As coastal populations continue to grow, so too do the pressures on our waterways.
Rivers and streams carry nitrogen from fertilizers and stormwater runoff right into estuaries. In excess, this nutrient can fuel large algal blooms that suck oxygen out of the water, killing fish and other aquatic life.
But nature has a solution — oysters! These unassuming shellfish are powerful filter feeders that can remove algae and organic particles that contain nitrogen. A single adult oyster can filter up to 50 gallons of water a day.
So, just how much nitrogen can oysters remove from the water?
Scientists with NOAA’s National Centers for Coastal Ocean Science and their partners are working with an oyster grower in South Carolina’s Lowcountry to answer this question.
The team found that harvesting one million, two and a half-inch farmed oysters is equivalent to removing roughly 300 pounds of nitrogen annually from the study area, making it possible for the state to include harvested oysters in its nutrient management plan. The researchers are also determining the value of the removed nitrogen that could be paid to oyster growers within a nutrient credit trading program.
Study results will help oyster growers fine tune production to maximize income. The data will also help state agencies with shellfish management decisions — such as approving more oyster farm leases, which benefit South Carolina’s economy and protect its coastal water quality.
NOAA preserves ocean sustainability and facilitates domestic aquaculture in the U.S. through the National Aquaculture Act of 1980, Executive Order 13921 on Promoting American Seafood Competitiveness and Economic Growth (May 7, 2020), and Executive Order 14276 on Restoring American Seafood Competitiveness (April 17, 2025).
