Quantifying the Impacts of Shoreline Armoring on Puget Sound Nearshore Ecosystems

Shoreline armoring is thought to be a major factor disrupting natural ecosystem functions in nearshore marine and estuarine environments, yet few studies have documented actual negative impacts of armoring on ecosystem health. The demand for shoreline armoring is likely to increase with heightened concerns about erosion caused by sea-level rise, and defensible scientific data are needed to inform responsible regulation of shoreline alterations and to guide relevant conservation and restoration actions. This study builds upon monitoring of a shoreline restoration site at Seahurst Park in Puget Sound, WA, to quantify the comprehensive ecological impacts of shoreline armoring. The objectives of this research are: (1) to characterize habitat functions and ecosystem services for fish and birds produced in the supralittoral ecotone of Puget Sound beaches, and (2) to quantify the physical and biological impacts of shoreline armoring on those functions and services. We measured sediment grain sizes, beach slope, wave energy, wrack abundance and composition and log abundance at multiple paired armored and unarmored beaches to characterize the physical setting and identify armoring-related differences. Quantitative amphipod and insect sampling, snorkel studies of juvenile salmon alongshore, and bird observations on the high shore were used to characterize organism assemblages and habitat use patterns in the nearshore, with particular focus on the upper intertidal ecotone and the impacts of armoring placed in the upper intertidal. This study will identify critical habitat features for juvenile salmon and birds that should be targeted for conservation, as well as data on the potential value of seawall removal as a restoration action.