Exploring anaerobic CO2 production response to elevated nitrate levels in Gulf of Mexico coastal wetlands: Phenomena and relationships

Zhuo Wei; Jim J Wang; Syam K Dodla; Lisa M Fultz; Lewis A Gaston; Jong-Hwan Park; Ronald D DeLaune; Yili Meng

doi:10.1016/j.scitotenv.2019.136158

Exploring anaerobic CO₂ production response to elevated nitrate levels in Gulf of Mexico coastal wetlands: Phenomena and relationships

Sci Total Environ. 2020 Mar 20:709:136158. doi: 10.1016/j.scitotenv.2019.136158. Epub 2019 Dec 17.

Authors

Zhuo Wei¹, Jim J Wang², Syam K Dodla³, Lisa M Fultz¹, Lewis A Gaston¹, Jong-Hwan Park⁴, Ronald D DeLaune⁵, Yili Meng¹

Affiliations

¹ School of Plant, Environment and Soil Sciences, Louisiana State University AgCenter, Baton Rouge, LA 70803, USA.
² School of Plant, Environment and Soil Sciences, Louisiana State University AgCenter, Baton Rouge, LA 70803, USA. Electronic address: jjwang@agcenter.lsu.edu.
³ Red River Research Station, Louisiana State University AgCenter, Bossier City, LA 71112, USA.
⁴ Division of Applied Life Science (BK21 Program) & Institute of Agriculture and Life Science, Gyeongsang National University, Jinju 52828, South Korea.
⁵ Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.

PMID: 31887499
DOI: 10.1016/j.scitotenv.2019.136158

Abstract

Recent studies have shown the effect of nitrate (NO₃^-) on carbon gas emissions from wetland soils that contradict thermodynamic predictions. In this study, CO₂ production in three Mississippi River deltaic plain wetland soils (forest swamp, freshwater and saline marshes) with the presence of different NO₃^- levels (0.2, 2.0, and 3.2 mM) was evaluated in an anaerobic microcosm. Molecular composition of dissolved organic matter (DOM) of these soils was investigated using pyrolysis-GC/MS, and soil microbial community was characterized based on phosphorus lipid fatty acid (PLFA) method to elucidate the underlying mechanisms. Addition of NO₃^- promoted CO₂ production in swamp forest soil, but inhibited CO₂ emission from marsh soils. Pyrolysis-GC/MS analysis showed that swamp soil contained more polysaccharides, whereas both marsh soils had high abundance of phenolic compounds. Total PLFAs of forest swamp soil were 34% and 66% higher than freshwater and saline marsh soils, respectively. The PLFA profiles indicated different microbial distribution along a salinity gradient with the forest swamp having a higher proportion of fungi and NO₃^- reducers but lower sulfate (SO₄²^-) reducers than marsh soils. Overall, the study indicated that the inherent differences in soil DOM and microbial community led to the contrasting response in soil CO₂ respiration between forest swamp and marsh ecosystems to NO₃^- loading. These differences should be considered in determining the fate of nitrate entering Louisiana coastal wetlands from river diversions and other sources and their management.

Keywords: Anaerobic respiration; Carbon dioxide; Electron acceptor; Marsh loss; Nitrate; Wetlands.