| 1. |
- Downing, J. A., et al.
(författare)
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Global abundance and size distribution of streams and rivers
- 2012
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Ingår i: Inland Waters. - 2044-2041 .- 2044-205X. ; 2:4, s. 229-236
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Tidskriftsartikel (refereegranskat)abstract
- To better integrate lotic ecosystems into global cycles and budgets, we provide approximations of the size-distribution and areal extent of streams and rivers. One approach we used was to employ stream network theory combined with data on stream width. We also used detailed stream networks on 2 continents to estimate the fraction of continental area occupied by streams worldwide and corrected remote sensing stream inventories for unresolved small streams. Our estimates of global fluvial area are 485 000 to 662 000 km2 and are +30–300% of published appraisals. Moderately sized rivers (orders 5–9) seem to comprise the greatest global area, with less area covered by low and high order streams, while global stream length, and therefore the riparian interface, is dominated by 1st order streams. Rivers and streams are likely to cover 0.30–0.56% of the land surface and make contributions to global processes and greenhouse gas emissions that may be +20–200% greater than those implied by previous estimates.
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| 2. |
- Abbott, Benjamin W., et al.
(författare)
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Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment
- 2016
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.
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| 3. |
- Cole, J.J., et al.
(författare)
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Plumbing the global carbon cycle : Integrating inland waters into the terrestrial carbon budget
- 2007
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Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 10:1, s. 172-185
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Forskningsöversikt (refereegranskat)abstract
- Because freshwater covers such a small fraction of the Earth’s surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically altered sources, on the order of 1.9 Pg C y−1 from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned to the atmosphere as gas exchange while the remaining 0.9 Pg y−1 is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described.
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| 4. |
- Downing, J. A., et al.
(författare)
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The global abundance and size distribution of lakes, ponds, and impoundments
- 2006
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 51:5, s. 2388-2397
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Tidskriftsartikel (refereegranskat)abstract
- One of the major impediments to the integration of lentic ecosystems into global environmental analyses has been fragmentary data on the extent and size distribution of lakes, ponds, and impoundments. We use new data sources, enhanced spatial resolution, and new analytical approaches to provide new estimates of the global abundance of surface-water bodies. A global model based on the Pareto distribution shows that the global extent of natural lakes is twice as large as previously known (304 million lakes; 4.2 million km(2) in area) and is dominated in area by millions of water bodies smaller than 1 km(2). Similar analyses of impoundments based on inventories of large, engineered dams show that impounded waters cover approximately 0.26 million km(2). However, construction of low-tech farm impoundments is estimated to be between 0.1% and 6% of farm area worldwide, dependent upon precipitation, and represents > 77,000 km(2) globally, at present. Overall, about 4.6 million km(2) of the earth's continental "land" surface (> 3%) is covered by water. These analyses underscore the importance of explicitly considering lakes, ponds, and impoundments, especially small ones, in global analyses of rates and processes.
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| 5. |
- Hansson, Lars-Anders, et al.
(författare)
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Consumption patterns, complexity and enrichment in aquatic food chains
- 1998
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 265:1399, s. 901-906
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between consumers and prey, and their impact on biomass distribution among trophic levels, are central issues in both empirical and theoretical ecology. In a long-term experiment, where all organisms, including the top predator, were allowed to respond to environmental conditions by reproduction, we tested predictions from `prey-dependent' and `ratio-dependent' models. Prey-dependent models made correct predictions only in the presence of strong interactors in simple food chains, but failed to predict patterns in more complex situations. Processes such as omnivory, consumer excretion, and unsuitable prey-size windows (invulnerable prey) increased the complexity and created patterns resembling ratio-dependent consumption. However, whereas the prey-dependent patterns were created by the mechanisms predicted by the model, ratio-dependent patterns were not, suggesting that they may be right for the wrong reason'. We show here that despite the enormous complexity of ecosystems, it is possible to identify and disentangle mechanisms responsible for observed patterns in community structure, as well as in biomass development of organisms ranging in size from bacteria to fish.
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| 6. |
- Tranvik, Lars J., et al.
(författare)
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Lakes and reservoirs as regulators of carbon cycling and climate
- 2009
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 54:6:2, s. 2298-2314
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Forskningsöversikt (refereegranskat)abstract
- We explore the role of lakes in carbon cycling and global climate, examine the mechanisms influencing carbon pools and transformations in lakes, and discuss how the metabolism of carbon in the inland waters is likely to change in response to climate. Furthermore, we project changes as global climate change in the abundance and spatial distribution of lakes in the biosphere, and we revise the estimate for the global extent of carbon transformation in inland waters. This synthesis demonstrates that the global annual emissions of carbon dioxide from inland waters to the atmosphere are similar in magnitude to the carbon dioxide uptake by the oceans and that the global burial of organic carbon in inland water sediments exceeds organic carbon sequestration on the ocean floor. The role of inland waters in global carbon cycling and climate forcing may be changed by human activities, including construction of impoundments, which accumulate large amounts of carbon in sediments and emit large amounts of methane to the atmosphere. Methane emissions are also expected from lakes on melting permafrost. The synthesis presented here indicates that (1) inland waters constitute a significant component of the global carbon cycle, (2) their contribution to this cycle has significantly changed as a result of human activities, and (3) they will continue to change in response to future climate change causing decreased as well as increased abundance of lakes as well as increases in the number of aquatic impoundments.
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| 7. |
- Barros, Nathan, et al.
(författare)
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Carbon emission from hydroelectric reservoirs linked to reservoir age and latitude
- 2011
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Ingår i: Nature Geoscience. - : Nature Publishing Group. - 1752-0894 .- 1752-0908. ; 4:9, s. 593-596
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Tidskriftsartikel (refereegranskat)abstract
- Hydroelectric reservoirs cover an area of 3.4 x 10(5) km(2) and comprise about 20% of all reservoirs. In addition, they contain large stores of formerly terrestrial organic carbon. Significant amounts of greenhouse gases are emitted(2), especially in the early years following reservoir creation, but the global extent of these emissions is poorly known. Previous estimates of emissions from all types of reservoir indicate that these human-made systems emit 321 Tg of carbon per year (ref. 4). Here we assess the emissions of carbon dioxide and methane from hydroelectric reservoirs, on the basis of data from 85 globally distributed hydroelectric reservoirs that account for 20% of the global area of these systems. We relate the emissions to reservoir age, location biome, morphometric features and chemical status. We estimate that hydroelectric reservoirs emit about 48 Tg C as CO(2) and 3 Tg C as CH(4), corresponding to 4% of global carbon emissions from inland waters. Our estimates are smaller than previous estimates on the basis of more limited data. Carbon emissions are correlated to reservoir age and latitude, with the highest emission rates from the tropical Amazon region. We conclude that future emissions will be highly dependent on the geographic location of new hydroelectric reservoirs.
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| 8. |
- Battin, Tom J., et al.
(författare)
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The boundless carbon cycle
- 2009
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Ingår i: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 2:9, s. 598-600
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Tidskriftsartikel (refereegranskat)
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| 9. |
- Beier, Sara, et al.
(författare)
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Pronounced seasonal dynamics of freshwater chitinase genes and chitin processing
- 2012
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 14:9, s. 2467-2479
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal variation in activity of enzymes involved in polymer degradation, including chitinases, has been observed previously in freshwater environments. However, it is not known whether the seasonal dynamics are due to shifts in the activity of bacteria already present, or shifts in community structure towards emergence or disappearance of chitinolytic organisms. We traced seasonal shifts in the chitinase gene assemblage in a temperate lake and linked these communities to variation in chitinase activity. Chitinase genes from 20 samples collected over a full yearly cycle were characterized by pyrosequencing. Pronounced temporal shifts in composition of the chitinase gene pool (beta diversity) occurred along with distinct shifts in richness (alpha diversity) as well as chitin processing. Changes in the chitinase gene pool correlated mainly with temperature, abundance of crustacean zooplankton and phytoplankton blooms. Also changes in the physical structure of the lake, e.g. stratification and mixing were associated with changes in the chitinolytic community, while differences were minor between surface and suboxic hypolimnetic water. The lake characteristics influencing the chitinolytic community are all linked to changes in organic particles and we suggest that seasonal changes in particle quality and availability foster microbial communities adapted to efficiently degrade them.
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| 10. |
- Besemer, Katharina, et al.
(författare)
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Unraveling assembly of stream biofilm communities
- 2012
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Ingår i: The ISME Journal: multidisciplinary journal of microbial ecology. - : Springer Science and Business Media LLC. - 1751-7362. ; 6:8, s. 1459-1468
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Tidskriftsartikel (refereegranskat)abstract
- Microbial biofilms assemble from cells that attach to a surface, where they develop into matrix-enclosed communities. Mechanistic insights into community assembly are crucial to better understand the functioning of natural biofilms, which drive key ecosystem processes in numerous aquatic habitats. We studied the role of the suspended microbial community as the source of the biofilm community in three streams using terminal-restriction fragment length polymorphism and 454 pyrosequencing of the 16S ribosomal RNA (rRNA) and the 16S rRNA gene (as a measure for the active and the bulk community, respectively). Diversity was consistently lower in the biofilm communities than in the suspended stream water communities. We propose that the higher diversity in the suspended communities is supported by continuous inflow from various sources within the catchment. Community composition clearly differed between biofilms and suspended communities, whereas biofilm communities were similar in all three streams. This suggests that biofilm assembly did not simply reflect differences in the source communities, but that certain microbial groups from the source community proliferate in the biofilm. We compared the biofilm communities with random samples of the respective community suspended in the stream water. This analysis confirmed that stochastic dispersal from the source community was unlikely to shape the observed community composition of the biofilms, in support of species sorting as a major biofilm assembly mechanism. Bulk and active populations generated comparable patterns of community composition in the biofilms and the suspended communities, which suggests similar assembly controls on these populations.
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| 11. |
- Cardoso, Simone J., et al.
(författare)
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Spatial variation of sediment mineralization supports differential CO2 emissions from a tropical hydroelectric reservoir
- 2013
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 4, s. 101-
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Tidskriftsartikel (refereegranskat)abstract
- Substantial amounts of organic matter (OM) from terrestrial ecosystems are buried as sediments in inland waters. It is still unclear to what extent this OM constitutes a sink of carbon, and how much of it is returned to the atmosphere upon mineralization to carbon dioxide (CO2). The construction of reservoirs affects the carbon cycle by increasing OM sedimentation at the regional scale. In this study we determine the OM mineralization in the sediment of three zones (river, transition, and dam) of a tropical hydroelectric reservoir in Brazil as well as identify the composition of the carbon pool available for mineralization. We measured sediment organic carbon mineralization rates and related them to the composition of the OM, bacterial abundance and pCO2 of the surface water of the reservoir. Terrestrial OM was an important substrate for the mineralization. In the river and transition zones most of the OM was allochthonous (56 and 48%, respectively) while the dam zone had the lowest allochthonous contribution (7%). The highest mineralization rates were found in the transition zone (154.80 ± 33.50 mg C m-2 d-1) and the lowest in the dam (51.60 ± 26.80 mg C m-2 d-1). Moreover, mineralization rates were significantly related to bacterial abundance (r2= 0.50, p < 0.001) and pCO2 in the surface water of the reservoir (r2 = 0.73, p < 0.001). The results indicate that allochthonous OM has different contributions to sediment mineralization in the three zones of the reservoir. Further, the sediment mineralization, mediated by heterotrophic bacteria metabolism, significantly contributes to CO2supersaturation in the water column, resulting in higher pCO2 in the river and transition zones in comparison with the dam zone, affecting greenhouse gas emission estimations from hydroelectric reservoirs.
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| 12. |
- Patriarca, Claudia, et al.
(författare)
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Investigating the Ionization of Dissolved Organic Matter by Electrospray
- 2020
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:20, s. 14210-14218
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Tidskriftsartikel (refereegranskat)abstract
- Electrospray ionization (ESI) operating in the negative mode coupled to high-resolution mass spectrometry is the most popular technique for the characterization of dissolved organic matter (DOM). The vast molecular heterogeneity and the functional group diversity of this complex mixture prevents the efficient ionization of the organic material by a single ionization source, so the presence of uncharacterized material is unavoidable. The extent of this poorly ionizable pool of carbon is unknown, is presumably variable between samples, and can only be assessed by the combination of analysis with a uniform detection method. Charged aerosol detection (CAD), whose response is proportional to the amount of nonvolatile material and is independent from the physicochemical properties of the analytes, is a suitable candidate. In this study, a fulvic acid mixture was fractionated and analyzed by high-pressure liquid chromatography–mass spectrometry in order to investigate the polarity and size distributions of highly and poorly ionizable material in the sample. Additionally, DOM samples of terrestrial and marine origins were analyzed to evaluate the variability of these pools across the land–sea aquatic continuum. The relative response factor values indicated that highly ionizable components of aquatic DOM mixtures are more hydrophilic and have lower molecular weight than poorly ionizable components. Additionally, a discrepancy between the samples of terrestrial and marine origins was found, indicating that marine samples are better represented by ESI than terrestrial samples, which have an abundant portion of hydrophobic poorly ionizable material.
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| 13. |
- Scharnweber, Kristin, 1983-, et al.
(författare)
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Comprehensive analysis of chemical and biological problems associated with browning agents used in aquatic studies
- 2021
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Ingår i: Limnology and Oceanography. - : Wiley. - 1541-5856. ; 19:12, s. 818-835
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Tidskriftsartikel (refereegranskat)abstract
- Inland waters receive and process large amounts of colored organic matter from the terrestrial surroundings. These inputs dramatically affect the chemical, physical, and biological properties of water bodies, as well as their roles as global carbon sinks and sources. However, manipulative studies, especially at ecosystem scale, require large amounts of dissolved organic matter with optical and chemical properties resembling indigenous organic matter. Here, we compared the impacts of two leonardite products (HuminFeed and SuperHume) and a freshly derived reverse osmosis concentrate of organic matter in a set of comprehensive mesocosm- and laboratory-scale experiments and analyses. The chemical properties of the reverse osmosis concentrate and the leonardite products were very different, with leonardite products being low and the reverse osmosis concentrate being high in carboxylic functional groups. Light had a strong impact on the properties of leonardite products, including loss of color and increased particle formation. HuminFeed presented a substantial impact on microbial communities under light conditions, where bacterial production was stimulated and community composition modified, while in dark potential inhibition of bacterial processes was detected. While none of the browning agents inhibited the growth of the tested phytoplankton Gonyostomum semen, HuminFeed had detrimental effects on zooplankton abundance and Daphnia reproduction. We conclude that the effects of browning agents extracted from leonardite, particularly HuminFeed, are in sharp contrast to those originating from terrestrially derived dissolved organic matter. Hence, they should be used with great caution in experimental studies on the consequences of terrestrial carbon for aquatic systems.
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| 14. |
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| 15. |
- Stepanauskas, Ramunas, et al.
(författare)
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Bioavailability of wetland-derived DON to freshwater and marine bacterioplankton
- 1999
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Ingår i: LIMNOLOGY AND OCEANOGRAPHY. - 0024-3590. ; 44:6, s. 1477-1485
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Tidskriftsartikel (refereegranskat)abstract
- Access to bioavailable nitrogen often limits primary production in marine and freshwater ecosystems. Around 70% of nitrogen transported by rivers worldwide consists of dissolved organic nitrogen (DON), but its bioavailability has been poorly investigated.
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| 16. |
- Algesten, Grete, et al.
(författare)
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Contribution of sediment respiration to summer CO2 emission from boreal and subarctic lakes
- 2005
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 50:4, s. 529-535
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Tidskriftsartikel (refereegranskat)abstract
- We measured sediment production of carbon dioxide (CO(2)) and methane (CH(4)) and the net flux of CO(2) across the surfaces of 15 boreal and subarctic lakes of different humic contents. Sediment respiration measurements were made in situ under ambient light conditions. The flux of CO(2) between sediment and water varied between an uptake of 53 and an efflux of 182 mg C m(-2) day(-1) from the sediments. The mean respiration rate for sediments in contact with the upper mixed layer (SedR) was positively correlated to dissolved organic carbon (DOC) concentration in the water (r(2) = 0.61). The net flux of CO(2) across the lake surface [net ecosystem exchange (NEE)] was also closely correlated to DOC concentration in the upper mixed layer (r(2) = 0.73). The respiration in the water column was generally 10-fold higher per unit lake area compared to sediment respiration. Lakes with DOC concentrations <5.6 mg L(-1) had net consumption of CO(2) in the sediments, which we ascribe to benthic primary production. Only lakes with very low DOC concentrations were net autotrophic (<2.6 mg L(-1)) due to the dominance of dissolved allochthonous organic carbon in the water as an energy source for aquatic organisms. In addition to previous findings of allochthonous organic matter as an important driver of heterotrophic metabolism in the water column of lakes, this study suggests that sediment metabolism is also highly dependent on allochthonous carbon sources.
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| 17. |
- Algesten, Grete, et al.
(författare)
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Contribution of sediment respiration to summer CO2 emission from low productive boreal and subarctic lakes
- 2005
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 50:4, s. 529-535
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Tidskriftsartikel (refereegranskat)abstract
- We measured sediment production of carbon dioxide (CO2) and methane (CH4) and the net flux of CO2 across the surfaces of 15 boreal and subarctic lakes of different humic contents. Sediment respiration measurements were made in situ under ambient light conditions. The flux of CO2 between sediment and water varied between an uptake of 53 and an efflux of 182 mg C m−2 day−1 from the sediments. The mean respiration rate for sediments in contact with the upper mixed layer (SedR) was positively correlated to dissolved organic carbon (DOC) concentration in the water (r 2 = 0.61). The net flux of CO2 across the lake surface [net ecosystem exchange (NEE)] was also closely correlated to DOC concentration in the upper mixed layer (r 2 = 0.73). The respiration in the water column was generally 10-fold higher per unit lake area compared to sediment respiration. Lakes with DOC concentrations <5.6 mg L−1 had net consumption of CO2 in the sediments, which we ascribe to benthic primary production. Only lakes with very low DOC concentrations were net autotrophic (<2.6 mg L−1) due to the dominance of dissolved allochthonous organic carbon in the water as an energy source for aquatic organisms. In addition to previous findings of allochthonous organic matter as an important driver of heterotrophic metabolism in the water column of lakes, this study suggests that sediment metabolism is also highly dependent on allochthonous carbon sources.
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| 18. |
- Algesten, Grete, et al.
(författare)
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Role of lakes for organic carbon cycling in the boreal zone
- 2004
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Ingår i: Global Change Biology. - Oxford : Blackwell Scientific. - 1354-1013 .- 1365-2486. ; 10:1, s. 141-147
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Tidskriftsartikel (refereegranskat)abstract
- We calculated the carbon loss (mineralization plus sedimentation) and net CO2 escape to the atmosphere for 79 536 lakes and total running water in 21 major Scandinavian catchments (size range 437–48 263 km2). Between 30% and 80% of the total organic carbon that entered the freshwater ecosystems was lost in lakes. Mineralization in lakes and subsequent CO2 emission to the atmosphere was by far the most important carbon loss process. The withdrawal capacity of lakes on the catchment scale was closely correlated to the mean residence time of surface water in the catchment, and to some extent to the annual mean temperature represented by latitude. This result implies that variation of the hydrology can be a more important determinant of CO2 emission from lakes than temperature fluctuations. Mineralization of terrestrially derived organic carbon in lakes is an important regulator of organic carbon export to the sea and may affect the net exchange of CO2 between the atmosphere and the boreal landscape.
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| 19. |
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| 20. |
- Algesten, Grete, 1974-, et al.
(författare)
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Seasonal variation of CO2 saturation in the Gulf of Bothnia : Indications of marine net heterotrophy
- 2004
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Ingår i: Global Biogeochemical Cycles. - Washington, D.C : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 18, s. 4021-4028
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal variation of pCO2 and primary and bacterioplankton production were measured in the Gulf of Bothnia during an annual cycle. Surface water was supersaturated with CO2 on an annual basis, indicating net heterotrophy and a source of CO2 to the atmosphere. However, the Gulf of Bothnia oscillated between being a sink and a source of CO2 over the studied period, largely decided by temporal variation in bacterial respiration (BR) and primary production (PP) in the water column above the pycnocline. The calculated annual respiration-production balance (BR-PP) was very similar to the estimated CO2 emission from the Gulf of Bothnia, which indicates that these processes were major determinants of the exchange of CO2 between water and atmosphere. The southern basin (the Bothnian Sea) had a lower net release of CO2 to the atmosphere than the northern Bothnian Bay (7.1 and 9.7 mmol C m−2 d−1, respectively), due to higher primary production, which to a larger extent balanced respiration in this basin.
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| 21. |
- Almeida, Rafael M., et al.
(författare)
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Correspondence : Emissions from Amazonian dams
- 2013
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 3:12, s. 1005-1005
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 22. |
- Andersson, Martin G. I., et al.
(författare)
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Effects of sterilization on dissolved organic carbon (DOC) composition and bacterial utilization of DOC from lakes
- 2018
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 82:2, s. 199-208
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Tidskriftsartikel (refereegranskat)abstract
- Sterilization of dissolved organic carbon (DOC) is an essential step in research on interactions between DOC and organisms, for example where the effect of different microbial communities on DOC is studied or vice versa. However, few studies have gone beyond acknowledging that sterilization of DOC influences its characteristics. Here, we aimed to provide further knowledge that enables scientists to better tailor their sterilization methods to their research question. To meet this aim, we conducted a sterilization experiment with DOC from 4 boreal lakes treated with 4 sterilization methods, i.e. 2 filtrations (0.2 µm, 0.1 µm) and 2 autoclaving approaches (single and double autoclaving with a single pH adjustment). Quantity and spectroscopic properties of DOC, before and after sterilization, were studied, and DOC was further tested as a substrate for bacterial growth. We found that the filtration methods better preserved the different DOC measures. In contrast, autoclaving caused major inconsistent shifts in both qualitative and quantitative measures of DOC, as well as an increase of the maximum abundance of bacteria in growth experiments. Nonetheless, there remains a trade-off between retaining the quality of DOC and achieving sterile conditions. Therefore, the sterilization method of choice should be guided by the scientific question at hand.
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| 23. |
- Anesio, Alexandre M, et al.
(författare)
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Decreased bacterial growth on vascular plant detritus due to photochemical modification
- 1999
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Ingår i: AQUATIC MICROBIAL ECOLOGY. - 0948-3055. ; 17:2, s. 159-165
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the effects of UV radiation on abiotic decomposition and dissolution of leaf Litter from the aquatic macrophyte Phragmites australis. Dead leaves were autoclaved and incubated in quartz tubes with autoclaved Milli-Q water, in darkness, und
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| 24. |
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| 25. |
- Attermeyer, Katrin, et al.
(författare)
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Potential terrestrial influence on transparent exopolymer particle (TEP) concentrations in boreal freshwaters
- 2019
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Ingår i: Journal of limnology. - : Wiley. - 1129-5767 .- 1723-8633. ; 64:6, s. 2455-2466
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Tidskriftsartikel (refereegranskat)abstract
- Transparent exopolymer particles (TEP) are ubiquitous in aquatic ecosystems and contribute, for example, to sedimentation of organic matter in oceans and freshwaters. Earlier studies indicate that the formation of TEP is related to the in situ activity of phytoplankton or bacteria. However, terrestrial sources of TEP and TEP precursors are usually not considered. We investigated TEP concentration and its driving factors in boreal freshwaters, hypoth- esizing that TEP and TEP precursors can enter freshwaters via terrestrial inputs. In a field survey, we measured TEP concentrations and other environmental factors across 30 aquatic ecosystems in Sweden. In a mesocosm experi- ment, we further investigated TEP dynamics over time after manipulating terrestrial organic matter input and light conditions. The TEP concentrations in boreal freshwaters ranged from 83 to 4940 μg Gum Xanthan equivalent L−1, which is comparable to other studies in freshwaters. The carbon fraction in TEP in the sampled boreal freshwaters is much higher than the phytoplanktonic carbon, in contrast to previous studies in northern temperate and Medi- terranean regions. Boreal TEP concentrations were mostly related to particulate organic carbon, dissolved organic carbon, and optical indices of terrestrial influence but less influenced by bacterial abundance, bacterial production, and chlorophyll a. Hence, our results do not support a major role of the phytoplankton community or aquatic bac- teria on TEP concentrations and dynamics. This suggests a strong external control of TEP concentrations in boreal freshwaters, which can in turn affect particle dynamics and sedimentation in the recipient aquatic ecosystem.
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