Hurricane-Induced Sedimentation Improves Marsh Resilience and Vegetation Vigor under High Rates of Relative Sea Level Rise

During the next century coastal marsh sustainability will largely depend on whether or not marshes can keep pace with rising sea levels while weathering more frequent and/or intense storms. In particular, hurricanes have the potential to inflict widespread damage to coastal systems, but can also deliver nourishing inorganic sediment. To determine if hurricane-induced sedimentation can enhance marsh condition and promote marsh sustainability, even in regions of high relative sea level rise (RSLR), we experimentally assessed primary productivity and marsh resilience in marshes that were subject to various levels of hurricane-induced sedimentation in 2005 and 2008 in coastal Louisiana, where RSLR is accelerated due to land subsidence. Primary production and marsh resilience, i.e., recovery rate of plant cover after an experimental disturbance, increased in response to hurricane-induced sedimentation. Sedimentation led to a more oxidized soil environment, reduced porewater sulfide concentrations, and increased porewater phosphorus and exchangeable soil iron and manganese concentrations. Improved soil physicochemical conditions were likely responsible for the increased productivity and resilience, even with the high rates of RSLR the area experiences. This suggests that when storm-induced sedimentation is sufficient, stability of coastal marshes may be enhanced, at least for some time, helping to cope with sea level rise.