OREGON INLET, N.C.
Seagrass is more plentiful within the North Carolina Outer Banks than along any other eastern state's coast except Florida, but it is losing ground.
State biologists are surveying seagrasses that prefer the saltier waters of the Pamlico Sound and waterways southward for the third time in a dozen years. A report is expected to come out early next year.
Spotters are seeing areas where seagrass is not present in places where it should be, said Jud Kenworthy, a retired NOAA marine scientist who is a volunteer team leader on the seagrass survey for the Albemarle Pamlico National Estuary Partnership.
Surveys in 2007 and in 2012 indicate the estuaries support about 150,000 acres of seagrass, but have declined at a rate of about a half percent to 1.5 percent per year, Kenworthy said.
"There is not a crisis, but the tide is flowing against us a little bit," he said.
Seagrasses have declined worldwide at a rate of 5 percent per year since 1980, he said. In contrast, Cheseapeake Bay teams counted last year a record 109,000 acres of seagrass following more than 30 years of conservation work.
The North Carolina estuary partnership is one of 28 programs established in the 1980s to research the health of water bodies including the Chesapeake Bay and the Pamlico Sound. Seagrasses are a key part of the research.
The prognosis could be worse for grasses that prefer fresher waters.
Low-salinity grasses such as wild celery and pondweed have declined much more drastically — as much as 50 percent in last three decades — in freshwater bodies such as the Albemarle and Currituck sounds, he said. Old surveys are incomplete, but anecdotal accounts indicate heavy losses brought on by runoff, he said.
New surveys in those waters will be done on a boat using sonar equipment, he said. The water is too dark for accurate aerial photos.
"It's difficult to monitor the whole thing," he said. "We try to strategically pick locations and monitor them."
Healthy grass beds should grow over large areas, said Anne Deaton, habitat assessment manager for the North Carolina Division of Marine Fisheries.
"I have heard that the beds seem to be getting less continuous and more patchy in some areas," Deaton said.
Seagrasses are known as the "lungs of the sea" for their oxygen producing powers and are a sentinel for water quality. They provide shelter and food for marine life, said Greg Allen, a conservation biologist for the marine fisheries division.
Allen and state environmental technician James Pace are among the teams who survey more than 600 selected sites. Recently, Allen motored from Oregon Inlet Fishing Center into the shallow waters nearby to take stock there. Pace used a long rake to pull a clump into the boat. Both men separated the tangled vegetation into individual strands for identification. Three high-salinity species grow here — eel grass, shoal grass and widgeon grass.
Eel grass has wider leaves. Crabbers use it to line boxes of fresh crabs as an insulator, Allen said. Widgeon grass has threadlike leaves. Shoal grass is relatively easy to identify.
"See those white roots? That is a telltale sign it's shoal grass," Allen said.
North Carolina is unique in that its waters sustain warm-water subaquatic vegetation like shoal grass and cool-water species like eel grass. Only Florida has more seagrass on the East Coast, Kenworthy said.
The surveys are time consuming. Biologists photographed the waterways from aircraft in the spring on clear days and at low tides for a better view into the water.
Led by the marine fisheries division, dozens of people spent hours on the water to verify the aerial photography, Deaton said. Surveyors on the water record temperature, salinity and bottom composition. They measure water clarity by lowering a white disk below the surface until it disappears, then noting the depth. They set a device about two feet square made from plastic pipe onto grass mats below to record density.
The surveys are setting a baseline, Kenworthy said. The work is well behind the success in the Chesapeake Bay, but the hope is to at least maintain what is there, he said.
"The loss of grass habitat is going to affect a lot of fisheries," he said.