Seagrass: The building blocks of coastal ecosystems

Retired National Oceanic and Atmospheric Administration scientist Jud Kenworthy of Beaufort lifts a small net dipped into a patch of grass submerged in shin-deep water near the edge of a salt marsh on the central North Carolina coast to reveal colorfully striped juvenile pinfish, no bigger than a pinky, among the strands of green and brown vegetation.

Pinfish are among dozens of fish species residing in estuaries for part of their lives, grazing on underwater grasses. Eventually, schools of the small fish, distinguished by a sharp dorsal fin, will spawn offshore in large groups and be hunted by predators: groupers, snappers and dolphins.

Their journey ends when hooked by a recreational angler from a pier or captured by a commercial fishing vessel to be used as bait for bigger catch.

But the pinfish depends on the rich estuarine habitat that flourishes along the North Carolina coast — an ecosystem that relies heavily on a meadow of grass covered by 12 inches of saltwater where land and sea merge. The threat of climate change to those seemingly mundane patches — which are seldom above water — is a threat to the entire oceanic ecosystem.

Marines invest in restoring NC shoreline

Why is NC seagrass a 'diamond in the rough?'

Underwater seagrasses are found throughout the coastal United States, where they support wildlife, improve water quality, and help buffer shorelines from waves and storms.

JK: North Carolina has the largest and healthiest seagrass ecosystem on the Atlantic seaboard. 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.

LC: What are the benefits of seagrass — broadly and in North Carolina?

JK: Seagrass is like salt marsh, only completely submerged. It anchors itself and takes up nutrients from the sediment, and then as it photosynthesizes, it pumps oxygen to its roots, which aerate 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, which are important to the ecosystem and to recreational and commercial fishermen. 

Seagrasses are also ecosystem engineers. As they grow, they make the water clearer and calmer, which is good for them and other species. They reduce wave energy, protecting shorelines from erosion. Seagrass, marsh and barrier islands are really parts of one big geological feature critical to the existence of our estuaries.

LC: How is seagrass faring in North Carolina?

JK: 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 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.

Edited from a published interview. Read the full interview.

Find out more: Disappearing Seagrass Protects Against Pathogens, Even Climate Change, Scientists Find (NY Times)