*WINNER* Spatial and temporal variation of uptake and retention rates of nitrogen and phosphorus in west Tennessee agricultural wetland


  • Morgan Michael


Excessive nutrient runoff from agriculture fields in the Mississippi River basin negatively affects local stream water and the Gulf of Mexico by creating hypoxic environments caused by harmful algal blooms. Strategies to reduce nutrients entering rivers has become a national priority. One strategy involves the restoration of riparian wetland ecosystems, as wetlands are important for buffering excessive nutrient runoff. My project focuses on a riparian wetland in west Tennessee, transitioning from agricultural fields to a restored wetland. Specifically, I am measuring spatial and temporal variation of nutrient retention within wetland soils/sediment. Nutrient uptake and denitrification estimates are obtained from sediment cores from two dominant habitat types, remnant forests and shallow water areas. Then cores were incubated in a controlled environmental chamber using a water flow through setup for 4 days. Nutrients and nitrogen gas samples were taken from the cores once each day, and uptake rates calculated as the difference between these measurements. After incubation, the sediment within the cores is analyzed for nutrients, organic matter content, and above/below ground vegetation. In general, nutrients are retained in the shallow water cores with time but forest nutrient retention is variable. Denitrification rates with shallow water cores increase. Overall understanding how habitat variation scale how the restored wetland is mitigating the effects of excessive nutrient runoff, is key. Given the high vegetation, water, and soil heterogeneity within wetlands, good understanding of potential spatial and temporal variability in ecosystem services is crucial to designing management practices to maximize their ecosystem function.