Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 672, Issue -, Pages 427-437Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2019.03.345
Keywords
Blue carbon; Land reclamation; Carbon stocks; Emissions; Sediment carbon; Tidal marsh; Carbon sequestration; Sediment carbon
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Funding
- Australian Institute of Nuclear Science and Engineering (AINSE) [ALNGRA 15530]
- Australian Government for the Centre for Accelerator Science at the Australian Nuclear Science and Technology Organisation (ANSTO) through the National Collaborative Research Infrastructure Strategy (NCRIS)
- CSIRO Carbon Cluster
- Australian Research Council [LP160100242]
- Deakin's Centre for Integrative Ecology
- University of Technology Sydney
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Tidal marsh ecosystems are among earth's most efficient natural organic carbon (C) sinks and provide myriad ecosystem services. However, approximately half have been 'reclaimed' - i.e. converted to other land uses - potentially turning them into sources of greenhouse gas emissions. In this study, we applied C stock measurements and paleoanalytical techniques to sediments from reclaimed and intact tidal marshes in southeast Australia. We aimed to assess the impacts of reclamation on: 1) the magnitude of existing sediment C stocks; 2) ongoing C sequestration and storage; and 3) C quality. Differences in sediment horizon depths (indicated by ltrax-XRF scanning) and ages (indicated by lead-210 and radiocarbon dating) suggest a physical loss of sediments following reclamation, as well as slowing of sediment accumulation rates. Sediments at one meter depth were between similar to 2000 and similar to 5300 years older in reclaimed cores compared to intact marsh cores. We estimate a 70% loss of sediment C in reclaimed sites (equal to 73 Mg C ha(-1)), relative to stocks in intact tidal marshes during a comparable time period. Following reclamation, sediment C was characterized by coarse particulate organic matter with lower alkyl-o-alkyl ratios and higher amounts of aromatic C, suggesting a lower extent of decomposition and therefore lower likelihood of being incorporated into long-term C stocks compared to that of intact tidal marshes. We conclude that reclamation of tidal marshes can diminish C stocks that have accumulated over millennial time scales, and these losses may go undetected if additional analyses are not employed in conjunction with C stock estimates. (C) 2019 Published by Elsevier B.V.
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