Encouraging outlook for bay grasses

By Linda Cicoira

Results from a survey of more than 76,000 acres of submerged aquatic vegetation in the Chesapeake Bay and its tributaries shows an overall 12 percent increase, according to 2022 research conducted by the Virginia Institute of Marine Science.

“For the most part, we had a really encouraging year … throughout the Bay,” said lead researcher Dr. Christopher Patrick.

Underwater bay grasses are a vital part of the Bay’s ecosystem. They provide habitat and nursery grounds for fish and blue crabs, serve as food for animals such as turtles and waterfowl, clear the water by reducing wave action, absorb excess nutrients, and reduce shoreline erosion.

VIMS tracks the abundance of underwater grasses as an indicator of Bay health for the Chesapeake Bay Program, the federal-state partnership established in 1983 to monitor and restore the ecosystem. Using aerial surveys made from late spring to early fall each year, researchers estimate the acreage.

Saltier areas continued to regain ground that was lost in the 2019 crash, with expansion of both eelgrass and widgeon grass. Dr. Patrick attributes this to continued nutrient management efforts and cool summers associated with La Niña.

“The real test for those zones will be (in the) summer of 2024 when hot summer temperatures, a known stressor of eelgrass, return with the predicted El Niño cycle.” The research team will assess those impacts, if they come to pass, in spring 2025. Grasses in the freshwater areas held nearly constant, with some areas within the zone exceeding attainment goals.

Between 2021 and 2022, grass abundance in the Bay’s fresh water fell 73 acres. In the slightly salty water, there was a decrease of 1,239 acres. In moderately salty water, bay grass increased by 6,841 acres, and in very salty waters, the number of acres rose by 2,829.

Roughly 1,500 acres of underwater grass were lost in Gunpower and Middle Rivers. The reasons for the significant losses seen in this small area are unknown, and will continue to be investigated.

The resurgence of underwater grass in the Susquehanna Flats has been occurring over the past several years, and in 2022, the segment gained another couple of hundred acres.

In both Maryland and Virginia portions of the Tangier Sound, thousands of acres of underwater grass increased by 54 percent. These healthy grass beds will serve as high quality habitat for blue crabs, which is good news for crabbers working around Smith and Tangier Islands.

Mobjack Bay to Poquoson Flats, which is an area of the Bay dominated by eelgrass and widgeon grass, increased by 27 percent. Underwater grass abundance came close to reaching the record high from 1997.