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Research article - Peer-reviewed, 2020

The CO2-equivalent balance of freshwater ecosystems is non-linearly related to productivity

Grasset, Charlotte; Sobek, Sebastian; Scharnweber, Kristin; Moras, Simone; Villwock, Holger; Andersson, Sara; Hiller, Carolin; Nydahl, Anna C.; Chaguaceda, Fernando; Colom, William; Tranvik, Lars J.


Eutrophication of fresh waters results in increased CO(2)uptake by primary production, but at the same time increased emissions of CH(4)to the atmosphere. Given the contrasting effects of CO(2)uptake and CH(4)release, the net effect of eutrophication on the CO2-equivalent balance of fresh waters is not clear. We measured carbon fluxes (CO(2)and CH(4)diffusion, CH(4)ebullition) and CH(4)oxidation in 20 freshwater mesocosms with 10 different nutrient concentrations (total phosphorus range: mesotrophic 39 mu g/L until hypereutrophic 939 mu g/L) and planktivorous fish in half of them. We found that the CO2-equivalent balance had a U-shaped relationship with productivity, up to a threshold in hypereutrophic systems. CO2-equivalent sinks were confined to a narrow range of net ecosystem production (NEP) between 5 and 19 mmol O-2 m(-3) day(-1). Our findings indicate that eutrophication can shift fresh waters from sources to sinks of CO2-equivalents due to enhanced CO(2)uptake, but continued eutrophication enhances CH(4)emission and transforms freshwater ecosystems to net sources of CO2-equivalents to the atmosphere. Nutrient enrichment but also planktivorous fish presence increased productivity, thereby regulating the resulting CO2-equivalent balance. Increasing planktivorous fish abundance, often concomitant with eutrophication, will consequently likely affect the CO2-equivalent balance of fresh waters.


carbon dioxide; eutrophication; food web structure; greenhouse gas; methane; oxidation

Published in

Global Change Biology
2020, volume: 26, number: 10, pages: 5705-5715
Publisher: WILEY

Authors' information

Grasset, Charlotte
Uppsala Univ
Sobek, Sebastian
Uppsala Univ
Scharnweber, Kristin
Uppsala Univ
Moras, Simone
Uppsala Univ
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Uppsala University
Andersson, Sara
Uppsala Univ
Hiller, Carolin
Univ Bayreuth
Nydahl, Anna C.
Uppsala Univ
Chaguaceda, Fernando
Uppsala Univ
Colom, William
Uppsala Univ
Tranvik, Lars J.
Uppsala Univ

Sustainable Development Goals

SDG6 Clean water

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