Oyster Reefs in Georgia
Marine Extension and Georgia Sea Grant is restoring oyster reefs to support healthy coastal ecosystems.
Oysters are vital for both the health of aquatic ecosystems and resilience of coastal communities. They provide essential fish habitat and shelter for a number of other living organisms, filter pollutants from water and are fished both recreationally and commercially. Oyster reefs also are popular sites for recreational fishing for spotted sea trout, red drum and black drum.
Natural History
The Eastern Oyster (Crassostrea virginica) is native to the eastern coast of America from St. Lawrence, Canada to the Yucatan Peninsula and the West Indies. In Georgia, Eastern Oysters were once in abundance and heavily fished along the coastal estuaries during the late 1800s and the early 1900s. In 1908, Georgia led the nation in oyster harvesting, primarily for the oyster canning industry.
However, their importance has declined since the 1930s because of overharvesting, and the industry serves only as a supplemental fishery resource today. Since the decline, there have been changes in the total area and decreases in total acreage of reefs, which is due to a variety of factors.
However, oyster reef restoration initiatives by Marine Extension and Georgia Sea Grant are successfully improving water quality and fish habitat.
Oyster Reef Restoration
Oyster reefs are vital habitats supporting biodiversity, water filtration, and shoreline stabilization. By putting oysters back in the water, we can enhance Georgia’s natural oyster population, protect communities against erosion, increase environmental literacy, and provide opportunities for community engagement in shell recycling and reef restoration.
We Recycle Shell
In response to the loss of oyster habitat, Marine Extension and Georgia Sea Grant launched We Recycle Shell, a statewide shell recycling initiative in partnership with Georgia DNR Coastal Resources Division and the nonprofit organization Shell to Shore. With the help of restaurants and the public, We Recycle Shell is diverting shell from the landfill and returning it to Georgia’s estuaries to serve as a foundation for new oyster reefs.
Importance of Reefs
Oysters are considered to be a keystone species, critically important in their communities and ecosystems. Here are some of the benefits that reefs provide:
Oyster reefs play a significant role for essential fish habitats, providing shelter for a wide variety of fish and invertebrate species.
- Oyster reefs play a significant role for essential fish habitats, providing shelter for a wide variety of fish and invertebrate species.
- Oysters are considered to be a keystone species, critically important in their communities and ecosystems. Their presence plays a crucial role in ecosystem development, providing a hard substrate for other organisms to settle, attach to and grow.
- Erosion is one of the biggest environmental threats in the world affecting estuarine ecosystems along coastal regions. To protect salt marshes, oyster reefs can be situated between shores and marshes to act as an excellent barrier against the tidal currents and waves produced by wind and boat wakes, which are the main causes of erosion.
- Oysters are filter feeders, feeding on phytoplankton and detritus in the water. Additionally, they cycle nutrients in marine systems through biodeposition. The oyster’s ability to remove chemical compounds from the environment is very important for the maintenance of healthy ecosystems. Oysters also have been known to filter out bacteria and viruses known to cause disease. In fact, a single oyster is capable of filtering out as much as 30 quarts of water a day.
Oyster Life Cycle
Oyster reef development occurs in four stages: initial colonization, clustering phase, accretionary phase and maturation. The initial colonization occurs with the settlement and growth of an oyster spat (larval baby oyster) and small, scattered clusters on a suitable substrate with a sufficient flow of water. The clustering phase occurs when more oyster larvae settle and attach to both dead and live oyster shells. Each small colony comprises three to seven generations of oysters, although the majority dies from overcrowding and suffocation.
Development of the oyster reef continues with the accumulation of live and dead oysters shells within the water level of the intertidal zone. A mature oyster reef may take a century or more to form and has an uninhabited central zone with living oysters occupying the periphery of the reef.
Oysters reproduce by broadcast spawning, in which both sperm and egg are released into the water. This process is seasonal and is affected by the water temperature, salinity and other physicochemical interactions.
Oysters start their reproductive cycle in January in Georgia and reach sexual maturity by April. In mid- to late-April, oyster begin to spawn by releasing their eggs or sperm into the water column. In Georgia, oysters spawn from April to September. Oyster spats reach sexual maturity in three to four months in Georgia and may spawn in fall. After spawning, oysters grow rapidly in fall and the cycle starts anew in January.
After spawning occurs, spats will settle on a hard, clean substrate where they rapidly grow and reach sexual maturity. Within two months, high levels of settlement occur on existing reefs, which create competition between spats for space to grow on the reefs as well as for food resources. In Georgia, recruitment may be very high with records of as many as 204,700 spats per meter squared settling in a month.