The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

摘要

The balance between organic matter production and decay determines how fastcoastal wetlands accumulate soil organic matter. Despite the importance ofsoil organic matter accumulation rates in influencing marsh elevation andresistance to sea-level rise, relatively little is known about howdecomposition rates will respond to sea-level rise. Here, we estimate thesensitivity of decomposition to flooding by measuring rates of decay in 87bags filled with milled sedge peat, including soil organic matter, roots andrhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations weremanipulated to influence the duration of tidal inundation. Although we foundno significant influence of inundation on decay rate when bags from allstudy sites were analyzed together, decay rates at two of the sitesincreased with greater flooding. These findings suggest that flooding mayenhance organic matter decay rates even in water-logged soils, but that theoverall influence of flooding is minor. Our experiments suggest thatsea-level rise will not accelerate rates of peat accumulation by slowing therate of soil organic matter decay. Consequently, marshes will requireenhanced organic matter productivity or mineral sediment deposition tosurvive accelerating sea-level rise.