Bay Basics

Underwater grasses

What happened to the underwater grasses? A rich legacy of Chesapeake Bay science

Walter Boynton on the disappearance-and resurgence-of Bay grasses

Estuarine ecologist Walter Boynton of Chesapeake Biological Laboratory discusses the mysterious disappearance—and eventual return—of underwater grasses in Chesapeake Bay.

Since its inception 90 years ago, the University of Maryland Center for Environmental Science has been on the forefront of Chesapeake Bay restoration. From the earliest documentation in the 1920s of the declining oyster fishery to more recent studies on harmful algal blooms and dead zones, UMCES has led the way in collaborative research in the Chesapeake and set the standard in environmental science of the Bay.

The greatest contribution to the scientific community is its ongoing work in environmental restoration. UMCES scientists made the initial discovery that the Bay was suffering from an excess of nutrients, particularly nitrogen and phosphorus. This high concentration of nutrients, a phenomenon known as eutrophication, caused a marked increase in algae blooms, killing off thousands of acres of underwater grasses and lowered dissolved oxygen concentration in bottom waters, suffocating bottom-dwelling organisms.

The effects of eutrophication had been gradually taking a toll on the Bay for some time, but it was not until 1972 when the devastating rains of Hurricane Agnes hit the Atlantic Coast, that citizens and scientists realized the Bay had changed dramatically for the worse. The abundant grasses of the 1950s that provided shelter for small fish and crabs and trapped sediments that washed from the land suddenly vanished. It became apparent that the hurricane alone did not cause the widespread changes observed in the early 1970s. Large amounts of pollutants and sediments were washing off the land, somehow hindering the return of underwater grasses and impairing the health of the estuary. 

A group of UMCES scientists set out to determine the cause of these changes. They particularly wanted to test the theory that it was the increased use of herbicides in agriculture that was affecting the grasses. As their research evolved, they demonstrated that it was not herbicide but the ever-increasing amounts of nutrients that caused the sea grasses to disappear and the dissolved oxygen levels in the Bay’s bottom waters to drop. 

More recently, underwater grasses have made an comeback in the Susquehanna Flats area of the Upper Bay, and scientists have been able to tie that comeback to efforts to reduce nutrients entering the Bay.

With these discoveries, it became clear the problems were not localized. Indeed, the entire Chesapeake Bay was in peril. Joining forces with other regional research institutions, government agencies, and citizens, UMCES has been a key catalyst for efforts to restore not only the Chesapeake but also other coastal ecosystems around the world suffering from nutrient pollution.

In 1983, the federal government, Pennsylvania, Maryland, Virginia, and the District of Columbia endorsed the first Chesapeake Bay Agreement, a commitment to restore the Bay. Recently the Chesapeake Executive Council announced new management strategies to meet the goals of the agreement, advancing the restoration, conservation and protection of the Bay, its tributaries and the lands that surround them. Many of these restoration goals and approaches have directly resulted from UMCES’ scientific discoveries.

Much work remains to be done and UMCES’ scientists continue to make important discoveries and apply their evolving knowledge of the Chesapeake ecosystem and its natural resources. The scientists who identified the root causes of the declining health of the Bay are joined by score of colleagues to not only diagnose problems but also develop solutions to improve the Bay and Maryland’s environment—and extending this experience to the rest of the world.