Mobilization of optically invisible dissolved organic matter in response to rainstorm events in a tropical forest headwater river

Ryan Pereira, C. Isabella Bovolo, Robert G. M. Spencer, Peter J. Hernes, Edward Tipping, Andrea Vieth-Hillebrand, Nikolai Pedentchouk, Nick A. Chappell, Geoff Parkin, Thomas Wagner

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Abstract

This study emphasizes the importance of rainstorm events in mobilizing carbon at the soil-stream interface from tropical rainforests. Half-hourly geochemical/isotopic records over a 13.5h period from a 20km(2) tropical rainforest headwater in Guyana show an order of magnitude increase in dissolved organic carbon (DOC) concentration in less than 30 mins (10.6-114mg/L). The composition of DOC varies significantly and includes optically invisible dissolved organic matter (iDOM) that accounts for a large proportion (4-89%) of the total DOC, quantified using size exclusion chromatography (SEC). SEC suggests that iDOM is comprised of low molecular weight organic moieties, which are likely sourced from fresh leaf litter and/or topsoil, as shown in soils from the surrounding environment. Although poorly constrained at present, the presence of iDOM further downstream during the wet season suggests that this organic matter fraction may represent an unquantified source of riverine CO2 outgassing in tropical headwaters, requiring further consideration.

Key Points

Extremely variable riverine DOC concentration ranging from 10.6 to 114 mg/L iDOM accounts for 4-89% of the DOM pool Large variability of riverine DOM source and composition

Original languageEnglish
Pages (from-to)1202-1208
Number of pages7
JournalGeophysical Research Letters
Volume41
Issue number4
DOIs
Publication statusPublished - 28 Feb 2014

Keywords

  • DOC
  • headwaters
  • tropics
  • iDOM
  • invisible
  • ULTRAVIOLET ABSORBENCY
  • AMAZONIAN RIVERS
  • CARBON FLUXES
  • TERRESTRIAL
  • SOILS
  • BIOGEOCHEMISTRY
  • CATCHMENTS
  • SORPTION
  • CLIMATE
  • EXPORT

Cite this

Pereira, R., Bovolo, C. I., Spencer, R. G. M., Hernes, P. J., Tipping, E., Vieth-Hillebrand, A., Pedentchouk, N., Chappell, N. A., Parkin, G., & Wagner, T. (2014). Mobilization of optically invisible dissolved organic matter in response to rainstorm events in a tropical forest headwater river. Geophysical Research Letters, 41(4), 1202-1208. https://doi.org/10.1002/2013GL058658