| 1. |
- Marotta, H., et al.
(författare)
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Greenhouse gas production in low-latitude lake sediments responds strongly to warming
- 2014
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Ingår i: Nature Climate Change. - : Nature Publishing Group. - 1758-678X .- 1758-6798. ; 4:6, s. 467-470
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Tidskriftsartikel (refereegranskat)abstract
- Inland water sediments receive large quantities of terrestrial organic matter(1-5) and are globally important sites for organic carbon preservation(5,6). Sediment organic matter mineralization is positively related to temperature across a wide range of high-latitude ecosystems(6-10), but the situation in the tropics remains unclear. Here we assessed temperature effects on the biological production of CO2 and CH4 in anaerobic sediments of tropical lakes in the Amazon and boreal lakes in Sweden. On the basis of conservative regional warming projections until 2100 (ref. 11), we estimate that sediment CO2 and CH4 production will increase 9-61% above present rates. Combining the CO2 and CH4 as CO2 equivalents (CO(2)eq; ref. 11), the predicted increase is 2.4-4.5 times higher in tropical than boreal sediments. Although the estimated lake area in low latitudes is 3.2 times smaller than that of the boreal zone, we estimate that the increase in gas production from tropical lake sediments would be on average 2.4 times higher for CO2 and 2.8 times higher for CH4. The exponential temperature response of organic matter mineralization, coupled with higher increases in the proportion of CH4 relative to CO2 on warming, suggests that the production of greenhouse gases in tropical sediments will increase substantially. This represents a potential large-scale positive feedback to climate change.
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| 2. |
- Peter, Hannes, et al.
(författare)
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Multifunctionality and diversity in bacterial biofilms
- 2011
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Ingår i: PLOS ONE. - San Fransisco : Public Library of Science (PLoS). - 1932-6203. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- Bacteria are highly diverse and drive a bulk of ecosystem processes. Analysis of relationships between diversity and single specific ecosystem processes neglects the possibility that different species perform multiple functions at the same time. The degradation of dissolved organic carbon (DOC) followed by respiration is a key bacterial function that is modulated by the availability of DOC and the capability to produce extracellular enzymes. In freshwater ecosystems, biofilms are metabolic hotspots and major sites of DOC degradation. We manipulated the diversity of biofilm forming communities which were fed with DOC differing in availability. We characterized community composition using molecular fingerprinting (T-RFLP) and measured functioning as oxygen consumption rates, the conversion of DOC in the medium, bacterial abundance and the activities of five specific enzymes. Based on assays of the extracellular enzyme activity, we calculated how the likelihood of sustaining multiple functions was affected by reduced diversity. Carbon source and biofilm age were strong drivers of community functioning, and we demonstrate how the likelihood of sustaining multifunctionality decreases with decreasing diversity.
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| 3. |
- Sobek, Sebastian, et al.
(författare)
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Temperature dependence of apparent respiratory quotients and oxygen penetration depth in contrasting lake sediments
- 2017
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Ingår i: Journal of Geophysical Research - Biogeosciences. - Washington : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 122:11, s. 3076-3087
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Tidskriftsartikel (refereegranskat)abstract
- Lake sediments constitute an important compartment in the carbon cycle of lakes, by burying carbon over geological timescales and by production and emission of greenhouse gases. The degradation of organic carbon (OC) in lake sediments is linked to both temperature and oxygen (O-2), but the interactive nature of this regulation has not been studied in lake sediments in a quantitative way. We present the first systematic investigation of the effects of temperature on the apparent respiratory quotient (RQ, i.e., the molar ratio between carbon dioxide (CO2) production and O-2 consumption) in two contrasting lake sediments. Laboratory incubations of sediment cores of a humic lake and an eutrophic lake across a 1-21 degrees C temperature gradient over 157days revealed that both CO2 production and O-2 consumption were positively, exponentially, and similarly dependent on temperature. The apparent RQ differed significantly between the lake sediments (0.630.26 and 0.990.28 in the humic and the eutrophic lake, respectively; meanSD) and was significantly and positively related to temperature. The O-2 penetration depth into the sediment varied by a factor of 2 over the 1-21 degrees C temperature range and was significantly, negatively, and similarly related to temperature in both lake sediments. Accordingly, increasing temperature may influence the overall extent of OC degradation in lake sediments by limiting O-2 supply to aerobic microbial respiration to the topmost sediment layer, resulting in a concomitant shift to less effective anaerobic degradation pathways. This suggests that temperature may represent a key controlling factor of the OC burial efficiency in lake sediments.
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| 4. |
- Steger, Kristin, et al.
(författare)
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Comparative study on bacterial carbon sources in lake sediments : the role of methanotrophy
- 2015
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 76:1, s. 39-47
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Tidskriftsartikel (refereegranskat)abstract
- Methane-derived carbon can be important in both benthic and pelagic food webs. Either generated in the anaerobic layers of the sediment or in the anaerobic hypolimnion of stratified eutrophic lakes, methane is an excellent carbon source for aerobic methanotrophic bacteria. The very negative methane δ13C-signal in the methanotrophic biomass provides an excellent opportunity to trace the use of methane-derived carbon in food webs. We studied carbon sources of benthic bacteria in a range of Swedish lakes with different inputs of terrestrial organic carbon and indigenous primary production. We analyzed the 13C:12C ratios in phospholipid-derived fatty acids, which serve as biomarkers for specific groups of Bacteria. We demonstrate that methane is an important carbon source for sediment bacteria, not only for the methanotrophic community but also for the non-methanotrophic heterotrophic bacteria. This most likely indirect utilization of isotopically highly depleted methane masks the stable isotope signatures for terrestrial input and local primary production in the heterotrophic bacterial community.
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| 5. |
- Steger, Kristin, et al.
(författare)
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Microbial biomass and community composition in boreal lake sediments
- 2011
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Ingår i: Limnology and Oceanography. - Waco : American Society of Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 56:2, s. 725-733
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Tidskriftsartikel (refereegranskat)abstract
- We used phospholipid fatty acids (PLFA) to determine microbial biomass and community structure in the sediments of eight boreal lakes with different loadings of allochthonous organic carbon and total phosphorus (TP) in the water during the course of a year. The total concentration of PLFA, an estimate of the microbial biomass, depended more on TP, a proxy for pelagic primary production, but not on dissolved organic carbon, a proxy for terrestrial organic carbon input. The composition of PLFAs varied considerably over time, demonstrating seasonal dynamics in microbial community composition. When PLFA profiles in all lakes and seasons are compared, community composition is more similar within season than within lakes.
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