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Oysters

Common Name: Eastern Oyster, Common Oyster, Atlantic Oyster, Virginia Oyster

Scientific Name: Crassostrea Virginica

10.03.11news-flickr-oysters-edit

Range:

Can be found as far north as the Gulf of St. Lawrence in Canada and south to the Caribbean and South America.

Physical Description:

The eastern oyster is a bivalve, meaning it has two rough shells that enclose and compress its soft body. Its shell length reaches between 8 and 10 inches long. The top shell is flat while the bottom shell is typically concaved or cupped and they vary in color from white to gray to tan. They have specially evolved respiration and digestive systems which allows them to simultaneously filter out food while they breathe in water.

Habitat:

Usually found in the intertidal and subtidal zones along muddy bays, harbors, and estuaries. The intertidal zone is the coastal area that is either submerged or unsubmerged with water depending on the height of the tide. The subtidal zone is the coastal area that is submerged under water most of the time, but may be exposed if the tide is extremely low.

Seasonal conditions can vary greatly but oysters are well adapted to survive. They can tolerate low temperatures, as low as 25°F, by closing their shells tightly and waiting for conditions to warm. Conversely, they are known to thrive in temperatures reaching 80-85°F. In addition, eastern oysters can withstand high fluctuations in salinity. However, the optimal salinity for growth and reproduction is 10 - 28 ppt. Larvae will not settle and metamorphose into spat when salinity is less than 6 ppt (brackish estuary). Adults can live in salinities up to 35 ppt (ocean salinity).

Environmental Importance:

Oysters are considered a “keystone” species or “environmental engineers”, meaning they have a disproportionately large effect on its environment compared to its relative abundance. Oysters influence nutrient cycling, water filtration, habitat structure, biodiversity, and food web dynamics.

As filter feeders, Oysters consume nitrogen-containing compounds (nitrates and ammonia), phosphates, plankton, detritus, bacteria, and dissolved organic matter, removing them from the water. Multiple studies have shown that individual oysters can filter up to 50 gallons of water per day. This assimilation of nitrogen and phosphorus into shellfish tissues provides an opportunity to remove these nutrients from the environment and improve overall water quality.

Oysters are reef building organisms. Juvenile oysters (also called spat) attach (with a glue-like substance) themselves to rocks, shells, or even other oysters. After time, this accumulation of oysters and shell forms a reef. Hundreds of animals, such as sea anemones, crabs, and fish inhabit oyster reefs. Many of these animals are prey to larger animals, including commercial fish stock, such as striped bass, summer flounder, and black fish.