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Peer-reviewedCC BY 4.0Biogeosciences

Warming vs. browning: a dual mechanism behind net ecosystem production of shallow brown aquatic systems

  • Aleksey Paltsev1
  • Isolde Callisto Puts1,2,3
  1. 1Umeå University (Umeå, Sweden)
  2. 2University of Oslo (Oslo, Norway)
  3. 3Aarhus University (Aarhus, Denmark)
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Abstract

Northern lakes are warming and browning due to increased cDOM inputs, altering water column C:N:P ratios and temperatures that regulate microbial production. Yet the relative importance of warming versus browning, and their combined effects on nutrient stoichiometry and microbial dynamics remain unclear. We experimentally manipulated boreal ponds along a cDOM gradient under ambient and +2 °C warming to quantify impacts on nutrient conditions and microbial production. Browning shifted C:N:P stoichiometry in both total and dissolved pools, with increased C:N and C:P ratios in the total nutrient pools, while reducing inorganic nutrient availability. Despite declining N:P ratios, both pools were strongly carbon-rich and depleted in both N and P. Nutrient-addition assays confirmed NP co-limitation. Browning increased bacterial production, while browning and warming combined reduced primary production, lowering PP:BP ratios. We show that browning -not warming- drives boreal freshwaters toward carbon-rich, N- and P- colimited conditions, while warming and browning together modulate microbial production by amplifying cDOM-driven heterotrophy and suppressing photoautotrophic production. Our study reveals a dual mechanism behind the shifting of brown systems toward heterotrophy. As browning and warming are pervasive trends across Northern lakes, these findings have wide applicability and advance general understanding of how freshwaters respond to ongoing environmental change.

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Cite

BibTeXRIS
BibTeX
@article{paltsev2026warming,
  title = {{Warming vs. browning: a dual mechanism behind net ecosystem production of shallow brown aquatic systems}},
  author = {Aleksey Paltsev and Isolde Callisto Puts},
  journal = {Biogeosciences},
  year = {2026},
  month = oct,
  doi = {10.5194/bg-23-7493-2026},
  url = {https://bg.copernicus.org/articles/23/7493/2026/},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Warming vs. browning: a dual mechanism behind net ecosystem production of shallow brown aquatic systems
AU  - Aleksey Paltsev
AU  - Isolde Callisto Puts
PY  - 2026
DA  - 2026/10/26
JO  - Biogeosciences
DO  - 10.5194/bg-23-7493-2026
UR  - https://bg.copernicus.org/articles/23/7493/2026/
AB  - Northern lakes are warming and browning due to increased cDOM inputs, altering water column C:N:P ratios and temperatures that regulate microbial production. Yet the relative importance of warming versus browning, and their combined effects on nutrient stoichiometry and microbial dynamics remain unclear. We experimentally manipulated boreal ponds along a cDOM gradient under ambient and +2 °C warming to quantify impacts on nutrient conditions and microbial production. Browning shifted C:N:P stoichiometry in both total and dissolved pools, with increased C:N and C:P ratios in the total nutrient pools, while reducing inorganic nutrient availability. Despite declining N:P ratios, both pools were strongly carbon-rich and depleted in both N and P. Nutrient-addition assays confirmed NP co-limitation. Browning increased bacterial production, while browning and warming combined reduced primary production, lowering PP:BP ratios. We show that browning -not warming- drives boreal freshwaters toward carbon-rich, N- and P- colimited conditions, while warming and browning together modulate microbial production by amplifying cDOM-driven heterotrophy and suppressing photoautotrophic production. Our study reveals a dual mechanism behind the shifting of brown systems toward heterotrophy. As browning and warming are pervasive trends across Northern lakes, these findings have wide applicability and advance general understanding of how freshwaters respond to ongoing environmental change.
SN  - 1726-4189
SN  - 1726-4170
ER  -