![]() In these ecogeomorphic models, progressive flocculation and settling of suspended particles as flooding tides breach marsh platforms drives sediment deposition on marsh edges - a process that leads to the formation of levees, or elevated bands of sediment, along the margins of marsh channels and tidal creeks. More sophisticated ecogeomorphic models of marsh accretion have also been developed to incorporate the direct and indirect feedbacks between salt marsh vegetation and physical processes ( 17, 18, 19, 22, 23, 24, 25, 26, 27 Fig. Zero-, one-, and two-dimensional models have been developed to assess marsh accretion and erosion processes under various environmental scenarios at a single point, along a transect, or across a marsh platform, respectively 17, 19, 22, 23, 24, 25, 26. These intertidal grasslands respond dynamically to tidal oscillations and sea level changes, as periodic flooding and draining of tidewaters control sediment delivery to marsh platforms, as well as plant zonation, productivity, and allocation to above- and belowground tissues 17. This lack of consideration of faunal influence is potentially problematic given the significant body of literature demonstrating that animals can modify sedimentation processes and vegetation coverage, density, and other above- and belowground traits (e.g., 20).įormed in temperate, low energy coastlines around the world 21, salt marshes are among the most well-studied vegetated coastal ecosystems. Despite the flourishing sophistication of such models, they do not yet consider the role of fauna in altering vertical and horizontal accretion and erosion processes 18, 19. More recent models also account for the effects of vegetation, such as the trapping of sediment by aboveground stems and leaves, the accumulation of organic matter via root and rhizome production belowground 16, and the feedbacks between vegetation and physical forcing factors 17, in influencing vegetated coastal ecosystem dynamics and stability. Historically, modeling efforts primarily focused on the relationships between physical factors including sediment supply, elevation, and tidal range 15. Given the valuable shoreline stabilization, wave attenuation, nutrient filtration, habitat provisioning, and carbon sequestration services provided by these ecosystems 10, 11, significant effort and resources have been invested in quantifying their past and current rates of vertical and horizontal accretion and erosion, and using both field data and modeling to forecast their size, stability, and spatial distribution under different sea-level rise scenarios 3, 6, 12, 13, 14. Since these systems often occupy a narrow elevational range, relatively small changes in sea level may lead to substantial ‘drowning’, or conversion of vegetated, intertidal habitat to open water 7, 8, 9. Thus, we highlight an urgent need for empirical, experimental, and modeling work to resolve the importance of faunal engineers in directly and indirectly modifying the persistence of coastal ecosystems globally.Īs rates of sea-level rise accelerate globally, the fate of vegetated coastal ecosystems, such as salt marshes, mangroves, and seagrasses is uncertain 1, 2, 3, 4, 5, 6. Our Delft-3D-BIVALVES model further predicts that mussels drive substantial changes to both the magnitude (☒00,000 mussels and find that this faunal engineer drives far greater changes to relative marsh accretion rates than predicted (±>0.4 cm Multi-season and -tidal stage surveys, in combination with field experiments, reveal that deposition is 2.8-10.7-times greater on mussel aggregations than any other marsh location. ![]() Here, we quantify effects of the mussel, Geukensia demissa, on southeastern US saltmarsh accretion. The fate of coastal ecosystems depends on their ability to keep pace with sea-level rise-yet projections of accretion widely ignore effects of engineering fauna.
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