How do oysters
Oysters consume algae by filtering water at a rate of up to five liters – or about 2 gallons – per hour. In abundance, oysters help clarify the water, which allows bay grasses to receive more sunlight. Then in turn, plentiful grasses increase oxygen levels, reduce wave energy and shoreline loss, and habitat for aquatic life.
It is estimated the Chesapeake’s historic oyster population could filter the Bay’s volume every three or four days. Today’s population -- estimated at less than one percent of historic highs – would take over a year to filter the same amount of water. Therefore, its filtering impact on the Bay today is negligible.
Beyond the filtering function of oysters, oyster reefs also provide excellent habitat for aquatic life. Fish and crabs hide in the small crevices and holes created by the oysters and shells that make up the reef.
Two diseases that first appeared in the Bay during the 1950s, MSX and Dermo, are largely blamed for the declining population, killing off most oysters within three years. Environmental factors such as sediment runoff also contribute to poor reproduction and the loss of oyster habitat.
Efforts have intensified over the past two decades to restore the oyster population. Information on current restoration efforts and studies is available at http://www.dnr.state.md.us/fisheries/oysters/
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