Restored oyster reefs function as living shorelines to reduce wave energy in intertidal marshes

Abstract

Many researchers have turned to “living shorelines” as a solution for coastal erosion, where foundational species such as oyster reefs are used to stabilize shorelines while concurrently restoring ecosystem function. However, few studies quantify the ability of oyster reefs to physically diminish wave energy, especially those constructed with traditional restoration methods in intertidal zones. In May 2023, two oyster reefs were constructed using spat-on-shell in the intertidal Savannah River (Savannah, Georgia, USA) which experiences significant recreational and commercial vessel traffic. Reefs were constructed at mean tidal height 1–2 m from the marsh edge to reduce wave energy as it approached the shoreline. We monitored biological condition (live oyster coverage, size, and abundance) on the reefs for approximately 18 months and quantified the energy flux of waves offshore and onshore of the reef using continuous water pressure measurements. Results indicate that constructed reefs decreased wave energy by up to 40 % compared to non-reef control sites and experienced live oyster coverage of 17–40 % almost 18 months post-deployment. This is one of few studies to quantify the efficacy of oyster reefs at diminishing wave energy in intertidal systems, and the first to do so in Georgia, which has a relatively shallow intertidal system due to its location on the South Atlantic Bight. Using oyster reefs as living shorelines can effectively diminish wave energy approaching marshlands in a river system, suggesting that constructed oyster reefs in coastal areas vulnerable to anthropogenically-caused erosion could potentially mitigate shoreline loss while bolstering oyster restoration efforts.