Underwater seagrasses are found throughout the coastal U.S., where they support wildlife, improve water quality, and help buffer shorelines from waves and storms. On the Atlantic coast, no state has more seagrass meadows than North Carolina. The Pew Charitable Trusts is working with state agencies and other North Carolina partners to protect this resource. One partner is Dr. Jud Kenworthy, who retired from the National Oceanic and Atmospheric Administration after 33 years working as a biologist focused on seagrass and salt marsh habitats. He is an adjunct professor at the University of North Carolina Wilmington and advises the Albemarle-Pamlico National Estuary Partnership and the state on seagrass monitoring and assessment. In this Q&A, Kenworthy explains the value of protecting North Carolina’s seagrass. This interview has been edited for clarity and length.
Q: How did you become an expert in underwater plants?
A: I was lucky to grow up on a coastal lagoon in southern Rhode Island. In the early 1950s, the lagoon was dredged and became a permanent inlet to the ocean, and the whole ecology changed. It filled with eelgrass, and it was spectacular. In the summer I made money clamming on the edges of the eelgrass and harvesting crabs. I realized later that it was a living laboratory, and once I settled on marine science as a career, the world of seagrass pulled me back like a magnet. I earned my undergraduate degree from the University of Rhode Island and my master’s in marine science at the University of Virginia. I did my master’s research in North Carolina and then worked for 10 years before I decided to go back to school to get my Ph.D. from North Carolina State University. Becoming an expert takes a long time.
Q: What makes North Carolina’s seagrass so special?
A: North Carolina has the largest and healthiest seagrass ecosystem on the Atlantic seaboard. There are probably only two or three places in the world like this, where major ocean current systems overlap and collide. It’s a fascinating confluence of systems, with the Gulf Stream bringing in some of the characteristics of the tropics and the North Atlantic countercurrent bringing in cold water and temperate species. Our expansive meadows also provide opportunities to explore and understand how ecosystems will respond to changing temperatures and rising sea levels. North Carolinians should realize that our marine seagrass is a diamond in the rough. And one important message is that we need to keep our marine seagrass that way. The other, equally important message is that our low-salinity underwater meadows—in rivers and closer to the mainland—are facing greater threats from watershed degradation and coastal development and need to be restored.
Q: Where do underwater grasses grow in North Carolina?
A: Wherever you have soft sediment, good enough water clarity so that sunlight can penetrate, and not too much wave energy, current, or turbulence—the conditions seagrasses need to root. Because seagrass needs good light, you generally won’t find it in water deeper than about 6 feet in North Carolina. We have three species that grow mostly in marine conditions, or salty water—the true seagrasses—and another seven to eight that prefer brackish, low salinity, or freshwater conditions, commonly referred to as submerged aquatic vascular plants, or SAV for short.
Q: What are the benefits of seagrass—broadly and in North Carolina?
A: Seagrass is like salt marsh, only completely submerged. It anchors itself and takes up nutrients from the sediment, and then as it photosynthesizes, pumps oxygen to its roots, aerating the water and submerged soils. This makes it possible for some species, like polychaete worms, to live in this sediment. And these species feed a lot of animals, like flounder, speckled trout, and red drum, that are important—to the ecosystem and to recreational and commercial fishermen. Some waterfowl also love seagrass, and North Carolina has a phenomenal duck-hunting economy that draws people from all over the world.
Seagrasses are also ecosystem engineers. As they grow, they make the water clearer and calmer, which is good for them and other species. And they reduce wave energy, protecting shorelines from erosion. Along with salt marsh, seagrass makes up the foundation for the barrier islands here, capturing and stabilizing a large volume of sediment as the islands move. Seagrass, marsh, and barrier islands are really parts of one big geological feature critical to the existence of our estuaries.
Q: How is seagrass faring in North Carolina?
A: Our large, high-salinity seagrass meadows are healthy, and our goal should be to conserve this good resource, although we should keep an eye on parts that may be experiencing issues, like in Bogue Sound. We have different problems with our low-salinity systems, which are sensitive to precipitation and are much closer to land-based threats such as runoff. And despite not having a comprehensive monitoring program, what we can piece together suggests that we may have lost at least 50% of our low-salinity SAV over the past 40 or 50 years. We need an intervention-recovery-restoration approach for our low-salinity meadows. The state is in the midst of updating its Coastal Habitat Protection Plan, and I’ve been pleased to see a diverse group of people with a range of expertise coming to it with energy and enthusiasm. I think we can make real progress conserving and restoring this amazing resource.
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