uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Do we have a weight problem? The discrepancy between actual and apparent molecular weight of dissolved organic matter in lakes
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.
(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:uu:diva-248668OAI: oai:DiVA.org:uu-248668DiVA: diva2:806841
Available from: 2015-04-21 Created: 2015-04-07 Last updated: 2016-03-05
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

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Tranvik, Lars J.
By organisation
Limnology
Natural Sciences

Search outside of DiVA

GoogleGoogle Scholar

Total: 325 hits
ReferencesLink to record
Permanent link

Direct link