Unraveling signatures of biogeochemical processes and the depositional setting in the molecular composition of pore water DOM across different marine environments

Schmidt, Frauke; Koch, Boris P.; Goldhammer, Tobias; Elvert, Marcus; Witt, Matthias; Lin, Yu‐Shih; Wendt, Jenny; Zabel, Matthias; Heuer, Verena B; Hinrichs, Kai‐Uwe

doi:10.1016/j.gca.2017.03.005

Cited by 105 publications

(78 citation statements)

References 118 publications

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“…The dramatic increase in CRAM resonance in the top 50 cm of the sediment column where remineralization rates are high (Burdige et al, 2016) strongly indicates net production of CRAM by the microbial community during sedimentary organic matter degradation. This corroborates the findings from laboratory experiments (Koch et al, 2005(Koch et al, , 2014Rossel et al, 2013;Lechtenfeld et al, 2015) and field observations (Schmidt et al, 2017) showing the importance of microbial activity in the generation of CRAM-like formulas from known biomolecules.…”

Section: Net Production Of Cram and The Reactivity Of Pore-water Dom supporting

confidence: 90%

Composition of Dissolved Organic Matter in Pore Waters of Anoxic Marine Sediments Analyzed by 1H Nuclear Magnetic Resonance Spectroscopy

et al. 2018

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Marine sediments are globally significant sources of dissolved organic matter (DOM) to the oceans, but the biogeochemical role of pore-water DOM in the benthic and marine carbon cycles remains unclear due to a lack of understanding about the molecular composition of DOM. To help fill this knowledge gap, we used 1 H nuclear magnetic resonance (NMR) spectroscopy to examine depth variability in the composition of pore-water DOM in anoxic sediments of Santa Barbara Basin, California Borderland. Proton detected spectra were acquired on whole samples without pre-concentration to avoid preclusion of any DOM components from the analytical window. Broad unresolved resonance (operationally assigned to carboxyl-rich alicyclic molecules, or CRAM) dominated all spectra. Most of the relatively well-resolved peaks (attributed to biomolecules or their derivatives) appeared at chemical shifts similar to those previously reported for marine DOM in the literature, but at different relative intensities. DOM composition changed significantly within the top 50 cm of the sediment column, where the relative intensity of CRAM increased, and the relative intensity of resolved resonances decreased. The composition of CRAM itself also changed throughout the entire length of the 4.5-m profile, as CRAM protons became increasingly aliphatic at the expense of functionalized protons. Given that pore-water DOM is generated from sedimentary organic matter that includes pre-aged and degraded material, and that DOM is theoretically subject to microbial reworking in the pore waters for centuries to millennia, these data suggest that marine sediments may be sources of CRAM that are compositionally unique from CRAM generated in the upper ocean.

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Section: Net Production Of Cram and The Reactivity Of Pore-water Dom supporting

confidence: 90%

Composition of Dissolved Organic Matter in Pore Waters of Anoxic Marine Sediments Analyzed by 1H Nuclear Magnetic Resonance Spectroscopy

et al. 2018

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“…For TOC analysis, an aliquot (ϳ3 g) of homogenized and freeze-dried sediment sample was decalcified by acidification with 10% HCl. After washing with water, centrifugation, and freeze drying, between 10 and 30 mg of decalcified sediment was weighed into tin capsules and analyzed in duplicate on a Thermo Scientific Flash 2000 elemental analyzer connected to a Thermo Delta V Plus IRMS (153). TOC concentrations refer to initial sediment dry weight (corrected for carbonate content determined by weighing before and after decalcification) and are reported in weight percent (wt%) with a limit of detection of 20 g C.…”

Section: Methodsmentioning

confidence: 99%

Isoprenoid Quinones Resolve the Stratification of Redox Processes in a Biogeochemical Continuum from the Photic Zone to Deep Anoxic Sediments of the Black Sea

Becker

Elling

Schröder

et al. 2018

Appl Environ Microbiol

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The stratified water column of the Black Sea serves as a model ecosystem for studying the interactions of microorganisms with major biogeochemical cycles. Here we provide detailed analysis of isoprenoid quinones to study microbial redox processes in the ocean. In a continuum from the photic zone through the chemocline into deep anoxic sediments of the southern Black Sea, diagnostic quinones and inorganic geochemical parameters indicate niche segregation between redox processes and corresponding shifts in microbial community composition. Quinones specific for oxygenic photosynthesis and aerobic respiration dominate oxic waters, while quinones associated with thaumarchaeal ammonia-oxidation and bacterial methanotrophy, respectively, dominate a narrow interval in suboxic waters. Quinone distributions indicate highest metabolic diversity within the anoxic zone, with anoxygenic photosynthesis being a major process in its photic layer. In the dark anoxic layer, quinone profiles indicate occurrence of bacterial sulfur and nitrogen cycling, archaeal methanogenesis, and archaeal methanotrophy. Multiple novel ubiquinone isomers, possibly originating from unidentified intra-aerobic anaerobes, occur in this zone. The respiration modes found in the anoxic zone continue into shallow subsurface sediments, but quinone abundances rapidly decrease within the upper 50 cm below sea floor, reflecting the transition to lower energy availability. In the deep subseafloor sediments, quinone distributions and geochemical profiles indicate archaeal methanogenesis/methanotrophy and potentially bacterial fermentative metabolisms. We observed that sedimentary quinone distributions track lithology, which supports prior hypotheses that deep biosphere community composition and metabolisms are determined by environmental conditions during sediment deposition. Microorganisms play crucial roles in global biogeochemical cycles. Yet, we have only a fragmentary understanding of the diversity of microorganisms and their metabolisms, as the majority remains uncultured. Thus, culture-independent approaches are critical for determining microbial diversity and active metabolic processes. In order to resolve the stratification of microbial communities in the Black Sea, we comprehensively analyzed redox process-specific isoprenoid quinone biomarkers in a unique continuous record from the photic zone through the chemocline into anoxic subsurface sediments. We describe an unprecedented quinone diversity that allowed us to detect distinct biogeochemical processes including oxygenic photosynthesis, archaeal ammonia oxidation, aerobic methanotrophy and anoxygenic photosynthesis in defined geochemical zones.

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“…Evidence from recent experiments with humic acid‐like substances at lower pH has shown reactions of sulfide with organic matter may be on par with re‐oxidation with oxygen or iron oxides (Yu et al , ). High resolution mass‐spectrometry‐based characterisation of dissolved organic matter in marine sediments has also directly shown a significant proportion of naturally occurring organic matter in sulfidic marine sediments can be sulfurized during early diagenesis, thereby increasing the molecular weight and diversity of the organic matter (Schmidt et al ., ). This therefore means that the activity of SRM has a significant but little acknowledged chemical impact on the molecular structure of organic matter in marine sediments.…”

Section: Organo‐sulfur Molecule Transformationsmentioning

confidence: 97%

The life sulfuric: microbial ecology of sulfur cycling in marine sediments

Wasmund

Mußmann

Loy

2017

Environ Microbiol Rep

275

266

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SummaryAlmost the entire seafloor is covered with sediments that can be more than 10 000 m thick and represent a vast microbial ecosystem that is a major component of Earth's element and energy cycles. Notably, a significant proportion of microbial life in marine sediments can exploit energy conserved during transformations of sulfur compounds among different redox states. Sulfur cycling, which is primarily driven by sulfate reduction, is tightly interwoven with other important element cycles (carbon, nitrogen, iron, manganese) and therefore has profound implications for both cellular‐ and ecosystem‐level processes. Sulfur‐transforming microorganisms have evolved diverse genetic, metabolic, and in some cases, peculiar phenotypic features to fill an array of ecological niches in marine sediments. Here, we review recent and selected findings on the microbial guilds that are involved in the transformation of different sulfur compounds in marine sediments and emphasise how these are interlinked and have a major influence on ecology and biogeochemistry in the seafloor. Extraordinary discoveries have increased our knowledge on microbial sulfur cycling, mainly in sulfate‐rich surface sediments, yet many questions remain regarding how sulfur redox processes may sustain the deep‐subsurface biosphere and the impact of organic sulfur compounds on the marine sulfur cycle.

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Unraveling signatures of biogeochemical processes and the depositional setting in the molecular composition of pore water DOM across different marine environments

Cited by 105 publications

References 118 publications

Composition of Dissolved Organic Matter in Pore Waters of Anoxic Marine Sediments Analyzed by 1H Nuclear Magnetic Resonance Spectroscopy

Composition of Dissolved Organic Matter in Pore Waters of Anoxic Marine Sediments Analyzed by 1H Nuclear Magnetic Resonance Spectroscopy

Isoprenoid Quinones Resolve the Stratification of Redox Processes in a Biogeochemical Continuum from the Photic Zone to Deep Anoxic Sediments of the Black Sea

The life sulfuric: microbial ecology of sulfur cycling in marine sediments

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