Chesapeake Bay Grass Beds Show Decline

Home Conservation Chesapeake Bay Grass Beds Show Decline
Chesapeake Bay Grass Beds Show Decline

The acreage of underwater grasses in the Chesapeake Bay declined 7% in 2020, the second consecutive year that the amount of critical underwater meadows has dropped since peaking three years ago.

The grass beds, which provide habitat and food for everything from waterfowl and turtles to finfish and blue crabs, covered 62,169 acres last year. That is 40% less than the recent record of 108,077 acres reported in 2018, before months of heavy rainfall sent a flood of murky water into the Bay.

The decline was far from uniform, though. Underwater grasses at both ends of the Bay — the low-salinity areas at the top of the Bay and the high-salinity areas closer to its mouth — saw rebounds last year after suffering major setbacks in 2019.

But the mid-salinity areas in the middle of the Chesapeake, which contain the vast majority of potential underwater grass habitat, continued to be hammered. Large beds around Tangier Sound and the Choptank and Little Choptank rivers took especially hard hits.

Those areas are dominated by widgeon grass, a species notorious for disappearing when conditions turn bad, but often reappearing a few years later.

“A lot of the 2019 decline was the widgeon grass story,” said Christopher Patrick, assistant professor of biology at the Virginia Institute of Marine Science, which conducts the annual aerial survey of the Bay’s grass beds. “The decline in 2020 can be largely attributed to continuing smaller declines in the Mid Bay, and a lot of that is losing more widgeon grass.”

The once-lush underwater meadows of Tangier Sound, which covered roughly 25,000 acres as recently as 2018, have since declined by three-quarters, to less than 7,000 acres, accounting for much of the Baywide loss.

Underwater grasses, also called submerged aquatic vegetation, are considered one of the most important indicators of Bay health because their survival depends on water clear enough to allow sufficient sunlight to penetrate.