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Chemodiversity of dissolved organic matter in lakes driven by climate and hydrology
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.ORCID iD: 0000-0003-3509-8266
2014 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, 3804- p.Article in journal (Refereed) Published
Abstract [en]

Despite the small continental coverage of lakes, they are hotspots of carbon cycling, largely due to the processing of terrestrially derived dissolved organic matter (DOM). As DOM is an amalgam of heterogeneous compounds comprising gradients of microbial and physicochemical reactivity, the factors influencing DOM processing at the molecular level and the resulting patterns in DOM composition are not well understood. Here we show, using ultrahigh-resolution mass spectrometry to unambiguously identify 4,032 molecular formulae in 120 lakes across Sweden, that the molecular composition of DOM is shaped by precipitation, water residence time and temperature. Terrestrially derived DOM is selectively lost as residence time increases, with warmer temperatures enhancing the production of nitrogen-containing compounds. Using biodiversity concepts, we show that the molecular diversity of DOM, or chemodiversity, increases with DOM and nutrient concentrations. The observed molecular-level patterns indicate that terrestrially derived DOM will become more prevalent in lakes as climate gets wetter.

Place, publisher, year, edition, pages
2014. Vol. 5, 3804- p.
National Category
Ecology
Identifiers
URN: urn:nbn:se:uu:diva-224267DOI: 10.1038/ncomms4804ISI: 000337372200015OAI: oai:DiVA.org:uu-224267DiVA: diva2:716137
Available from: 2014-05-08 Created: 2014-05-08 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Molecular-level dissolved organic matter dynamics in lakes: Constraints on reactivity and persistence
Open this publication in new window or tab >>Molecular-level dissolved organic matter dynamics in lakes: Constraints on reactivity and persistence
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dissolved organic matter (DOM) is a central component of the global carbon cycle. Thus, small changes to the amount of DOM imported, processed and produced within lakes can have a large effect on regional carbon budgets. In addition to being a vital energy source at the base of the aquatic food web, DOM is physico-chemically reactive. However, identifying and understanding the controls of DOM processing has remained challenging due to the complex composition of DOM. DOM comprises a mixture of decomposition by-products of terrestrial origin as well as newly synthesized material from in situ production. DOM compounds form gradients of reactivity to biogeochemical processes, such as photodegradation, biodegradation, and flocculation, and they perform a suite of functions in aquatic systems. The overarching goal of this thesis was to investigate controls of DOM processing in Swedish lakes. We do this in two ways: 1) by characterizing the molecular-level composition of DOM in lakes, and 2) by investigating interactions between very labile and relatively recalcitrant DOM. The first three chapters utilize ultrahigh resolution mass spectrometry to show that the detailed chemical composition of DOM varies along a hydrology gradient, and secondarily along a temperature gradient that co-varies with agriculture and nutrients. Next, we illustrate the coherence between molecular-level characteristics and bulk optical characteristics. Together, these studies suggest that protein-like fluorescence, aliphatic compounds, and N-containing compounds are either resistant to degradation or tightly cycled in the system, and thus persist at long water residence times. The most oxidized compounds, such as vascular plant-derived polyphenolic compounds, are abundant in areas with high precipitation and are lost with increasing water residence time. Vascular plant-derived polyphenolic compounds were most strongly related to DOM with high apparent molecular weight, suggesting that hydrophobic interactions drive aggregate formation. Furthermore, the association of high molecular weight DOM with polyphenolic compounds suggests that aggregates are hotspots of reactivity in aquatic systems. Finally, we find no indication that the addition of labile organic matter enhances the biodegradation of less reactive DOM. Thus, we suggest that in freshwaters, intrinsic molecular properties, such as the basic structural features of compounds, dominate over extrinsic factors.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 49 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1260
Keyword
dissolved organic matter, DOM, dissolved organic carbon, organic matter characterization, fluorescence, PARAFAC, molecular weight, mass spectrometry, FT-ICR-MS, boreal lakes
National Category
Natural Sciences
Research subject
Biology with specialization in Limnology
Identifiers
urn:nbn:se:uu:diva-248671 (URN)978-91-554-9260-1 (ISBN)
Public defence
2015-06-12, Friessalen, Norbyvägen 14, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2015-05-22 Created: 2015-04-07 Last updated: 2015-07-07

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Kellerman, Anne M.Kothawala, Dolly N.Tranvik, Lars J.

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