Living Shorelines Support Nearshore Benthic Communities in Upper and Lower Chesapeake Bay

Abstract

Human population growth and sea-level rise are increasing the demand for protection of coastal property against shoreline erosion. Living shorelines are designed to provide shoreline protection and are constructed or reinforced using natural elements. While living shorelines are gaining popularity with homeowners, their ability to provide ecological services (e.g., habitat provision and trophic transfer) is not well understood, and information is needed to improve coastal and resource management decision-making. We examined benthic community responses to living shorelines in two case-study subestuaries of Chesapeake Bay using a before-after control-impact study design. At Windy Hill, a bulkhead was removed and replaced by three tombolos, sand fill, and native marsh vegetation. At Lynnhaven, 25 m of eroding marsh shoreline was stabilized with coir logs, sand fill, and native marsh vegetation. Communities of large (> 3 mm) infauna adjacent to living shorelines at both locations tended to increase in biomass by the end of the study period. Community compositions changed significantly following living shoreline construction at Windy Hill, reflecting a trend toward higher density and biomass of large bivalves at living shorelines compared to pre-construction. Increasing trends in density and biomass of clams and simultaneously decreasing density and decreasing trends in biomass of polychaetes suggest a transition toward stable infaunal communities at living shorelines over time, though longer-term studies are warranted.

Living shorelines enhanced the resilience of saltmarshes to Hurricane Matthew (2016)

“…), and increasing benthic infaunal biomass (Davenport et al. ). There are certainly coastal areas where vertical walls are the only feasible shoreline stabilization option (e.g., man‐made canal systems, regions of extremely high wave action), but in areas where either a bulkhead or living shoreline would suffice, living shorelines may be more economically and ecologically sustainable in the long term.…”

“…This is in contrast to hardened shorelines, which necessarily weaken over time and require the continual investment of money for maintenance and repair (Smith et al 2017). Furthermore, the benefits of living shorelines extend beyond their ability to prevent erosion; unlike hardened shorelines, living shorelines come with a suite of ecological co-benefits, such as maintaining coastal saltmarsh, enhancing the nursery value of coastal habitats for fish and crustaceans (Gittman et al 2016a), and increasing benthic infaunal biomass (Davenport et al 2017). There are certainly coastal areas where vertical Vol.…”

Impacts of Coastal Land Use and Shoreline Armoring on Estuarine Ecosystems: an Introduction to a Special Issue

“…Some hybrid armored features (e.g., marsh-sills) may provide improved habitat relative to traditional riprap, but only when they have a small footprint that minimally impacts the infauna displaced when structures are installed on the sediment surface (Bilkovic and Mitchell 2013). In this issue, Davenport et al (2017) (Living shorelines support nearshore benthic communities in upper and lower Chesapeake Bay) monitored biological responses of shallow estuarine benthic communities to living shoreline construction for two case studies in Chesapeake Bay with before-after control-impact study designs. Communities of large (> 3 mm) infauna adjacent to living shorelines at both study locations increased in biomass within 3 years of installation.…”