Underwater Grasses

By providing food and habitat for wildlife, reducing shoreline erosion and improving water clarity, underwater grasses play an important role in the Bay ecosystem.

Underwater Grasses

In 2018, an estimated 91,559 acres of underwater grasses were mapped in the Chesapeake Bay and its tidal tributaries. While this is less than the previous year, it is likely that substantially more underwater grasses grew in the Bay than the mapped acreage suggests. Frequent rain, cloudy water and security restrictions prevented researchers from successfully collecting aerial imagery over portions of the Bay.

Using 2017 levels for the unmapped areas, it is estimated that the Bay may have actually supported 108,960 acres of underwater grasses in 2018. This would mark a 59% achievement of the 185,000-acre goal adopted by Chesapeake Bay Program partners in the Chesapeake Bay Watershed Agreement. This would also be a 4% increase from last year’s total which surpassed 100,000 acres and was the highest amount of underwater grasses ever recorded in the Bay.


Acres of underwater grasses in the Chesapeake Bay

Experts attribute the steady underwater grass abundance to the presence of widgeon grass in the southern half of the Bay. However, widgeon grass is a “boom and bust” species whose abundance can rise and fall sharply from year to year and therefore a widgeon-heavy spike is not guaranteed to last. The wild celery, water stargrass and other species that have returned to the tidal fresh waters of the Bay are less prone to such changes in abundance. 

A continued rise in bay grasses will benefit the entire Bay ecosystem: underwater grasses absorb nutrient pollution, improve water clarity, reduce shoreline erosion, release oxygen into the water, sequester carbon and provide food and shelter to striped bass, blue crabs and other critters.