| 1. |
- Bastviken, David, et al.
(författare)
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Freshwater Methane Emissions Offset the Continental Carbon Sink
- 2011
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 331:6013, s. 50-50
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Tidskriftsartikel (refereegranskat)abstract
- Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH4) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets. Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least 103 teragrams of CH4 year−1, corresponding to 0.65 petagrams of C as carbon dioxide (CO2) equivalents year−1, offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and freshwaters need to be recognized as important in the global carbon cycle.
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| 2. |
- Bastviken, David, et al.
(författare)
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Methane Emissions from Pantanal, South America, during the Low Water Season : Toward More Comprehensive Sampling
- 2010
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 44:14, s. 5450-5455
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Tidskriftsartikel (refereegranskat)abstract
- Freshwater environments contribute 75% of the natural global methane (CH4) emissions. While there are indications that tropical lakes and reservoirs emit 58-400% more CH4 per unit area than similar environments in boreal and temperate biomes, direct measurements of tropical lake emissions are scarce. We measured CH4 emissions from 16 natural shallow lakes in the Pantanal region of South America, one of the world's largest tropical wetland areas, during the low water period using floating flux chambers. Measured fluxes ranged from 3.9 to 74.2 mmol m(-2) d(-1) with the average from all studied lakes being 8.8 mmol m(-2) d(-1) (131.8 mg CH4 m(-2) d(-1)), of which ebullition accounted for 91% of the flux (28-98% on individual lakes). Diel cycling of emission rates was observed and therefore 24-h long measurements are recommended rather than short-term measurements not accounting for the full diel cycle. Methane emission variability within a lake may be equal to or more important than between lake variability in floodplain areas as this study identified diverse habitats within lakes having widely different flux rates. Future measurements with static floating chambers should be based on many individual chambers distributed in the various subenvironments of a lake that may differ in emissions in order to account for the within lake variability.
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| 3. |
- Lucia Santoro, Ana, et al.
(författare)
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Simultaneous measurements of dark carbon fixation and bacterial production in lake sediment
- 2013
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Ingår i: Limnology and Oceanography. - : Association for the Sciences of Limnology and Oceanography (ASLO). - 1541-5856. ; 11, s. 298-303
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Tidskriftsartikel (refereegranskat)abstract
- Carbon fixation by chemoautotrophic bacteria represents an autochthonous source of organic matter, and may be of particular importance close to redox boundaries. Despite the known sediment chemoautotrophic potential, the quantitative role and the importance of dark carbon fixation (DCF) in lake sediments are still unknown. We provide here a method to measure DCF and bacterial production simultaneously in stratified sediment cores, using C-14 labeled dissolved inorganic carbon ((DIC)-C-14) and H-3-leucine incorporation. Beyond the total activity, the method allows measurements of the processes over depth, as a profile into the sediment. DCF increased with depth in our profiles, indicating a predominance of anoxic processes. In addition, the method can yield information about the extent (DIC)-C-14 was allocated into the bacterial proteins (DCFp). Slurry and stratified core incubations were compared and yielded similar results for total DCF activity.
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| 4. |
- 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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| 5. |
- Pedroni Barreto, Davi, et al.
(författare)
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Distance-Decay and Taxa-Area Relationships for Bacteria, Archaea and Methanogenic Archaea in a Tropical Lake Sediment
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 9:10, s. e110128-
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Tidskriftsartikel (refereegranskat)abstract
- The study of of the distribution of microorganisms through space (and time) allows evaluation of biogeographic patterns, like the species-area index (z). Due to their high dispersal ability, high reproduction rates and low rates of extinction microorganisms tend to be widely distributed, and they are thought to be virtually cosmopolitan and selected primarily by environmental factors. Recent studies have shown that, despite these characteristics, microorganisms may behave like larger organisms and exhibit geographical distribution. In this study, we searched patterns of spatial diversity distribution of bacteria and archaea in a contiguous environment. We collected 26 samples of a lake sediment, distributed in a nested grid, with distances between samples ranging from 0.01 m to 1000 m. The samples were analyzed using T-RFLP (Terminal restriction fragment length polymorphism) targeting mcrA (coding for a subunit of methyl-coenzyme M reductase) and the genes of Archaeal and Bacterial 16S rRNA. From the qualitative and quantitative results (relative abundance of operational taxonomic units) we calculated the similarity index for each pair to evaluate the taxa-area and distance decay relationship slopes by linear regression. All results were significant, with mcrA genes showing the highest slope, followed by Archaeal and Bacterial 16S rRNA genes. We showed that the microorganisms of a methanogenic community, that is active in a contiguous environment, display spatial distribution and a taxa-area relationship.
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| 6. |
- Sanseverino, Angela M, et al.
(författare)
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Methane Carbon Supports Aquatic Food Webs to the Fish Level
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 7:8
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Tidskriftsartikel (refereegranskat)abstract
- Large amounts of the greenhouse gas methane (CH4) are produced by anaerobic mineralization of organic matter in lakes. In spite of extensive freshwater CH4 emissions, most of the CH4 is typically oxidized by methane oxidizing bacteria (MOB) before it can reach the lake surface and be emitted to the atmosphere. In turn, it has been shown that the CH4-derived biomass of MOB can provide the energy and carbon for zooplankton and macroinvertebrates. In this study, we demonstrate the presence of specific fatty acids synthesized by MOB in fish tissues having low carbon stable isotope ratios. Fish species, zooplankton, macroinvertebrates and the water hyacinth Eichhornia crassipes were collected from a shallow lake in Brazil and analyzed for fatty acids (FA) and carbon stable isotope ratios (delta C-13). The fatty acids 16:1 omega 8c, 16:1 omega 8t, 16:1 omega 6c, 16:1 omega 5t, 18:1 omega 8c and 18:1 omega 8t were used as signature for MOB. The delta C-13 ratios varied from -27.7 parts per thousand to -42.0 parts per thousand and the contribution of MOB FA ranged from 0.05% to 0.84% of total FA. Organisms with higher total content of MOB FAs presented lower delta C-13 values (i.e. they were more depleted in C-13), while organisms with lower content of MOB signature FAs showed higher delta C-13 values. An UPGMA cluster analysis was carried out to distinguish grouping of organisms in relation to their MOB FA contents. This combination of stable isotope and fatty acid tracers provides new evidence that assimilation of methane-derived carbon can be an important carbon source for the whole aquatic food web, up to the fish level.
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| 7. |
- Santoro, Ana Lucia, et al.
(författare)
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Dark Carbon Fixation : An Important Process in Lake Sediments
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:6, s. e65813-
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Tidskriftsartikel (refereegranskat)abstract
- Close to redox boundaries, dark carbon fixation by chemoautotrophic bacteria may be a large contributor to overall carbon fixation. Still, little is known about the relative importance of this process in lake systems, in spite the potentially high chemoautotrophic potential of lake sediments. We compared rates of dark carbon fixation, bacterial production and oxygen consumption in sediments from four Swedish boreal and seven tropical Brazilian lakes. Rates were highly variable and dark carbon fixation amounted up to 80% of the total heterotrophic bacterial production. The results indicate that non-photosynthetic carbon fixation can represent a substantial contribution to bacterial biomass production, especially in sediments with low organic matter content.
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