Wetland Sediment Nutrient Flux in Response to Proposed Hydrologic Reconnection and Climate Warming

Wetland restoration and creation are common practices, but wetlands restored or created on former agricultural land may act as a source of nutrients, rather than as a sink. I studied P sediment-water exchange in two flooded celery fields (west and east), which are designated for wetland restoration, in order to assess the effects that hydrologic reconnection of the area to an adjacent creek would have on P dynamics. We also examined the influence of climate change, specifically warming temperatures, by conducting the sediment-water exchange experiments at ambient and plus 2°C temperature conditions. Lab-based sediment core incubations revealed that TP release rates were significantly larger when sediment from the west pond was flooded with water from the creek (~40-60 mg m-2 d-1), simulating reconnection, than when west pond sediment was flooded with water from the same pond (~6-20 mg m-2 d-1), simulating the current condition. Increasing ambient water temperatures by 2°C did not produce a consistently significant effect on P release rates from west pond sediment. Additionally, I did not observe a consistently significant effect of flooding or increased temperature on the release of N from west pond sediment. There was no consistently significant effect of flooding with creek water or increased temperature on east pond sediment N and P release, although the sediments still served as a net source of P, with release rates of ~2.2-4.73 mg TP m-2 d-1. The difference in response between the two ponds may have been due to prior dredging in the east pond, but not in the west. The results of this study showed that wetlands converted from agricultural areas can potentially act as a significant source of P to downstream locations. Overall, the effects of warming on nutrient dynamics were much less pronounced than effects related to prior land use