Rivers under the sea: Mapping finds ancient bottom habitat
The Lowcountry offshore is mostly barren sand bottom to the edge of the Continental Shelf - that's conventional wisdom.
Lives on the Sea
This is part of an occasional series looking at how the coast and the ocean are changing and what it means for a region where people have made a life and a living for generations in tune with the sea.
But three times now, College of Charleston geologists have dropped high-tech imaging devices to map that bottom, and three times they found "these amazing features" they didn't expect - ancient river channels.
"These are the ancient sea level shorelines," said Prof. Leslie Sautter. "It looked just like the Lowcountry (does) today."
The seafloor offshore, in other words, appears to be webbed with the three-foot-high, hardbottom ridge contours of large river deltas. Hardbottom attracts fish - sought-after snapper-grouper species that are considered overfished and catch-restricted by regulators, species generally believed to be found only in a few select spots along reefs and wrecks.
If there's more hardbottom and more fish out there, those "barren" sandy flats could be a far more prized resource than ever thought. With the federal government looking to lease offshore bottom for commercial exploration, the stakes for people who live in the Lowcountry could get very high very quickly, and the task of conserving the waters and wildlife much harder.
All this from College of Charleston research into the history and dynamics of a sea rise that unexpectedly became groundbreaking.
Sautter and Prof. Scott Harris are using side-scan and multi-beam sonar, looking closer with a remotely operated submersible and pulling grab samples. They nicknamed the first channel they found "Transect River" after the back-and-forth search pattern used to map it. Their biggest discovery so far is a vast river-delta swath of sand guesstimated to be some 1 billion cubic yards sitting about 60 miles offshore.
Detailed studies of the offshore bottom are rare. The last time anything of any detail was plotted off the Lowcountry was the 1960s, with equipment now obsolete. So, with only three swaths of ocean floor plotted so far, the geologists have everyone from the National Oceanic and Atmospheric Administration to private companies wanting to look at their results.
As teachers, they're getting an even better result - every graduate of the mapping studies, every single one, has a well-paid job waiting if she or he wants it, Sautter said. The skill is highly sought after: Research vessels and equipment to do the work largely have been loaned or donated by NOAA and equipment industries looking for those trained workers. The equipment can cost a half-million at a shot. A research vessel can cost several thousand dollars per day.
But the knowledge to be gained crosses marine geology and marine biology boundaries.
Rachel Bassett was a marine biology major at the college when the geologists first discovered river channels a few years back. It was a wow moment.
"Like discovering buried treasure," she said. "I mean, this was huge." Bassett, 44, of Summerville, is a former public relations professional, "panty hose, suit, fluorescent lighting, making my way up the corporate ladder," she said, smiling and nodding her head. One day she looked around and thought, "God, this is awful." So she shucked the suit for graduate studies at the college, and "conservation biology" lit a passion in her.
"We're really starting to devastate our oceans, and if there's any way I can make a difference, that's what I wanted to do," she said.
In May, she starts an internship at the S.C. Department of Natural Resources, using the mapping she's taken part in at the college to catalogue fish habitats for DNR to research and monitor.
"Ultimately, we want to fish our ocean sustainably and not have anything go extinct," she said.
The research is a lot less romantic than it sounds. Mapping involves the boat winding back and forth across a few hundred yards for miles at a time, in whatever seas are waiting. On the most recent trip, those seas were 6-8 feet with occasional 10-foot swells.
One good drop left senior Sonja Tyson suspended in mid-air for a moment above her bunk. That was in the midst of 28 seasick hours when she and a lot of the other two dozen students aboard went down for the count.
"Heaving, pitching, yawing, rocking," Harris said.
Back ashore, students and teachers must merge multiple sonar signals and clear out background noise to produce coherent images of a bottom that can end up looking like a moonscape. The software is complex and not user-friendly, Harris pointed out. The work is demanding - and addictive.
Junior Matt Platt, 20, was a chemistry major when he gravitated to marine geology studies. The recent trip was his first exposure to seafloor mapping.
The seas didn't bother him - "a three-day roller coaster," he kidded. The job fascinated him.
"I like it better out here than on land - and discovering things that have never been seen before," he said. "This is what I want to do."
Reach Bo Petersen at 937-5744, @bopete on twitter or Bo Petersen Reporting on Facebook.