CAREER: Understanding the role of ribbed mussels on salt marsh sedimentation by a combination of field work and numerical modeling

This project addresses a critical challenge for coastal communities and the nation: how to sustain and strengthen natural salt marshes. These ecosystems are essential to the health and prosperity of coastal communities across the United States. They help protect shorelines from storms, support biodiversity, filter pollutants, sequester carbon, and sustain local economies through fisheries, recreation, and tourism. Rising sea levels threaten these ecosystems and the benefits they provide. Ribbed mussels, which form clusters known as mussel mounds, may help marshes keep pace with rising waters by filtering sediments, depositing material, and enhancing plant growth. However, the extent of their impact at the scale of an entire marsh remains unknown. This research will fill that gap by quantifying how mussels influence sediment accumulation and marsh resilience to sea level rise. In doing so, it directly promotes the progress of science and advances the national interest by contributing to sustainable coastal protection. The project also engages rising high school seniors in hands-on research, increasing engagement in coastal engineering and training the next generation of scientists and engineers, on which national competitiveness depends. Results will guide restoration efforts and support nature-based solutions for coastal protection. To achieve these goals, this project will combine field measurements and numerical simulations. Field work at Little Sapelo Island, Georgia, will include mapping marsh topography and mussel mound distribution using drone-based LiDAR, tracking water flow with dye release and aerial imagery, measuring current profiles and sediment concentration with acoustic and laser sensors, and collecting sediment samples with traps and surface elevation tables. Sediment will be analyzed by size and composition. An open-source numerical model, solving for hydrodynamics and morphological evolution, will be extended to simulate mussel filtration processes and will be calibrated and validated against field data. Simulations will compare scenarios with and without mussel mounds to quantify sediment budgets and the increase in marsh elevation due to presence of mounds. The project will deliver open-source software, detailed sediment budgets for different sediment sizes, and practical guidelines for using mussel transplants as a nature-based restoration strategy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.