Engineering wave climate produces additional seagrass cover and in-kind services prior to anticipated project-related effects

CSA Ocean Sciences Inc. (CSA) has been contracted by the State of North Carolina Department of Transportation to conduct novel seagrass enhancement using the manipulation of wind wave energy to provide new and sustained seagrass acreage in anticipation of unavoidable impacts. The Bonner Bridge, which connects Pea and Bodie islands at the Oregon Inlet, is a lifeline for tourism and tropical storm evacuation of the North Carolina northern outer banks—has reached its engineering limits and is slated for replacement. The least impact estimated from the new bridge alignment still requires the recovery of no less than 1.28 acres of highly productive seagrasses (eelgrass [Zostera marina] and shoalgrass [Halodule wrightii]).

Approved by both federal and state regulatory agencies, this project will build on extensive research previously conducted by current CSA staff in order to exploit and manipulate the relationship between seagrass bed patchiness and waves and currents as an enhancement strategy. Using wave forecasting techniques to guide the size and location of a 500-ft long wave break, CSA will design and install the wave break among chronically patchy seagrass beds near the bridge. This will alleviate disruption of seagrass beds from waves and allow the beds to coalesce, ultimately creating more complete seagrass cover of the estuarine seafloor. Added seagrass cover provides increased nursery and refuge areas for ecologically and economically important fish, shrimp, and crabs as well as increasing their abundance. Importantly, through this ecological engineering approach to seagrass enhancement, ecosystem services are provided even before any existing habitat is disrupted—a vital consideration in resource management where limited opportunities exist for enhancement. This novel approach provides a new opportunity to recover seagrass habitat loss associated with unavoidable project-related effects as well as in the face of declining seagrass cover globally.

For more information on this project or regarding our habitat mitigation services, please contact Dr. Mark Fonseca at +1 (772)-219-3065.