Inefficient microbial production of refractory dissolved organic matter in the ocean

Osterholz, Helena; Niggemann, Jutta; Giebel, Helge-Ansgar; Simon, Meinhard; Dittmar, Thorsten

doi:10.1038/ncomms8422

Cited by 153 publications

(163 citation statements)

References 47 publications

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“…This notion may be explained by functional redundancy either in plankton communities regarding production of similarly stable compounds, or in degradation processes. Our results from a natural system support previous small-scale mesocosm experiments indicating production of similar compounds over long timescales despite variability in phytoplankton composition (Osterholz et al, 2015).…”

Section: Production Of a Fraction Of Compounds With Similar Molecularsupporting

confidence: 90%

Ocean Acidification Experiments in Large-Scale Mesocosms Reveal Similar Dynamics of Dissolved Organic Matter Production and Biotransformation

et al. 2017

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Dissolved organic matter (DOM) represents a major reservoir of carbon in the oceans. Environmental stressors such as ocean acidification (OA) potentially affect DOM production and degradation processes, e.g., phytoplankton exudation or microbial uptake and biotransformation of molecules. Resulting changes in carbon storage capacity of the ocean, thus, may cause feedbacks on the global carbon cycle. Previous experiments studying OA effects on the DOM pool under natural conditions, however, were mostly conducted in temperate and coastal eutrophic areas. Here, we report on OA effects on the existing and newly produced DOM pool during an experiment in the subtropical North Atlantic Ocean at the Canary Islands during an (1) oligotrophic phase and (2) after simulated deep water upwelling. The last is a frequently occurring event in this region controlling nutrient and phytoplankton dynamics. We manipulated nine large-scale mesocosms with a gradient of pCO 2 ranging from ∼350 up to ∼1,030 µatm and monitored the DOM molecular composition using ultrahigh-resolution mass spectrometry via Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). An increase of 37 µmol L −1 DOC was observed in all mesocosms during a phytoplankton bloom induced by simulated upwelling. Indications for enhanced DOC accumulation under elevated CO 2 became apparent during a phase of nutrient recycling toward the end of the experiment. The production of DOM was reflected in changes of the molecular DOM composition. Out of the 7,212 molecular formulae, which were detected throughout the experiment, ∼50% correlated significantly in mass spectrometric signal intensity with cumulative bacterial protein production (BPP) and are likely a product of microbial transformation. However, no differences in the produced compounds were found with respect to CO 2 levels. Comparing the results of this experiment with a comparable OA experiment in the Swedish Gullmar Fjord, reveals similar succession patterns for individual compound pools during a phytoplankton bloom Zark et al. DOM Dynamics during an Oligotrophic OA Experiment and subsequent accumulation of these compounds were observed. The similar behavior of DOM production and biotransformation during and following a phytoplankton bloom irrespective of plankton community composition and CO 2 treatment provides novel insights into general dynamics of the marine DOM pool.

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Section: Production Of a Fraction Of Compounds With Similar Molecularsupporting

confidence: 90%

Ocean Acidification Experiments in Large-Scale Mesocosms Reveal Similar Dynamics of Dissolved Organic Matter Production and Biotransformation

et al. 2017

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“…In addition, solid-phase extraction of the samples with an efficiency of~52% on a carbon basis may not have representatively captured the most labile components of the DOM such as amino acids, DNA-based unrooted tree DOM-bacteria associations in the North Sea H Osterholz et al peptides, mono-and polysaccharides (Hertkorn et al, 2013;Osterholz et al, 2015), which are rapidly turned over by the diverse, active BC (Simon and Rosenstock, 2007;Zubkov et al, 2008). The applied electrospray ionization in negative mode potentially adds a further bias constraining our analytical window Herlemann et al, 2014).…”

Section: Identifying the Key Factors-dom Moleculesmentioning

confidence: 99%

Deciphering associations between dissolved organic molecules and bacterial communities in a pelagic marine system

et al. 2016

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Dissolved organic matter (DOM) is the main substrate and energy source for heterotrophic bacterioplankton. To understand the interactions between DOM and the bacterial community (BC), it is important to identify the key factors on both sides in detail, chemically distinct moieties in DOM and the various bacterial taxa. Next-generation sequencing facilitates the classification of millions of reads of environmental DNA and RNA amplicons and ultrahigh-resolution mass spectrometry yields up to 10 000 DOM molecular formulae in a marine water sample. Linking this detailed biological and chemical information is a crucial first step toward a mechanistic understanding of the role of microorganisms in the marine carbon cycle. In this study, we interpreted the complex microbiological and molecular information via a novel combination of multivariate statistics. We were able to reveal distinct relationships between the key factors of organic matter cycling along a latitudinal transect across the North Sea. Total BC and DOM composition were mainly driven by mixing of distinct water masses and presumably retain their respective terrigenous imprint on similar timescales on their way through the North Sea. The active microbial community, however, was rather influenced by local events and correlated with specific DOM molecular formulae indicative of compounds that are easily degradable. These trends were most pronounced on the highest resolved level, that is, operationally defined 'species', reflecting the functional diversity of microorganisms at high taxonomic resolution.

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“…The planktonic mesocosm experiments were conducted as in Osterholz et al (2015). The mesocosms were set up in triplicates (M1, M2, M3) each consisting of 4.95 L artificial nutrientenriched seawater (DOC 18 µmol C L −1 ) (Osterholz et al, 2015) mixed with 0.05 L prefiltered (poresize: 100 µm) coastal North Sea water containing the natural communities of phytoand bacterioplankton as inoculum (Spiekeroog, Germany, March 18th 2015, 53 • 01.30' N, 8 • 27.10'E, low tide, DOC 157 µmol C L −1 ) in acid-rinsed 5 L glass bottles (final DOC concentration of artificial seawater plus inoculum 19-20 µmol C L −1 ). The mesocosms were incubated at approximately 17 • C and illuminated for 12-h per day (400-700 nm) while the water was constantly stirred using magnetic stirrers.…”

Section: Mesocosm Experiments and Samplingsmentioning

confidence: 99%

Experimental Evidence for Abiotic Sulfurization of Marine Dissolved Organic Matter

et al. 2017

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Dissolved organic sulfur (DOS) is the largest pool of organic sulfur in the oceans, and as such it is an important component of the global sulfur cycle. DOS in the ocean is resistant against microbial degradation and turns over on a millennium time scale. However, sources and mechanisms behind its stability are largely unknown. Here, we hypothesize that in sulfate-reducing sediments sulfur is abiotically incorporated into dissolved organic matter (DOM) and released to the ocean. We exposed natural seawater and the filtrate of a plankton culture to sulfidic conditions. Already after 1-h at 20 • C, DOS concentrations had increased 4-fold in these experiments, and 14-fold after 4 weeks at 50 • C, indicating that organic matter does not need long residence times in natural sulfidic environments to be affected by sulfurization. Molecular analysis via ultrahigh-resolution mass spectrometry showed that sulfur was covalently and unselectively bound to DOM. Experimentally produced and natural DOS from sediments were highly similar on a molecular and structural level. By combining our data with published benthic DOC fluxes we estimate that 30-200 Tg DOS are annually transported from anaerobic and sulfate reducing sediments to the oceans. Uncertainties in this first speculative assessment are large. However, this first attempt illustrates that benthic DOS flux is potentially one order of magnitude larger than that via rivers indicating that this could balance the estimated global net removal of refractory DOS.

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Inefficient microbial production of refractory dissolved organic matter in the ocean

Cited by 153 publications

References 47 publications

Ocean Acidification Experiments in Large-Scale Mesocosms Reveal Similar Dynamics of Dissolved Organic Matter Production and Biotransformation

Ocean Acidification Experiments in Large-Scale Mesocosms Reveal Similar Dynamics of Dissolved Organic Matter Production and Biotransformation

Deciphering associations between dissolved organic molecules and bacterial communities in a pelagic marine system

Experimental Evidence for Abiotic Sulfurization of Marine Dissolved Organic Matter

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