Effects of Varying Salinity On Greenhouse Gas Emissions From Oiled and Unoiled Coastal Louisiana Salt Marsh Soils.

We quantified the effects of altering salinity regime (5, 15, 25, 35 ppt) and the Deepwater Horizon Oil spill on greenhouse gas (GHG) (CH₄, CO₂, N₂O) production from laboratory incubated oiled and unoiled salt marsh soils of Terrebonne and Barataria Bays, Louisiana. Terrebonne soils, which exhibited higher percentage organic matter and water content, had greater (p= <0.05) CO₂ production (869 ± 30 nmol dry g^-1 hr^-1) than Barataria soils (707 ± 30 nmol dry g^-1 hr^-1).  CH₄ production in Terrebonne soils (5 ± 0.5 nmol dry g^-1 hr^-1) was also greater (p= <0.05) than Barataria soils (3 ± 0.5 nmol dry g^-1 hr^-1) which exhibited declines in CH₄ production at salinities above 5.  As salinity was increased relative to field conditions, we observed increased CO₂ production from marsh soils (p= <0.001). No response was observed in N₂O production across sites or experimental treatments. No significant differences were observed in GHG production between oiled and unoiled sites. Results indicate that salinity changes and site characteristics may be more influential on marsh GHG production compared to oil exposure; information critical to improving global carbon cycling and climatic variation models.