After the Storm: Assessing the Content, Transformation, and Fate of Nitrogen in Floodplain Sediments in Aquatic Ecosystems
Abstract:
matter (POM) within the fluvial network. Floodplain sediments following these events can contain large
amounts of particulate organic C (POC) and N (PN) forms. The C and N processing at these sites could
have a significant impact on aquatic nutrient cycling, water quality, and global C and N budgets. The fate
of deposited PN and the role the storm deposits play in C and N processing is still poorly understood and
warrants further investigation.
This study investigates the role of the large storm floodplain sediment deposits as sites of N
sequestration or leaching. This is achieved through the use of a laboratory sediment incubation
experiment coupled with in-situ field monitoring. The incubation experiment investigated the response
of watershed sediments, specifically the large storm deposits, to contrasting moisture regimes and the
implications this has on the fate of N. Sediment samples were collected from a range of potential
sources in a 1-2 nd order stream within a forested catchment of the Piedmont region of Maryland. The
moisture regimes included “consistently moist” and “wet-dry” cycles and were achieved through the
application of different volumes of water to the sediment columns. The incubation was performed for a
period of 60 days. Sediment/soil chemistry, pore-water chemistry, and microbial community diversity
were monitored for the various sediment treatments.
It is expected that the sediments experiencing the wet-dry cycles will episodically leach N at a higher
rate than the sediments that remain continuously moist, and that the floodplain sediments will release
substantial N in both scenarios. These insights are critical as climate-change predictions indicate that
both intensity and frequency of large storms are expected to increase in the Northeastern US, thus
directly impacting the creation and behavior of these storm deposits as N sources or sinks.