Dark Carbon Fixation: An Important Process in Lake Sediments

Santoro, Ana Lúcia; Bastviken, David; Gudasz, Cristian; Tranvik, Lars J.; Enrich‐Prast, Alex

doi:10.1371/journal.pone.0065813

Cited by 40 publications

(43 citation statements)

References 49 publications

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“…1, (18)). While these are point measurements and should be taken with caution, they are well in line with dark carbon fixation values measured from lake sediments (19).…”

Section: Resultssupporting

confidence: 85%

Novel autotrophic organisms contribute significantly to the internal carbon cycling potential of a boreal lake

Peura

Buck

Aalto

et al. 2018

Preprint

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36Oxygen stratified lakes are typical for the boreal zone, and also a major source of 37 greenhouse gas emissions in the region. Due to shallow light penetration, restricting 38 the growth of phototrophic organisms, and large allochthonous organic carbon 39 inputs from the catchment area, the lake metabolism is expected to be dominated by 40 heterotrophic organisms. In this study we test this assumption and show that the 41 potential for autotrophic carbon fixation and internal carbon cycling is high 42 throughout the water column. Further, we show that during the summer 43 stratification carbon fixation can exceed respiration in a boreal lake even below the 44 euphotic zone. Metagenome assembled genomes and 16S profiling of a vertical 45 transect of the lake revealed multiple organisms in oxygen depleted compartment 46 belonging to novel or poorly characterized phyla. Many of these organisms were 47Importance 58Autotrophic organisms at the base of the food web are the only life form capable of 59 turning inorganic carbon into organic form, facilitating the survival of all other 60 organisms. In certain environments the autotrophic production is limited by 61 environmental conditions and the food web is supported by carbon coming from 62 outside the ecosystem. One such environment is stratified boreal lakes, which are 63 one of the biggest sources of greenhouse gas emissions in the boreal region. Thus, 64 carbon cycling in these habitats is of outmost importance for the future climate. 65Here we demonstrate a high potential for internal carbon cycling via phototrophic 66 and novel chemolithotrophic organisms in the dark and anoxic layers of a boreal 67 lake. Our results significantly increase our knowledge on the microbial communities 68 and their metabolic potential in oxygen depleted freshwaters and help to 69 understand and predict how climate change induced alterations could impact the 70 lake carbon dynamics. 71 72 73 74 75

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“…1, (18)). While these are point measurements and should be taken with caution, they are well in line with dark carbon fixation values measured from lake sediments (19).…”

Section: Resultssupporting

confidence: 85%

Novel autotrophic organisms contribute significantly to the internal carbon cycling potential of a boreal lake

Peura

Buck

Aalto

et al. 2018

Preprint

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“…It should be noted that two of these studies are based on laboratory incubations with homogenized sediments [12], [15]. Thomsen and Kristensen [12] reported maximum rates of approximately 0.35 µmol C cm −3 d −1 (averaged over the same depth as in the present study) similar to site ZK, whereas rates found by Enoksson and Samuelsson [13] and Lenk et al [14] are lower at about 0.12 µmol C cm −3 d −1 .…”

Section: Discussionsupporting

confidence: 49%

Chemoautotrophic Carbon Fixation Rates and Active Bacterial Communities in Intertidal Marine Sediments

et al. 2014

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Chemoautotrophy has been little studied in typical coastal marine sediments, but may be an important component of carbon recycling as intense anaerobic mineralization processes in these sediments lead to accumulation of high amounts of reduced compounds, such as sulfides and ammonium. We studied chemoautotrophy by measuring dark-fixation of 13C-bicarbonate into phospholipid derived fatty acid (PLFA) biomarkers at two coastal sediment sites with contrasting sulfur chemistry in the Eastern Scheldt estuary, the Netherlands. At one site where free sulfide accumulated in the pore water right to the top of the sediment, PLFA labeling was restricted to compounds typically found in sulfur and ammonium oxidizing bacteria. At the other site, with no detectable free sulfide in the pore water, a very different PLFA labeling pattern was found with high amounts of label in branched i- and a-PLFA besides the typical compounds for sulfur and ammonium oxidizing bacteria. This suggests that other types of chemoautotrophic bacteria were also active, most likely Deltaproteobacteria related to sulfate reducers. Maximum rates of chemoautotrophy were detected in first 1 to 2 centimeters of both sediments and chemosynthetic biomass production was high ranging from 3 to 36 mmol C m−2 d−1. Average dark carbon fixation to sediment oxygen uptake ratios were 0.22±0.07 mol C (mol O2)−1, which is in the range of the maximum growth yields reported for sulfur oxidizing bacteria indicating highly efficient growth. Chemoautotrophic biomass production was similar to carbon mineralization rates in the top of the free sulfide site, suggesting that chemoautotrophic bacteria could play a crucial role in the microbial food web and labeling in eukaryotic poly-unsaturated PLFA was indeed detectable. Our study shows that dark carbon fixation by chemoautotrophic bacteria is a major process in the carbon cycle of coastal sediments, and should therefore receive more attention in future studies on sediment biogeochemistry and microbial ecology.

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“…In addition, dark CO 2 fixation may contribute to low apparent RQ values. Even though dark carbon fixation has been shown to correspond to 3–15% of the sediment O 2 consumption in four Swedish lakes (Santoro et al, ), it remains unknown in how far chemoautotrophic CO 2 fixation may have contributed to the temperature dependence of apparent RQ observed in the study lakes.…”

Section: Discussionmentioning

confidence: 90%

Temperature Dependence of Apparent Respiratory Quotients and Oxygen Penetration Depth in Contrasting Lake Sediments

et al. 2017

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Lake sediments constitute an important compartment in the carbon cycle of lakes, by burying carbon over geological timescales and by production and emission of greenhouse gases. The degradation of organic carbon (OC) in lake sediments is linked to both temperature and oxygen (O2), but the interactive nature of this regulation has not been studied in lake sediments in a quantitative way. We present the first systematic investigation of the effects of temperature on the apparent respiratory quotient (RQ, i.e., the molar ratio between carbon dioxide (CO2) production and O2 consumption) in two contrasting lake sediments. Laboratory incubations of sediment cores of a humic lake and an eutrophic lake across a 1–21°C temperature gradient over 157 days revealed that both CO2 production and O2 consumption were positively, exponentially, and similarly dependent on temperature. The apparent RQ differed significantly between the lake sediments (0.63 ± 0.26 and 0.99 ± 0.28 in the humic and the eutrophic lake, respectively; mean ± SD) and was significantly and positively related to temperature. The O2 penetration depth into the sediment varied by a factor of 2 over the 1–21°C temperature range and was significantly, negatively, and similarly related to temperature in both lake sediments. Accordingly, increasing temperature may influence the overall extent of OC degradation in lake sediments by limiting O2 supply to aerobic microbial respiration to the topmost sediment layer, resulting in a concomitant shift to less effective anaerobic degradation pathways. This suggests that temperature may represent a key controlling factor of the OC burial efficiency in lake sediments.

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Dark Carbon Fixation: An Important Process in Lake Sediments

Cited by 40 publications

References 49 publications

Novel autotrophic organisms contribute significantly to the internal carbon cycling potential of a boreal lake

Novel autotrophic organisms contribute significantly to the internal carbon cycling potential of a boreal lake

Chemoautotrophic Carbon Fixation Rates and Active Bacterial Communities in Intertidal Marine Sediments

Temperature Dependence of Apparent Respiratory Quotients and Oxygen Penetration Depth in Contrasting Lake Sediments

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