Miss Christina Asanopoulos1,2, Dr Lynne Macdonald2,1, Dr Jeff Baldock2,1, A/Prof Timothy Cavagnaro1
1University of Adelaide, Glen Osmond, Australia, 2CSIRO Agriculture and Food, Glen Osmond, Australia
Blue carbon environments contain significant amounts of carbon in their above and below ground biomass and soils, the latter accounting for 46.9% of oceanic carbon stores. Frequent carbon inputs coupled with slow rates of soil organic matter decomposition results in long term carbon storage (i.e. millennia). The retention of carbon in the blue carbon environment is, however, a function of the chemical nature of the organic matter it is contained within. Little is known about the chemical composition of the soil organic carbon (SOC) stored in the blue carbon environment. The objective of this study was to quantify the content and chemical composition of SOC stored in mangrove and tidal marsh surface soils. Surface soil samples were collected from nine blue carbon sites spanning the eastern coastline of Gulf St Vincent and Spencer Gulf, South Australia. Organic carbon contents and chemical composition of mangrove and tidal marsh soils were quantified by dry combustion and solid state 13C nuclear magnetic resonance spectroscopy. Overall, mangrove and tidal marsh surface soils had similar carbon stocks but differed in chemical composition. We found that the organic carbon in mangrove soils exhibited a composition consistent with enhanced degradation relative to that in tidal marsh soils. Our findings suggest different rates of decomposition for the two soil types and mangrove SOC to be more stable than tidal marsh SOC. Despite that, based on their chemical composition, the carbon stored in both soil types would be highly susceptible to rapid decomposition with environmental disturbances.
Christina Asanopoulos is an early career research scientist based at the University of Adelaide. In 2011, she successfully completed a bachelor’s degree in marine biology (hons) and commenced working at the CSIRO as a research assistant in the soil carbon and nitrogen cycling group. Christina’s research interests are in investigating the impacts of anthropogenic activity and climate induced change on natural ecosystems to improve their conservation. Since 2016 she has been undertaking a PhD affiliated with the University of Adelaide and CSIRO. The research focus of Christina’s PhD is the biogeochemistry of carbon in South Australia’s temperate coastal wetlands.