Oyster Reefs in Georgia

UGA Marine Extension and Georgia Sea Grant are leading oyster reef restoration initiatives to help revive the state’s oyster industry.

Oysters are vital for both the health of aquatic ecosystems and development 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 the UGA Marine Extension and Georgia Sea Grant have successfully improved water quality and marine health in designated areas.

Oyster Mapping

Oyster mapping determines the location and acreage of live oyster reefs and works to aid in conservation and resource management of reefs along the coast. Through geographic information systems (GIS), researchers can survey the distribution of oyster reefs along the Georgia coastline and establish the optimum sites to create newly restored oyster habitat. These results assist restoration projects by providing baseline data about habitat conditions and distributions at each location. Data from GIS and handheld GPS also helps researchers monitor water quality, assess the geography of shorelines and plan management strategies for the future of coastal resources.

Artificial Oyster Reefs

Artificial oyster reefs reduce shoreline erosion, filter out contaminants and improve water quality.

Constructing Artificial Reefs
As part of the G.E.O.R.G.I.A (Generating Enhanced Oyster Reefs in Georgia’s Inshore Areas) program, community-based restoration projects have created new reefs and raised public awareness. The shells are first collected from restaurants and private oyster roasts and taken to a collection center. Coordinated by UGA Marine Extension and Georgia Sea Grant, volunteers prepare the shells for construction using a variety of methods. These methods include the bag method, bag/pallets, crab traps and living shorelines. The effectiveness of artificial reefs depends on a variety of different factors: temperature, oyster growth and oyster survival, as well as shell heights and widths.

Using Artificial Reefs to Control Water Quality
Non-point source pollution is a type of water pollution that comes from a variety of diffuse sources. Urbanization, agricultural processes and improper discharge of sewage are all types of non-point source pollution that eventually end up into coastal waters.Research in the UGA Environmental Health Science department, funded by Georgia Sea Grant, has been investigating the possible benefits oysters have on the restoration of coastal communities through the filtration of possible contaminants from coastal septic tanks.

Beach Creek Restoration Project
Beach Creek, Jekyll Island, is the site of a successful bioremediation project that worked to increase the shellfish population and filter out bacterial contaminants. In continuation of G.E.O.R.G.I.A, this community-based restoration program worked to increase the shellfish population and filter out excessive bacteria in the creek. The project successfully raised awareness and served as a tool to educate the community about local water quality issues.

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.

Oyster Restoration

Oysters are considered ecosystem engineers, providing essential fish habitat and reducing phytoplankton and pollutants in the water column through filtration.

Eastern oysters (Crassostrea virginica Gmelin, 1791) are a keystone species, and an essential component of the estuaries in the southeastern U.S.

In response to the loss of oyster habitat, UGA Marine Extension and Georgia Sea Grant began the G.E.O.R.G.I.A. project in 2004. Through G.E.O.R.G.I.A., oyster shells are collected from private oyster roasts and restaurants, and then bagged and planted in the estuaries to provide habitat for oyster spat to adhere to. Placement of oyster bags in the field occurs in April and May at the start of the six month long oyster spawning season.

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