Eelgrass (Zostera marina). Maryland Department of Natural Resources photo.
Underwater grass abundance–a key indicator of water quality and habitat–remained steady in 2023 in the state’s portion of Chesapeake Bay, reaching 37,770 acres, according to data released this week by the Chesapeake Bay Program and Maryland’s Department of Natural Resources (DNR).
Overall, an estimated 82,937 acres of underwater grasses, also called submerged aquatic vegetation (SAV), were distributed throughout Chesapeake Bay and its tidal tributaries in 2023, a 7% increase over 2022 acreage.
In Maryland, all or part of four rivers surpassed their restoration goals. These include the Northeast River at 109%, the Upper Chester River at 432%, the Honga River at 138%, and the Wicomico River at 270%. An additional three segments reached 75 percent or more of their restoration goals, including the Northern Chesapeake Bay that encompasses the Susquehanna Flats at 86%, the Bush River at 83%, and Mattawoman Creek at 98% of their goals.
“I’m glad to see the Bay’s underwater grasses continue to recover following losses in 2019, and despite some declines in the upper Bay, the Susquehanna Flats are holding strong and the news is positive,” said Brooke Landry, Maryland DNR’s Program Chief of Living Resource Assessment and Chair of Chesapeake Bay Program SAV Workgroup. “ I am confident that we will continue to make progress on restoration, especially with species like Horned pondweed and Sago pondweed becoming so abundant in the mid-Bay. Their skyrocketing expansion in recent years, according to observations that my colleagues and I are making along with data collected by Chesapeake Bay SAV Watchers program volunteers, is exciting to see since both plants offer such beneficial ecosystem services.”
Submerged aquatic vegetation (SAV), also known as underwater grasses, play a critical role in maintaining the health of the Chesapeake Bay ecosystem. These grasses absorb and filter out nutrients and sediment, reduce shoreline erosion, provide habitat and protection for important species such as blue crabs and largemouth bass, support and sustain migrating waterfowl, and mitigate climate impacts.
The annual underwater grass survey was conducted by the Virginia Institute of Marine Science between May and November 2023. While the acreage falls short of Maryland’s 2025 restoration goal of 79,800 acres, airspace restrictions prevented complete surveys of the Upper and Middle Potomac River, including Piscataway Creek. If these areas had been fully mapped, observations suggest that Maryland’s SAV acreage would have been higher in 2023.
A significant loss of freshwater grasses in the upper Bay in 2023 offset an equally significant expansion of brackish water grasses in the mid- and lower portions of Maryland’s Chesapeake Bay. The loss of freshwater grasses did not extend to the iconic Susquehanna Flats grass beds, which continued to expand and now cover over 11,000 acres. Grass beds in the mid-Bay were bolstered by the continued expansion of Sago pondweed (Stuckenia pectinata), a species that doesn’t get much attention in the grand scheme of Chesapeake Bay SAV dynamics. According to observations made by Bay scientists and data collected by Chesapeake SAV Watchers volunteers, Sago pondweed is possibly the most abundant species in several Maryland rivers on both the eastern and western shores, including the Severn and Choptank Rivers, and Eastern Bay.
Further south and into slightly saltier water, widgeon grass (Ruppia maritima) continued to recover from major losses in 2019. Both widgeon grass and eelgrass (Zostera marina) are common in Tangier Sound, where grass beds gained 1,285 acres of SAV between 2022 and 2023.
The overall health and expansion of SAV in the Chesapeake Bay are vital for the ecosystem’s resilience and the overall water quality. These underwater grasses are essential for providing habitat, food, and shelter for various aquatic species, thus supporting the biodiversity of the region.