Lignin chemistry of wetland soil profiles in two contrasting basins of the Louisiana Gulf coast

•Atchafalaya and Barataria basin wetland soils show different organic matter sources.•Two basin marshlands have varying degradation status of lignin.•Soil lignin degradation was negatively affected by pH in Atchafalaya Basin.•In contrast, it was primarily affected by N in the Barataria Basin.•Barataria Basin wetlands contribute more SOC than Atchafalaya to GOM hypoxia.