Salt marsh habitat provides essential ecosystem services on a global scale, yet these systems are at risk of widespread loss due to sea level rise. There is an increasing need within coastal communities for restoration projects that can increase salt marsh elevation while preserving native vegetation. Sediment addition, also known as thin layer placement (TLP) or sediment augmentation, addresses this need by depositing thin sediment layers on top of deteriorating marsh habitat. Though this technique is a promising strategy for preventing marsh habitat loss, pilot studies have been limited within New England. Addition of ribbed mussels (Geukensia demissa) has the potential to facilitate vegetation growth and stabilize newly added soils, but no sediment addition studies have yet been paired with this technique. Sediment addition studies also have not yet incorporated analyses of microbial community composition throughout the restoration process, though soil microbiome structure can lend insight into both biotic and abiotic processes within a restored marsh. In this pilot study within Great Bay, New Hampshire, paired sediment and mussel addition took place in 2023 at three marsh locations with different hydrologic regimes. Marsh recovery is being evaluated through parameters that include hydrology, water chemistry, vegetation, fauna, and soil microbial community composition. Ongoing analysis of these parameters post-restoration will reveal the influence of this technique on expected outcomes and patterns of restoration trajectory. Results will be valuable to the regulatory community in determining whether these techniques can improve ecosystem services and should be used on larger scales to enhance coastal resilience.
