Large porewater exchange reshapes saltmarsh carbon and greenhouse gas budgets on local and global scales

Saltmarshes, renowned for their carbon-rich nature, have long been recognized as crucial ecosystems in regulating climate by effectively sequestering atmospheric CO₂. However, the alarming specter of climate change poses a significant threat to saltmarshes, endangering their vital role in carbon sequestration. In this regard, a noteworthy revelation has emerged – the pivotal contribution of porewater-derived carbon outwelling to the overall carbon sequestration process in saltmarshes, a factor that has hitherto been largely overlooked.

Scientists from Westlake University, University of Gothenburg, and Hohai University conducted a study in the saltmarsh tidal creeks of Dafeng Milu National Nature Reserve in Yancheng City, Jiangsu Province, China. The research revealed that porewater-derived carbon outwelling plays a crucial role in driving the dynamic changes of carbon and greenhouse gases in saltmarsh ecosystems. The study also found that porewater exchange acts as a long-term and significant carbon sink, comparable to soil carbon burial. These findings enhance our understanding of saltmarshes' carbon sequestration potential.

Incorporating the local findings with 33 other studies conducted in saltmarshes worldwide, it has been determined that porewater-derived carbon fluxes account for approximately 48% of the average global saltmarsh primary productivity, surpassing global organic carbon burial by 2.2 times. These results provide compelling evidence for the significant contribution of porewater exchange to saltmarsh carbon budgets at both local and global scales. While a portion of dissolved inorganic carbon is released as CO₂ into the atmosphere, the remaining bicarbonate fraction undergoes long-term storage in the ocean. These findings reinforce global assessments of blue carbon in saltmarshes and underscore the potential of utilizing saltmarshes as nature-based solutions to combat global climate change.

 

Chen X, Santos I R, Zhan L, Yau Y Y, Zhang Y, Li L. 2024. Large porewater exchange reshapes saltmarsh carbon and greenhouse gas budgets on local and global scales. Science China Earth Sciences, 67(7): 2195–2209, https://doi.org/10.1007/s11430-023-1305-6

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