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Quantifying photodegradation of peatland-derived dissolved organic carbon in the coastal ocean of Southeast Asia
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  • Yongli Zhou,
  • Moritz Müller,
  • Nagur RC Cherukuru,
  • Patrick Martin
Yongli Zhou
Nanyang Technological University

Corresponding Author:[email protected]

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Moritz Müller
Swinburne University of Technology Sarawak Campus
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Nagur RC Cherukuru
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
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Patrick Martin
Nanyang Technological University
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The terrigenous dissolved organic carbon (tDOC) exported from the peatlands in Southeast Asia appears to be extensively remineralized in the shelf sea, but the processes that drive this remineralization remain unclear. Here, we combined incubation experiments and model simulations to quantify the rate and extent of photodegradation of tDOC in the Sunda Shelf Sea. Laboratory photodegradation experiments indicate that up to 74% of the peatland tDOC is potentially labile to photochemical remineralization. Based on our estimated apparent quantum yield for tDOC remineralization, modeled in-situ solar irradiance, and measured inherent optical properties of the water column, we simulated peatland tDOC photoremineralization for two coastal regions of the Sunda Shelf Sea. These simulation results show that natural solar radiation can directly remineralize 20±11% of tDOC over 2 years, which corresponds to the approximate residence time of water in the Sunda Shelf Sea, and that significant photobleaching of tDOC can occur in coastal waters over shorter time-scales. We further derived a simplified photochemical decay constant of 0.008–0.017day-1 for Southeast Asia’s peatland-derived tDOC, which can be used to parameterize the recently proposed UniDOM model framework. We conclude that direct photodegradation may be a greater sink for tDOC in Southeast Asia’s coastal ocean compared to higher latitudes, although it is insufficient to account for the total tDOC remineralization observed in the Sunda Shelf Sea.