Underwater Grass in the Bay Improves

Gloucester Point, Virginia – Seagrass growth in the Chesapeake Bay and its tributaries increased in 2023 by 7%, according to newly released data, giving scientists another reason to believe that water quality in the Bay is improving.

No matter what they’re called—underwater grasses, bay grasses, or submerged aquatic vegetation (SAV)—underwater flowering plants play a key role in the health of the Chesapeake Bay and coastal waters worldwide.

Researchers at the Virginia Institute of Marine Science have monitored the Bay’s changing SAV coverage since 1978, conduct research on SAV ecology, and pioneered methods to restore eelgrass to Virginia’s seaside lagoons—the world’s most successful seagrass restoration project.

The SAV Restoration and Monitoring Program at the Virginia Institute of Marine Science mapped 79,234 acres of underwater grasses using aerial and satellite imagery and estimated an additional 3,703 acres of coverage in portions of the Potomac River that cannot be mapped due to security reasons.

The Chesapeake Bay is grouped into four different salinity zones. In 2023, the mesohaline — or moderately salty — zone had widespread gains. In the polyhaline — or very salty — zone, eelgrass was abundant

Seagrasses, which scientists and ecologists call “submerged aquatic vegetation,” or SAV, shelter animals such as blue crabs and other fish. They make the water clear for swimming and also buffer against ocean acidification.

While a 7% growth may sound modest, Brooke Landry, who runs SAV programming at the state Department of Natural Resources, said a good range for yearly growth is between 3 and 5%.

Some freshwater zones and “slightly salty” parts of the Chesapeake saw SAV declines, with particular losses in the Gunpowder and Middle rivers. It’s not certain what caused those decreases, but Landry suspects phytoplankton blooms and suspended sediment observed in the spring and summer of 2022 could be to blame.