Response of a salt marsh plant to sediment deposition disturbance

Salt marshes (a type of coastal wetland with herbaceous plants) are one of the most productive ecosystems. The organic matter accumulated by plants, together with deposition of inorganic mineral sediments, contributes to vertical marsh growth and determines the marsh ability to cope with regional sea level rise. Deposition of mineral sediment, in turn, alters the growth of plant roots and shoots, and further marsh morphology and blue carbon storage. Based on mesocosm experiments simulating the sedimentation intensity, this paper examined the responses of Spartina alterniflora (a plant widely distributed in global salt marshes) to sediment deposition events (0–24 cm thicknesses). The plant height increased by 1.51 cm on average with 1 cm sediment deposition. New roots grew into the deposited sediment layers, resulting in a significant increase in the below-ground biomass. The below-ground biomass doubled with the treatment of 24 cm deposition thickness in comparison with that without deposition. The depth-dependent distribution of below-ground biomass changed from a monotonous (decreasing with soil depth) to a non-monotonic (increasing first and then decreasing) trend. This illustrates the growth of marsh plants in response to sediment deposition disturbance (similar to artificial or storm-induced sediment deposition) and have important implications for further investigations on marsh resiliency, blue carbon storage and marsh morphology.