Oyster reef restoration
Oyster reef restoration refers to the process of rebuilding or restoring of oyster reefs all over the globe. Over time, oysters have been negatively affected by environmental change, such as harmful fishing techniques, over harvesting, water pollution, and other factors. The results of these factors have been disease and ultimately, a large decline in the global population of oysters and the prevalence and sustainability of oyster reefs. Apart from the ecological importance of oyster reefs, oyster farming is an important industry, particularly in coastal areas. Both artificial materials and natural components have been used to rebuild the reefs in an attempt to regenerate the oyster population thus fostering the reformation of reefs.
Ecosystem and history
The first stage in an oyster’s life cycle is the free-swimming larval stage. After about three weeks, the larva attaches to a hard substrate—surface area to attach to—such as prop roots, dock pilings, natural rock, and other oysters becoming an oyster spat—oysters that have just settled to the bottom. A large number of oysters often join together, thus forming an oyster reef (also referred to as oyster bed, oyster mat). Once attached to a surface, oysters will stay there for the remainder of their lives.
Oyster beds provide a number of ecological, economical and recreational benefits to the environment. On the Atlantic coast of the United States, the Eastern Oyster acts as a keystone species by filtering estuaries and maintaining healthy coastal ecosystems. In addition to being a keystone species, oysters also serve as an indicator species—they are used to gather information on the overall health of the ecosystem.
Since the early Americas, oyster beds have been beneficial for the North American Indians, who harvested oysters for subsistence purposes, and for the European colonists in the region. Since the 19th century oyster beds have been vital for commercial harvests and have generated substantial income. However, the majority of oyster populations have greatly declined within the last century due to over-harvesting, dredging, increased sedimentation, invasive species, pollution and disease. It is estimated that more than 85% of oyster reefs are gone, making it the most threatened marine habitat in the world.
As a result, this has spawned a need for oyster restoration projects in order to revitalize the depleted natural resource of the oyster population. In response to this decline, many oyster restoration projects have been put into place throughout the southeastern United States. The projects develop a long-term strategy of sustained productivity for oyster reefs and restore the ecological role they provide to nearby reef habitats.
The first step in oyster restoration is to determine the locations for potential reefs. This is often done by comprehensive surveys that measure salinity levels, water quality, previous existence of oyster reefs, substrate conditions, prevalence of diseases, tidal range, oxygen concentration, algae concentration, prevalence of predators, accessibility and security.
Once the location is determined, cultch—fossilized shell, coral or other similar materials produced by living organisms designed to provide points of attachment for oysters—is often obtained from sustainable recycling programs. Used oyster and clam shells from farmers and restaurants are collected and disinfected by volunteers to be used in oyster restoration.
Once returned to the water, these recycled shells provide substrate for oyster larval eggs to begin populating oyster beds laid out by volunteers programs such as those implemented in Southwest Florida, North Carolina, South Carolina, Georgia Southern California, and Alabama. A common species of oysters used in oyster restoration is the Eastern American oyster (Crassostrea virginica), which is also called the American Oyster, Atlantic Oyster, Common Oyster, and Virginia Oyster.
According to the Southern Regional Aquaculture Center (SRAC), oysters in the southern part of the United States spawn when water temperatures are above 68 degrees. But they are affected more by the specific site where oyster restoration projects occur, the species of oysters used in a project, and if they are native to the surrounding area and disease free.
Commonly in the southeastern U.S., mangroves and other shoreline vegetation are often planted in conjunction with oyster restoration efforts to provide substrate – surface area to attach to – and reduce shoreline erosion resulting in less sediment deposits within estuaries.
Oyster restoration in public waters often requires permits and licenses from various agencies with requirements varying from state to state. Most often permits typically involve the U.S. Army Corps of Engineers, state natural resource agencies and state public health departments.
The typical desired outcomes of these restoration projects are the restoration of oyster reefs to produce a fully functioning, three-dimensional bed system that provides associated ecosystem services and biological functions, such as marine biodiversity, shoreline protection, sediment trapping, water quality improvement, and recreational fishing opportunities.
NOAA provides some of the major goals of an oyster restoration project:
- Augment commercial harvest
- Serve as habitat
- Improve water quality
- Increase or improve spat set in an area by creating oyster sanctuaries
- Maintain or increase biodiversity
- Restore ecological function
- Provide a barrier to prevent beach or shoreline erosion
- Protect and enhance sea grass restoration projects
Intertidal oysters act as a keystone species by maintaining a healthy coastal ecosystem. They filter the water and increase water clarity by extracting organic and inorganic particles. The filtration capacity of an average adult oyster is estimated to be 50 gallons per day. Oysters not only clean the water, but also act as effective shoreline buffers by dissipating the energy caused by boat wakes and waves. Oyster reefs also support critical fisheries by providing habitat for numerous species of fish, crustaceans and shellfish.
The ecological value of reusing oyster shells for oyster restoration projects is vital not only for producing zero waste, but also for diversifying and increasing the number of oyster beds in a given area. In addition to environmental benefits, oyster restoration is also economically beneficial since coastal communities rely heavily on oysters for profit and subsistence.
Environmental preventative issues
Some ancient reefs are used to make restorative oyster reefs in nearby sites. However, to reduce the risk of environmental damage when dredging, many projects tend to stay away from this method of transplanting. Another issue of environmental harm is placing invasive or newly introduced oyster species in an unknown habitat that can cause more harm than good. Therefore, it is important to correctly place oyster species in their respective habitats to prevent environmental harm to nearby oyster reefs. More information is available in local extension agencies within the state you live in.
Oyster reefs provide essential habitats for many ecological and economically important fish as well as invertebrate species. Healthy oyster populations improve the quality of water, which in turn improves commercial and recreational fishing, recreational boating, and ecotourism. Not only does oyster restoration create additional jobs through the duration of projects, but it also safeguards many other jobs ranging from marine construction to scientific research jobs. Dr. Paul Zimba, Director of the Center for Coastal Studies at Texas A&M-Corpus Christi said, "Oysters are an important ecological and economic resource. They create habitats for fish and shellfish, filter and clean bay waters, protect shorelines from erosion, and are a valued commercial fishery element."
The research in aquaculture has been a major contributor to the development of viable oyster strains to assist the commercial aquaculture industry and local ecosystems. The industry of aquaculture is booming with global profits exceeding $3,000,000,000 annually. Oyster restoration projects assist in the production of aquaculture harvests and have different procedural measures for different areas of the United States.
Aquaculture techniques vary geographically and represent regional differences. Some areas of the U.S. have enacted policies to lease out areas for aquaculture businesses to utilize the oyster-restored beds. These leasing policies will prove beneficial to job creation in coastal areas, improve the surrounding economy, and restore habitats where oyster restoration projects and commercial businesses occur.
All in all, aquaculture has and will continue to gain recognition for providing sustainable harvesting methods.
Oyster restoration has many recreational benefits. Improved water clarity and overall cleaner water greatly increases recreational fishing, boating and swimming. This allows locals and tourists to appreciate the environment around them.
In many parts of the southeastern United States volunteer efforts are responsible for oyster restoration. Community-based oyster restoration programs allow people to become knowledgeable on the important benefits oysters provide to an ecosystem. This volunteerism connects individuals with their environment as well as ensures the existence of oyster populations for future generations to appreciate. Areas of the southeastern United States, such as the coastal areas in the Gulf of Mexico, have a rich tradition related to oysters and other marine food that coastal areas provide. Oysters are part of the social culture in these areas and oyster restoration is a step towards preserving their traditions.
In addition to volunteering with oyster restoration projects, individuals with shoreline property—or those who have access to it—have the option of backyard shellfish gardening. This sustainable form of oyster harvesting allows for personal consumption or environmental enhancement and usually does not require special licenses or permits.
Specific examples in the southeastern United States
The Oyster Reef Restoration began in June 2009 and is expected to be completed by the fall of 2010. The project is funded by the National Oceanic and Atmospheric Administration (NOAA) as part of the American Recovery and Reinvestment Act of 2009. The goal of the project is to restore the important oyster habitat in the St. Lucie and Loxahatchee Estuaries, two of the largest brackish water systems on the east coast of Florida, where over the last 50 years oyster populations have declined by as much as 75%.
South Carolina Oyster Restoration and Enhancement (SCORE) is another volunteer oyster restoration movement. SCORE operates under the direction of the South Carolina Department of Natural Resources (SCDNR) and began in May 2001. The sites span approximately 200 miles (320 km) of the South Carolina coastline and have constructed 188 oyster reefs at 35 sites since the program began.
The Eastern Oyster populations of the Tar-Pamlico and Neuse River basins have plunged 97% to 3% of historic numbers throughout the last century. In response to this drastic change, the Citizens’ Oyster Gardening Project (COGP) began. COGP is an environmental demonstration project that encourages oyster gardening aimed to reestablish populations of native Eastern Oysters in North Carolina through education and aquaculture methods. Educational workshops teach volunteers how to measure water quality and give information on oyster gardening techniques as well as necessary tools and materials. Advocacy through networking by volunteers is key to COGP’s success.
- Pollack, Jennifer Beseres; Cleveland, Andrew; Palmer, Terence A. (July 2012). "A Restoration Suitability Index Model for the Eastern Oyster (Crassostrea virginica) in the Mission-Aransas Estuary, TX, USA.". PLoS ONE 7 (7): 1–11.
- Brown, Laura A.; Furlong, Jessica N.; Brown, Kenneth M. (March 2014). "Oyster Reef Restoration in the Northern Gulf of Mexico: Effect of Artificial Substrate and Age on Nekton and Benthic Macroinvertebrate Assemblage Use". Restoration Ecology 22 (2): 214–222.
- George, Lindsey; De Santiago, Kevin; Palmer, Terence (February 2015). "Oyster reef restoration: effect of alternative substrates on oyster recruitment and nekton habitat use.". Journal of Coastal Conservation (Springer Science and Business Media B.V.) 19 (1): 13–22.
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