| 1. |
- Attermeyer, Katrin, et al.
(författare)
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Bacterial processes and biogeochemical changes in the water body of kettle holes : mainly driven by autochthonous organic matter?
- 2017
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Ingår i: Aquatic Sciences. - : Springer Science and Business Media LLC. - 1015-1621 .- 1420-9055. ; 79:3, s. 675-687
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Tidskriftsartikel (refereegranskat)abstract
- Kettle holes are small inland waters formed from glacially-created depressions often situated in agricultural landscapes. Due to their high perimeter-to-area ratio facilitating a high aquatic-terrestrial coupling, kettle holes can accumulate high concentrations of organic carbon and nutrients, fueling microbial activities and turnover rates. Thus, they represent hotspots of carbon turnover in the landscape, but their bacterial activities and controlling factors have not been well investigated. Therefore, we aimed to assess the relative importance of various environmental factors on bacterial and biogeochemical processes in the water column of kettle holes and to disentangle their variations. In the water body of ten kettle holes in north-eastern Germany, we measured several physico-chemical and biological parameters such as carbon quantity and quality, as well as bacterial protein production (BP) and community respiration (CR) in spring, early summer and autumn 2014. Particulate organic matter served as an indicator of autochthonous production and represented an important parameter to explain variations in BP and CR. This notion is supported by qualitative absorbance indices of dissolved molecules in water samples and C:N ratios of the sediments, which demonstrate high fractions of autochthonous organic matter (OM) in the studied kettle holes. In contrast, dissolved chemical parameters were less important for bacterial activities although they revealed strong differences throughout the growing season. Pelagic bacterial activities and dynamics might thus be regulated by autochthonous OM in kettle holes implying a control of important biogeochemical processes by internal primary production rather than facilitated exchange with the terrestrial surrounding due to a high perimeter-to-area ratio.
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| 2. |
- Attermeyer, Katrin, et al.
(författare)
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Invasive floating macrophytes reduce greenhouse gas emissions from a small tropical lake
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Floating macrophytes, including water hyacinth (Eichhornia crassipes), are dominant invasive organisms in tropical aquatic systems, and they may play an important role in modifying the gas exchange between water and the atmosphere. However, these systems are underrepresented in global datasets of greenhouse gas (GHG) emissions. This study investigated the carbon (C) turnover and GHG emissions from a small (0.6 km(2)) water-harvesting lake in South India and analysed the effect of floating macrophytes on these emissions. We measured carbon dioxide (CO2) and methane (CH4) emissions with gas chambers in the field as well as water C mineralization rates and physicochemical variables in both the open water and in water within stands of water hyacinths. The CO2 and CH4 emissions from areas covered by water hyacinths were reduced by 57% compared with that of open water. However, the C mineralization rates were not significantly different in the water between the two areas. We conclude that the increased invasion of water hyacinths and other floating macrophytes has the potential to change GHG emissions, a process that might be relevant in regional C budgets.
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| 3. |
- Bartels, Pia, et al.
(författare)
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Terrestrial subsidies to lake food webs : an experimental approach
- 2012
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Ingår i: Oecologia. - New York : Springer. - 0029-8549 .- 1432-1939. ; 168:3, s. 807-818
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Tidskriftsartikel (refereegranskat)abstract
- Cross-ecosystem movements of material and energy are ubiquitous. Aquatic ecosystems typically receive material that also includes organic matter from the surrounding catchment. Terrestrial-derived (allochthonous) organic matter can enter aquatic ecosystems in dissolved or particulate form. Several studies have highlighted the importance of dissolved organic carbon to aquatic consumers, but less is known about allochthonous particulate organic carbon (POC). Similarly, most studies showing the effects of allochthonous organic carbon (OC) on aquatic consumers have investigated pelagic habitats; the effects of allochthonous OC on benthic communities are less well studied. Allochthonous inputs might further decrease primary production through light reduction, thereby potentially affecting autotrophic resource availability to consumers. Here, an enclosure experiment was carried out to test the importance of POC input and light availability on the resource use in a benthic food web of a clear-water lake. Corn starch (a C-4 plant) was used as a POC source due to its insoluble nature and its distinct carbon stable isotope value (delta C-13). The starch carbon was closely dispersed over the bottom of the enclosures to study the fate of a POC source exclusively available to sediment biota. The addition of starch carbon resulted in a clear shift in the isotopic signature of surface-dwelling herbivorous and predatory invertebrates. Although the starch carbon was added solely to the sediment surface, the carbon originating from the starch reached zooplankton. We suggest that allochthonous POC can subsidize benthic food webs directly and can be further transferred to pelagic systems, thereby highlighting the importance of benthic pathways for pelagic habitats.
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| 4. |
- Gudasz, Cristian, et al.
(författare)
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Constrained microbial processing of allochthonous organic carbon in boreal lake sediments
- 2012
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 57:1, s. 163-175
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Tidskriftsartikel (refereegranskat)abstract
- We investigated sediment bacterial metabolism in eight lakes with different inputs of allochthonous and autochthonous organic carbon in south-central Sweden. Sediment bacterial production, mineralization and biomass were measured on a seasonal basis and along a lake depth gradient together with different water and sediment characteristics. Sediment bacterial metabolism was primarily controlled by temperature but also regulated by organic carbon quality/origin. Metabolism was positively correlated to measures of autochthonous influence on the sediment organic carbon, but did not show a similar increase with increasing input of allochthonous organic carbon. Hence, in contrast to what is currently known for the water column, increasing amounts of terrestrial organic carbon do not result in enhanced sediment bacterial metabolism. Meio- and macrobenthic invertebrate biomass were at most weakly correlated to bacterial metabolism and biomass, suggesting limited control of sediment bacteria by grazing. We suggest that the bacterial metabolism in boreal lake sediments is constrained by low temperatures and by the recalcitrant nature of the dominant organic carbon, resulting in sediments being an effective sink of organic carbon.
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| 5. |
- Gudasz, Cristian, et al.
(författare)
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Temperature-controlled organic carbon mineralization in lake sediments
- 2010
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 466:7305, s. 478-481
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands, soils and the ocean floor are well-recognized as sites of organic carbonaccumulation andrepresentimportant global carbon sinks(1,2). Although the annual burial of organic carbon in lakes and reservoirs exceeds that of ocean sediments(3), these inland waters are components of the global carbon cycle that receive only limited attention(4-6). Of the organic carbon that is being deposited onto the sediments, a certain proportion will be mineralized and the remainder will be buried over geological timescales. Here we assess the relationship between sediment organic carbon mineralization and temperature in a cross-system survey of boreal lakes in Sweden, and with input froma compilation of published data from awide range of lakes that differ with respect to climate, productivity and organic carbon source. We find that the mineralization of organic carbon in lake sediments exhibits a strongly positive relationship with temperature, which suggests that warmer water temperatures lead to more mineralization and less organic carbon burial. Assuming that future organic carbon delivery to the lake sediments will be similar to that under present-day conditions, we estimate that temperature increases following the latest scenarios presented by the Intergovernmental Panel on Climate Change(7) could result in a 4-27 per cent (0.9-6.4 Tg Cyr(-1)) decrease in annual organic carbon burial in boreal lakes.
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| 6. |
- Premke, Katrin, et al.
(författare)
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Metabolism and physiological traits of the deep sea amphipod Eurythenes gryllus
- 2009
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Ingår i: Vie et milieu (1980). - 0240-8759. ; 59:3-4, s. 251-260
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory experiments were carried out to measure standard (starved animals) and active (animals exposed to food odour) metabolic rates of the deep-sea amphipod Eurythenes gryllus. Six individuals could be kept alive and in good condition in the lab for several months and were used for measuring respiration rates. A considerable increase in oxygen consumption was observed following the addition of food odour. Mean specific oxygen consumption rate ranged from 0.11 to 2.05 ml O-2 g(-1) AFDW h(-1) for standard animals and 0.45 to 1.51 ml O-2 g(-1) AFDW h(-1) for active animals. Amphipods are adapted to a sporadic food source in a food limited environment by having two levels of metabolism: a standard (minimal) rate much like a state of dormancy and an active rate for optimal utilisation of food fall. The active rate was three times higher than the standard rate. Total lipid content (ranging from 22.1 to 37.6 % DW) of individuals collected from the Arctic Fram Strait was measured to calculate food energy stores. Oxygen consumption rates can be combined with lipid content analyses to estimate the energy reserves. We calculated that scavenging amphipods such as Eurythenes gryllus have energy storage capabilities for long term sustenance, up to 76 d for an active rate and for up to 203 d at standard rate of metabolism.
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| 7. |
- Premke, Katrin, et al.
(författare)
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Stable isotope analysis of benthic fauna and their food sources in boreal lakes
- 2010
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Ingår i: Journal of The North American Benthological Society. - : University of Chicago Press. - 0887-3593 .- 1937-237X. ; 29:4, s. 1339-1348
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Tidskriftsartikel (refereegranskat)abstract
- The origin of organic C supporting zoobenthic communities in 8 boreal lakes with different concentrations of dissolved organic C (DOC) was assessed by stable-isotope analysis. Profundal zoobenthos was depleted in C-13 compared to littoral zoobenthos, and this difference increased with decreasing DOC concentration. The delta C-13 of littoral zoobenthos suggested reliance on benthic algae, whereas depleted C-13 of profundal zoobenthos could be explained by contributions from allochthonous and autochthonous C sources. In deeper lakes, profundal zoobenthos diets also included C processed by methanotrophic bacteria. Littoral zoobenthos delta C-13 decreased with increasing DOC concentration in the lake water. Our results suggest that littoral benthic fauna are mainly supported by benthic algae in low-DOC lakes and by phytoplankton and allochthonous organic C in high-DOC lakes and that this difference is a result of light absorbance and energy supply by allochthonous organic C. Increasing allochthonous DOC inputs, as expected in a warmer and wetter climate, might reduce benthic algal production and alter the organic C base for benthic food webs in lake ecosystems.
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| 8. |
- 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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