A Pearl of Wisdom for the Chesapeake

Rivers and streams that empty into the Chesapeake Bay not only give life to the nation’s largest estuary; they also carry enough nitrogen and phosphorus from agricultural, suburban, and urban lands to threaten ecosystems throughout the 64,000 square-mile watershed. Although much of Virginia Tech’s research on the Chesapeake Bay involves reducing excess nutrients and sediments before they enter the water, some has focused on reducing nutrients after the fact.

Kurt Stephenson, associate professor of agricultural and applied economics, has teamed up with Bonnie Brown, associate professor of biology at Virginia Commonwealth University, to investigate native oyster aquaculture as a possible way to filter nitrogen and phosphorus already in the bay.

“We are looking at the nutrient loads that might be removed from ambient waters around oyster aquaculture test sites,” Stephenson says.

Project leaders have established three field sites in Virginia and Maryland to estimate the amount of nitrogen and phosphorus removed by the shellfish. The filter feeders are a natural choice for anyone looking to eliminate contaminants and restore a native species. An adult Crassostrea virginica, or Eastern oyster, can filter as many as 48 gallons of water in a single day, but a disease in the 1950s all but decimated the population.

As a resources and environmental economist, Stephenson is studying the feasibility and cost-effectiveness of incorporating nutrient-assimilation credits into state-sponsored, nutrient-reduction programs – a proposal that he believes could not only diminish water contaminants but may also help advance the aquaculture industry.

“Right now there is limited opportunity for oyster aquaculture to expand in the Chesapeake Bay, but if oyster producers could have two sources of revenue, the industry might develop further,” he explains. “These producers are already making money for the first service they provide, the food, but they may need to be paid for the second – the water-quality service – to expand.”

Stephenson says this project, which focuses on changes in government policy to promote cleaner waters, is one of several ways “to remove excess nutrients from the Chesapeake Bay without changing the source.”

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Alex Miller, graduate student, and Bonnie Brown (center) deploy oyster floats. Each float holds about 600 oysters.