Accumulation of humic-like fluorescent dissolved organic matter in the Japan Sea

Tanaka, Kazuki; Kuma, Kenshi; Hamasaki, Koji; Yamashita, Youhei

doi:10.1038/srep05292

Cited by 75 publications

(80 citation statements)

References 52 publications

(118 reference statements)

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“…This fluorophore also corresponded to a fluorophore that was found to be microbial recalcitrant FDOM with the time scale of the thermohaline circulation (Yamashita and Tanoue, 2008). Fluorescent components similar to H2 were obtained through parallel factor analysis (PARAFAC) of FDOM from the open ocean and were found to be related to apparent oxygen utilization in the deep ocean (Jørgensen et al, 2011; Tanaka et al, 2014), implying that H2 produced by A. macleodii is possibly recalcitrant DOM. On the other hand, peak M was produced by phytoplankton isolates (Romera-Castillo et al, 2010) and consumed partially by bacterial communities (Romera-Castillo et al, 2011).…”

Section: Discussionmentioning

confidence: 97%

“…Notably, in Shimotori’s incubation studies (Shimotori et al, 2009), this fluorophore appeared in EEMs during the period of increasing bacterial abundance but disappeared from EEMs during the period of decreasing bacterial abundance. In the open ocean, this fluorophore is generally not present (Jørgensen et al, 2011; Tanaka et al, 2014). Thus, A. macleodii may be one of the key species that produces this fluorophore, and this fluorophore might be consumed by other microbes in natural environments.…”

Section: Discussionmentioning

confidence: 99%

“…Excitation–emission matrix was measured using a fluorometer (FluoroMax-4, Horiba) according to the procedure of Tanaka et al (2014). Samples were allowed to reach near room temperature before the EEM measurements were undertaken.…”

Section: Methodsmentioning

confidence: 99%

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Production and Reutilization of Fluorescent Dissolved Organic Matter by a Marine Bacterial Strain, Alteromonas macleodii

et al. 2017

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The recalcitrant fraction of marine dissolved organic matter (DOM) plays an important role in carbon storage on the earth’s surface. Bacterial production of recalcitrant DOM (RDOM) has been proposed as a carbon sequestration process. It is still unclear whether bacterial physiology can affect RDOM production. In this study, we conducted a batch culture using the marine bacterial isolate Alteromonas macleodii, a ubiquitous gammaproteobacterium, to evaluate the linkage between bacterial growth and DOM production. Glucose (1 mmol C L-1) was used as the sole carbon source, and the bacterial number, the DOM concentration in terms of carbon, and the excitation–emission matrices (EEMs) of DOM were monitored during the 168-h incubation. The incubation period was partitioned into the exponential growth (0–24 h) and stationary phases (24–168 h) based on the growth curve. Although the DOM concentration decreased during the exponential growth phase due to glucose consumption, it remained stable during the stationary phase, corresponding to approximately 4% of the initial glucose in terms of carbon. Distinct fluorophores were not evident in the EEMs at the beginning of the incubation, but DOM produced by the strain exhibited five fluorescent peaks during exponential growth. Two fluorescent peaks were similar to protein-like fluorophores, while the others could be categorized as humic-like fluorophores. All fluorophores increased during the exponential growth phase. The tryptophan-like fluorophore decreased during the stationary phase, suggesting that the strain reused the large exopolymer. The tyrosine-like fluorophore seemed to be stable during the stationary phase, implying that the production of tyrosine-containing small peptides through the degradation of exopolymers was correlated with the reutilization of the tyrosine-like fluorophore. Two humic-like fluorophores that showed emission maxima at the longer wavelength (525 nm) increased during the stationary phase, while the other humic-like fluorophore, which had a shorter emission wavelength (400 nm) and was categorized as recalcitrant, was stable. These humic-like fluorophore behaviors during incubation indicated that the composition of bacterial humic-like fluorophores, which were unavailable to the strain, differed between growth phases. Our results suggest that bacterial physiology can affect RDOM production and accumulation in the ocean interior.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

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Production and Reutilization of Fluorescent Dissolved Organic Matter by a Marine Bacterial Strain, Alteromonas macleodii

et al. 2017

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“…In open ocean surface waters, the fluorescence signature of humics appear to be best related to oxygen utilization and chlorophyll a concentrations as a result of in-situ production (Stolpe et al, 2014), hence a biologically-mediated distribution has been proposed (Yamashita et al, 2010;Tanaka et al, 2014;Catala et al, 2016). In this case, the peak in ligand concentrations associated with higher stocks of phytoplankton and bacteria could be associated with HS-like produced by biological excretion.…”

Section: Humicsmentioning

confidence: 99%

Toward a Regional Classification to Provide a More Inclusive Examination of the Ocean Biogeochemistry of Iron-Binding Ligands

2017

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Iron-binding ligands are paramount to understanding iron biogeochemistry and its potential to set the productivity and the magnitude of the biological pump in >30% of the ocean. However, the nature of these ligands is largely uncharacterized and little is known about their sources, sensitivity to photochemistry and biological transformation, or scavenging behavior. Despite many uncertainties, there is no doubt that ligands are produced by a wide range of biotic and abiotic processes, and that the bulk ligand pool encompasses a diverse range of molecules. Despite widespread recognition of the likelihood of a continuum of ligand classes making up the bulk ligand pool, studies to date largely focused on the dominant ligand. Thus, most studies have overlooked the need to assess where these targeted molecules fit across the spectrum of ligands that comprise the bulk ligand pool. Here we summarize present knowledge to critically assess the source(s), function(s), production pathways, and loss mechanisms of three important iron-binding organic ligand groups in order to assess their distinctive characteristics and how they link with observed ligand distributions. We considered that ligands are contained in broad groupings of exopolymer substances (EPS), humic substances (HS), and siderophores; using literature data for speciation modeling suggested that this adequately described the iron speciation reported in the ocean. We hypothesize that a holistic viewpoint of the multi-faceted controls on ligands dynamics is essential to begin to understand why some ligands can be expected to dominate in particular oceanic regions, depth strata, or exhibit seasonality and/or lateral gradients. We advocate that the development of a regional classification will enhance our understanding of the changing composition of the bulk ligand pool across the global ocean and to help address to what extent seasonality influences the makeup of this pool. This classification, based on selected functional ligand classes, can act as a bridge to use future ligand datasets to fill in the gaps in the continuum.

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“…Also a region known to be associated with phenolic fluorescence. (Murphy et al, 2006), 8 (Murphy et al, 2014), 9 (Murphy et al, 2008), 22 (Kothawala et al, 2012), 26 (Stedmon et al, 2011b), 28 (Stedmon et al, 2007), 29 (Stedmon and Markager, 2005), 31 (Søndergaard et al, 2003), 32 (Jørgensen et al, 2011), 33 , 34 (Stedmon and Markager, 2005), 35 (Osburn and Stedmon, 2011), 37 (Walker et al, 2009), 39 (Yamashita et al, 2011), 41 (Yamashita et al, 2010a), 44 (Yamashita et al, 2010b), 47 (Kowalczuk et al, 2009), 48 (Graeber et al, 2012), 53 (Kothawala et al, 2013), 54 (Osburn et al, 2012), 55 , 64 (Walker et al, 2013), 68 (Tanaka et al, 2014), 69 (Lapierre and del Giorgio, 2014).…”

Section: Parallel Factor Analysis (Parafac)mentioning

confidence: 99%

Pan-Arctic Trends in Terrestrial Dissolved Organic Matter from Optical Measurements

et al. 2016

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Climate change is causing extensive warming across Arctic regions resulting in permafrost degradation, alterations to regional hydrology and shifting amounts and composition of dissolved organic matter (DOM) transported by streams and rivers. Here, we characterize the DOM composition and optical properties of the six largest Arctic rivers draining into the Arctic Ocean to examine the ability of optical measurements to provide meaningful insights into terrigenous carbon export patterns and biogeochemical cycling. The chemical composition of aquatic DOM varied with season, spring months were typified by highest lignin phenol and dissolved organic carbon (DOC) concentrations with greater hydrophobic acid content, and lower proportions of hydrophilic compounds, relative to summer and winter months. Chromophoric DOM (CDOM) spectral slope (S 275-295 ) tracked seasonal shifts in DOM composition across river basins. Fluorescence and parallel factor analysis identified seven components across the six Arctic rivers. The ratios of "terrestrial humic-like" vs. "marine humic-like" fluorescent components co-varied with lignin monomer ratios over summer and winter months, suggesting fluorescence may provide information on the age and degradation state of riverine DOM. CDOM absorbance (a 350 ) proved a sensitive proxy for lignin phenol concentrations across all six river basins and over the hydrograph, enabling for the first time the development of a single pan-arctic relationship between a 2 350 and terrigenous DOC (R = 0.93). Combining this lignin proxy with high-resolution monitoring of a 350 , pan-arctic estimates of annual lignin flux were calculated to range from 156 to 185 Gg, resulting in shorter and more constrained estimates of terrigenous DOM residence times in the Arctic Ocean (spanning 7 months to 2½ years). Furthermore, multiple linear regression models incorporating both absorbance and fluorescence variables proved capable of explaining much of the variability in lignin composition across rivers and seasons. Our findings suggest that synoptic, high-resolution optical measurements can provide improved understanding of northern high-latitude organic matter cycling and flux, and prove an important technique for capturing future climate-driven changes.

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Accumulation of humic-like fluorescent dissolved organic matter in the Japan Sea

Cited by 75 publications

References 52 publications

Production and Reutilization of Fluorescent Dissolved Organic Matter by a Marine Bacterial Strain, Alteromonas macleodii

Production and Reutilization of Fluorescent Dissolved Organic Matter by a Marine Bacterial Strain, Alteromonas macleodii

Toward a Regional Classification to Provide a More Inclusive Examination of the Ocean Biogeochemistry of Iron-Binding Ligands

Pan-Arctic Trends in Terrestrial Dissolved Organic Matter from Optical Measurements

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