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Oyster Reef Habitat

Oysters live in salty or brackish coastal waters, clustering on older shells, rock, piers, or any hard, submerged surface. They fuse together as they grow, forming rock-like reefs that provide habitat for other marine animals and plants.

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Underwater view of an oyster reef
A restored oyster reef in a tributary of the Chesapeake Bay provides habitat for a number of species. Credit: Oyster Recovery Partnership.

The Value of Oyster Reef Habitat

Oysters begin life as free-floating larvae—tiny, swimming creatures. Before long, they settle down and attach to a solid surface where they will grow for the rest of their lives. Rocks, old shells, wrecks, and piers accumulate oysters that grow together, shell upon shell. As the reef takes shape, it becomes an excellent shelter for other sea life.

Oyster reefs create important habitat for hundreds of species. Organisms like mussels, barnacles, and sea anemones settle on them, creating abundant food sources for commercially valuable fish. Oyster reefs provide habitat to forage fish, invertebrates, and other shellfish. They also provide a safe nursery for commercially valuable species including:

Oysters are a crucial component of global ocean health. These animals filter and clean the surrounding water and provide habitat, food, and jobs. In some places, oyster reefs can serve as barriers to storms and tides, preventing erosion and protecting productive estuary waters.

Ongoing threats to oysters mean that, unless deliberate efforts are made to protect and restore them, we are in danger of losing the benefits oyster reefs provide. When oyster reefs are only used as a place to harvest commercial oyster meat, they can become degraded. When they are restored and managed as a sustainable resource, oyster reefs and the habitat they provide can contribute billions of dollars in value to the economy.

NOAA has identified oyster reef restoration as a conservation priority. We work with partners to restore native oysters and regain the critical ecosystem functions they provide across the United States.

Benefits of Oyster Reef Habitat

Habitat for Other Species

The structure that oyster reefs create provide crevices that fish and crabs use to hide from predators. Oyster reefs are also a great place for smaller forage species to live. Many of the species that spend time around oyster reefs are recreationally and commercially valuable.

Water Quality

Besides being seafood, oysters make waters healthier. Because oysters feed by filtering algae from the water, they function as a natural filter and improve water overloaded with nutrients. Under certain conditions, a single oyster can filter up to 50 gallons of water per day. The clearer, cleaner water can support plentiful underwater grasses, which—like the oyster reef—create a stable bottom and a safe, nurturing habitat for juvenile crabs, scallops, and fish.

Storm Protection

In some locations, oyster reefs can protect underwater vegetation and waterfront communities from some effects of waves, floods, and tides. Well-established eelgrass beds help stabilize the bottom, providing additional resilience against wave action. Healthy reefs and established vegetation protect valuable habitat. Depending on where the reefs are located, they may also be able to reduce wave energy, prevent erosion, and fortify wetlands as a protective barrier.

Seafood

Oyster cultivation and harvest provide significant economic value to regional coastal communities. Farmed oysters, clams, and mussels account for about two-thirds of total U.S. marine aquaculture production. In some areas, there is a wild fishery for oysters as well. Research has shown that restored oyster reefs can provide significant economic benefits as well.

Challenges for Oyster Reefs

Oysters were once plentiful in coastal areas throughout the country. In 1607, when Captain John Smith explored the Chesapeake Bay, there were oyster reefs so prominent, ships had to navigate around them. When Henry Hudson arrived in New York in 1609, the harbor’s oyster reefs were the largest source of oysters worldwide. 

Today, however, oyster populations are at historic lows. Erosion from development, wetland loss, and excessive nutrient pollution have proved devastating for the shellfish. Diseases have caused problems, too. Overfishing and outdated harvest methods have destroyed or damaged reef structures and reduced oyster populations. Unsustainable harvesting habits and a steady decline in water quality have led to greatly diminished oyster reef habitat on all our coasts.

Unsustainable Harvesting

Dredges and tong harvesting, which scrape living oysters off the reef, can destroy reef height and structure. It may take decades for a reef harvested with these methods to recover, diminishing habitat for young fish and crabs. Continual dredging in Atlantic Coast estuaries has resulted in significant loss of three-dimensional reef structures. Overfishing has reduced many oyster reefs to a thin layer close to the bottom. But oysters grow faster and larger when they are higher in the water column, atop reef structures.

Pollution

Many factors adversely affect water quality and oyster reef health. Runoff and erosion from industry, farming, and development contribute to lower salinity, low oxygen levels, and silt overload. Waste, toxins, and excess nutrients end up in the water, weakening oysters and increasing the spread of disease. Sedimentation reduces available nutrition and silts over the hard bottom habitat that these shellfish require. As oysters decline in health and numbers, their remarkable ability to filter water is diminished, resulting in poorer water quality. The cycle is difficult to reverse.

What We Do

We Protect Oyster Habitat

NOAA does extensive research on the science and techniques behind oyster restoration to address decades of reef damage and loss. To bolster oyster populations and oyster reef habitat, we map oyster bed conditions, monitor water quality, and share our findings with industry and conservation partners.

Turning the tide on the oyster decline requires cooperative efforts from committed partners. We play an active role in convening workgroups, establishing goals, and measuring progress. We also offer grants for developing oyster aquaculture and habitat improvement. Our partners include:

  • Local and national waterway and oyster organizations
  • Universities
  • State wildlife and environment officials
  • Federal agencies, such as the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers

We Restore Oyster Habitat

The Office of Habitat Conservation’s NOAA Restoration Center provides funding and technical assistance to habitat restoration projects across the country, including oyster restoration efforts. The NOAA Restoration Center has funded more than 70 oyster restoration projects in 15 states. 

Some of our restoration techniques include:

  • Quickly distributing large amounts of shell with high pressure hoses to provide a suitable base for oysters to attach to and grow.
  • Constructing a linear reef of shell and rock to stabilize the shoreline and protect seagrass plantings behind the reef, enhancing shoreline stability and providing additional habitat for other reef inhabitants.
  • Collecting and bagging oyster shell for use as cultch—the mass of stones, shell, and grit that oyster beds are made of—for spat. Like a quick-start habitat, these bags of oyster shell will help establish new reefs in intertidal areas.
  • Creating hatcheries to provide seed oysters in areas where oyster reproduction is nonexistent or unreliable. This will establish new reefs and improve local water quality.

We’re Part of the World's Largest Oyster Reef Restoration Effort

In the Chesapeake Bay, oyster populations are only at about 1-2 percent of historical levels due to disease, pollution, habitat loss, and overharvesting. The NOAA Chesapeake Bay Office is an active partner in the Chesapeake Bay Program’s work to restore oysters in 10 Chesapeake Bay tributaries by 2025. We lead the workgroups in Maryland and Virginia that coordinate this large-scale restoration effort. While there is still work to be done, we are well on the way.

As part of this effort, the NOAA Chesapeake Bay Office conducts sonar surveys and develops analyses of existing habitat. This information helps planners decide where to restore oyster reefs and track reef health after the restoration is completed.

We measure the success of oyster restoration projects against high standards to track things like reef size, complexity, oyster density, and reef biomass. To ensure there are enough oysters in a tributary to produce a self-sustaining population, these projects are significantly larger than similar projects completed only a decade ago.

Since 2011, NOAA has worked with partners to restore more than 1,200 acres of oyster reef in the Chesapeake Bay. And recently, using sonar and other techniques to track the health of these restored reefs, scientists noted that six years after restoration was completed, the vast majority of the reefs met the criteria for oyster density, biomass, reef footprint, and reef height (PDF, 25 pages).

We also have conducted and funded research to quantify the benefits restored oyster reefs bring to both the ecosystem and our economy.

We Partner to Support Oyster Reef Habitat

NOAA’s community-based oyster restoration projects draw strength from partnerships with other federal agencies, as well as local stakeholders. Local organizations are especially important because they engage their members in volunteer efforts.

In the Pacific Northwest, for example, we work with tribes, states, the shellfish industry, and local organizations to rebuild dense, breeding populations of Olympia Oysters in Puget Sound. NOAA maintains a native shellfish hatchery, providing seed stock for restoration efforts. 

Nationwide, nearly 17,000 volunteers have participated in this and other NOAA oyster restoration projects.

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Last updated by Office of Habitat Conservation on 02/04/2022