Hydrologic Export Is A Major Component Of Coastal Wetland Carbon Budgets

Details

• Journal Title:
  Global Biogeochemical Cycles
• Personal Author:
  Bogard, Matthew J. ; Bergamaschi, Brian A. ; Butman, David E. ; Anderson, Frank ; Knox, Sara H. ; Windham‐Myers, Lisamarie
• NOAA Program & Office:
  Sea Grant ; OAR (Oceanic and Atmospheric Research)
• Sea Grant Program:
  CASG/CUIMR (California Sea Grant)
• Description:
  Coastal wetlands are among the most productive habitats on Earth and sequester globally significant amounts of atmospheric carbon (C). Extreme rates of soil C accumulation are widely assumed to reflect efficient C storage. Yet the fraction of wetland C lost via hydrologic export has not been directly quantified, since comprehensive budgets including direct estimates of lateral C loss are lacking. We present a complete net ecosystem C budget (NECB), demonstrating that lateral losses of C are a major component of the NECB for the largest stable brackish tidal marsh on the U.S. Pacific coast. Mean annual net ecosystem exchange of CO2 with the atmosphere (NEE = −185 g C m2 year−1, negative NEE denoting ecosystem uptake) was compared to long-term soil C burial (87–110 g C m2 year−1), suggesting only 47–59% of fixed atmospheric C accumulates in soils. Consistently, direct monitoring in 2017–2018 showed NEE of −255 g C m−2 year−1, and hydrologic export of 105 g C m−2 year−1 (59% of NEE remaining on site). Despite their high C sequestration capacity, lateral losses from coastal wetlands are typically a larger fraction of the NECB when compared to other terrestrial ecosystems. Loss of inorganic C (the least measured NECB term) was 91% of hydrologic export and may be the most important term limiting C sequestration. The high productivity of coastal wetlands thus serves a dual function of C burial and estuarine export, and the multiple fates of fixed C must be considered when evaluating wetland capacity for C sequestration.
• Keywords:
  Carbon Cycle (Biogeochemistry) Coastal Ecology Hydrology Carbon Cycle (Biogeochemistry) Coastal Ecology
• Source:
  Global Biogeochemical Cycles, 34, e2019GB006430
• DOI:
  https://doi.org/10.1029/2019GB006430
• Sea Grant Document Number:
  CASG-R-20-030
• Document Type:
  Journal Article
• Funding:
  Grant no. NA18OAR4170073
• Rights Information:
  Other
• Compliance:
  Library
• Main Document Checksum:
  urn:sha256:39f444244046db7ad500870a8191789195ea4aaa496826c165f095d3d85d4ffb
• Download URL:
  https://repository.library.noaa.gov/view/noaa/37307/noaa_37307_DS1.pdf
• File Type:
  [PDF - 7.44 MB ]