Significant Organic Carbon Accumulation in Two Coastal Acid Sulfate Soil Wetlands

Abstract

Abstract Restoring degraded freshwater wetlands may help to maximize soil carbon sequestration. In this study, we use 18 210 Pb‐dated sediment cores to determine the organic carbon (OC) accumulation rates from two hydrologically restored freshwater coastal acid sulfate soil (CASS) wetlands. Recent OC accumulation rates (from ~1980 to present) were estimated to be 251 ± 26 g·m −2 ·year −1 in the seasonally inundated CASS and 227 ± 50 g·m −2 ·year −1 in the permanently inundated CASS. The average OC accumulation during the previous century (190 ± 20 g·m −2 ·year −1 ) was within the range of blue carbon ecosystems (saltmarshes, mangroves, and seagrasses). Considering their large area and carbon accumulation rate, we estimate that Australian CASS wetlands sequester approximately 7.8 ± 0.8 Tg of carbon annually, which is equivalent to ~8% of the CO 2 emission from fossil fuels in Australia. Hence, preserving or restoring CASS may be a good climate change mitigation strategy.