Salt marshes provide ecosystem services including carbon sequestration, flood mitigation, and nutrient removal, and climate change is threatening coastal salt marshes through sea level rise and reduction in sediment supply. Climate change may alter the intensity or frequency of storm events, and this study provides needed information that will be useful in assessing the resilience of marshes. Storms can result in high-energy waves that may cause erosion, wind damage, flooding, and result in storm-surge sediment deposition onto marshes. Storms may hasten the loss of marshes through erosion or sustain them through vertical sediment integration. The type and timing of storm events may alter the quantity and composition of sediment delivered to the marsh surface.
We investigate how sediment type, thickness of deposit, and elevation interact to determine the fate of storm sediment deposition. Our factorial design experiment assesses different scenarios, including Nor’easter ice raft deposition events (fine-grained sediment) and hurricane deposition events (coarse-grained sediment). Sediment was deposited at two high marsh sites and two low marsh sites on 0.5 m2 plots with three different depths of coarse and fine sediment deposition (2, 6 and 10 cm).
Results/Conclusions
Change in deposition was measured 6 months apart. The majority of control plots were within 4 mm except one site gained over a centimeter of sediment, showing the dynamic nature of sediment in the salt marsh ecosystem. In both high marsh sites, plots with higher sediment deposition lost more sediment (up to 37%); however low marsh sites exhibited slight differences (up to 74% and 60%). The differences at the low marsh sites may be attributed to variation in plot location in relation to the river channel. Low marsh sites have overall higher sediment loss, likely due to higher flooding frequencies.