Significant Organic Carbon Accumulation in Two Coastal Acid Sulfate Soil Wetlands

Abstract

Restoring degraded freshwater wetlands may help to maximize soil carbon sequestration. In this study, we use 18 210Pb-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 CO2 emission from fossil fuels in Australia. Hence, preserving or restoring CASS may be a good climate change mitigation strategy.