Life on the Rocks

North Carolina's rocky offshore reefs provide nurseries for juvenile fish, foraging grounds, hiding places, and spawning grounds. Research into offshore wind energy has prompted a new look at the health and diversity of life on the rocky reefs off the NC coast, where wind turbines could be located.

BEAUFORT — The quest for renewable energy sources has focused attention on North Carolina’s coastline, which boasts some of the strongest and steadiest winds in the nation.

But before any giant offshore wind turbines are built to harness the ocean winds, power companies must know where on the ocean floor to anchor the structures. And that question of just where to build offshore wind turbines is forcing researchers to take a new look at the ocean floor, which is a place nobody has thought much about.

But that’s changing, thanks in part to the work of Avery Paxton, a graduate student in Biology at the University of North Carolina Institute of Marine Sciences.

“Every time I dive on the reefs I have to stop and take a second and adjust to how beautiful it is out there,” says Paxton, as she shows me some of the video she has captured while diving on the reefs off the North Carolina coast. “Most people think of reefs in Florida or the Caribbean, but those reefs are made of coral. These are made of rock, but they are still reefs, covered with living creatures and these reefs are just off the coast of North Carolina and it is right in our backyard.”

Paxton is part of a new research effort to study the rocky reefs that range from three to 40 miles off North Carolina’s coast. Researchers are already amazed at the undersea world they have found. The rocky reefs are not continuous; some are small outcroppings, others cover large areas. Some are flat, some tower 30 or more feet above the ocean floor. The reefs are found in water that is 40-100 feet deep. Each reef is different, but they are all amazingly diverse islands of life.

Paxton says she and other researchers have already discovered that the reefs serve as a nursery for a variety of fish species. Juvenile fish live on the reefs closer to shore and as the fish mature they move offshore into deeper waters.

“And as part of their nursery function, the reefs also serve as foraging grounds and as hiding grounds,” Paxton explains, showing more videos that show fish hiding under rock outcroppings and amongst coral and sponges.  While the reefs themselves are dark gray, the living creatures on and around the reefs are brightly colored. The reefs are dark islands in a sea of sand.

“All of these hiding places provide areas places where the fish spawn and reproduce, and they provide stepping stones or safe corridors, as the fish move farther offshore,” Paxton adds.

Scientists are still working to understand what specific fish species and other creatures lives on and around each reef as well as what attracts them to that area. But it’s believed that one of the reasons North Carolina’s rocky reefs are so productive is because of their unique location. It’s a place where warm water currents from the south, which tropical fish prefer, mixes with cold water currents from the north, which cold water fish favor. Scientists have already spotted giant sponges and soft coral along with many species of tropical fish to support that theory.

The world of the rocky reef is constantly changing, not only because fish species are on the move but also because the reefs are covered and uncovered by shifting sands moved by storms.

Scientists want to better understand the time scale for these changes, and what happens to the fish that the state’s recreational and commercial fisheries depend upon. That’s because the reefs are the nurseries for both industries. Younger fish appear to live on reefs close to shore and then move to deeper water reefs as they mature. Researchers believe the best way to understand the question of what happens to the fish is to simply count them.

“When we dive onto the reefs we have go-pro cameras with us so as we look around we are recording the fish that we see,” explains Paxton, who shows a video with what appears to be a large tape measure strung across a portion of a reef. “That is the transect tape that we use to do our fish counts. We actually go back to look at the video, and refer to the transect tape as a way to record what area of the reef we are in. Then we start to physically count the fish and the other creatures in an area that we spot on the video. It’s not a perfect system, but it gives us a reference point for what is living in an area of reef.”

Besides learning how to better protect the reef systems, scientists want to identify the most important reefs so offshore wind turbines won’t be placed in those locations. It turns out the quest for energy to power life on land has revealed new worlds of life offshore.

“It’s a complex, fascinating community of interactions and complex interactions, that is wonderful in a conceptual sense to understand but important to understand for so many reasons,” says Dr. Pete Peterson, Professor of Marine Sciences, Biology and Ecology at the University of North Carolina Institute of Marine Sciences. “Knowing more about the reef systems will help us conserve our fish stocks and the ecosystems they provide, preserve the wonderment for divers and the opportunity for the dive shop owners, and preserve opportunity for fisherman and the resource for commercial and recreational fishermen."

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