Publications by authors named "David Bastviken"

47 Publications

Chlorine cycling and the fate of Cl in terrestrial environments.

Environ Sci Pollut Res Int 2021 Feb 5;28(7):7691-7709. Epub 2021 Jan 5.

Department of Thematic Studies - Environmental Change, Linköping University, SE-581 83, Linkoping, Sweden.

Chlorine (Cl) in the terrestrial environment is of interest from multiple perspectives, including the use of chloride as a tracer for water flow and contaminant transport, organochlorine pollutants, Cl cycling, radioactive waste (radioecology; Cl is of large concern) and plant science (Cl as essential element for living plants). During the past decades, there has been a rapid development towards improved understanding of the terrestrial Cl cycle. There is a ubiquitous and extensive natural chlorination of organic matter in terrestrial ecosystems where naturally formed chlorinated organic compounds (Cl) in soil frequently exceed the abundance of chloride. Chloride dominates import and export from terrestrial ecosystems while soil Cl and biomass Cl can dominate the standing stock Cl. This has important implications for Cl transport, as chloride will enter the Cl pools resulting in prolonged residence times. Clearly, these pools must be considered separately in future monitoring programs addressing Cl cycling. Moreover, there are indications that (1) large amounts of Cl can accumulate in biomass, in some cases representing the main Cl pool; (2) emissions of volatile organic chlorines could be a significant export pathway of Cl and (3) that there is a production of Cl in tissues of, e.g. plants and animals and that Cl can accumulate as, e.g. chlorinated fatty acids in organisms. Yet, data focusing on ecosystem perspectives and combined spatiotemporal variability regarding various Cl pools are still scarce, and the processes and ecological roles of the extensive biological Cl cycling are still poorly understood.
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http://dx.doi.org/10.1007/s11356-020-12144-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7854439PMC
February 2021

Unraveling the chemodiversity of halogenated disinfection by-products formed during drinking water treatment using target and non-target screening tools.

J Hazard Mater 2021 01 15;401:123681. Epub 2020 Aug 15.

Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07, Uppsala, Sweden.

To date, there is no analytical approach available that allows the full identification and characterization of highly complex disinfection by-product (DBP) mixtures. This study aimed at investigating the chemodiversity of drinking water halogenated DBPs using diverse analytical tools: measurement of adsorbable organic halogen (AOX) and mass spectrometry (MS)-based target and non-target analytical workflows. Water was sampled before and after chemical disinfection (chlorine or chloramine) at four drinking water treatment plants in Sweden. The target analysis had the highest sensitivity, although it could only partially explain the AOX formed in the disinfected waters. Non-target Fourier transform ion cyclotron resonance (FT-ICR) MS analysis indicated that only up to 19 Cl and/or Br-CHO formulae were common to all disinfected waters. Unexpectedly, a high diversity of halogenated DBPs (presumed halogenated polyphenolic and highly unsaturated compounds) was found in chloraminated surface water, comparable to that found in chlorinated surface water. Overall, up to 86 DBPs (including isobaric species) were tentatively identified using liquid chromatography (LC)-Orbitrap MS. Although further work is needed to confirm their identity and assess their relevance in terms of toxicity, they can be used to design suspect lists to improve the characterization of disinfected water halogenated mixtures.
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http://dx.doi.org/10.1016/j.jhazmat.2020.123681DOI Listing
January 2021

Diel variability of methane emissions from lakes.

Proc Natl Acad Sci U S A 2020 09 17;117(35):21488-21494. Epub 2020 Aug 17.

Department of Thematic Studies-Environmental Change, Linköping University, 58183 Linköping, Sweden.

Lakes are considered the second largest natural source of atmospheric methane (CH). However, current estimates are still uncertain and do not account for diel variability of CH emissions. In this study, we performed high-resolution measurements of CH flux from several lakes, using an automated and sensor-based flux measurement approach (in total 4,580 measurements), and demonstrated a clear and consistent diel lake CH flux pattern during stratification and mixing periods. The maximum of CH flux were always noted between 10:00 and 16:00, whereas lower CH fluxes typically occurred during the nighttime (00:00-04:00). Regardless of the lake, CH emissions were on an average 2.4 higher during the day compared to the nighttime. Fluxes were higher during daytime on nearly 80% of the days. Accordingly, estimates and extrapolations based on daytime measurements only most likely result in overestimated fluxes, and consideration of diel variability is critical to properly assess the total lake CH flux, representing a key component of the global CH budget. Hence, based on a combination of our data and additional literature information considering diel variability across latitudes, we discuss ways to derive a diel variability correction factor for previous measurements made during daytime only.
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http://dx.doi.org/10.1073/pnas.2006024117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7474682PMC
September 2020

Effect of Cobalt, Nickel, and Selenium/Tungsten Deficiency on Mesophilic Anaerobic Digestion of Chemically Defined Soluble Organic Compounds.

Microorganisms 2020 Apr 20;8(4). Epub 2020 Apr 20.

Department of Thematic Studies-Environmental Change, Linköping University, SE-581 83 Linköping, Sweden.

Trace elements (TEs) are vital for anaerobic digestion (AD), due to their role as cofactors in many key enzymes. The aim of this study was to evaluate the effects of specific TE deficiencies on mixed microbial communities during AD of soluble polymer-free substrates, thus focusing on AD after hydrolysis. Three mesophilic (37 °C) continuous stirred-tank biogas reactors were depleted either of Co, Ni, or a combination of Se and W, respectively, by discontinuing their supplementation. Ni and Se/W depletion led to changes in methane kinetics, linked to progressive volatile fatty acid (VFA) accumulation, eventually resulting in process failure. No significant changes occurred in the Co-depleted reactor, indicating that the amount of Co present in the substrate in absence of supplementation was sufficient to maintain process stability. Archaeal communities remained fairly stable independent of TE concentrations, while bacterial communities gradually changed with VFA accumulation in Ni- and Se-/W-depleted reactors. Despite this, the communities remained relatively similar between these two reactors, suggesting that the major shifts in composition likely occurred due to the accumulating VFAs. Overall, the results indicate that Ni and Se/W depletion primarily lead to slower metabolic activities of methanogenic archaea and their syntrophic partners, which then has a ripple effect throughout the microbial community due to a gradual accumulation of intermediate fermentation products.
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http://dx.doi.org/10.3390/microorganisms8040598DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7232481PMC
April 2020

Molecular differences between water column and sediment pore water SPE-DOM in ten Swedish boreal lakes.

Water Res 2020 Mar 22;170:115320. Epub 2019 Nov 22.

Helmholtz Zentrum Munich, German Research Center for Environmental Health, Research Unit Analytical Biogeochemistry (BGC), Ingolstädter Landstraße 1, P. O. Box 1129, D-85758, Neuherberg, Germany. Electronic address:

Boreal lakes are considered hot spots of dissolved organic matter (DOM) processing within the global carbon cycle. This study has used FT-ICR mass spectrometry and comprehensive data evaluation to assess the molecular differences of SPE-DOM between lake column water SPE-DOM and sedimentary pore water SPE-DOM in 10 Swedish boreal lakes of the Malingsbo area, which were selected for their large diversity of physicochemical and morphological characteristics. While lake column water is well mixed and fairly oxygenated, sedimentary pore water is subject to depletion of oxygen and to confinement of molecules. Robust trends were deduced from molecular compositions present in all compartments and in all 10 lakes ("common compositions") with recognition of relative abundance. Sedimentary pore water SPE-DOM featured higher proportions of heteroatoms N and S, higher average H/C ratios in presence of higher DBE/C ratios, and higher average oxygenation than lake column water SPE-DOM. These trends were observed in all lakes except Ljustjärn, which is a ground water fed kettle lake with an unique lake biogeochemistry. Analogous trends were also observed in case of single or a few lakes and operated also for compounds present solely in either lake column water or sedimentary pore water. Unique compounds detected in either compartments and/or in a few lakes showed higher molecular diversity than the "common compositions". Processing of DOM molecules in sediments included selective preservation for polyphenolic compounds and microbial resynthesis of selected molecules of considerable diversity.
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http://dx.doi.org/10.1016/j.watres.2019.115320DOI Listing
March 2020

Forest streams are important sources for nitrous oxide emissions.

Glob Chang Biol 2020 02 25;26(2):629-641. Epub 2019 Sep 25.

Department of Earth Sciences, Air, Water and Landscape Sciences, Uppsala University, Uppsala, Sweden.

Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N O). N O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N O concentration data from low-order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N O concentrations of 1.6 ± 2.1 and 1.3 ± 1.8 µg N/L, respectively (mean ± SD) despite higher total N (TN) concentrations in agricultural streams (1,520 ± 1,640 vs. 780 ± 600 µg N/L). Although clear patterns linking N O concentrations and environmental variables were difficult to discern, the percent saturation of N O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N O emissions. An estimate of the N O emission from low-order streams at the national scale revealed that ~1.8 × 10  g N O-N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N O sources in the landscape with 800 × 10  g CO -eq emitted annually in Sweden, equivalent to 25% of the total N O emissions from the Swedish agricultural sector.
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http://dx.doi.org/10.1111/gcb.14812DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7027446PMC
February 2020

Innovative drinking water treatment techniques reduce the disinfection-induced oxidative stress and genotoxic activity.

Water Res 2019 May 28;155:182-192. Epub 2019 Feb 28.

Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Box 7028, SE-750 07, Uppsala, Sweden.

Disinfection of drinking water using chlorine can lead to the formation of genotoxic by-products when chlorine reacts with natural organic matter (NOM). A vast number of such disinfection by-products (DBPs) have been identified, making it almost impossible to routinely monitor all DBPs with chemical analysis. In this study, a bioanalytical approach was used, measuring oxidative stress (Nrf2 activity), genotoxicity (micronucleus test), and aryl hydrocarbon receptor (AhR) activation to evaluate an innovative water treatment process, including suspended ion exchange, ozonation, in-line coagulation, ceramic microfiltration, and granular activated carbon. Chlorination was performed in laboratory scale after each step in the treatment process in order to investigate the effect of each treatment process to the formation of DBPs. Suspended ion exchange had a high capacity to remove dissolved organic carbon (DOC) and to decrease UV absorbance and Nrf2 activity in non-chlorinated water. High-dose chlorination (10 mg Cl L) of raw water caused a drastic induction of Nrf2 activity, which was decreased by 70% in water chlorinated after suspended ion exchange. Further reduction of Nrf2 activity following chlorination was achieved by ozonation and the concomitant treatment steps. The ozonation treatment resulted in decreased Nrf2 activity in spite of unchanged DOC levels. However, a strong correlation was found between UV absorbing compounds and Nrf2 activity, demonstrating that Nrf2 inducing DBPs were formed from pre-cursors of a specific NOM fraction, constituted of mainly aromatic compounds. Moreover, high-dose chlorination of raw water induced genotoxicity. In similarity to the DOC levels, UV absorbance and Nrf2 activity, the disinfection-induced genotoxicity was also reduced by each treatment step of the innovative water treatment technique. AhR activity was observed in the water produced by the conventional process and in the raw water, but the activity was clearly decreased by the ozonation step in the innovative water treatment process.
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http://dx.doi.org/10.1016/j.watres.2019.02.052DOI Listing
May 2019

Structure, function and resilience to desiccation of methanogenic microbial communities in temporarily inundated soils of the Amazon rainforest (Cunia Reserve, Rondonia).

Environ Microbiol 2019 05 19;21(5):1702-1717. Epub 2019 Mar 19.

Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Str. 10, 35043, Marburg, Germany.

The floodplain of the Amazon River is a large source for the greenhouse gas methane, but the soil microbial communities and processes involved are little known. We studied the structure and function of the methanogenic microbial communities in soils across different inundation regimes in the Cunia Reserve, encompassing nonflooded forest soil (dry forest), occasionally flooded Igapo soils (dry Igapo), long time flooded Igapo soils (wet Igapo) and sediments from Igarape streams (Igarape). We also investigated a Transect (four sites) from the water shoreline into the dry forest. The potential and resilience of the CH production process were studied in the original soil samples upon anaerobic incubation and again after artificial desiccation and rewetting. Bacterial and archaeal 16S rRNA genes and methanogenic mcrA were always present in the soils, except in dry forest soils where mcrA increased only upon anaerobic incubation. NMDS analysis showed a clear effect of desiccation and rewetting treatments on both bacterial and archaeal communities. However, the effects of the different sites were less pronounced, with the exception of Igarape. After anaerobic incubation, methanogenic taxa became more abundant among the Archaea, while there was only little change among the Bacteria. Contribution of hydrogenotrophic methanogenesis was usually around 40%. After desiccation and rewetting, we found that Firmicutes, Methanocellales and Methanosarcinaceae became the dominant taxa, but rates and pathways of CH production stayed similar. Such change was also observed in soils from the Transects. The results indicate that microbial community structures of Amazonian soils will in general be strongly affected by flooding and drainage events, while differences between specific field sites will be comparatively minor.
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http://dx.doi.org/10.1111/1462-2920.14535DOI Listing
May 2019

Dynamics of a Perturbed Microbial Community during Thermophilic Anaerobic Digestion of Chemically Defined Soluble Organic Compounds.

Microorganisms 2018 Oct 11;6(4). Epub 2018 Oct 11.

Department of Thematic Studies-Environmental Change, Linköping University, 581 83 Linköping, Sweden.

Knowledge of microbial community dynamics in relation to process perturbations is fundamental to understand and deal with the instability of anaerobic digestion (AD) processes. This study aims to investigate the microbial community structure and function of a thermophilic AD process, fed with a chemically defined substrate, and its association with process performance stability. Next generation amplicon sequencing of 16S ribosomal RNA (rRNA) genes revealed that variations in relative abundances of the predominant bacterial species, and were not linked to the process performance stability, while dynamics of bacterial genera of low abundance, and (other than ), were associated with microbial community function and process stability. A decrease in the diversity of the archaeal community was observed in conjunction with process recovery and stable performance, implying that the high abundance of specific archaeal group(s) contributed to the stable AD. Dominance of hydrogenotrophic particularly corresponded to an enhanced microbial acetate and propionate turnover capacity, whereas the prevalence of hydrogenotrophic and acetoclastic was associated with instable AD. Acetate oxidation via syntrophic interactions between and was potentially the main methane-formation pathway during the stable process. We observed that supplementation of Se and W to the medium improved the propionate turnover by the thermophilic consortium. The outcomes of our study provided insights into the community dynamics and trace element requirements in relation to the process performance stability of thermophilic AD.
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http://dx.doi.org/10.3390/microorganisms6040105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6313639PMC
October 2018

Large but variable methane production in anoxic freshwater sediment upon addition of allochthonous and autochthonous organic matter.

Limnol Oceanogr 2018 Jul 6;63(4):1488-1501. Epub 2018 Feb 6.

Limnology, Department of Ecology and Genetics Uppsala University Uppsala Sweden.

An important question in the context of climate change is to understand how CH production is regulated in anoxic sediments of lakes and reservoirs. The type of organic carbon (OC) present in lakes is a key factor controlling CH production at anoxic conditions, but the studies investigating the methanogenic potential of the main OC types are fragmented. We incubated different types of allochthonous OC (alloOC; terrestrial plant leaves) and autochthonous OC (autoOC; phytoplankton and two aquatic plants species) in an anoxic sediment during 130 d. We tested if (1) the supply of fresh alloOC and autoOC to an anoxic refractory sediment would fuel CH production and if (2) autoOC would decompose faster than alloOC. The addition of fresh OC greatly increased CH production and the δC-CH partitioning indicated that CH originated exclusively from the fresh OC. The large CH production in an anoxic sediment fueled by alloOC is a new finding which indicates that all systems with anoxic conditions and high sedimentation rates have the potential to be CH emitters. The autoOC decomposed faster than alloOC, but the total CH production was not higher for all autoOC types, one aquatic plant species having values as low as the terrestrial leaves, and the other one having values as high as phytoplankton. Our study is the first to report such variability, suggesting that the extent to which C fixed by aquatic plants is emitted as greenhouse gases or buried as OC in sediment could more generally differ between aquatic vegetation types.
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http://dx.doi.org/10.1002/lno.10786DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6108407PMC
July 2018

Evaluating gas chromatography with a halogen-specific detector for the determination of disinfection by-products in drinking water.

Environ Sci Pollut Res Int 2019 Mar 28;26(8):7305-7314. Epub 2018 Feb 28.

Department of Thematic Studies-Environmental Change, Linköping University, SE-581 83, Linköping, Sweden.

The occurrence of disinfection by-products (DBPs) in drinking water has become an issue of concern during the past decades. The DBPs pose health risks and are suspected to cause various cancer forms, be genotoxic, and have negative developmental effects. The vast chemical diversity of DBPs makes comprehensive monitoring challenging. Only few of the DBPs are regulated and included in analytical protocols. In this study, a method for simultaneous measurement of 20 DBPs from five different structural classes (both regulated and non-regulated) was investigated and further developed for 11 DBPs using solid-phase extraction and gas chromatography coupled with a halogen-specific detector (XSD). The XSD was highly selective towards halogenated DBPs, providing chromatograms with little noise. The method allowed detection down to 0.05 μg L and showed promising results for the simultaneous determination of a range of neutral DBP classes. Compounds from two classes of emerging DBPs, more cytotoxic than the "traditional" regulated DBPs, were successfully determined using this method. However, haloacetic acids (HAAs) should be analyzed separately as some HAA methyl esters may degrade giving false positives of trihalomethanes (THMs). The method was tested on real water samples from two municipal waterworks where the target DBP concentrations were found below the regulatory limits of Sweden.
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http://dx.doi.org/10.1007/s11356-018-1419-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6447507PMC
March 2019

Remote sensing of methane and nitrous oxide fluxes from waste incineration.

Waste Manag 2018 May 1;75:319-326. Epub 2018 Feb 1.

Department of Thematic Studies - Environmental Change, Linköping University, Sweden.

Incomplete combustion processes lead to the formation of many gaseous byproducts that can be challenging to monitor in flue gas released via chimneys. This study presents ground-based remote sensing approaches to make greenhouse gas (GHG) flux measurements of methane (CH) and nitrous oxide (NO) from a waste incineration chimney at distances of 150-200 m. The study found emission of NO (corresponding to 30-40 t yr), which is a consequence of adding the reduction agent urea to decrease NO emissions due to NO regulation; a procedure that instead increases NO emissions (which is approximately 300 times more potent as a GHG than CO on a 100-year time scale). CH emissions of 7-11 t yr was also detected from the studied chimney despite the usage of a high incineration temperature. For this particular plant, local knowledge is high and emission estimates at corresponding levels have been reported previously. However, emissions of CH are often not included in GHG emission inventories for waste incineration. This study highlights the importance of monitoring combustion processes, and shows the possibility of surveying CH and NO emissions from waste incineration at distances of several hundred meters.
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http://dx.doi.org/10.1016/j.wasman.2018.01.031DOI Listing
May 2018

Large emissions from floodplain trees close the Amazon methane budget.

Nature 2017 12 4;552(7684):230-234. Epub 2017 Dec 4.

School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK.

Wetlands are the largest global source of atmospheric methane (CH), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH in the tropics, consistently underestimate the atmospheric burden of CH determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH emissions. Here we report CH fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δC) of -66.2 ± 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 ± 1.8 to 21.2 ± 2.5 teragrams of CH a year, in addition to the 20.5 ± 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a 'top-down' regional estimate of CH emissions of 42.7 ± 5.6 teragrams of CH a year for the Amazon basin, based on regular vertical lower-troposphere CH profiles covering the period 2010-2013. We find close agreement between our 'top-down' and combined 'bottom-up' estimates, indicating that large CH emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH source when trees are combined with other emission sources.
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http://dx.doi.org/10.1038/nature24639DOI Listing
December 2017

Influence of Multiple Environmental Factors on Organic Matter Chlorination in Podsol Soil.

Environ Sci Technol 2017 Dec 12;51(24):14114-14123. Epub 2017 Dec 12.

Department of Thematic Studies, Environmental Change, Linköping University , SE-581 83 Linköping, Sweden.

Natural chlorination of organic matter is common in soils. The abundance of chlorinated organic compounds frequently exceeds chloride in surface soils, and the ability to chlorinate soil organic matter (SOM) appears widespread among microorganisms. Yet, the environmental control of chlorination is unclear. Laboratory incubations with Cl as a Cl tracer were performed to test how combinations of environmental factors, including levels of soil moisture, nitrate, chloride, and labile organic carbon, influenced chlorination of SOM from a boreal forest. Total chlorination was hampered by addition of nitrate or by nitrate in combination with water but enhanced by addition of chloride or most additions including labile organic matter (glucose and maltose). The greatest chlorination was observed after 15 days when nitrate and water were added together with labile organic matter. The effect that labile organic matter strongly stimulated the chlorination rates was confirmed by a second independent experiment showing higher stimulation at increased availability of labile organic matter. Our results highlight cause-effect links between chlorination and the studied environmental variables in podsol soil-with consistent stimulation by labile organic matter that did overrule the negative effects of nitrate.
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http://dx.doi.org/10.1021/acs.est.7b03196DOI Listing
December 2017

Extensive processing of sediment pore water dissolved organic matter during anoxic incubation as observed by high-field mass spectrometry (FTICR-MS).

Water Res 2018 02 7;129:252-263. Epub 2017 Nov 7.

Helmholtz Zentrum Munich, German Research Center for Environmental Health, Neuherberg, Germany. Electronic address:

Dissolved organic matter (DOM) contained in lake sediments is a carbon source for many microbial degradation processes, including aerobic and anaerobic mineralization. During anaerobic degradation, DOM is partially consumed and transformed into new molecules while the greenhouse gases methane (CH) and carbon dioxide (CO) are produced. In this study, we used ultrahigh resolution mass spectrometry to trace differences in the composition of solid-phase extractable (PPL resin) pore water DOM (SPE-DOM) isolated from surface sediments of three boreal lakes before and after 40 days of anoxic incubation, with concomitant determination of CH and CO evolution. CH and CO production detected by gas chromatography varied considerably among replicates and accounted for fractions of ∼2-4 × 10 of sedimentary organic carbon for CO and ∼0.8-2.4 × 10 for CH. In contrast, the relative changes of key bulk parameters during incubation, such as relative proportions of molecular series, elemental ratios, average mass and unsaturation, were regularly in the percent range (1-3% for compounds decreasing and 4-10% for compounds increasing), i.e. several orders of magnitude higher than mineralization alone. Computation of the average carbon oxidation state in CHO molecules of lake pore water DOM revealed rather non-selective large scale transformations of organic matter during incubation, with depletion of highly oxidized and highly reduced CHO molecules, and formation of rather non-labile fulvic acid type molecules. In general, proportions of CHO compounds slightly decreased. Nearly saturated CHO and CHOS lipid-like substances declined during incubation: these rather commonplace molecules were less specific indicators of lake sediment alteration than the particular compounds, such as certain oxygenated aromatics and carboxyl-rich alicyclic acids (CRAM) found more abundant after incubation. There was a remarkable general increase in many CHNO compounds during incubation across all lakes. Differences in DOM transformation between lakes corresponded with lake size and water residence time. While in the small lake Svarttjärn, CRAM increased during incubation, lignin-and tannin-like compounds were enriched in the large lake Bisen, suggesting selective preservation of these rather non-labile aromatic compounds rather than recent synthesis. SPE-DOM after incubation may represent freshly synthesized compounds, leftover bulk DOM which is primarily composed of intrinsically refractory molecules and/or microbial metabolites which were not consumed in our experiments. In spite of a low fraction of the total DOM being mineralized to CO and CH, the more pronounced change in molecular DOM composition during the incubation indicates that diagenetic modification of organic matter can be substantial compared to complete mineralization.
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http://dx.doi.org/10.1016/j.watres.2017.11.015DOI Listing
February 2018

Temporal variations in methane emissions from emergent aquatic macrophytes in two boreonemoral lakes.

AoB Plants 2017 Jul 4;9(4):plx029. Epub 2017 Jul 4.

Department of Thematic Studies - Environmental Change, Linköping University, SE 581 83, Linköping, Sweden.

Methane (CH) emissions via emergent aquatic macrophytes can contribute substantially to the global CH balance. We addressed temporal variability in CH flux by using the static chamber approach to quantify fluxes from plots dominated by two species considered to differ in flux transport mechanisms (, ). Temporal variability in daily mean emissions from early June to early October was substantial. The variable that best explained this variation was air temperature. Regular and consistent diel changes were absent and therefore less relevant to include when estimating or modelling CH emissions. Methane emissions per m from nearby plots were similar for and indicating that CH production in the system influenced emissions more than the species identity. This study indicates that previously observed diel patterns and species-effects on emissions require further evaluation to support improved local and regional CH flux assessments.
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http://dx.doi.org/10.1093/aobpla/plx029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5544890PMC
July 2017

Dynamics of dissolved nutrients in the aquaculture shrimp ponds of the Min River estuary, China: Concentrations, fluxes and environmental loads.

Sci Total Environ 2017 Dec 23;603-604:256-267. Epub 2017 Jun 23.

School of Geographical Sciences, Fujian Normal University, Fuzhou 350007, PR China; Key Laboratory of Humid Subtropical Eco-geographical Process of Ministry of Education, Fujian Normal University, Fuzhou 350007, PR China; Research Centre of Wetlands in Subtropical Region, Fujian Normal University, Fuzhou 350007, PR China. Electronic address:

Dissolved inorganic nutrients (NO-N, NO-N, NH-N, and PO-P) play a critical role in the effective management of water quality and prevention of fish and shrimp diseases in aquaculture systems. In this study, dissolved inorganic nutrient concentrations in the water column and sediment porewater, and the fluxes across the sediment-water interface (SWI) were investigated in three intensive shrimp ponds with zero water exchange to examine nutrient cycling during the different growth stages of shrimps. Distinct changes in the dissolved inorganic nutrient concentrations in both the water column and sediment porewater were observed among the three growth stages. Average NO-N, NO-N, NH-N, and PO-P concentrations in the sediment porewater were 3.53, 2.81, 29.68, and 6.44 times higher, respectively, than those in the water column over the study period, indicating that the pond sediment acted as a net source of nutrients to the water column. This was further supported by the net release of nutrients from the sediments to the water column observed during the incubation experiment. Nutrient fluxes were dominated by NH-N, while NO-N (NO-N and NO-N) and PO-P fluxes remained low. The high rates of NH-N release from the sediment highlight the need of taking into account the biogeochemical role of sediments in mitigating the problem of water quality degradation in coastal shrimp ponds. Based on a total water surface area of mariculture ponds and a total mariculture production of 2.57×10ha and 2.30×10kg, respectively, we estimated conservatively that approximately 4.77×10tons of total nitrogen and 3.75×10tons of total phosphorus are being discharged annually from the mariculture ponds into the adjacent coastal zones across China. Results demonstrated the importance of aquaculture pond effluent as a major contributor of water pollution in the coastal areas of China, and called for actions to properly treat these effluents in alleviating the eutrophication problem in the Chinese coastal zones.
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http://dx.doi.org/10.1016/j.scitotenv.2017.06.074DOI Listing
December 2017

Spatio-temporal patterns of stream methane and carbon dioxide emissions in a hemiboreal catchment in Southwest Sweden.

Sci Rep 2017 01 3;7:39729. Epub 2017 Jan 3.

Department of Thematic Studies-Environmental Change, Linköping University, 581 83 Linköping, Sweden.

Global stream and river greenhouse gas emissions seem to be as large as the oceanic C uptake. However, stream and river emissions are uncertain until both spatial and temporal variability have been quantified. Here we investigated in detail the stream CH and CO emissions within a hemiboreal catchment in Southwest Sweden primarily covered by coniferous forest. Gas transfer velocities (k), CH and CO concentrations were measured with multiple methods. Our data supported modelling approaches accounting for various stream slopes, water velocities and discharge. The results revealed large but partially predictable spatio-temporal variabilities in k, dissolved gas concentrations, and emissions. The variability in CO emission was best explained by the variability in k, while dissolved CH concentrations explained most of the variability in CH emission, having implications for future measurements. There were disproportionately large emissions from high slope stream reaches including waterfalls, and from high discharge events. In the catchment, stream reaches with low slope and time periods of moderate discharge dominated (90% of area and 69% of time). Measurements in these stream areas and time periods only accounted for <36% of the total estimated emissions. Hence, not accounting for local or episodic high emissions can lead to substantially underestimated emissions.
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http://dx.doi.org/10.1038/srep39729DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5206626PMC
January 2017

Chlorination and dechlorination rates in a forest soil - A combined modelling and experimental approach.

Sci Total Environ 2016 Jun 5;554-555:203-10. Epub 2016 Mar 5.

Department of Thematic Studies - Environmental Change, Linköping University, 581 83 Linköping, Sweden.

Much of the total pool of chlorine (Cl) in soil consists of naturally produced organic chlorine (Clorg). The chlorination of bulk organic matter at substantial rates has been experimentally confirmed in various soil types. The subsequent fates of Clorg are important for ecosystem Cl cycling and residence times. As most previous research into dechlorination in soils has examined either single substances or specific groups of compounds, we lack information about overall bulk dechlorination rates. Here we assessed bulk organic matter chlorination and dechlorination rates in coniferous forest soil based on a radiotracer experiment conducted under various environmental conditions (additional water, labile organic matter, and ammonium nitrate). Experiment results were used to develop a model to estimate specific chlorination (i.e., fraction of Cl(-) transformed to Clorg per time unit) and specific dechlorination (i.e., fraction of Clorg transformed to Cl(-) per time unit) rates. The results indicate that chlorination and dechlorination occurred simultaneously under all tested environmental conditions. Specific chlorination rates ranged from 0.0005 to 0.01 d(-1) and were hampered by nitrogen fertilization but were otherwise similar among the treatments. Specific dechlorination rates were 0.01-0.03d(-1) and were similar among all treatments. This study finds that soil Clorg levels result from a dynamic equilibrium between the chlorination and rapid dechlorination of some Clorg compounds, while another Clorg pool is dechlorinated more slowly. Altogether, this study demonstrates a highly active Cl cycling in soils.
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http://dx.doi.org/10.1016/j.scitotenv.2016.02.208DOI Listing
June 2016

Oxidative mitigation of aquatic methane emissions in large Amazonian rivers.

Glob Chang Biol 2016 Mar 9;22(3):1075-85. Epub 2016 Feb 9.

Center of Nuclear Energy in Agriculture, University of São Paulo, Av. Centenário, 303, Piracicaba, SP 13400-970, Brazil.

The flux of methane (CH4 ) from inland waters to the atmosphere has a profound impact on global atmospheric greenhouse gas (GHG) levels, and yet, strikingly little is known about the dynamics controlling sources and sinks of CH4 in the aquatic setting. Here, we examine the cycling and flux of CH4 in six large rivers in the Amazon basin, including the Amazon River. Based on stable isotopic mass balances of CH4 , inputs and outputs to the water column were estimated. We determined that ecosystem methane oxidation (MOX) reduced the diffusive flux of CH4 by approximately 28-96% and varied depending on hydrologic regime and general geochemical characteristics of tributaries of the Amazon River. For example, the relative amount of MOX was maximal during high water in black and white water rivers and minimal in clear water rivers during low water. The abundance of genetic markers for methane-oxidizing bacteria (pmoA) was positively correlated with enhanced signals of oxidation, providing independent support for the detected MOX patterns. The results indicate that MOX in large Amazonian rivers can consume from 0.45 to 2.07 Tg CH4 yr(-1) , representing up to 7% of the estimated global soil sink. Nevertheless, climate change and changes in hydrology, for example, due to construction of dams, can alter this balance, influencing CH4 emissions to atmosphere.
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http://dx.doi.org/10.1111/gcb.13169DOI Listing
March 2016

Spatial versus day-to-day within-lake variability in tropical floodplain lake CH4 emissions--developing optimized approaches to representative flux measurements.

PLoS One 2015 10;10(4):e0123319. Epub 2015 Apr 10.

Department of Thematic Studies-Environmental Change, Linköping University, 58183, Linköping, Sweden.

Inland waters (lakes, rivers and reservoirs) are now understood to contribute large amounts of methane (CH4) to the atmosphere. However, fluxes are poorly constrained and there is a need for improved knowledge on spatiotemporal variability and on ways of optimizing sampling efforts to yield representative emission estimates for different types of aquatic ecosystems. Low-latitude floodplain lakes and wetlands are among the most high-emitting environments, and here we provide a detailed investigation of spatial and day-to-day variability in a shallow floodplain lake in the Pantanal in Brazil over a five-day period. CH4 flux was dominated by frequent and ubiquitous ebullition. A strong but predictable spatial variability (decreasing flux with increasing distance to the shore or to littoral vegetation) was found, and this pattern can be addressed by sampling along transects from the shore to the center. Although no distinct day-to-day variability were found, a significant increase in flux was identified from measurement day 1 to measurement day 5, which was likely attributable to a simultaneous increase in temperature. Our study demonstrates that representative emission assessments requires consideration of spatial variability, but also that spatial variability patterns are predictable for lakes of this type and may therefore be addressed through limited sampling efforts if designed properly (e.g., fewer chambers may be used if organized along transects). Such optimized assessments of spatial variability are beneficial by allowing more of the available sampling resources to focus on assessing temporal variability, thereby improving overall flux assessments.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0123319PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4393096PMC
December 2015

Experimental evidence of large changes in terrestrial chlorine cycling following altered tree species composition.

Environ Sci Technol 2015 Apr 1;49(8):4921-8. Epub 2015 Apr 1.

†Department of Thematic Studies-Environmental Change, Linköping University, SE-581 83, Linköping, Sweden.

Organochlorine molecules (Clorg) are surprisingly abundant in soils and frequently exceed chloride (Cl(-)) levels. Despite the widespread abundance of Clorg and the common ability of microorganisms to produce Clorg, we lack fundamental knowledge about how overall chlorine cycling is regulated in forested ecosystems. Here we present data from a long-term reforestation experiment where native forest was cleared and replaced with five different tree species. Our results show that the abundance and residence times of Cl(-) and Clorg after 30 years were highly dependent on which tree species were planted on the nearby plots. Average Cl(-) and Clorg content in soil humus were higher, at experimental plots with coniferous trees than in those with deciduous trees. Plots with Norway spruce had the highest net accumulation of Cl(-) and Clorg over the experiment period, and showed a 10 and 4 times higher Cl(-) and Clorg storage (kg ha(-1)) in the biomass, respectively, and 7 and 9 times higher storage of Cl(-) and Clorg in the soil humus layer, compared to plots with oak. The results can explain why local soil chlorine levels are frequently independent of atmospheric deposition, and provide opportunities for improved modeling of chlorine distribution and cycling in terrestrial ecosystems.
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http://dx.doi.org/10.1021/acs.est.5b00137DOI Listing
April 2015

Anaerobic digestion of alkaline bleaching wastewater from a kraft pulp and paper mill using UASB technique.

Environ Technol 2015 May-Jun;36(9-12):1489-98

a Department of Thematic Studies, Environmental Change , Linköping University , 581 83 Linköping , Sweden.

Anaerobic digestion of alkaline kraft elemental chlorine-free bleaching wastewater in two mesophilic, lab-scale upflow anaerobic sludge bed reactors resulted in significantly higher biogas production (250±50 vs. 120±30 NmL g [Formula: see text]) and reduction of filtered total organic carbon (fTOC) (60±5 vs. 43±6%) for wastewater from processing of hardwood (HW) compared with softwood (SW). In all cases, the gas production was likely underestimated due to poor gas separation in the reactors. Despite changes in wastewater characteristics, a stable anaerobic process was maintained with hydraulic retention times (HRTs) between 7 and 14 h. Lowering the HRT (from 13.5 to 8.5 h) did not significantly affect the process, and the stable performance at 8.5 h leaves room for further decreases in HRT. The results show that this type of wastewater is suitable for a full-scale implementation, but the difference in methane potential between SW and HW is important to consider both regarding process dimensioning and biogas yield optimization.
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http://dx.doi.org/10.1080/09593330.2014.994042DOI Listing
October 2015

Changes in dissolved organic matter during the treatment processes of a drinking water plant in Sweden and formation of previously unknown disinfection byproducts.

Environ Sci Technol 2014 Nov 27;48(21):12714-22. Epub 2014 Oct 27.

Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science , Solomons, Maryland 20688, United States.

The changes in dissolved organic matter (DOM) throughout the treatment processes in a drinking water treatment plant in Sweden and the formation of disinfection byproducts (DBPs) were evaluated by using ultra-high-resolution mass spectrometry (resolution of ∼500,000 at m/z 400) and nuclear magnetic resonance (NMR). Mass spectrometric results revealed that flocculation induced substantial changes in the DOM and caused quantitative removal of DOM constituents that usually are associated with DBP formation. While half of the chromophoric DOM (CDOM) was removed by flocculation, ∼4-5 mg L(-1) total organic carbon remained in the finished water. A conservative approach revealed the formation of ∼800 mass spectrometry ions with unambiguous molecular formula assignments that contained at least one halogen atom. These molecules likely represented new DBPs, which could not be prevented by the flocculation process. The most abundant m/z peaks, associated with formed DBPs, could be assigned to C5HO3Cl3, C5HO3Cl2Br, and C5HO3ClBr2 using isotope simulation patterns. Other halogen-containing formulas suggested the presence of halogenated polyphenolic and aromatic acid-type structures, which was supported by possible structures that matched the lower molecular mass range (maximum of 10 carbon atoms) of these DBPs. 1H NMR before and after disinfection revealed an ∼2% change in the overall 1H NMR signals supporting a significant change in the DOM caused by disinfection. This study underlines the fact that a large and increasing number of people are exposed to a very diverse pool of organohalogens through water, by both drinking and uptake through the skin upon contact. Nontarget analytical approaches are indispensable for revealing the magnitude of this exposure and to test alternative ways to reduce it.
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http://dx.doi.org/10.1021/es504349pDOI Listing
November 2014

Response: Inland water greenhouse gas emissions: when to model and when to measure?

Glob Chang Biol 2015 Apr 18;21(4):1379-80. Epub 2014 Oct 18.

Department of Thematic Studes - Environmental Change, Linköping University, Linköping, S-58183, Sweden.

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http://dx.doi.org/10.1111/gcb.12730DOI Listing
April 2015

Methane emissions from Amazonian Rivers and their contribution to the global methane budget.

Glob Chang Biol 2014 Sep 23;20(9):2829-40. Epub 2014 Jun 23.

Environmental Analysis and Geoprocessing Laboratory, Center for Nuclear Energy in Agriculture, University of São Paulo, Av. Centenário 303, Piracicaba, SP, 13400-970, Brazil.

Methane (CH4 ) fluxes from world rivers are still poorly constrained, with measurements restricted mainly to temperate climates. Additional river flux measurements, including spatio-temporal studies, are important to refine extrapolations. Here we assess the spatio-temporal variability of CH4 fluxes from the Amazon and its main tributaries, the Negro, Solimões, Madeira, Tapajós, Xingu, and Pará Rivers, based on direct measurements using floating chambers. Sixteen of 34 sites were measured during low and high water seasons. Significant differences were observed within sites in the same river and among different rivers, types of rivers, and seasons. Ebullition contributed to more than 50% of total emissions for some rivers. Considering only river channels, our data indicate that large rivers in the Amazon Basin release between 0.40 and 0.58 Tg CH4  yr(-1) . Thus, our estimates of CH4 flux from all tropical rivers and rivers globally were, respectively, 19-51% to 31-84% higher than previous estimates, with large rivers of the Amazon accounting for 22-28% of global river CH4 emissions.
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http://dx.doi.org/10.1111/gcb.12646DOI Listing
September 2014

Methane fluxes show consistent temperature dependence across microbial to ecosystem scales.

Nature 2014 Mar 19;507(7493):488-91. Epub 2014 Mar 19.

Département des sciences biologiques, Université du Québec à Montréal, Montréal, Province of Québec, H2X 3X8, Canada.

Methane (CH4) is an important greenhouse gas because it has 25 times the global warming potential of carbon dioxide (CO2) by mass over a century. Recent calculations suggest that atmospheric CH4 emissions have been responsible for approximately 20% of Earth's warming since pre-industrial times. Understanding how CH4 emissions from ecosystems will respond to expected increases in global temperature is therefore fundamental to predicting whether the carbon cycle will mitigate or accelerate climate change. Methanogenesis is the terminal step in the remineralization of organic matter and is carried out by strictly anaerobic Archaea. Like most other forms of metabolism, methanogenesis is temperature-dependent. However, it is not yet known how this physiological response combines with other biotic processes (for example, methanotrophy, substrate supply, microbial community composition) and abiotic processes (for example, water-table depth) to determine the temperature dependence of ecosystem-level CH4 emissions. It is also not known whether CH4 emissions at the ecosystem level have a fundamentally different temperature dependence than other key fluxes in the carbon cycle, such as photosynthesis and respiration. Here we use meta-analyses to show that seasonal variations in CH4 emissions from a wide range of ecosystems exhibit an average temperature dependence similar to that of CH4 production derived from pure cultures of methanogens and anaerobic microbial communities. This average temperature dependence (0.96 electron volts (eV)), which corresponds to a 57-fold increase between 0 and 30°C, is considerably higher than previously observed for respiration (approximately 0.65 eV) and photosynthesis (approximately 0.3 eV). As a result, we show that both the emission of CH4 and the ratio of CH4 to CO2 emissions increase markedly with seasonal increases in temperature. Our findings suggest that global warming may have a large impact on the relative contributions of CO2 and CH4 to total greenhouse gas emissions from aquatic ecosystems, terrestrial wetlands and rice paddies.
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http://dx.doi.org/10.1038/nature13164DOI Listing
March 2014

Methane and carbon dioxide emissions from inland waters in India - implications for large scale greenhouse gas balances.

Glob Chang Biol 2014 Nov 30;20(11):3397-407. Epub 2014 Apr 30.

Department of Thematic Studies - Water and Environmental Studies, Linköping University, 58183, Linköping, Sweden.

Inland waters were recently recognized to be important sources of methane (CH4 ) and carbon dioxide (CO2 ) to the atmosphere, and including inland water emissions in large scale greenhouse gas (GHG) budgets may potentially offset the estimated carbon sink in many areas. However, the lack of GHG flux measurements and well-defined inland water areas for extrapolation, make the magnitude of the potential offset unclear. This study presents coordinated flux measurements of CH4 and CO2 in multiple lakes, ponds, rivers, open wells, reservoirs, springs, and canals in India. All these inland water types, representative of common aquatic ecosystems in India, emitted substantial amounts of CH4 and a major fraction also emitted CO2 . The total CH4 flux (including ebullition and diffusion) from all the 45 systems ranged from 0.01 to 52.1 mmol m(-2)  d(-1) , with a mean of 7.8 ± 12.7 (mean ± 1 SD) mmol m(-2)  d(-1) . The mean surface water CH4 concentration was 3.8 ± 14.5 μm (range 0.03-92.1 μm). The CO2 fluxes ranged from -28.2 to 262.4 mmol m(-2)  d(-1) and the mean flux was 51.9 ± 71.1 mmol m(-2)  d(-1) . The mean partial pressure of CO2 was 2927 ± 3269 μatm (range: 400-11 467 μatm). Conservative extrapolation to whole India, considering the specific area of the different water types studied, yielded average emissions of 2.1 Tg CH4  yr(-1) and 22.0 Tg CO2  yr(-1) from India's inland waters. When expressed as CO2 equivalents, this amounts to 75 Tg CO2 equivalents yr(-1) (53-98 Tg CO2 equivalents yr(-1) ; ± 1 SD), with CH4 contributing 71%. Hence, average inland water GHG emissions, which were not previously considered, correspond to 42% (30-55%) of the estimated land carbon sink of India. Thereby this study illustrates the importance of considering inland water GHG exchange in large scale assessments.
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http://dx.doi.org/10.1111/gcb.12575DOI Listing
November 2014

Dark carbon fixation: an important process in lake sediments.

PLoS One 2013 11;8(6):e65813. Epub 2013 Jun 11.

Department of Ecology, Institute of Biology, University Federal of Rio de Janeiro, Rio de Janeiro, Brazil.

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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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0065813PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3679121PMC
January 2014