CHESEAPEAKE BAY GRASSES DECLINE

The underwater acreage of the bay is decreasing, meaning that habitats for species such as blue crabs are shrinking. It’s a signal that too much pollution is still reaching the bay.

The underwater grasses that are the nurseries for the Chesapeake Bay’s blue crabs shrank dramatically last year, down 38% from the estimated total in 2018, the Chesapeake Bay Program said.

It’s a signal that too much pollution is still reaching the Chesapeake; that a shrinking number of juvenile crabs will have less space to grow and that the bay’s hard-pressed striped bass, particularly juveniles, will have less area to forage for food.

While grass acreage varies from year to year, responding quickly to algae blooms and sediment that blocks sunlight, last year’s total was down 17% from the running 10-year average, the bay program said.

The drop was dramatic in Virginia’s lower bay, where the acreage of underwater grasses fell by nearly 80%, to just 583 acres — less than a square mile.

“The significant loss of bay grasses this year is a sobering reminder that the Chesapeake Bay is still a system dangerously out of balance,” said Beth McGee, the Chesapeake Bay Foundation’s director of science and agricultural policy.

“The extreme flows of polluted runoff that damaged the grasses are also a clear sign that climate change is threatening the bay’s recovery. This setback should be a wake-up call that climate change and increasing pollution cannot be ignored,” she added.

The biggest acreage decline came in the moderately salty waters around Tangier Sound, which accounted for more than 40% of last year’s nearly 42,000 acre decline. That’s mostly due to a decline in widgeon grass, which bay program experts said may be due to higher flows of river water, which carry sediments that block sunlight from reaching the plants.

Widgeon grass moved in as climate change caused major losses of eelgrass, a vitally important species that remains under stress, said Chris Moore, senior regional ecosystem scientist for the Bay Foundation.

In addition to being a nursery for blue crabs, underwater grasses are foraging turf for the bay’s hard-pressed striped bass, especially when they are juveniles, Moore said.

The grasses are also an important food source for shrimp and waterfowl. They play an important role in taking up the nutrients from farm runoff that otherwise feed the algae that create dead zones, and by reducing wave action help prevent shoreline erosion.

Grasses in rivers feeding the bay did better, though. Acreage in the upper tidal reaches of the James River increased 33% to 536 acres, while the Chickahominy River saw a nearly 50% increase to 1,059 acres.

The bay program is a partnership of Chesapeake watershed states and the federal government. The Bay Foundation is a nonprofit that works for a healthier bay.