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Dissolved organic carbon transformations and microbial community response to variations in recharge waters in a shallow carbonate aquifer

Research output: Contribution to journalArticle

  • Katie Cooper
  • Fiona Whitaker
  • Alexandre Anesio
  • Miranda Naish
  • Darren Reynolds
  • Emma Evans
Original languageEnglish
Pages (from-to)215-234
Number of pages20
JournalBiogeochemistry
Volume128
Early online date29 Jul 2016
DOIs
DateAccepted/In press - 18 Jun 2016
DateE-pub ahead of print - 29 Jul 2016
DatePublished (current) - Aug 2016

Abstract

In carbonate aquifers, dissolved organic carbon from the surface drives heterotrophic metabolism, generating CO2 in the subsurface. Although this has been a proposed mechanism for enhanced dissolution at the water table, respiration rates and their controlling factors have not been widely evaluated. This study investigates the composition and concentration of dissolved organic carbon (DOC) reaching the water table from different recharge pathways on a subtropical carbonate island using a combination of DOC concentration measurements, fluorescence and absorption characterisation. In addition, direct measurements of the microbial response to the differing water types were made. Interactions of rainfall with the vegetation, via throughfall and stemflow, increase the concentration of DOC. The highest DOC concentrations are associated with stemflow, overland recharge and dissolution hole waters which interact with bark lignin and exhibit strong terrestrial-derived characteristics. The groundwater samples exhibit the lowest concentrations of DOC and are comprised of refractory humic-like organic matter. The heterotrophic response seems to be controlled by the concentration of DOC in the sample. The terrestrially sourced humic-like matter in the stemflow and dissolution hole samples was highly labile, thus increasing the amount of biologically produced CO2 to drive dissolution. Based on the calculated respiration rates, microbial activity could enhance carbonate dissolution, increasing porosity generation by a maximum of 1 % kyr−1 at the top of the freshwater lens.

    Research areas

  • Dissolved organic carbon Carbonate Heterotrophic respiration Recharge waters Fluorescence EEM Karstification

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    Rights statement: This is the final published version of the article (version of record). It first appeared online via Springer at DOI 10.1007/s10533-016-0226-4. Please refer to any applicable terms of use of the publisher.

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