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by Joan Smedinghoff

March 06, 2018

Underwater grasses are a critical part of the Chesapeake Bay ecosystem. Also known as submerged aquatic vegetation or SAV, underwater grasses are plants that grow in the shallow waters of the Chesapeake Bay and its tributaries. Now, a new study finds that on-land nutrient reductions along with conservation initiatives have resulted in a rebounding underwater grass population, and ultimately a healthier Chesapeake Bay.

The study, published in the Proceedings of the National Academy of Sciences, analyzes the positive impact of nutrient reductions from the Chesapeake Bay Total Maximum Daily Load (TMDL). Implemented in 2010, the TMDL is a comprehensive “pollution diet” that limits nutrient and sediment pollution necessary to restore the health of the Bay and its waterways. These pollution limits are divided across the seven Chesapeake Bay watershed jurisdictions—Delaware, the District of Columbia. Maryland, New York, Pennsylvania, Virginia and West Virginia—in order to gradually decrease pollution in the region.

Researchers found that a 23 percent reduction of average nitrogen levels and an eight percent reduction of average phosphorus levels in the Bay have resulted in a four times the amount of underwater grasses. This represents the biggest resurgence of underwater grasses ever recorded, not only in the Chesapeake Bay, but in the entire world.

These findings are from a collaborative effort among many institutions, including the Virginia Institute of Marine Science, University of Maryland Center for Environmental Science (UMCES), Environmental Protection Agency’s Chesapeake Bay Program Office, U.S. Geological Survey, Smithsonian Environmental Research Center, Maryland Department of Natural Resources and others.

“[We] have had the distinct privilege of facilitating research that confirms a direct correlation between conservation actions undertaken by a broad partnership and ecosystem responsiveness that is leading to positive ecological outcomes,” said Bill Dennison of UMCES, one of the study’s co-authors. “The Chesapeake Bay Program is working and can serve as a model for the rest of the world.”

“These efforts began before I was even born,” said lead author Jonathan Lefcheck of the Bigelow Laboratory for Ocean Science, “but we are at a stage now where the all these different threads can be pulled together to unveil a picture of unprecedented success.”

In the 2014 Chesapeake Bay Watershed Agreement, our partners committed to achieve and sustain 185,000 acres of underwater grasses Bay-wide.

“This is a message of hope,” said Lefcheck, “and I look forward to a future when the Bay is filled with grasses, something I never thought I would see during my lifetime!”

Learn more about our partnership’s progress toward restoring underwater grasses in the Bay.