New study examines ecological and coastal restoration benefits of oyster reefs
By Alisha Renfro, National Wildlife Federation
“Oysters are the most tender and delicate of all seafoods. They stay in bed all day and night. They never work or take exercise, are stupendous drinkers, and wait for their meals to come to them.” – Hector Bolitho
Oysters are remarkable organisms. Not only are they delicious, but each oyster can filter up to 50 gallons of water per day, which provides food for the oyster and improves local water quality. A collection of oysters form an oyster reef, which can provide food and habitat for a wide variety of fish and birds. In addition to these benefits, oyster reefs can also be an important tool for coastal restoration.
Oyster reef restoration project. Credit: NOAA.
Oyster barrier reef restoration can reduce the erosion and retreat of nearby shorelines. An alternative to rocks in some areas of coastal Louisiana, oyster reef restoration can be a low maintenance project, as reefs can build themselves vertically over time, helping them keep pace with rising sea levels.
The benefits of oyster reef restoration can be great, but are all those benefits present as soon as the reef restoration project is finished or do they develop over time? A study published this year in Ecological Engineering, “Temporal variation in development of ecosystem services from oyster reef restoration,” examines the development of oyster reef benefits over time, including improved water quality, stabilization of nearby shorelines and use as fish and bird habitat.
In the study, led by Megan La Peyre, researchers built six experimental oyster reef projects along the shoreline of Sister Lake in Terrebonne Parish, La. The oyster reefs were created using shell material. The researchers found that:
- Reefs were populated by oysters and other filter feeding organisms that provided water filtration benefits within the first year of post-project construction and continued for the duration of the study.
- Shoreline stabilization benefits provided by the restored reef to nearby marshes varied with results suggesting that shoreline stabilization benefits only occurred during periods of high winds and more powerful waves.
- Created oyster reefs immediately provided habitat and had increases in the abundance of fish species associated with them. This remained consistent throughout the study.
Forming bagged oyster shell reefs. Credit: NOAA.
The results of this study suggest that oyster restoration projects can provide multiple benefits to the ecosystem that surrounds them fairly quickly after their construction, but that their ability to stabilize nearby shorelines may be limited in areas where waves are small but persistent. However, the researchers in the study suggest that modifications to the design and footprint of oyster reef restoration projects exposed to low energy wave may increase the shoreline stabilization benefits and should be explored further.
Oyster barrier reef restoration projects are an important component in our arsenal of coastal restoration tools. Prominently featured in Louisiana’s 2012 Coastal Master Plan, this project type can have multiple benefits under the right conditions. However, like all types of restoration projects, there are factors that can limit project success. Oyster reef restoration projects depend on the recruitment and survival of oysters, which flourish under very specific conditions. Water that is too cold, too fresh, too salty or doesn’t have enough oxygen can limit the success of the project – if not dooming it to complete failure.
No one type of restoration project is the cure-all for combatting the rapid loss of land in coastal Louisiana. Instead, we need to use a combination of science-based projects in our restoration toolbox to staunch the rapid loss of our coast and build a more sustainable future.