Chesapeake Bay Underwater Grasses: Resurgence and Restoration

The return of underwater grasses in the Chesapeake Bay is proof that restoration efforts are working in a big way, which is excellent news for the health of the nation’s largest estuary and the 17 million people and countless animals in its watershed.

Published March 23, 2018

Imagine a Chesapeake Bay with clear water where fishes, blue crabs and diamondback terrapins are abundant, weaving in and out of vast meadows of underwater grasses. For most Marylanders, that image may be hard to conjure—but that was the reality of a vibrant, healthy Bay up until the late 1960s and early 1970s. From the look of underwater grasses that are starting to rebound in the nation’s largest estuary, it could be the Bay of our future, too.

Maryland blue crab in underwater grasses

Photo courtesy of Jay Fleming

If you’re not familiar with the health of watershed ecosystems, underwater grass may not seem significant, but the importance of these underwater meadows can’t be overstated. They’re a telltale sign of a healthy ecosystem, and welcome proof that the path of degradation in the Bay has been reversed toward one of restoration. 

According to a recent 30-year study, beds of submerged aquatic vegetation (SAV) in the Chesapeake have increased from 38,000 acres in 1984 to 97,433 acres in 2016. That’s a 156 percent increase in SAV—the largest resurgence of aquatic grasses ever recorded. The restoration of the Bay’s grasses is key to sustaining healthy populations of Maryland blue crabs and other economically important marine life, such as striped bass and yellow perch, which use these underwater gardens as a place to hide, forage, lay eggs and, in the case of blue crabs, a safe place to molt. A restored ecosystem is important not only for the animals that depend on it, but also for the humans who do: we all drink water and breathe air, the quality of which is directly correlated to the health of our ecosystem. 

There’s one clear driving force for the resurgence of this SAV: the reduction of nitrogen pollution. Since 1984, nitrogen concentrations have dropped off by 23 percent in the Bay, thanks to a management plan that includes support from the federal government and the cooperation of six states in the Bay’s watershed. 

Excess nitrogen, which comes in the form of polluted urban storm water runoff and fertilizer runoff from agriculture, drains into the Bay, where it fuels a population boom of phytoplankton that leads to harmful algal blooms. Phytoplankton species quickly respond to this rapid influx of fertilizer, forming a dense cloud near the water’s surface that blocks sunlight from reaching underwater grass beds, which eventually die—and the  species that depend on them for their survival suffer, too. Lower levels of nitrogen in polluted runoff means a lower frequency and duration of algal blooms, allowing sea grasses to gain a foothold and flourish.

The effectiveness of this watershed-level “pollution diet” solution is not only great news for the Bay, but also for estuaries around the world. It provides evidence that even in heavily populated areas, such as the Chesapeake Bay watershed, these complex, valuable ecosystems can be restored and continue to be productive if they’re managed correctly. 

Multi-state cooperation is vital to restoring the health of the Bay, but Individuals can have an impact, too. Planting trees, cutting out fertilizers from your lawn maintenance routine and reducing runoff from your property by installing rain gardens planted with native species are all ways you can be a responsible watershed resident and help keep the positive momentum going. 

The Chesapeake Bay ecosystem has suffered a great deal of damage over several decades, but the recent resurgence in underwater grasses proves that if we give it a chance, the resilient Bay can flourish—and we can all enjoy its benefits. Nature and humans are inextricably connected, and positive changes for the Bay are positive changes for us!

If you want to do your part to help restore the Chesapeake Bay, volunteer at an upcoming conservation event!

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