Soil Organic Carbon Stocks and CO2 Emission from Tidal Marsh Soils of the Western Sector of the Russian Arctic

We studied SOC stocks and CO₂ emissions from soils of coastal zone of the White, Barents and Kara seas. On the White Sea coast, the tide level varies from 1.0 to 3.5 m, and three marsh zones are formed: low, medium and high. The maximum SOC stocks in the upper 30 cm of soil of the low marsh are up to 31.6, on the medium 36.5, and in high zone up to 39.5 t·ha^–1. CO₂ emissions from tidal marsh soils are 0.64 gCO₂·m^–2·h^–1. The tide level on the coast of the Barents Sea exceeds 4-5 m. The maximum values of SOC reserves reach 190 t·ha^–1. The lowest SOC stocks (8-60 t·ha^–1) are in the zones of wave accumulation. CO₂ emissions from marsh soils averaged 4.03 gCO₂·m^–2·day^–1. The tidal fluctuations on the coasts of the Kara Sea do not exceed 0.6–1 m. The coasts of the Kara Sea have only one marsh zone with the dominance of obligate halophytes. SOC stocks range from 20 to 118 t·ha^–1 in marsh soils. CO₂ emissions from coastal soils averaged 1.35 gCO₂·m^–2·day^–1. The mean values of CO₂ emissions from the coastal soils decreased from macro- and meso-tidal to micro-tidal Arctic seas with an exception of the White Sea. Funded by the projects "’Blue carbon’ stock and dynamics of the seacoasts of the western sector of the Russian Arctic" (Russian Science Foundation 23-67-10006) and "Coastal wetlands potential for carbon sequestration under climatic change" (COASTCARB–BRICS2023-078).