected by fossilized coral that washes up on the beach as well, “but it’s trickier. It’s easier to measure them when they’re alive.

These days, Sanchez and others are using the data to give researchers a picture of what was, a clearer understanding of what’s happening now, and an ability to predict what might happen in the future. “We’re creating 3D gridded fields of what’s happened in the past from 1800 through to the present,” she says.  She knows too much to deliver a falsely rosy picture of what’s going on in the world of corals, and speaks of the much-publicized worldwide bleaching event. “It’s super sad,” she says. “There are basically three issues causing it:  the increasing temperatures, the increasing Co2, and pollution and runoff.”

In New Zealand for a conference this past summer, Sanchez used the opportunity to visit the Great Barrier Reef. She says while some species of coral had been ravaged, surprisingly, others were surviving. “Some species are more tolerant than others,” she says. “The Great Barrier Reef is definitely changing.”

These days she’s not using a coral drill for her work, but Sanchez says using them at Palmyra Atoll frequently drew some curious visitors. The drill’s vibrations attract reef sharks who “sneak up behind you. They don’t have much exposure to humans,” she says, “and once we annoyed about 10 sharks. I looked behind us, and they were everywhere!”