The tropical peatlands of Southeast Asia deliver roughly 10% of the global land–ocean flux of terrestrial DOC (tDOC). The land boundaries and seasonally reversing ocean circulation of Southeast Asia’s shelf sea ensure that this tDOC has a relatively long residence time on the shelf, creating ideal conditions to track tDOC biogeochemical processing. We will present results from our recent work to better understand the flux and fate of this tDOC in the shelf sea. Using satellite remote sensing, we have detected a significant increase in coastal tDOC concentrations by about 0.3 micro-mol l^-1 year^-1over the last two decades that is likely linked to large-scale peatland deforestation and drainage. Moreover, a mass balance analysis of carbon stable isotopes between the dissolved organic and inorganic carbon pools indicates that at least 60–70% of the peatland tDOC is remineralized within the shelf sea, creating significant acidification in the shelf waters. Degradation experiments with peatland tDOC and model simulations indicate that the rates of purely microbial and purely photochemical remineralization are slow, but that partial photodegradation greatly enhances the rate of subsequent microbial remineralization. We will also discuss efforts to incorporate tDOC transport and degradation into a regional shelf sea biogeochemical model for Southeast Asia.

Primary Presenter: Patrick Martin, Nanyang Technological University (pmartin@ntu.edu.sg)

Authors:

Yuan Chen, Nanyang Technological University  (YUAN006@e.ntu.edu.sg)

Yongli Zhou, Marine Biological Laboratory  (yzhou@mbl.edu)

Moritz Müller, Swinburne University of Science and Technology  (mmueller@swinburne.edu.my)

Nagur Cherukuru, Commonwealth Scientific and Industrial Research Organisation  (nagur.cherukuru@csiro.au)

Bernhard Mayer, Nanyang Technological University  (bernhard.mayer@ntu.edu.sg)

A'an Wahyudi, Nanyang Technological University  (aanj001@brin.go.id)

Norlaila Zanuri, Universiti Sains Malaysia  (lailazanuri@usm.my)