Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/bg-2017-279
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
14 Jul 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Biogeosciences (BG).
Quality transformation of dissolved organic carbon during water transit through lakes: contrasting controls by photochemical and biological processes
Martin Berggren1, Marcus Klaus2, Balathandayuthabani Panneer Selvam1, Lena Ström1, Hjalmar Laudon3, Mats Jansson2, and Jan Karlsson2 1Department of Physical Geography and Ecosystem Science, Lund University, SE-223 62, Lund, Sweden
2Department of Ecology and Environmental Science, Umeå University, SE-90187, Umeå, Sweden
3Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183, Umeå, Sweden
Abstract. Dissolved organic carbon (DOC) may be removed, transformed or added during water transit through lakes, resulting in qualitative changes in DOC composition and pigmentation (color). However, the process-based understanding of these changes is incomplete, especially for headwater lakes. We hypothesized that because heterotrophic bacteria preferentially consume non-colored DOC, while photochemical processing remove colored fractions, the overall changes in DOC quality and color (absorbance) upon water passage through a lake depends on the relative importance of these two processes, accordingly. To test this hypothesis we combined laboratory experiments with field studies in nine boreal lakes, assessing both the relative importance of different DOC decay processes (biological or photo-chemical) and the loss of color during water transit time (WTT) through the lakes. We found that photo-chemistry qualitatively dominated the DOC transformation in the epilimnia of relatively clear headwater lakes, resulting in selective losses of colored DOC. However, in highly pigmented brown-water lakes (absorbance at 420 nm > 7 m−1) biological processes dominated, and there was no systematic relationship between color loss and WTT. Instead in situ data and dark experiments supported our hypothesis of selective microbial removal of non-pigmented DOC, mainly of low molecular weight, leading to persistent water color over time in these lakes. Our study shows that individual brown headwater lakes do not conform to the commonly reported pattern of selective removal of colored constituents in freshwaters, but rather the DOC shows a sustained degree of pigmentation upon transit through these lakes.

Citation: Berggren, M., Klaus, M., Panneer Selvam, B., Ström, L., Laudon, H., Jansson, M., and Karlsson, J.: Quality transformation of dissolved organic carbon during water transit through lakes: contrasting controls by photochemical and biological processes, Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-279, in review, 2017.
Martin Berggren et al.
Martin Berggren et al.
Martin Berggren et al.

Viewed

Total article views: 226 (including HTML, PDF, and XML)

HTML PDF XML Total Supplement BibTeX EndNote
163 61 2 226 18 1 2

Views and downloads (calculated since 14 Jul 2017)

Cumulative views and downloads (calculated since 14 Jul 2017)

Viewed (geographical distribution)

Total article views: 226 (including HTML, PDF, and XML)

Thereof 217 with geography defined and 9 with unknown origin.

Country # Views %
  • 1

Saved

Discussed

Latest update: 17 Oct 2017
Publications Copernicus
Download
Short summary
The quality of dissolved organic carbon (DOC), especially its pigmentation, is a defining feature of freshwater ecosystems. We found that colored DOC fractions are surprisingly persistent to natural degradation during water transit through many brown-water lakes. This is explained by the dominance of microbial processes that appear to selectively remove non-colored DOC. However, in lakes where sunlight degradation play a relatively larger role, DOC bleaching occurs.
The quality of dissolved organic carbon (DOC), especially its pigmentation, is a defining...
Share