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Colored organic matter increases CO 2 in meso‐eutrophic lake water through altered light climate and acidity
Author(s) -
Nydahl Anna C.,
Wallin Marcus B.,
Tranvik Lars J.,
Hiller Carolin,
Attermeyer Katrin,
Garrison Julie A.,
Chaguaceda Fernando,
Scharnweber Kristin,
Weyhenmeyer Gesa A.
Publication year - 2019
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.11072
Subject(s) - mesocosm , dissolved organic carbon , carbon dioxide , eutrophication , photosynthesis , shading , environmental chemistry , chemistry , organic matter , heterotroph , carbonate , primary production , ecosystem , environmental science , ecology , nutrient , biology , art , biochemistry , genetics , organic chemistry , bacteria , visual arts
Many surface waters across the boreal region are browning due to increased concentrations of colored allochthonous dissolved organic carbon (DOC). Browning may stimulate heterotrophic metabolism, may have a shading effect constraining primary production, and may acidify the water leading to decreased pH with a subsequent shift in the carbonate system. All these effects are expected to result in increased lake water carbon dioxide (CO 2 ) concentrations. We tested here these expectations by assessing the effects of both altered allochthonous DOC input and light conditions through shading on lake water CO 2 concentrations. We used two mesocosm experiments with water from the meso‐eutrophic Lake Erken, Sweden, to determine the relative importance of bacterial activities, primary production, and shifts in the carbonate system on CO 2 concentrations. We found that DOC addition and shading resulted in a significant increase in partial pressure of CO 2 ( p CO 2 ) in all mesocosms. Surprisingly, there was no relationship between bacterial activities and p CO 2 . Instead the experimental reduction of light by DOC and/or shading decreased the photosynthesis to respiration ratio leading to increased p CO 2 . Another driving force behind the observed pC O 2 increase was a significant decrease in pH, caused by a decline in photosynthesis and the input of acidic DOC. Considering that colored allochthonous DOC may increase in a warmer and wetter climate, our results could also apply for whole lake ecosystems and p CO 2 may increase in many lakes through a reduction in the rate of photosynthesis and decreased pH.