A study led by researcher Lisa Kellogg of the Virginia Institute of Marine Science shows that a restored oyster reef can remove up to 10 times more nitrogen from Chesapeake Bay waters than an unrestored area nearby, providing additional evidence that reef-restoration can contribute to efforts to improve water quality in the nation's largest estuary.
The study, "Denitrification and nutrient assimilation on a restored oyster reef," is the feature article in this month's issue of Marine Ecology Progress Series. Co-authors are Jeff Cornwell, Michael Owens, and Ken Paynter of the University of Maryland Center for Environmental Science.
To date, the justification for restoring oysters to Chesapeake Bay has focused on their capacity to clear the water, provide habitat for their own young and for other species, and to sustain both watermen and seafood lovers.
The new study, says Kellogg, aimed to quantify another potential benefit of restored oyster reefs—their ability to remove nutrients from the water. Input of nitrogen and phosphorous from fertilizers, wastewater treatment plants, and other sources is one of the main reasons for impaired water quality in the Bay, with reduction and removal of these excess nutrients a key goal of Bay restoration efforts.
In Maryland's Choptank River, the team compared a restored oyster reef that had 131 large oysters per square meter to an adjacent unrestored site that was suitable for restoration. They carefully measured flows of nitrogen and phosphorous compounds at each site, along with salinity, temperature, oxygen levels, sediment characteristics, and the abundance of oysters and other marine life such as mussels, clams, barnacles, and worms.
"Our study showed that a successfully restored oyster reef can remove significant levels of nutrients from the water column," says Kellogg. "We found that annual denitrification rates at the restored site were enhanced by an order of magnitude and that rates in August were among the highest ever recorded for an aquatic system. It's important to recognize, however, that the density of oysters on the reef we studied far exceeds current success criteria for oyster-reef restoration."
Read the full story at the Chincoteague Beacon>>
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