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Microbially induced flocculation of allochthonous dissolved organic carbon in lakes
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.ORCID-id: 0000-0003-3509-8266
2009 (engelsk)Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 54, nr 5, s. 1811-1818Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The flocculation of allochthonous dissolved organic carbon (DOC) in lakes was investigated in a series of laboratory experiments. Flocculation was enhanced by increased temperatures, and addition of glucose increased the flocculation further. A change in pH within the range of 3.3 to 7.3 resulted in decreased flocculation with increasing deviation from the original pH. Flocculation was similar under oxic and anoxic conditions. For all treatments (i.e., temperature and glucose, pH, and O2 regime), occulation was positively correlated to bacterial respiration. However, bacterial biomass made up a negligible fraction of the formed flocs, suggesting that the formation of detrital particles was a result of bacterial activity, but there was no significant contribution of bacteria to the mass of the particles formed. In all experiments, both the concentration of DOC and concentration of colored dissolved organic matter (CDOM) decreased concomitantly with flocculation, suggesting that CDOM is the precursor of the flocs. Bacteria mediate a translocation of DOC in the water column into particles prone to gravitational settling.

sted, utgiver, år, opplag, sider
2009. Vol. 54, nr 5, s. 1811-1818
HSV kategori
Identifikatorer
URN: urn:nbn:se:uu:diva-97915ISI: 000268325300036OAI: oai:DiVA.org:uu-97915DiVA, id: diva2:173032
Tilgjengelig fra: 2008-12-17 Laget: 2008-12-17 Sist oppdatert: 2017-12-14bibliografisk kontrollert
Inngår i avhandling
1. Flocculation of Allochthonous Dissolved Organic Matter – a Significant Pathway of Sedimentation and Carbon Burial in Lakes
Åpne denne publikasjonen i ny fane eller vindu >>Flocculation of Allochthonous Dissolved Organic Matter – a Significant Pathway of Sedimentation and Carbon Burial in Lakes
2008 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Inland waters receive substantial amounts of organic carbon from adjacent watersheds. Only about half of the carbon exported from inland waters reaches the oceans, while the remainder is lost en route. This thesis identifies flocculation as an important and significant fate of carbon in the boreal landscape. Flocculation reallocates organic carbon from the dissolved state into particles which are prone to settle. Thus, flocculation relocates organic carbon from the water column to the sediment.

The dissolved organic carbon (DOC), mainly originating from terrestrial sources, in a set of Swedish lakes was found to determine the extent of sedimentation of particulate organic carbon. A major fraction of the settling particles were of allochthonous origin. This implies that allochthonous DOC was the precursor of the settling matter in these lakes. The gross sedimentation was of the same magnitude as the evasion of carbon dioxide to the atmosphere.

Sunlight, especially in the photosynthetically active region, stimulated flocculation of DOC. The effect of light appeared to involve a direct photochemical reaction. Iron was involved in the flocculation but it could not be unravelled whether the iron catalyzes the flocculation or just co-precipitates with the settling matter. Microbial activity was identified as the main regulator of the flocculation rates. Accordingly, alteration of temperature, oxygen concentration and pH did not affect flocculation only indirectly, via their effects on microbial metabolism.

A comparison of fluorescence characteristics of organic matter collected in sediment trap and in the sediment surface layer revealed that autochthonous organic carbon was preferentially lost in the sediments while allochthonous matter increased. The recalcitrant nature of the flocculated matter could favour sequestration of this matter in the lake sediment. Hence, the lakes will act as sinks of organic carbon due to a slower mineralization of the flocculated matter in the sediments.

sted, utgiver, år, opplag, sider
Uppsala: Universitetsbiblioteket, 2008. s. 42
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 586
Emneord
flocculation, dissolved organic carbon, allochthonous, carbon sequestration, carbon cycle, boreal lakes
HSV kategori
Identifikatorer
urn:nbn:se:uu:diva-9500 (URN)978-91-554-7374-7 (ISBN)
Disputas
2009-01-21, Ekmansalen, Kärnhuset, EBC, Norbyvägen 18, Uppsala, 10:00
Opponent
Veileder
Tilgjengelig fra: 2008-12-17 Laget: 2008-12-17 Sist oppdatert: 2016-04-28bibliografisk kontrollert

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