Restoring seagrasses can bring coastal bays back to life

Restoring seagrasses can bring coastal bays back to life
Eelgrasses covered with small snails, which keep the leaves clean by feeding on algae that live on them. Credit: Jonathan Lefcheck, CC BY-ND

A century ago Virginia’s coastal lagoons were a natural paradise. Fishing boats bobbed on the waves as geese flocked overhead. Beneath the surface, miles of seagrass gently swayed in the surf, making the seabed look like a vast underwater prairie.

More than 70 species of seagrasses grow in shallow waters around the world, on every continent except Antarctica. In Virginia, beds of eelgrass (Zostera marina) provided habitat for bay scallops and food for birds, and kept barrier islands from washing away. Eelgrass was so common that people who lived near the shore packed and baled it to use as insulation for homes, schools and hospitals.

In the 1930s, however, pandemic plant disease and repeated hurricanes eliminated the eelgrass along Virginia’s eastern shore. The once-vibrant seafloor became barren mud, leading to a loss of “wildfowl, the cream of salt-water fishing, most of the clams and crabs, and all of the bay scallops,” sportsman and publisher Eugene V. Connett wrote in 1947.

We are marine scientists who study seagrasses, marine biodiversity and coastal ecosystems. In a newly published study, we describe the results of a 20-year mission to reintroduce eelgrass into Virginia coastal bays using a novel seed-based approach.

This project has now restored 9,600 acres of seagrasses across four bays—one of the most successful marine restoration efforts anywhere in the world. It has triggered large increases in fishes and invertebrates, made the water clearer and trapped large quantities of carbon in seafloor sediments, helping to slow climate change. We see this work as a blueprint for restoring and maintaining healthy ecosystems along coastlines around the world.

Why didn’t seagrasses recover naturally?

Development, nutrient runoff and other human impacts have damaged marshes, mangroves, coral reefs and seagrasses in many bays and estuaries worldwide. Loss or shrinkage of these key habitats has reduced commercial fisheries, increased erosion, made coastlines more vulnerable to floods and storms and harmed many types of aquatic life. Rapid climate change has compounded these effects through rising global temperatures, more frequent and severe storms and ocean acidification.

In the late 1990s, local residents told two of us who are longtime students of seagrasses (Robert “JJ” Orth and Karen McGlathery) that they had spotted small patches of eelgrass in shallow waters off Virginia’s eastern shore. For years the conventional view had been that seagrasses in this area had not recovered from the events of the 1930s because human activities had made the area inhospitable for them.

But studies showed that water quality in these coastal bays was comparatively good. This led us to explore a different explanation: Seeds from healthy seagrass populations elsewhere along the Atlantic coast simply weren’t reaching these isolated bays. Seagrasses are underwater flowering plants, so seeds are among the main ways they reproduce and spread to new environments.

Restoring seagrasses can bring coastal bays back to life
Eelgrass beds were restored in four bays at the southern tip of Virginia’s