Old Dominion University scientists seeking corals for climate change study try, try again
By Chris Patrick, science writer
On a Monday in October, two sounds can be heard several hundred yards offshore of Virginia’s Kiptopeke State Park. The first is waves lapping against nine partially sunken World War II ships. The second is two scientists hunting for a coral that might be growing on the ships, who periodically surface to clear water from their snorkels with forceful exhales.
One of the scientists is Hannah Aichelman, a graduate student studying biology at Old Dominion University (ODU). The other is Dan Barshis, a biology professor at ODU researching how climate change affects corals. Barshis is Aichelman’s mentor for her master’s project as a Virginia Sea Grant graduate research fellow. Aichelman wants to see how a species of coral found off Virginia’s coast, Astrangia poculata or the Northern star coral, responds to rising temperatures. And to do that, she needs to harvest her test subject from its natural habitat—an undertaking that’s more challenging than one might think.
The pair’s original plan was to dive at a shipwreck in the Atlantic Ocean, where they’d found coral before. But the winds picked up unexpectedly that morning, summoning waves six- to eight-feet tall. To avoid a potentially dangerous situation, along with certain seasickness, the captain of ODU’s research vessel called off the dive.
So Aichelman and Barshis came up with a new scheme.
Plan B: Science by Kayak
Astrangia likes salty water, and lives on hard surfaces offshore from the Gulf of Mexico to Cape Cod. But since the waves were too high to dive in the ocean, Aichelman and Barshis, ever hopeful, turn to the next best thing: the mouth of the Chesapeake Bay.
Kiptopeke State Park sits at the southern tip of Virginia’s Eastern Shore. The two scientists think the water might be salty enough for Astrangia off the park’s shore, where Chesapeake Bay spills into the Atlantic Ocean. They hope to find it growing on nine partially sunken concrete ships paralleling the shore. When the ships were intentionally sunk in 1949, there was no Chesapeake Bay Bridge Tunnel to connect Virginia’s Eastern Shore with its western shore. Instead, those wanting to cross the mouth of the Bay took a ferry. The ships were sunk to form a breakwater that shielded the ferry’s pier from the onslaught of waves.
Aichelman and Barshis load a two-person kayak with gear—including their so-called “basket of science,” a grocery shopping basket they hope to fill with corals—and paddle out to the ships. The above-water portions of the ships are plastered in guano from the brown pelicans that guard them like sentinels. After tethering their kayak to one ship, Aichelman, donning a wetsuit, snorkel mask, and flippers, slips into the opaque bay water. When she resurfaces a few moments later, “creepy” is the first word out of her mouth.
“It’s like another world down there!” she exclaims. Soon, Barshis slides into the water too, and both search the ships’ underbellies for Astrangia.
To see what the scientists saw, watch the video Hannah Aichelman shot while snorkeling.
Astrangia doesn’t look like tropical coral. It’s drabber, less conspicuous. It sort of looks like little tufts of hair, about the size of a small cookie, in shades of brown, yellow, white, and sometimes pink. It’s understudied, despite its prevalence off the Atlantic coast of Virginia.
“We know very little about this species in general and, more specifically, about this Virginia population,” Aichelman explains. “Most of the research so far on this species has been conducted on populations farther north in its range, including Rhode Island and Cape Cod.”
Because it’s understudied, scientists aren’t sure what Astrangia’s ecological role is. It might create a habitat, and offer shelter for larval fishes and invertebrates. It also might help cement shipwrecks together, which provide additional shelter, and support dive tourism. Aichelman wants to know how it will react to the rising sea surface temperatures resulting from climate change.
To find out, she’ll heat up the corals she collects in what Barshis calls a “coral treadmill.” A coral treadmill is really a respiration chamber—a container that measures how corals’ energy usage changes as the temperature of their water changes. “We want to know how they will react when we increase the temperature,” Barshis explains. “We’re hoping this will give us insights into the mechanism of bleaching of tropical corals.”
Though it doesn’t resemble them, Astrangia is closely related to tropical coral species.
Corals grow in colonies, a collection of individual polyps supported by a calcium carbonate skeleton. They eat via two methods. In one method, the individual polyps have tentacles to grab zooplankton drifting nearby and shove it in their mouths. But most corals get 75 to 80 percent of their energy from symbiotic algae that live inside of their cells. The algae, which are photosynthetic, use energy from sunlight to make sugars for the coral.
When water temperature increases, some scientists believe it overwhelms the cellular machinery algae use to make those sugars, and produces harmful molecules that prompt coral cells to spit out the algae cell living inside them. The coral loses its main source of energy, and turns white because algae are what give coral its color. This is coral bleaching. It’s not always permanent. Some colonies recover; others die.
Astrangia, however, doesn’t seem to rely on algae like its tropical counterparts. “Not all Astrangia have algae, but they seem just as healthy without it,” Barshis says. Astrangia also seem to be tolerant to a wider range of environmental conditions.
“So figuring out why Astrangia is able to survive such extreme environmental conditions while tropical corals can only withstand a one to two degrees Celsius change in temperature [before bleaching] could be very informative in understanding corals in the context of climate change,” Aichelman says.
After a couple hours of snorkeling among the ships in search for Astrangia, the pair realize the coral doesn’t grow this far up the bay—it probably isn’t salty enough. They leave with an empty “basket of science.”
A-Tisket, A-Tasket, a Coral-Filled Basket
A little over two weeks later, they are on the hunt again.
Today, the weather cooperates. Aichelman and Barshis depart the Owl Creek Boat Ramp in Virginia Beach on an ODU research vessel piloted by Captain Curtis Barnes. As the Virginia Beach skyline fades into the blue horizon, there are again two sounds. The first is the boat’s grumbling motor. The second is the hull crashing through the swells, whose size and intensity seem to grow as the vessel moves further offshore.
The crew’s destination is a fully submerged shipwreck 13 miles offshore. Captain Barnes uses the boat’s sonar to locate the wreck, which is 70 feet below the surface. After Aichelman and Barshis struggle into their wetsuits and weighty diving gear, they take a trip down to the bottom. After searching for some time, they eventually collect around 30 colonies—all the corals Aichelman will need for the year—which they then transfer to an aerated cooler of water to take back to the lab at ODU. She will keep them alive and healthy until she begins running them on the “treadmills.”
Watch the video below to see Hannah and Dan diving for coral.
