Not all nitrogen is created equal: Quantifying the effects of different nitrogen forms on marsh resilience
Nitrogen delivery from watersheds to the coastal zone is well documented and leads to harmful consequences in coastal waters, including the formation of dead zones, where oxygen concentrations drop below levels that can support much aquatic life. Salt marshes provide an important line of defense against nutrient pollution by intercepting watershed nitrogen before it enters estuaries. Within marshes this nitrogen can enhance the growth of marsh plants, much as fertilizers enhance plant growth in gardens. Depending on the form of nitrogen, though, it can also be used by microbes that can use some forms of nitrogen as a substitute for oxygen to decompose organic matter in low oxygen sediments. Understanding which of these two outcomes is most likely to occur is important because if marsh plants take up that nitrogen and grow more robustly, they will allow the marsh to gain elevation by trapping more sediment and increasing more plant material in the soils. This will increase salt marsh resilience to sea level rise. However, if marsh microbes can outcompete marsh plants for the added nitrogen, then it could enhance decomposition and slow the ability of marshes to keep up with rising seas. To better understand how the form of nitrogen and the genetic diversity of marsh grasses affect the ability of salt marshes to keep pace with sea level rise, this research had three goals: quantify how environmental nitrogen availability alters responses of the coupled plant-microbe system, determine how these responses vary under different flooding regimes, and assess how different populations of marsh cordgrass respond to different nitrogen sources. The data in this repository address the first goal.