Mechanisms of wetland deterioration in a sinking deltaic lagoon

Coastal wetlands are vegetated landforms that offer a multitude of ecosystem services to society. The vulnerability of these ecosystems to relative sea-level rise (RSLR) is connected to the amount of suspended sediment available in the adjacent water bodies. Sediment is transported by numerous processes onto the wetland surface, where it can contribute to vertical accretion and counteract RSLR. Here, we used maps of total suspended solids (TSS) concentration from the NASA Airborne Visible InfraRed Imaging Spectrometer Next Generation (AVIRIS-NG), numerical modeling, aerial imagery, and field observations to infer the mechanisms controlling wetland dynamics within western Terrebonne Bay, a sinking lagoon in the Mississippi River Deltaic Plain. Specifically, we aimed to understand how wetlands respond when land sinks, using western Terrebonne Bay as a test case. This study revealed that subsidence can augment suspended sediment in the water column by increasing tidal prism and triggering channel erosion. Sediment resuspension can support accretion in the remaining wetland platforms, ultimately affecting their elevation. Understanding these feedback mechanisms has direct implications for forecasting and managing the impacts of RSLR on wetlands in lagoons and river deltas.