Living Shorelines

 

Tidal marshes are vital to the overall health of the Delaware Estuary. They act as the estuary's kidneys by filtering water. They act as the estuary's maternity ward by providing a variety of animals with spawning sites, nurseries, foraging areas, and nesting grounds. And when waters rise, marshes act like sponges, retaining floodwaters and buffering against powerful storm surges.

Our tidal marshes are being lost or degraded due to a variety of factors. One of these is erosion associated with sea level rise and boat wakes. Marshes often cannot keep pace. Another widespread problem is the degradation of interior areas and their conversion to open water.

     
By September of 2008, (from left to right) bags of oyster and clam shells, coconut-fiber logs, and coconut-fiber matting are being used to prevent the tide from eroding marshland into the Maurice River outside Bivalve, New Jersey. Note the build up of mud behind the logs. After months of preparation, researchers from the Partnership for the Delaware Estuary and Rutgers University install what they hope will become a “living shoreline” along Bivalve, New Jersey’s Maurice River in July of 2008.

Marshes usually move inland when sea level rises. However, marshlands are now unable to do this because of human development along shorelines. Taken together, it's easy to see how marshes are being lost.

One technique that may help marshes keep pace is to work with nature to enhance or restore shellfish reefs that line the edges of wetlands. Such communities are often capable of buffering marshes from wave action, slowing erosion, and buying more time for marshes to accumulate in place (vertical accretion) or move inland (horizontal relocation).

What is the Delaware Estuary Living Shoreline Initiative (DELSI)?
The DELSI is a pilot project designed to stabilize eroding shorelines of tidal marshes. We are developing tactics where intertidal shellfish such as ribbed mussels are used to form a natural breakwater. This "living shoreline" traps sediment and absorbs waves that would otherwise wash away plants. The goal of this project is to provide an economical approach to communities in the Delaware Estuary that are struggling to combat the erosion of their tidal marshes.

How can mussels stabilize and restore shorelines?
Inside the marshes of the mid-Atlantic region, ribbed mussels (Geukensia demissa) are kingpins, collectively outweighing all other animals combined. Like many bivalve shellfish, these are referred to as "ecosystem engineers" because they have the ability to build their own habitats and transform the landscape for other species. The DELSI is attempting to take advantage of this unique "mussel power."

Ribbed mussels bind to the roots of vegetation and can form clusters as dense as hundreds per square meter. In exchange for this shelter, mussels fertilize marsh plants and trap sediment for their use.

Where is the DELSI being implemented?
Study sites are being targeted between the Maurice River and Cohansey River watersheds of southern New Jersey. Installations have only been completed to date at the Maurice River. The Partnership for the Delaware Estuary (PDE) hopes to expand the DELSI in time using the lessons being learned through pilot studies.

How is the DELSI being implemented?
Treatments consisting of coconut-fiber logs and mats were first deployed in 2008 in areas experiencing various levels and types of erosion. Tests reveal that mussels attach to the fibers of these products similar to the way they attach to marsh plants. In addition, bagged oyster and clam shells and coated wooden stakes are also being tested as potential treatments.

The PDE is currently monitor the performance of each tactic to determine which attracts the greatest amount of ribbed mussels and other animals, and which has the most benefits for marsh plants. Elevation is also being monitored to determine if marshes are sinking, eroding, stabilizing, or rising vertically.

Beginning in 2009, scientists will conduct tests to determine if living-shoreline development can be accelerated by "seeding" treatments with hatchery-born mussels and plants salvaged from marsh clumps that have already eroded away. Expansion to additional study sites in the tidal Delaware Estuary is also expected if additional funding is found.

Who is involved?
The PDE is collaborating with Rutgers University and other non-governmental organizations and academic institutions to carry out the DELSI. Support for this work has been generously provided by the National Fish and Wildlife Foundation, New Jersey Department of Environmental Protection, New Jersey Sea Grant, and the U.S. Environmental Protection Agency’s Region 2 Office.

If you would like more information about this project, please contact Angela Padeletti at (800) 445-4935, extension 103, or APadeletti@DelawareEstuary.org.