Lyntana Brougham

Mentors: Tom Mozdzer and Don Barber

Biology Department

Nutrient Loading Affects Marshes Belowground

Salt marshes are an extremely important ecosystem, particularly in the face of relative sea level rise and climate change, because they are highly productive (allowing for carbon storage) and are a barrier between the land and the ocean. As a barrier it is crucial that the elevation of the marsh peat rises proportionally with the sea level, or “keeps pace.” If the peat does not increase quickly enough through accumulation of organic matter and roots, the marsh will be inundated with sea water, and the ecosystem will be damaged. In Massachusetts there has been a long term study since 2004 looking at the effects of nutrient loading on the marsh. This study has resulted in the observation that marsh plants produce fewer roots when there is an abundance of nitrogen, instead reallocating their resources to aboveground growth. This observation provided a potential cause of a simultaneous event occurring in the fertilized plots: marsh collapse. Marshes are an important ecosystem and their ability to survive may be threatened by excess nitrogen. Additionally, by reallocating their resources to above ground biomass, the marsh plants would not store as much carbon belowground, especially considering that the above ground organic matter is comparatively quick to decompose.

In order to investigate the effect of nutrient loading on the amounts of carbon stored in marsh peat, I will analyze the carbon concentration as a function of depth and distance from the water source in cores collected from two different treatment sites, ambient and excess nitrogen, in the Massachusetts study area. Carbon content will be determined using two analytical methods: loss on ignition (LOI) and carbon coulometry. The LOI technique provides weight percent organic matter through muffle furnace combustion for four hours at 550 degrees C. Coulometry yields weight percent carbon data based on titration of CO2 evolved by combustion of a known sample mass. The coulometric technique is more costly and labor intensive, and therefore will be used primarily to establish a relationship between organic matter and carbon content in the samples. Comparison of these properties in the collected cores may shed light on how nutrient loading affects carbon storage in salt marsh peat.