Title:

Response of Fluvial Wetlands to Storm Events and Elevated Nitrogen Inputs from the Landscape

Fluvial wetlands, found within networks of flowing water, act as buffers in headwaters to limit nitrogen (N) from reaching downstream coastal ecosystems and causing problems, such as coastal eutrophication and loss of habitat. However, as significant hotspots for N removal, they are also natural sources of greenhouse gas (GHG) to the atmosphere and contribute largely to global climate change. With ongoing changes to the flow regime from increased climate variability and intensification of storm events, as well as landscape urbanization, the ability for fluvial wetland systems to regulate these tradeoffs may decline as a result. To better understand how climate variability impacts headwater fluvial wetland systems, we investigated storm influence on broad scale saturation dynamics for N removal and GHG production along two fluvial wetland dominated pathways in an urbanizing coastal watershed in New England. We collected dissolved nutrient and gas samples synoptically along these pathways before and after storms over a six-month time period. Samples were analyzed for dissolved concentrations of major anions (nitrate, ammonium, sulfate, and chloride) and gases (nitrous oxide, carbon dioxide, methane and N2:Ar). Results from this study suggest that fluvial wetlands withstand high rates of N retention and removal under storm flow conditions, while also displaying variable responses in GHG emission. The study of fluvial wetlands across flow conditions is critical for understanding their functional role in river networks as N loading increases in a changing climate.

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