Shellfish from the Chesapeake Bay, namely blue crabs and oysters, has long been a Maryland and Delaware seafood specialty. What makes it possible for these species to thrive in the bay, the largest estuary in the U.S., is its unique mix of fresh water and salt water.
Today, the Chesapeake yields more fish and shellfish than any other estuary in the country, close to 45,000 tons annually. But due to increasing acidity in some parts of the bay, the shells of young oysters are growing as thick as in the past, making them easy prey for crabs.
According to a study conducted at the University of Maryland Center for Environmental Science, acidity is increasing in some parts of the Chesapeake Bay faster than it is occurring in the open ocean. The study, published online in the journal Estuaries and Coasts, looked at 23 years of water quality data.
Yet while acidity is increasing in the more saline regions of the bay, the opposite is happening in the less saline waters, according to the study. Lead author of the study, Dr. George Waldbusser of Oregon State University, said “The regional changes in acidity revealed in our analysis are greater than what could be caused by increasing atmospheric carbon dioxide alone.”
The scientists believe that the diversity in acidity levels within the bay waters causes significant changes in the estuary's ecosystem. Nutrients from sewage systems and agricultural runoff promote an increase in phytoplankton in the upper bay. As these plants grow they absorb large amounts of carbon dioxide, resulting in less acidic waters in those regions. At the same time, when the phytoplankton are carried toward the ocean by the bay's currents, they are consumed by bacteria and animals that then release the carbon dioxide taken up the by phytoplankton. This stays in the water making it more acidic.
According to University of Maryland Center of Environmental Science marine biologist, Robert Newell, “With oyster populations already at historically low levels, increasingly acidic waters are yet another stressor limiting the recovery of the bay's oyster population.”
The state of Maryland is taking steps to help rebuild the Chesapeake Bay's depleted native oyster population as part of Maryland's Proposed Oyster Restoration and Aquaculture Development Plan introduced by Governor Martin O'Malley. The plan will attempt to increase the state's network of oyster sanctuaries, add areas open to leasing for oyster aquaculture, streamline the permit process, and identify areas that are off limits to leasing.
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