Oyster Reefs
Table of Contents
Introduction
"As much as 85% of all oyster reefs globally have been lost in the last two centuries, making oyster reefs among the most threatened habitats in the world. A combination of overfishing, habitat destruction, and water quality degradation have conspired to significantly impact oyster reefs in the United States. While the status of oyster reefs globally is dire, concerted efforts to address water quality and recreate habitat – largely by recycling used oyster shells to create new substrate for juvenile oysters to attach to – have shown some promise of starting to restore wild oyster populations." - Naturally Resilient Communities
Oyster Reef Lifecycle
Oysters can live for 20 years, and once they die their shells can form the base for future oyster reefs. Baby oystrs or "spat" attach to hard surfaces including mangrove roots, and shells of other organisms. Over the generations, and as older oysters die off, oyster colonies can become hardened reefs, protecting other wildlife including seagrass and fish.
Carbon-Sinking Oysters
Dredging for oysters (an unsustainable harvesting method) has been shown to release greenhouse gases into our atmosphere, but oyster farming has been pinpointed as an effective way to sequester carbon. It takes oysters around 2-4 years to be considered "plate" sized.
In just two years the following amount of carbon can be sequestered:
Per oyster - 8.36388 grams of carbon
Per hectare - between 1,400 to 2,500 kilograms of carbon
Rewilding areas that have lost oyster reefs, can help sequester carbon while providing other benefits including erosion control, storm surge protection, and a reduction of ocean acidification.
How Oysters Mitigation Coastal Hazards
"Oyster reefs serve as natural breakwaters – their physical structure absorbs the force of waves, creating calmer waters on the shoreline side of the reef and reducing the impacts of erosion. Studies from the Gulf of Mexico have found that oyster reefs are capable of reducing the energy of high power waves by as much as 76 to 93 percent. The effectiveness of any single reef will depend on its size, orientation, and location. In northern latitudes, where reefs are entirely subtidal, their ability to reduce wave energy may be reduced." - Naturally Resilient Communities
Oysters are Water-Purification Specialists
"The water filtering capacity of oysters is another tremendous benefit. An individual oyster can filter plankton, nitrogen, and other pollutants from as much as 50 gallons of water per day, providing an enormous benefit to coastal waters that are increasingly impacted by runoff and pollution. Before suffering massive declines, its estimated that historically the oysters in the Chesapeake Bay could filter the entire volume of the bay once a week." - Naturally Resilient Communities
The Incredible Oyster Reef
10:08 minute video about oysters, how they support other species, how they protect wetlands, and what threatens them.
Useful Vocabulary
Oyster Castles - "Essentially modified concrete blocks that become living reefs as oyster larvae attach to them and grow. They reduce the impacts of future storms, provide habitat for wildlife and improve water quality."
Oyster Gardens - preeding projects/areas where volunteers raise spat into oysters for oyster reef projects.
Oyster T's - T-shaped rods which help suspend old oyster shells where spat can attach and be used in oyster gardens.
Spat - baby oysters.
Tombolo - "A tombolo is formed when a spit connects the mainland coast to an island. A spit is a feature that is formed through deposition of material at coastlines. The process of longshore drift occurs and this moves material along the coastline."
Major Threats
Deforestation Forests help keep water clean and cool, which is important for water quality even when it goes out to sea, where it effects biomes including oyster reefs.
Inadequate Erosion Control
Overharvesting of Oysters & Other Important Species
"Oyster dredges are intended to scrape the oysters off of the reef substrate at a faster rate but many times during that harvest the reef material is removed along with the oyster. Over time that results in a loss of elevation of that reef material and in most cases a reduced capacity to sustain oyster development year after year."
Climate Change
Acid Rain (thanks to livestock farming and industrial processes)
Livestock Waste
Ocean Acidification
Deforestation
Benefits of Oyster Reefs
Improved Water Quality
They reduce over nutrification from farm and garden run off as well as sewage.
They combat algae blooms
They can absorb microplastics, making them easier to remove from their ecosystems.
Reduce Erosion by reducing wave impact, absorbing the force, and protecting shorelines. They can protect shorelines from hurricane and storm surge damage.
Reduce Flooding
Encourage Increased Biodiversity
How Oysters Can Stop a Flood
5:50 minute video about the benefits of oyster reefs, including protection from flooding and storm surges.
Types of Oyster
Magallana gigas (commonly known as the Pacific Oyster) "is native to the Northwest Pacific including Russia, China, and Korea. It is the most widely cultivated and harvested shellfish species in the world, introduced to at least 52 countries. It has established breeding populations in the Northeast Pacific (US-Canada), Southwest Pacific (Australia-New Zealand), Northeast Atlantic-Mediterranean (Europe), Southwest Atlantic (Argentina-Brazil), and Indian Ocean (South Africa). In introduced locations, M. gigas often starts by being confined to culture areas, with only sporadic and limited reproduction, but later becomes a major biomass component and ecosystem engineer. This process, which has taken 3-10 decades, has occurred in British Columbia, Washington, the North Sea, the Atlantic coast of Patagonia, Hawaii, and Australia. In some cases, M. gigas poses risks to native oyster populations, including competition, hybridization, and introductions of associated organisms (e.g. parasites, fouling species and oyster predators)."
Indicator Species
Common Grass Shrimp
Keystone Species
Oysters A single oyster can pump and purify 50 gallons (227.3 Liters) of water a day through it's gills.
Phytoplankton
New York's "Billion Oyster Project"
3:27 minute video about the project.
Species Supported by Oyster Reefs
Anchovies
Croaker
Flounder
Herring
Sea Grasses
Shrimp
Silver perch
Speckled trout
Spot
Stone crab
Resources & Guides
International
This section is divided into general info and location-specific. If you don't find the info you need in the general section, then see if the location-specific resources could suit or be adapted to your area.
Center for Coastal Resource Management: Pre-Cast Reef Structures Includes general info, plus sections on suitable sites, and long-term guidelines.
Center for Coastal Resource Management: Shell-Based Reefs Includes general info, plus sections on suitable sites, and long-term guidelines.
Florida Oceanographic Society: Oyster Gardening includes and infographic of how spat are collected, and allowed to grow big enough for use in oyster reef projects.
Oyster Habitat Restoration: Monitoring and Assessment Handbook
Oyster Reefs as Carbon Sources and Sinks scientific paper with graphs and diagrams.
Setting Objectives for Oyster Habitat Restoration Using Ecosystem Services A Manager’s Guide (PDF) "This guide is accompanied by an online calculator. The interactive webpage can calculate the area of oyster habitat needed to restore a specified level of filtration and the number or weight of fish that would be produced from that area of restored oyster habitat."
Oyster Calculator "To use the calculator, first select a bay location from our database. If using your own site, select the closest site within our database to load oyster mass formula and fish benefits data."
Restoration Guidelines for Shellfish Reefs (PDF) "This publication is intended to provide foundational information to serve as a useful starting point for shellfish reef restoration."
Restoration and Protection of Coral and Oyster Reefs from the UN Climate Technology Centre & Network. The first page is an overview, but there are a lot of resources at the bottom of the page.
The Use of Non-Plastic Materials for Oyster Reef and Shoreline Restoration: Understanding What Is Needed and Where the Field Is Headed (PDF) "Oyster and shoreline restoration is occurring around the globe to recover lost ecosystem services. In the state of Florida, USA, dozens of estuarine habitat restoration projects are underway. These projects have traditionally relied on both natural and man-made materials, including plastics. As the impacts of plastics on marine ecosystems are better understood, practitioners are increasingly focused on plastic-free restoration..."
Videos
Mordecai Pilot Oyster Castle Project Part 1 of the videos exploring oyster castles, the blocks they are made of, and how the blocks and bags of oyster shells were inoculated with oyster spat before being assembling by volunteers at low tide. Structure shapes and their intended purpouses arediscussed.
Oyster Castle Living Breakwater Project~Phase 2 am 8:05 minute video showing how oyster castles are build, and how they can help rebuild coastlines.
Africa
European Native Oyster Habitat Restoration Handbook: UK & Ireland (PDF) "aims to provide foundational and practical guidance on the restoration and conservation of native oysters (Ostrea edulis) and native oyster habitat across the UK and Ireland. The guidance outlined throughout the Handbook is also of relevance to projects across the native oyster’s biogeographic range." This could be helpful for coastal countries of northern Africa including Algeria, Egypt, Libya, Morocco, and Tunisia.
The Gambia
Video: Protecting mangroves using old oyster shells | DW English
3:50 minute video talking about the damage inflicted on mangroves from oyster harvesting, vs the new methods being taught by the TRY Oyster Women’s Association, which are now helping to protect mangroves as well as human lives. The mangroves have started to recover, fish are returning, and locals are actively planting new mangroves.
Asia
European Native Oyster Habitat Restoration Handbook: UK & Ireland (PDF) "aims to provide foundational and practical guidance on the restoration and conservation of native oysters (Ostrea edulis) and native oyster habitat across the UK and Ireland. The guidance outlined throughout the Handbook is also of relevance to projects across the native oyster’s biogeographic range." This could be useful for western Asian countries including Georgia, Israel, Lebanon, Turkey, and Syria.
Europe
European Native Oyster Habitat Restoration Handbook: UK & Ireland (PDF) "aims to provide foundational and practical guidance on the restoration and conservation of native oysters (Ostrea edulis) and native oyster habitat across the UK and Ireland. The guidance outlined throughout the Handbook is also of relevance to projects across the native oyster’s biogeographic range."
Rich Reefs in the North Sea (PDF) "Exploring the possibilities of promoting the establishment of natural reefs and colonisation of artificial hard substrate"
Ireland
European Native Oyster Habitat Restoration Handbook: UK & Ireland (PDF) "aims to provide foundational and practical guidance on the restoration and conservation of native oysters (Ostrea edulis) and native oyster habitat across the UK and Ireland. The guidance outlined throughout the Handbook is also of relevance to projects across the native oyster’s biogeographic range."
UK
European Native Oyster Habitat Restoration Handbook: UK & Ireland (PDF) "aims to provide foundational and practical guidance on the restoration and conservation of native oysters (Ostrea edulis) and native oyster habitat across the UK and Ireland. The guidance outlined throughout the Handbook is also of relevance to projects across the native oyster’s biogeographic range. "
Scotland
SMEEF Restoration Toolkit "Whether you are starting your first coastal or marine restoration or enhancement project, or have been working on an established programme, this toolkit aims to guide you through the maze of supporting information available.
Each section covers the key facts and there are links to the latest advice. The Toolkit also enables you to create a bespoke action list for your group.
Please note this toolkit is a live document and will be updated regularly. If you believe there may be something missing or incorrect, please email us..."
North America
The Business of Restoration (PDF) "Examining the oyster reef restoration industry in the U.S. with recommendations for how conservation organizations can increase efficiencies and decrease costs to scale restoration efforts"
"Oyster reef restoration was assessed as an industry using similar approaches to private sector market studies. Practically, this means assessing the industry solely through a ‘business’ lens, and explicitly avoiding making any technical recommendations which others in the industry are more adept to make. Therefore, while this report may reference ecosystem service values, discuss substrate types, and other more technical elements, it does not comment on the efficacy of these decisions. This ‘business’ lens approach involves two main components: [1] conducting a current market assessment and [2] identifying ‘business’ opportunities to improve performance."Chesapeake Oyster Reefs, Their Importance, Destruction and Guidelines for Restoring Them (PDF)
A Guide to Olympia Oyster Restoration and Conservation "This guide identifies key environmental conditions that affect Olympia oysters. A qualitative evaluation of 28 embayments along much of the range of the species identifies the areas at risk due to low population sizes or unreliable recruitment, and characterizes patterns of exposure to stressors. The most frequently encountered stressors were sedimentation and predation. Competition, cold water temperatures, warm air temperatures, and freshwater inputs were also common concerns at many bays. Quantitative site evaluations incorporating oyster attributes and environmental conditions were conducted at six estuaries in California and Oregon to prioritize sites for conservation value and restoration potential. Development of an online site evaluation tool allows end-users to conduct similar evaluations in new regions, thereby guiding future restoration and management efforts."
NEMESIS "Welcome to the Smithsonian Environmental Research Center's National Estuarine and Marine Exotic Species Information System (NEMESIS). Here you will find information on marine and estuarine invertebrates and algae introduced to the United States."
Restoring Oyster Reefs in the Chesapeake Bay Takes Four Steps
Restoration Goals, Quantitative Metrics and Assessment Protocols for Evaluating Success on Restored Oyster Reef Sanctuaries (PDF) includes photos, graph, a map of Eastern US streams, plus a classification chart for rivers and creeks in Maryland and Virginia.
Florida
Florida Living Shorelines: Explore by Region "Click on a county to see examples of living shoreline projects constructed in the region, suitable plant species, and contacts to assist with design and permitting."
Maryland
Arundel Rivers Federation: Oyster Growers Manual (PDF) "The goal of this project is to make a contribution to the ecology of the river. The oysters you grow will be planted in a sanctuary where an oyster reef community of fish, crabs and other organisms can develop."
Oceana
Australia
Tasmania
Natural Resource Management South: Resource Library includes PDFs such as the Tasmanian Shellfish Grower Handbook
Substrates, Anchors, & Other Project Supplies
The following include supplies used by existing restoration projects. Being listed here is not a guarantee that they are "the best", only that they have been used by existing organizations at various stages in their programs.
The following are listed alphabetically.
Biodegradable Products
BESE "The products designed by BESE are made from waste streams, like potato mesh which is a leftover product from the chips industry." Their products include cable ties, mini reefs, reef paste which can be applies to many things and encourages recruitment, mesh, and BESE-elements which can be used to anchor coral, seagrasses, or even floating plantings.
Ceramic "Razorfish" Plates
The reef regeneration project off the shore of Kangaroo Island has used ceramic razorfish-style plates for oyster spat to attach to, much like they do to organic razorfish (a large bivalve mollusk species who buries their pointed end into the sand, with most of their shell above water, creating a divers ecosystem). An artist was asked to create razorfish-like plates for the restoration project, and spat have successfully attached to these.
Razorfish to the rescue: A Ceramic Solution to Restore Kangaroo Island's Native Oyster Populations
Gabions
"Gabions are cages made of galvanized steel that can hold around 30 pounds of oyster shell. ..."
"These cages are a plastic-free alternative to the industry-standard mesh bags we currently use to contain oyster shell, and they have larger holes that may offer better water circulation—which is great for live oysters." - Brevard Zoo
The gabions mentioned above a small enough to be picked up and moved by volunteers. In the video to the left, the gabions are much larger, and need to be lifted with heavy duty machinary.
Calcasieu Oyster Reef Restoration
2:46 minute video shows gabions full of oyster shells being lifted and placed on the site of a new oyster reef.
Oyster Bags
Many oyster restoration progras use cages or bags to keep oysters together instead of being scattered by wave or tidal action. Most of the examples we've seen while researching for this page involved plastic net bags, but these can release plastic into the environment. Alternatively you can use organic fibers such as the coconut fiber bag pictured in this article.
Basalt bags have also been used instead of plastic. Basalt being a rock which can be melted down into fibers.
Oyster Reef Restoration Project - Flume Testing
1:15 minute video showing how coconut fiber bags might hold up to real life waves, while holding oysters together till they can naturally stick.
Oyster Castle Blocks
Grow Oyster Reefs LLC offers 3D printed supplies including round disks call Spat Catchers, Reef Tiles, Reef Disks, Reef Tangle, Reef Rock, and Settlement Plates for your oyster growing projects. They are formulated from a concrete mix designed to provide early stage nutrition, and help grow oysters faster.
Sound Recordings
Despite having no brain, oysters have been found to prefer the sounds of a healthy reef. When their preferred sounds are heard, spat are more likely to settle down to begin their transformation into adult oysters.
Baby Oysters Follow the Crackling Sound of Snapping Shrimp "Though oysters may be brainless bivalves, they can “hear” and swim towards attractive sounds of the sea." Link includes a 1 minute playable clip of the shrimp audio.
To help demonstrate the different sounds of healthy vs. unhealthy reefs, we found the following two examples:
Sounds from a Degraded Oyster Reef 30 seconds.
Here's What A Healthy Coral Reef Sounds Like 4:01 minutes
Restoring Oyster Reefs with Marine Music
2:10 minute video explaining how scientists have played recordings of different ocean environments to oysters, finding which ecosystem sounds have encouraged the spat to settle down and begin colonization.
Spat Tree or "T"
These PVC poles are planted in appropriate areas with adequate water flow and salt levels. Then string or rope is attached at either end of the top bar, allowing oyster shells or similar substrate hang down, allowing oyster spat to collect and begin growing. The oyster shells (plates or rings) can then be removed and adopted by oyster gardeners or taken to labs or nurseries so they can safely grow before being placed on reefs.
Projects & Programs
Interested in joining or replicating existing projects or programs? Check out our growing international directory of programs and projects including spat nurseries/hatcheries, reef buildings, school programs, shell recycling drop offs or pick ups, and more.
Conservationists Work to Restore Hong Kong’s Oyster Reefs
2:26 minute video about the abandoned oyster farms being revived into oyster reefs to help revitalize Hong Kong's marine ecosystems and restore their water quality.
Organizations
Search our growing directory of organizations tackling the problems facing oyster reefs, and helping to rebuild existing or create new oyster reefs.
Maps
International
Oyster Habitat Restoration Monitoring and Assessment Handbook: Map Showing the Global Condition of Oyster Populations "with condition ratings based on the percent of current to historical abundance of oyster reefs remaining: < 50% lost (good); 50-89 % lost (fair); 90-99% lost (poor); > 99% lost (functionally extinct) (from Beck et al. 2009)."
Asia
Rich Reefs in the North Sea (PDF) "Exploring the possibilities of promoting the establishment of natural reefs and colonisation of artificial hard substrate" Maps of the UK, North Sea, some include parts of the Mediterranean, Black Sea, and Sea of Azov
Europe
European Native Oyster Habitat Restoration Handbook: UK & Ireland (PDF) Includes maps around the UK, for Europe in general, a North Sea map, the Dornoch Firth
Rich Reefs in the North Sea (PDF) "Exploring the possibilities of promoting the establishment of natural reefs and colonisation of artificial hard substrate" Maps of the UK, North Sea, some include parts of the Mediterranean, Black Sea, and Sea of Azov
The Netherlands
Platte Oester: Dutch Flat Oyster Consortium (POC) Projects "Our mission is to restore flat oyster (Ostrea edulis) beds in the North Sea." Scroll down to see the map of their conservation projects.
Shellfish Reef Restoration Pilots: Voordelta The Netherlands (PDF) Includes a satellite image and a map of the flats of Voordelta and the oyster reef projects.
North America
NOOC - Native Olympia Oyster Collaborative Story Map scroll down and click the stories or points on the map to learn more. This link offers a static version of the map.
North America and Caribbean Ecoregional Estimates of Condition (PDF) is one of the two maps in this document. Showing approximate health of ecoregions from Canada to some northern shores of South America.
USA
Oyster Calculator "To use the calculator, first select a bay location from our database. If using your own site, select the closest site within our database to load oyster mass formula and fish benefits data." This was included because there is an interactive map when you click "Select site", from which you can select your bay location and relevant info.
Delaware
The Delaware Estuary Living Shoreline Initiative "Presented by Partnership of the Delaware Estuary" Full of photos, interactive before/after photos, map of PDE installations, and more.
Florida
Florida Fish & Wildlife Conservation Commission: Marine & Estuarine Habitats Map Interactive
Florida Living Shorelines: Explore by Region "Click on a county to see examples of living shoreline projects constructed in the region, suitable plant species, and contacts to assist with design and permitting."
Restore Our Shores: Indian River Lagoon: Viable Sites Approved for Study
Georgia
Georgia’s Oyster Reef Interactive Map scroll down after clicking this link, to see the map.
Maryland
Maryland: Stations & Current Classifications this interactive maps shows orange for restricted areas, and green for conditionally approved harvesting.
MGO Tributaries "Locations of active MGO Tributary groups"
Oyster Recovery Partnership: Public Oyster Fishery Plantings "The data below shows ORP’s support for the public fishery since 2015. Mapped planting locations are approximations and not precise." Scroll down to see the maps and their data.
New Jersey
American Littoral Society: Shell Recycling Scroll down to see the interactive map
New York
How a New Program Is Restoring Oyster Populations maps of New York Harbor's oyster restoration projects.
North Carolina
The Coastal Resilience Decision-Support Tool "provides communities access to the best available science and local data on coastal hazards to visualize their risks and examine where nature can increase resilience and reduce risk through conservation and restoration activities."
The North Carolina Coastal Atlas is a collaborative effort to enable access to coastal data and inform coastal managers, scientists, students and the interested public. We provide selected geospatial data, visualization tools and thematic maps focused on coastal resources and hazards."
North Carolina Coastal Federation: Sanctuary Handout (PDF) This documents shows maps of existing oyster sanctuaries near Swan Island and North Carolina's sounds.
The North Carolina Shellfish Lease Siting Tool "created and maintained by the University of North Carolina Wilmington, is an interactive decision-support tool for the North Carolina coastline that will assist new or current growers in siting new or expanding shellfish operations by providing a simple tool to assess conditions based on existing datasets. The tool is designed to provide information to help potential shellfish growers determine site feasibility and help them identify potential risks and long-term suitability for particular areas. This project is a data visualization tool providing information on data specifically related to shellfish aquaculture including salinity, bottom type, depth soundings, shellfish growing area classifications, boat access areas, surrounding land cover and current shellfish growing operations."
Oyster Shell Drop-Off Sites Use the interactive map, or scroll down for the lost of locations. There is also a phone number for questions.
Oregon
The Netarts Bay Watershed "Habitat Study, Restoration Plan, and Limiting Factors Analysis" Includes a variety of useful maps.
South Carolina
Texas
Galveston Bay Foundation "Click the program area icons to learn more about what Galveston Bay Foundation does around Galveston Bay."
Virginia
VDH: Shellfish Harvesting Area Map this interactive maps shows red for restricted areas, and green for conditionally approved harvesting.
Oceana
Australia
Reef Builder: Rebuilding Australia's Lost Shellfish Reefs Scroll down to see a map of current and future sites.
Tasmania
Reef Builder South-East Tasmania Project: Native Oyster Reef Restoration (PDF) "includes maps of the reef restoration project in South-East Tasmania, as well as a Tasmania-wide map showing the catchment areas and pathways of the water ways which affect the reef sites."
New Zealand
Historic Mussel Beds "A history of the Firth of Thames dredge fishery for mussels: use and abuse of a coastal resource." Scroll down to see map of existing beds vs dredged areas.
South America
North America and Caribbean Ecoregional Estimates of Condition (PDF) is one of the two maps in this document. Showing approximate health of ecoregions from Canada to some northern shores of South America.
Grants & Funding
Europe
UK
Scotland
SMEEF Restoration Toolkit "Whether you are starting your first coastal or marine restoration or enhancement project, or have been working on an established programme, this toolkit aims to guide you through the maze of supporting information available.
Each section covers the key facts and there are links to the latest advice. The Toolkit also enables you to create a bespoke action list for your group.
Please note this toolkit is a live document and will be updated regularly. If you believe there may be something missing or incorrect, please email us..."
North America
USA
Delaware
Delaware Sea Grant "helps put together ecotourism and resilience investment strategy for Milford, Slaughter Beach"
North Carolina
Albemarle-Pamlico National Estuary Program "routinely offers grants which may be of interest to agricultural communities, coastal nonprofits, educators, engineers, local governments, planners and other watershed partners. In the recent past, APNEP has funded several outdoor classroom projects that serve the dual purposes of environmental education and water quality restoration. APNEP has also funded implementation projects that benefit stormwater runoff, coastal and watershed planning efforts, and best management practice implementation."
Permitting
Europe
Ireland
European Native Oyster Habitat Restoration Handbook: UK & Ireland (PDF) includes a map and listing of permitting info for the Republic of Ireland.
UK
European Native Oyster Habitat Restoration Handbook: UK & Ireland (PDF) includes a map and listing of permitting info for England, Northern Ireland, Scotland, and Wales.