LAUSR

Coastal wetland sustainability in the future will likely depend on the extent to which increases in sea level drive flooding duration, plant submergence, and higher salinities, and how wetlands respond to these changes. Coastal wetlands will need to grow vertically to cope with rising seas, and sedimentation, often observed following hurricane passage, could play a role. A greenhouse mesocosm experiment was conducted to investigate if the impacts of sea level rise (SLR) and elevated salinity on the productivity and resilience of Spartina alterniflora marshes could be mediated by simulated hurricane sedimentation. Overall, sedimentation ameliorated the negative impacts of moderate SLR on plant productivity and resilience. Sedimentation improved growth conditions at current and moderate increases in sea level by reducing flooding duration, which in-turn, increased soil Eh, and lowered porewater sulfide. This led to greater productivity of vegetation above- and belowground and improved plant resilience. However, at the highest sea levels, inundation stress was too great for the benefits of added sediment to be realized. Thus, it is likely that the sustainability of coastal marshes will be improved by hurricane-generated sedimentation under moderate SLR scenarios, but will see no improvement with more extreme SLR.