Using 14C to investigate methane production and DOC reactivity in northern peatlands

1
Using 14C to investigate methane production and
DOC reactivity in northern peatlands Liz
Corbett, Jeffrey P. Chanton, Paul A. Glaser,
William T. Cooper, Donald I. Siegel, Mimi Sarkar,
Julianna DAndrilli Department of Oceanography,
Florida State University, Tallahassee, FL
32306 corresponding author corbett_at_ocean.fsu.edu

Introduction Peatlands are a large carbon
reservoirs. These ecosystems are saturated with
water, and therefore, have an extremely low rate
of decomposition. In this way, they have stored
and accumulated carbon for over 6,000 years. With
the current threat of global warming, they have
the potential to become a carbon source to the
outside environment by either leaching large
amounts of DOC into connecting rivers or by
producing CO2 and CH4 into the atmosphere by
increased microbial respiration.

• Purpose of Study
• Understand why microbes in a fen environment show
  a
• shift from acetate fermentation to CO2
  reduction at depth,
• but microbes in a bog environment utilize CO2
  reduction
• at all depths
• Quantify the DOC size reservoirs in the peatland
  
• environment
• Differentiate between bog and fen DOC
• Differentiate between deep and surface DOC
• Determine which DOC sizes serve as a microbial
  food
• source
• Categorize DOC based on size, aromaticity and
  structure

• Conclusions
• Data suggests that the structure or quality of
  DOC may differ
• between the bog and fen environments
• Fen DOC is more labile than bog DOC suggesting it
  as a better
• food source for bacteria
• The concentration of LMW DOC increases with depth
  
• suggesting LMW accumulates because it is not
  utilized by
• bacteria, whereas HMW concentrations increase
  as the bacteria
• metabolize it as a food source
• DOC degradation by UV light suggests that the DOC
  is made
• up of aromatic groups
• The cross-plot shows a shift in metabolic
  pathways in the fen but
• not in the bog

• Size Filtration study showing larger
  concentrations of LMW DOC suggesting bacterial
  preferentially choose HMW DOC as a resource and
  leave behind LMW DOC to accumulate

• Microbes seem to prefer fen DOC to bog DOC since
  the
• 14C value of their respiration products (CO2
  and CH4)
• exactly matches DOC in the fen environments,
  but only
• partly matches bog DOC.