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Quality transformation of dissolved organic carbon during water transit through lakes : contrasting controls by photochemical and biological processes

Berggren, Martin LU ; Klaus, Marcus; Panneer Selvam, Balathandayuthabani LU ; Ström, Lena LU ; Laudon, Hjalmar; Jansson, Mats and Karlsson, Jan (2018) In Biogeosciences 15(2). p.457-470
Abstract
Dissolved organic carbon (DOC) may be removed, transformed, or added during water transit through lakes, resulting in 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 noncolored DOC, while photochemical processing removes colored fractions, the overall changes in DOC color upon water passage through a lake depend 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... (More)
Dissolved organic carbon (DOC) may be removed, transformed, or added during water transit through lakes, resulting in 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 noncolored DOC, while photochemical processing removes colored fractions, the overall changes in DOC color upon water passage through a lake depend 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 photochemical) and the loss of color during water transit time (WTT) through the lakes. We found that influence from photo-decay dominated changes in DOC quality in the epilimnia of relatively clear headwater lakes, resulting in systematic and selective net 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. Moreover, in situ data and dark experiments supported our hypothesis on the selective microbial removal of nonpigmented DOC, mainly of low molecular weight, leading to persistent water color in these highly colored lakes. Our study shows that brown headwater lakes may not conform to the commonly reported pattern of the selective removal of colored constituents in freshwaters, as DOC can show a sustained degree of pigmentation upon transit through these lakes. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biogeosciences
volume
15
issue
2
pages
457 - 470
publisher
Copernicus Publications
external identifiers
  • scopus:85041210115
ISSN
1726-4189
DOI
10.5194/bg-15-457-2018
language
English
LU publication?
yes
id
81b0da0b-b87a-46a5-88f4-9b8c7ac95446
date added to LUP
2018-01-24 15:50:28
date last changed
2018-05-29 10:37:36
@article{81b0da0b-b87a-46a5-88f4-9b8c7ac95446,
  abstract     = {Dissolved organic carbon (DOC) may be removed, transformed, or added during water transit through lakes, resulting in 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 noncolored DOC, while photochemical processing removes colored fractions, the overall changes in DOC color upon water passage through a lake depend 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 photochemical) and the loss of color during water transit time (WTT) through the lakes. We found that influence from photo-decay dominated changes in DOC quality in the epilimnia of relatively clear headwater lakes, resulting in systematic and selective net 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. Moreover, in situ data and dark experiments supported our hypothesis on the selective microbial removal of nonpigmented DOC, mainly of low molecular weight, leading to persistent water color in these highly colored lakes. Our study shows that brown headwater lakes may not conform to the commonly reported pattern of the selective removal of colored constituents in freshwaters, as DOC can show a sustained degree of pigmentation upon transit through these lakes.},
  author       = {Berggren, Martin and Klaus, Marcus and Panneer Selvam, Balathandayuthabani and Ström, Lena and Laudon, Hjalmar and Jansson, Mats and Karlsson, Jan},
  issn         = {1726-4189},
  language     = {eng},
  month        = {01},
  number       = {2},
  pages        = {457--470},
  publisher    = {Copernicus Publications},
  series       = {Biogeosciences},
  title        = {Quality transformation of dissolved organic carbon during water transit through lakes : contrasting controls by photochemical and biological processes},
  url          = {http://dx.doi.org/10.5194/bg-15-457-2018},
  volume       = {15},
  year         = {2018},
}