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

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doi: 10.1007/s10533-016-0226-4
Authors:Cooper, Katherine J.; Whitaker, Fiona F.; Anesio, Alexandre M.; Naish, Miranda; Reynolds, Darren M.; Evans, Emma L.
Author Affiliations:Primary:
University of Bristol, School of Earth Sciences, Bristol, United Kingdom
University of the West of England, Center for Research in Biosciences, Bristol, United Kingdom
Volume Title:Biogeochemistry (Dordrecht)
Source:Biogeochemistry (Dordrecht), 129(1-2), p.215-234. Publisher: Springer, Dordrecht - Boston - Lancaster, International. ISSN: 0168-2563
Publication Date:2016
Note:In English. 60 refs.; illus., incl. 2 tables, sketch map
Summary: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. Copyright 2016 Springer International Publishing Switzerland and The Author(s)
Subjects:Aquifers; Atmospheric precipitation; Biochemistry; Biogenic processes; Boreholes; Carbon; Carbon dioxide; Carbonaceous composition; Fluorescence; Forests; Fresh water; Geochemistry; Ground water; Hydrologic cycle; Hydrology; Karst; Karstification; Meteoric water; Microorganisms; Organic carbon; Porosity; Rain; Recharge; Respiration; Soils; Solutes; Solution; Surface water; Unsaturated zone; Vegetation; Andros Island; Bahamas; Caribbean region; West Indies; Absorbance; North Andros Island; Overland flow; Stemflow; Throughfall
Coordinates:N245300 N251200 W0775600 W0780800
Record ID:782342-13
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by Springer Verlag, Berlin, Federal Republic of Germany
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