Chesapeake Bay seeing return of underwater grasses after rapid decline from 2019

Efforts to sustain underwater grasses in the Chesapeake Bay are seeing some success, but probably not enough to meet a key 2025 goal.

An estimated 82,937 acres of underwater grasses were distributed throughout Chesapeake Bay and its tidal tributaries in 2023, marking a 7 percent increase from the previous year, according to a report from the Chesapeake Bay Program that was released on Wednesday.

This marks a 45 percent attainment of the ultimate goal of achieving and sustaining the 185,000 acres of underwater grasses needed for a restored Chesapeake Bay, and a 61 percent achievement of the target to restore 130,000 acres by 2025 set by the terms of the Chesapeake Bay Watershed Agreement.

In 2019, underwater grasses in the Chesapeake Bay experienced a rapid decline following two years of above average rainfall and heavy river flows.

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“I’m glad to see the Bay’s SAV 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, chief for the Living Resource Assessment Program at the Maryland Department of Natural Resources and chair of the Chesapeake Bay Program’s 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,” Landry said. “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.”

Underwater grasses are greatly impacted by the weather. Excess precipitation, as well as the pollution that heavy flows bring into the Chesapeake, can cause grass beds to die off. On the flip side, healthy grass beds can help trap and absorb nutrient and sediment pollution, helping to improve water clarity.

Underwater grasses also provide critical habitat for the Bay’s critters, including blue crabs. The loss of underwater grass habitat means the loss of nursery grounds for blue crabs. In the 2024 Bay-wide Blue Crab Winter Dredge Survey, the population of juvenile blue crabs was 138 million, an increase of 22 million from the previous year.

“It’s been exciting to observe some tremendous expansion in some areas of the Polyhaline with eelgrass growing at depths we haven’t seen in decades.” says Christopher J. Patrick, director of the SAV Monitoring and Restoration Program at the Virginia Institute of Marine Science. “We often call these plants the canary in the coal mine for the Chesapeake, as they tell us a lot about how the Bay is doing.”