Mudflat Biostabilization Alters Coastal Landscape Sediment Connectivity

Abstract

Connectivity between adjacent ecosystems is thought to increase ecosystem resilience and function. In coastal ecosystems, the exchange of sediment and nutrients between mudflats and marshes is important for the long-term dynamics of both systems. Mudflat morphodynamics are driven by the interaction of waves and sediment erodibility, which is a function of sediment type and the presence of biostabilizers such as microphytobenthos. However, there is a poor understanding about how the evolution of mudflats may impact the morphodynamics and function of adjacent salt marshes. Here, we use a Coastal Landscape Transect model connecting mudflats and marshes to investigate how microphytobenthos influence the coupled behavior of mudflats and marshes, and how that coupled behavior influences carbon storage. We find that biofilms reduce the connectivity between mudflats and marshes by reducing erodibility and sediment exchange. Reduced connectivity associated with microphytobenthos leads to a shallower mudflat and more carbon stored in the mudflat sediments, which in turn cascades to a higher combined marsh and mudflat carbon stock. Furthermore, our results highlight the role of connectivity across the coastal landscape and suggest that biostabilization leads to relatively small changes in morphodynamics but relatively large changes in ecosystem function.