Do Small, Patchy, Constructed Intertidal Oyster Reefs Reduce Salt Marsh Erosion As Well As Natural Reefs?

Abstract

AbstrAct:One ecological service that oyster reefs provide is stabilization of shorelines through reduced wave energy and erosion from boat traffic, storms, and predominant wind direction. Additionally, increasing sedimentation can enhance the growth of emergent marsh vegetation which further stabilizes unconsolidated sediments. A 21 mo study of constructed (with only 30-35% coverage) and natural oyster reefs in 3 bayous in the Grand Bay National Estuarine Research Reserve (NERR) suggested constructed reefs benefit this retrograding deltaic ecosystem. The marsh edge adjacent to all constructed reefs was less eroded (mean = 0.043 m) than edges adjacent to natural reefs (mean = 0.728 m), although all natural and constructed sites, regardless of bayou, illustrated large variations in marsh edge growth. The marsh edge in constructed sites in one bayou retreated more than in the other bayous, most likely due to its coarser sediments, greater boat traffic, and its apparent higher energy location within the landscape. By the end of this study, the ecological function of constructed oyster reefs in all bayous, as measured by marsh edge erosion reduction, was equivalent or exceeded the function in nearby natural oyster reefs. The physical structure of the reef further served to reduce erosion and marsh loss and this approach may be useful for management of a retrograding deltaic estuarine ecosystem like the Grand Bay NERR.

High carbon accumulation rates in sediment adjacent to constructed oyster reefs, Northeast Florida, USA

“…For example, a marsh fronted by an oyster reef sill or breakwater may show greater accretion or decreased erosion (Gittman et al 2016;Smith et al 2018;Chowdhury et al 2019). Restored or constructed oyster reefs have been shown to reduce erosion of salt marsh edges as well or better than natural oyster reefs, showing that they contribute to shoreline stabilization (Stricklin et al 2010;Ridge et al 2017) while others have shown that they may only be effective under certain conditions (La Peyre et al 2017;de Paiva et al 2018). Nonetheless, if restored or constructed oyster beds can protect salt marsh sediments, they will protect the carbon stored within that ecosystem as well, improving the carbon sequestration of the entire coastline (Ridge et al 2017).…”

Assessing shoreline exposure and oyster habitat suitability maximizes potential success for sustainable shoreline protection using restored oyster reefs

“…Hundreds of miles of shorelines are protected throughout the United States in efforts to stabilize and prevent the loss of coastal lands, including marshes ( Restore America’s Estuaries, 2015 ). While there are a multitude of approaches used for shoreline protection, recent focus on the use of natural and self-sustaining systems has promoted the development of fringing oyster reefs within estuarine systems ( La Peyre et al, 2014 ; Scyphers et al, 2011 ; Stricklin et al, 2009 ). Oyster reefs are promoted as they may combat marsh erosion by altering water flow patterns and attenuating waves ( Borsje et al, 2011 ), and trapping and stabilizing sediment ( Walles et al, 2015a ; Walles et al, 2015b ; Van Leeuwen et al, 2010 ; Meyer, Townsend & Thayer, 1997 ).…”

Impacts of Fringing Oysters Reefs on Wave Attenuation and Marsh Erosion Rates

“…Fringing oyster reefs, a recommended Living Shorelines structure, are becoming a more common erosion mitigation method. Studies conducted in Alabama, Louisiana, Mississippi, and North Carolina have shown that these reefs help reduce the impact of waves on the shoreline, increase sediment size, and enhance the growth of seagrass (Stricklin et al 2009;Piazza et al 2005;Meyer et al 1997, Scyphers et al 2011, all of which are major variables in stabilizing marsh shorelines. The majority of these studies suggested that oyster reefs are most effective in low energy environments, such as lagoons and shallow bays, and have little to no effect in higher energy areas.…”

“…Four previous studies, summarized below, have investigated the efficacy of oyster reefs as a form of erosion control. These studies concluded that reefs are successful in this capacity though only in low energy environments (Piazza et al 2005, Stricklin et al 2009. Each study approached oyster reef erosion control with different objectives in various locations ( Figure 2).…”