Oyster Reefs—Habitat of the Month

What are Oyster Reefs?

Oysters are a type of shellfish that live in brackish and saltwater bays, estuaries, and tidal creeks. Their larvae typically settle on the shells of other oysters, forming dense, expansive clusters known as oyster reefs or beds. Oysters are considered a “keystone species” due to their critical roles in maintaining water quality and biodiversity and cycling water and nutrients within an ecosystem.

Not Just a Menu Item

Just about everyone has seen an oyster in the supermarket, if not eaten one on the half shell. Their popularity as a delicacy cannot be denied—in 2010, the United States harvested more than 28 million pounds of oysters valued at nearly $118 million and imported another estimated 12 million pounds from around the world.

What you might not know is that oysters aren’t just animals: they’re habitat, too. Species like mussels, barnacles, and sea anemones settle on their reefs. Not only does this increase biodiversity, but also serves as a veritable buffet for commercially important fisheries species such as striped bass and crabs.

Oysters are filter feeders: they filter plankton and particles from the water for food. At the same time, they also remove nutrients, chemicals, and other pollutants from the water. A single oyster can filter as much as 50 gallons of water per day.

Oyster reefs benefit humans, as well. They stabilize shorelines and prevent erosion and act as a buffer against hurricanes and tropical storms. They are also part of the rich cultural heritage of coastal communities, whose economies and populations grew in part because of the bountiful oyster reefs in their regions.

Oyster Reefs in Distress

Early U.S. explorers described the country’s oyster reefs as being so thick and abundant in areas that they were a navigation hazard. Today in the Chesapeake Bay—once one of the country’s most prolific oyster markets—oyster populations are estimated at only 1 percent of historic levels. Many factors have contributed to the demise of oysters in the United States, but three to note include:

• Over-harvesting
• Pollution/sedimentation
• Disease

Over-harvesting has not only reduced the number of oysters in the population, but also reduced the amount of space available on which new larvae can settle, thus perpetuating the decline of the population. Also, reducing the height of the reefs means that sediment can more easily cover and smother the immobile oysters, with increased sedimentation from land development and erosion exacerbating the problem.

Land use practices leads to an increase in nutrients in surface runoff that make their way into bays and estuaries. These nutrients can cause massive algal blooms that deplete oxygen from the water and create “dead zones” where animals like oysters and other shellfish are unable to survive. With the animals already stressed from over-harvesting, pollution, and sedimentation, disease is often the final nail in the coffin.

The loss of oyster reefs means more than just the loss of a popular dinner item.  It also means that we lose critical habitat for sustaining other commercially important species and species important to ecosystem stability. We lose a whole host of ecosystem services such as the oyster’s ability to provide storm protection and act as a natural filter in our bays and estuaries. And sadly, we lose a part of our culture and way of life.

NOAA is Working to Protect and Restore Oyster Reefs

NOAA’s Office of Habitat Conservation is working all along the East, West and Gulf Coasts to protect and restore oyster populations. The NOAA Chesapeake Bay Office offers Geographic Information System (GIS)-ready acoustic mapping products that identify current distribution, structure, and quality of oyster habitat. The NOAA Restoration Center has supported more than 200 shellfish restoration projects. The office is also collaborating on a national shellfish initiative to increase shellfish populations through restoration, aquaculture, and science activities, thus, stimulating coastal economies and improving ecosystem health.

Posted on 12/14/2011