CURRITUCK COUNTY — Bam. Bam. Bam.
The sounds of the sledgehammer echoes across the marshes of Currituck Sound, seemingly carried with the winds that move the tall grasses back and forth.
If you want to understand the dynamics and complexity of a marsh, you’ve got to dig into it. That’s why these researchers from Chowan University are taking core samples beneath the tall grasses of Currituck Sound.
Bo Dame, an associate biology professor at Chowan University measures how deep the plastic pipe used to collect the sample has been driven into the muck.
“So we’re about 60 centimeters inside, and about 59 centimeters outside, so we’re looking good,” Dame reports. “Not much compaction.”
The research team is wading through the chilly waters of Currituck Sound because the area is so unique.
Currituck Sound is about three miles wide and roughly 42 miles long. It stretches from around Kitty Hawk at the south end to Back Bay and the Virginia border at the north end. It’s a large body of water but it’s not very deep. The depth ranges from one to three feet.
But what makes this jewel of the Outer Banks so unique is that its only connection to the ocean is far south at Oregon Inlet. With so little contact with the ocean, Currituck Sound is essentially filled with fresh water.
“Currituck is different because most of the sounds in North Carolina are brackish, which means they have a high level of salt,” explains Robbie Fearn, Director of Audubon’s Pine Island Sanctuary. “Currituck Sound has a low level of salt and is in essence a nearly fresh water estuary, so that makes the dynamics really different here.”
Currituck also has very few rivers flowing into it so the levels of sediment in the sound are low.
In addition, Currituck Sound is not a tidal estuary—a far cry from the situation found at the beach just a few hundred yards away.
There, beachgoers are accustomed to the lunar tides; high tides come in, low tides come out, regular as clockwork. Not so in the sound.
“Here we are dominated by wind tides,” explains Fearn. “If the wind is coming from northeast, all the water is pushed to the lower sound. But if the wind comes from southwest, it pushes tee water from the lower part of the sound into the upper part. And since that water has a bit more salt in it from the lower sound, that changes the dynamics on a regular basis.”
Big storms from the southwest, coupled with sea level rise, are inundating and eroding all of the marshes around the sound. Fearn says Audubon surveys show Currituck Sound loses 72 acres of marsh every year to erosion. And those marshes provide critical habitat for waterfowl, breeding grounds for fish and protection from storms.
Fearn points to the dock just outside the almost century-old lodge Audubon uses as its office on Pine Island to illustrate his point.
The dock was built around 1913 as part of a hunt club. There’s a section that is routinely covered by roughly an inch of water. That’s the original dock. There’s a section about one foot higher that was recently added. Fearn says it’s an indication of how sea level rise is affecting the sound.
Which brings us back to the core samples researchers are taking from the marshes on Currituck Sound.
Ironically, as large and as unique as Currituck Sound is, not much is known about it.
So, North Carolina Sea Grant is helping to fund a study of Currituck Sound, which will create a detailed habitat map of the area as well as look at how the marsh is coping with rising sea levels.
Professor Dame points out some features of the core sample before it is sliced up and placed into plastic bags for later analysis at a lab.
“You can see a lot of the fibrous root matter from all of the grasses and this dark material is sediment, which is really clay and silt,” explains Dame. “And the way a marsh maintains its level with sea level rise, is the accumulation of organic matter, both organic matter from above the surface and root matter from below, and the buildup of sediment brought on from storm events and flooding.”
Researchers hope the multiple core samples, taken over time, will help to quantify whether or not the marsh is growing or eroding.
The plants in and around the sound and the marshes have adapted to the wet environment. It’s not known whether they can survive the rising seas.
“There is a special tissue for these plants and it is just filled with holes, which allows diffusion from the surface into the root systems,” explains Heather McGuire, Ph.D, a biology professor and chair of the biology department at Chowan University. She points out the hollow roots of the plants found in the core sample.
“That’s because oxygen will diffuse much faster in air than in water, so wetland plants typically have very spongy, hollow stems,” adds McGuire.
The study is also surveying which plants make up the marsh. Senior biology and environmental science student Jomecka Deloatch is cutting down a section of grass that is marked off by a grid.
“Right now I’m taking a vegetation plot,” Deloatch explains, “So I’ll be cutting the grass stalks and collecting them along with all of the plant litter that is only in this plot.”
Researchers also want to know if rising seas will speed up erosion in the marsh and whether the marshes in Currituck Sound will be able to grow fast enough to keep up with rising seas.
“With climate change, there are predictions that sea level rise will go up from half a foot to a foot over the next 30 years,” says Dame.
“Our goal is to not only better understand the marsh but also begin to understand how we can help the marshes help themselves,” says Fearn, as he looks out at the part of the dock which is once again covered with water.
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