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Oyster Restoration Projected to Provide Significant Boost to Bay Grasses While Removing Nitrogen Pollution from the Bay
Second component of Oyster Environmental Impact Statement Unveiled today
ANNAPOLIS � Increasing Maryland�s oyster population 25-fold would result in a 21 percent increase in Bay Grasses and would remove 11 million pounds of nitrogen from the Chesapeake Bay. Similarly, increasing the oyster population 50-fold would double those benefits, according to model presented today to the Department of Natural Resources (DNR).Dr. Carl Cerco from the U.S. Army Corps of Engineers Research and Development Center presented an evaluation and analysis of the ecosystem effects of oyster restoration in Chesapeake Bay, based on a model that projected the benefits of oyster restoration on submerged aquatic vegetation, nitrogen, and dissolved oxygen levels based on a series of scientific assumptions.
Cerco spoke at DNR�s second public outreach event today to present the key findings from research, modeling and assessment projects being conducted as part of the Environmental Impact Statement (EIS) on alternative oyster restoration approaches for the Chesapeake Bay. The purpose of the EIS is to identify a strategy for establishing an oyster population, whether native or nonnative, that reaches a level of abundance in the Chesapeake Bay comparable to the 1920-1970 time periods, approximately 25 times the current levels.
�The results from this model confirm that the strategies of Maryland�s multifaceted approach to restoring the Chesapeake Bay are focused in the right areas � oyster restoration, nutrient reduction and SAV restoration,� said DNR Secretary C. Ronald Franks. �We recognize that oyster restoration alone will not restore the Bay, but it is an integral component. A strategy to restore the Bay�s oyster population is critically needed, and we believe the EIS process will lead us to that answer.�
The model presented today suggests that the most significant ecosystem benefits of oyster restoration will be an increase in submerged aquatic vegetation (SAV). A 50-fold increase in Maryland�s oyster population would result in a 43 percent increase in the amount of SAV in Maryland, while increasing the Bay�s oyster population to a level observed during the 1920-70 time period would result in about half this amount or a 21 percent increase in SAV.
The model also indicates that a 50-fold increase in Maryland�s oyster population would remove 19.8 million pounds of nitrogen annually. That number is equivalent to Maryland�s nitrogen reduction goal as established in the Chesapeake 2000 Bay Agreement, which seeks to cut the amount of nitrogen entering the Bay by 19 million pounds a year by 2010. An increase in the Bay�s oyster population to the 1920-70 year levels would remove about half this amount, 11.0 million pounds of nitrogen removed annually.
A restored oyster population would also provide improvements to the Bay�s dissolved oxygen levels. The model indicates an improvement of 0.4 mg/L in Maryland�s deep-water summer dissolved oxygen with a 50-fold increase in oysters, and 0.2 mg/L for an increase to the 1920-70 year levels. This effect is averaged over large expanses of the Bay, and greater and lesser improvements are projected in specific locations. Greater benefits are projected in shallower waters.
During his presentation, Cerco cautioned the audience that oyster restoration alone is not likely to bring the deep channel of the mainstem, where complete anoxia may occur, into compliance with dissolved oxygen standards.
�There are multiple reasons for the absence of a more significant dissolved oxygen response to oyster restoration. The obvious explanation is that oysters are found in the shoals rather than over the deep trench,� Cerco said. �Still, this modest improvement in dissolved oxygen through oyster restoration is not insignificant when compared to the level of effort and costs of land management practices to acquire similar results.�
The information presented today will be incorporated into an Ecological Risk Assessment that is being prepared in support of the EIS. The State of Maryland, Commonwealth of Virginia and Army Corps of Engineers, Norfolk District, are preparing an EIS to evaluate oyster restoration alternatives, including an introduction of a nonnative oyster and various native oyster restoration alternatives.
Today�s Power Point presentation on the ecosystem effects of oyster restoration can be found in its entirety at http://www.dnr.state.md.us/dnrnews/infocus/oysters.asp. A schedule of upcoming presentations will be posted on the DNR website in September.
August 15, 2005The Maryland Department of Natural Resources (DNR) is the state agency responsible for providing natural and living resource-related services to citizens and visitors. DNR manages more than 446,000 acres of public lands and 18,000 miles of waterways, along with Maryland's forests, fisheries and wildlife for maximum environmental, economic and quality of life benefits. A national leader in land conservation, DNR-managed parks and natural, historic and cultural resources attract 11 million visitors annually. DNR is the lead agency in Maryland's effort to restore the Chesapeake Bay, the state's number one environmental priority. Learn more at www.dnr.maryland.gov
