Effects of nitrogen loading on greenhouse gas emissions in salt marshes

Wednesday, 17 December 2014: 8:15 AM
Jianwu Tang1, Serena Moseman-Valtierra2, Kevin D Kroeger3, Kate Morkeski1, Jordan Mora4, Xuechu Chen1 and Joanna Carey5, (1)The Ecosystems Center, MBL, Woods Hole, MA, United States, (2)University of Rhode Island, Kingston, RI, United States, (3)USGS, Woods Hole, MA, United States, (4)Waquoit Bay National Estuarine Research Reserve, Waquiot Bay, MA, United States, (5)Marine Biological Laboratory, Woods Hole, MA, United States
Salt marshes play an important role in global and regional carbon and nitrogen cycling. We tested the hypothesis that anthropogenic nitrogen loading alters greenhouse gas (GHG, including CO2, CH4, and N2O) emissions and carbon sequestration in salt marshes. We measured GHG emissions biweekly for two growing seasons across a nitrogen-loading gradient of four Spartina salt marshes in Waquoit Bay, Massachusetts. In addition, we conducted nitrogen addition experiments in a pristine marsh by adding low and high nitrate to triplicate plots bi-weekly during the summer. The GHG flux measurements were made in situ with a state-of-the-art mobile gas measurement system using the cavity ring down technology that consists of a CO2/CH4 analyzer (Picarro) and an N2O/CO analyzer (Los Gatos). We observed strong seasonal variations in greenhouse gas emissions. The differences in gas emissions across the nitrogen gradient were not significant, but strong pulse emissions of N2O were observed after nitrogen was artificially added to the marsh. Our results will facilitate model development to simulate GHG emissions in coastal wetlands and support methodology development to assess carbon credits in preserving and restoring coastal wetlands.