Underwater grass, a key indicator of bay health, stays strong in survey

Bird and marsh grass along the Chesapeake Bay. Image via the Virginia Office of Natural Resources.

Despite record rainfall last year, a survey of underwater grasses that are key indicators of Chesapeake Bay health found that they remain abundant. 

The Chesapeake Bay Program, the regional partnership that has led the restoration of the bay since 1983, says 91,559 acres of underwater grasses were mapped, not including areas that it says were inaccessible due to “weather conditions, cloudy water and security restrictions.” With these areas, the report estimates that underwater grasses could cover up to 108,960 acres. This estimated expansion would mark a 59% achievement of the program’s goal of 185,000 acres of underwater grasses by 2025.

The grasses are essential to the ecosystem because “they keep our waters clean by absorbing excess nutrients, trapping suspended sediment and slowing wave action that helps to stabilize shorelines, protect wetlands and reduce erosion. Bay grasses also offer food to small invertebrates and migratory waterfowl and shelter fish and blue crabs,” the program said in a statement. 

Experts are encouraged by the growth, especially after the record-breaking rainfall in the Chesapeake region last summer. High rainfall, the report states, can result in “nutrient- and sediment-laden stormwater runoff into the bay” that can damage the underwater grass.  According to the report, “the persistence of underwater grasses seen last year suggests increasing resilience to such stresses, an indication that the restoration actions taken by the Chesapeake Bay Program and its many partners are working.”

The foundation’s report also noted significant expansion in grass acreage this year, like the Patapsco River where the grass abundance saw a 114% increase from 2017 to 2018 after years of restoration work starting in the early 2000s. 

A critical part of this development, according to experts cited in the report, is the widgeon grass, which is highly sensitive to environmental changes. The report called it a “’boom and bust’ species whose abundance can rise and fall sharply from year to year.” Underwater grasses need sunlight to survive, so cloudy and polluted waters are a major concern for those trying to protect the vegetation. 

“What we need to do now is to double down on our efforts to decrease nutrient and sediment pollution and give our underwater grasses a chance to continue their recovery,” said Brooke Landry, a natural resources biologist with the program.

Earlier this month, stock assessments of blue crabs in the bay, conducted by the Maryland Department of Natural Resources and the Virginia Institute of Marine Sciences, estimated that the crab population was 594 million, a 60 percent increase from the year before, and found that the crabs were “not depleted or overfished.”