Coastal saltmarshes and mangroves serve as substantial long-term reservoirs of organic carbon. Rising temperatures drive tropicalization, resulting in the northward expansion of Avicennia germinans (black mangroves) into coastal Louisiana. Concomitantly, accelerating relative sea-level rise rates increase inundation, exacerbating edge erosion and saltwater intrusion. These processes potentially alter carbon cycling within coastal wetlands. The goal of this study was to determine how oxygenation and saltwater intrusion impact mineralization rates in mangrove and marsh soils with ramifications for understanding coastal carbon resistance to decomposition (‘stability’). We hypothesize that (1) mangrove soils will have lower mineralization rates than marsh soils (high stability) (2) increased salinity will increase mineralization rates more in marsh soils than mangrove soils (3) increasing oxygen (a proxy for erosion) will increase mineralization rates more in marsh soils than mangrove soils. We found that while mangrove soils had higher organic matter (18.5 ± 2.09 %) than saltmarsh (12.9 ± 1.60%) soils, these differences did not translate into higher mineralization rates (r < 0.5). Vegetation type did not significantly influence CO₂ production (p = 0.33), indicating that carbon stability may not differ between mangroves and saltmarshes. Salinity additions had no positive effect on mineralization (p = 0.45). Oxygen additions (p = 0.0012) and oxygen additions with salinity additions (p = 0.003) increased mineralization in both vegetation types. Results suggest oxygen additions like those from wave action at the coastal fringe generally increase mineralization rates and endanger coastal carbon stores, though mangrove encroachment might not affect coastal carbon stability.