| 1. |
- 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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| 2. |
- Berggren, Martin, et al.
(författare)
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Systematic microbial production of optically active dissolved organic matter in subarctic lake water
- 2020
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Ingår i: Limnology and Oceanography. - : Association for the Sciences of Limnology and Oceanography (ASLO). - 0024-3590 .- 1939-5590. ; 65:5
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Tidskriftsartikel (refereegranskat)abstract
- The ecology and biogeochemistry of lakes in the subarctic region are particularly sensitive to changes in the abundance and optical properties of dissolved organic matter (DOM). External input of colored DOM to these lakes is an extensively researched topic, but little is known about potential reciprocal feedbacks between the optical properties of DOM and internal microbial processes in the water. We performed 28-day dark laboratory incubation trials on water from 101 subarctic tundra lakes in northern Sweden, measuring the microbial decay of DOM and the resulting dynamics in colored (CDOM) and fluorescent (FDOM) DOM components. While losses in dissolved oxygen during the incubations corresponded to a 20% decrease in mean DOM, conversely the mean CDOM and total FDOM increased by 22% and 30%, respectively. However, the patterns in microbial transformation of the DOM were not the same in all lakes. Notably, along the gradient of increasing ambient CDOM (water brownness), the lakes showed decreased microbial production of protein-like fluorescence, lowered DOM turnover rates and decreasing bacterial growth per unit of DOM. These trends indicate that browning of subarctic lakes systematically change the way that bacteria interact with the ambient DOM pool. Our study underscores that there is no unidirectional causal link between microbial processes and DOM optical properties, but rather reciprocal dependence between the two.
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| 3. |
- Gudasz, Cristian, 1973-
(författare)
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Boreal Lake Sediments as Sources and Sinks of Carbon
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inland waters process large amounts of organic carbon, contributing to CO2 and CH4 emissions, as well as storing organic carbon (OC) over geological timescales. Recently, it has been shown that the magnitude of these processes is of global significance. It is therefore important to understand what regulates OC cycling in inland waters and how is that affected by climate change. This thesis investigates the constraints on microbial processing of sediment OC, as a key factor of the carbon cycling in boreal lakes. Sediment bacterial metabolism was primarily controlled by temperature but also regulated by OC quality/origin. Temperature sensitivity of sediment OC mineralization was similar in contrasting lakes and over long-term. Allochthonous OC had a strong constraining effect on sediment bacterial metabolism and biomass, with increasingly allochthonous sediments supporting decreasing bacterial metabolism and biomass. The bacterial biomass followed the same pattern as bacterial activity and was largely regulated by similar factors. The rapid turnover of bacterial biomass as well as the positive correlation between sediment mineralization and bacterial biomass suggest a limited effect of bacterial grazing. Regardless of the OC source, the sediment microbial community was more similar within season than within lakes. A comparison of data from numerous soils as well as sediments on the temperature response of OC mineralization showed higher temperature sensitivity of the sediment mineralization. Furthermore, the low rates of areal OC mineralization in sediments compared to soils suggest that lakes sediments are hotspots of OC sequestration. Increased sediment mineralization due to increase in temperature in epilimnetic sediments can significantly reduce OC burial in boreal lakes. An increase of temperature, as predicted for Northern latitudes, under different climate warming scenarios by the end of the twenty-first century, resulted in 4–27% decrease in lake sediment OC burial for the entire boreal zone.
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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, 1973-, et al.
(författare)
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Contributions of terrestrial organic carbon to northern lake sediments
- 2017
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Ingår i: Limnology and Oceanography Letters. - : Wiley. - 2378-2242. ; 2:6, s. 218-227
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Tidskriftsartikel (refereegranskat)abstract
- Sediments of northern lakes sequester large amounts of organic carbon (OC), but direct evidence of the relative importance of their sources is lacking. We used stable isotope ratios of nonexchangeable hydrogen (δ2Hn) in topsoil, algae, and surface sediments in order to measure the relative contribution of terrestrial OC in surface sediments of 14 mountainous arctic and lowland boreal lakes in Sweden. The terrestrial contribution to the sediment OC pool was on average 66% (range 46–80) and similar between arctic and boreal lakes. Proxies for the supply of terrestrial and algal OC explained trends in the relative contribution of terrestrial OC across lakes. However, the data suggest divergent predominant sources for terrestrial OC of sediments in Swedish lakes, with dissolved matter dominating in lowland boreal lakes and particulate OC in mountainous arctic lakes.
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| 6. |
- Gudasz, Cristian, et al.
(författare)
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Mineralization of organic carbon in lake sediments: temperature sensitivity and a comparison to soils
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Temperature alone can explain a great amount of variation in sediment organic carbon (OC) mineralization. Studies on decomposition of soil OC suggest that the temperature sensitivity is different for the decomposition of labile and recalcitrant OC, but lake sediments with different contributions of labile and recalcitrant components have been reported to show similar temperature sensitivities. Sediment mineralization is typically measured in short-term incubations. However, whether the mineralization of OC in sediments dominated by recalcitrant and labile OC have different temperature sensitivities at the longer term is not clear. Here we show that during 5 months of continuous incubation of contrasting boreal lake sediments, sediment mineralization was strongly dependent on temperature and OC quality/origin but temperature sensitivity was similar across lakes and over time. Sediment mineralization showed low overall rates in spite of low apparent activation energy (Ea) compared to published rates of soil and litter mineralization. The fraction of the total OC pool that was lost during 5 months varied between 0.4 and 14%. The non-buried sediment OC pool was lost slowly, with apparent turnover times between 2.5 and 32 years. At a large scale, lake sediments, by showing lower mineralization rates than soils are more effective as carbon sinks.
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| 7. |
- 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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| 8. |
- Gudasz, Cristian, et al.
(författare)
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Temperature sensitivity of organic carbon mineralization in contrasting lake sediments
- 2015
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 120:7, s. 1215-1225
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Tidskriftsartikel (refereegranskat)abstract
- Temperature alone explains a great amount of variation in sediment organic carbon (OC) mineralization. Studies on decomposition of soil OC suggest that (1) temperature sensitivity differs between the fast and slowly decomposition OC and (2) over time, decreasing soil respiration is coupled with increase in temperature sensitivity. In lakes, autochthonous and allochthonous OC sources are generally regarded as fast and slowly decomposing OC, respectively. Lake sediments with different contributions of allochthonous and autochthonous components, however, showed similar temperature sensitivity in short-term incubation experiments. Whether the mineralization of OC in lake sediments dominated by allochthonous or autochthonous OC has different temperature sensitivity in the longer term has not been addressed. We incubated sediments from two boreal lakes that had contrasting OC origin (allochthonous versus autochthonous), and OC characteristics (C/N ratios of 21 and 10) at 1, 3, 5, 8, 13, and 21 degrees C for five months. Compared to soil and litter mineralization, sediment OC mineralization rates were low in spite of low apparent activation energy (E-a). The fraction of the total OC pool that was lost during five months varied between 0.4 and 14.8%. We estimate that the sediment OC pool not becoming long-term preserved was degraded with average apparent turnover times between 3 and 32years. While OC mineralization was strongly dependent on temperature as well as on OC composition and origin, temperature sensitivity was similar across lakes and over time. We suggest that the temperature sensitivity of OC mineralization in lake sediments is similar across systems within the relevant seasonal scales of OC supply and degradation.
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| 9. |
- Gudasz, Cristian, 1973-, et al.
(författare)
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When does temperature matter for ecosystem respiration?
- 2021
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Ingår i: Environmental Research Communications (ERC). - : Institute of Physics (IOP). - 2515-7620. ; 3:12
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Tidskriftsartikel (refereegranskat)abstract
- The temperature response of ecosystem processes is key to understand and predict impacts of climate change. This is especially true for respiration, given its high temperature sensitivity and major role in the global carbon cycle. However, similar intrinsic temperature sensitivity for respiration does not mean comparable temperature effects across ecosystems and biomes because non-temperature factors can be more important. Here we analyzed soil and sediment respiration data and found that in temperature ranges corresponding to high latitude mean temperatures, absolute respiration rates aremore sensitive to non-temperature factors than to projected direct temperature effects. However, at higher temperatures (>20 °C) the direct effect of temperature mediated by temperature sensitivity will likely be more important over changes in non-temperature factors in shaping how respiration change over time. This supports past suggestions that the relatively small projected temperature increase at low (tropical) latitudes may have a large direct impact on absolute respiration. In contrast, absolute respiration rates at high (boreal/arctic) latitudes will likely bemore sensitive on the development of the non-temperature factors than on the direct effects of the large projected temperature increase there.Social media abstract: Respirationmay be less dependent to changes in temperature at higher than lower latitudes.
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| 10. |
- Karlsson, Jan, et al.
(författare)
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Terrestrial organic matter input suppresses biomass production in lake ecosystems
- 2015
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Ingår i: Ecology. - : Ecological Society of America. - 0012-9658 .- 1939-9170. ; 96:11, s. 2870-2876
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Tidskriftsartikel (refereegranskat)abstract
- Terrestrial ecosystems export large amounts of organic carbon (t-OC) but the net effect of this OC on the productivity of recipient aquatic ecosystems is largely unknown. In this study of boreal lakes, we show that the relative contribution of t-OC to individual top consumer (fish) biomass production, and to most of their potential prey organisms, increased with the concentration of dissolved organic carbon (DOC; dominated by t-OC sources) in water. However, the biomass and production of top consumers decreased with increasing concentration of DOC, despite their substantial use (up to 60%) of t-OC. Thus, the results suggest that although t-OC supports individual consumer growth in lakes to a large extent, t-OC input suppresses rather than subsidizes population biomass production.
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