Composition and bioavailability of dissolved organic matter in different water masses of the East China sea

Guo, Jinqiang; Liang, Shan; Li, Xiao‐Jiao; Li, Wei; Wang, Yunfei; Su, Rongguo

doi:10.1016/j.ecss.2018.07.009

Cited by 23 publications

(19 citation statements)

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“…6.90 ± 1.31 μM) in September 2015. The DON concentrations in the ECS were slightly lower than those in the surface layer of the Atlantic Ocean (4–11 µM), Pacific Ocean (7–13 µM) 30 – 32 , and the Changjiang estuary (14.12 μM) 33 and its adjacent sea (6.7 μM) 34 , and fell within the range of those of the East/Japan Sea (4–7 μM) 35 . In the surface layer, the concentrations of DOC and DON were relatively lower in July 2015 (avg.…”

Section: Resultsmentioning

confidence: 73%

Factors controlling the distributions of dissolved organic matter in the East China Sea during summer

Kim

Park

et al. 2020

Sci Rep

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to determine the distribution of dissolved organic matter (DoM) in the east china Sea (ecS) during the summer, we measured the dissolved organic carbon (DOC) and nitrogen (DON), fluorescent dissolved organic matter (fDoM), and chlorophyll a (chl. a) in the upper 100-m layer of this region during July and September 2015. The DOC (r 2 = 0.72 and 0.78 in July and September, respectively) and DON (r 2 = 0.43 and 0.33) were significantly correlated with salinity, suggesting that the river is the primary origin of DOM. However, we found that at a DOC "pulse" under a salinity ranging from 24 to 35, the extrapolating DOC values (304 ± 11 μM) were twice higher than those with a salinity of close to 0, as found in a previous study. the excess Doc concentration seemed to be attributed to the microbial metabolism during transport from the estuary based on the good relationships between Doc and marine humic-like fDoM (r 2 = 0.42 and 0.47), as well as the fluorescence, humification, and biological indexes, but showed no correlation with chl. a. thus, the results of our study indicate that microbial activities can be a significant factor controlling the distribution of DOM in the ECS during summer. Dissolved organic matter (DOM) in the oceans is one of the largest reservoirs of carbon and nitrogen on Earth, and its distribution and behaviour play crucial roles not only in biogeochemical processes in the ocean but also in the carbon and nitrogen cycles 1. Dissolved organic carbon (DOC), the carbon component of DOM, can be preserved for thousands of years in the deep open oceans with relatively lower and uniform concentrations because more than 90% of DOC is recalcitrant to microbial utilization in the water column 2,3. Thus, this carbon fixed in dissolved organic form could contribute to the sinking of atmospheric CO 2 in the ocean through the biological pump 4,5. By contrast, high and significant variations in DOC concentrations have been found in the coastal and marginal oceans owing to intense biological activities and large terrestrial inputs 6. Dissolved organic nitrogen (DON), the nitrogen component of DOM, including urea, amino acids, nucleic acids, and amino sugars, is a primary reservoir of reactive nitrogen in the oceans. When dissolved inorganic nitrogen (DIN) is depleted, DON is the dominant pool of fixed nitrogen, and can become a direct energy source for marine microorganisms 7. By the microbial carbon pump, microbial transformation of DOM from labile to recalcitrant state, nitrogen was preferentially removed relative to carbon within the DOM pool, then the recalcitrant DOM shows ultimately the high DOC to DON ratio 8. The northwestern Pacific marginal seas, including the East China Sea (ECS) and the southern sea off Korea, are among the largest continental shelves in the world 9. These seas receive huge amounts of freshwater (0.9 × 10 12 m 3 year −1) from the Changjiang River 10 and seawater from the Kuroshio branch water, a strong western boundary current 11. Here, the mixing of freshwater driven by the Changjian...

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Section: Resultsmentioning

confidence: 73%

Factors controlling the distributions of dissolved organic matter in the East China Sea during summer

Kim

Park

et al. 2020

Sci Rep

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“…Gaye et al (2007) calculated a new degradation index for sediment traps from the Kara Sea whereas Unger et al (2005) used the established DI and RI to classify sediment and suspended water samples from the river endmembers Ob and Yenisei into the brackish-marine Kara Sea. The DI was even applied to trace dissolved AA degradation (Davis and Benner, 2005;Guo et al, 2018), although the DI is originally based on marine sediments only (Dauwe et al, 1999). An indicator of oxic vs. anoxic organic matter degradation in the water column and in sediments was proposed by Menzel et al (2015) for lake samples.…”

Section: Amino Acid Derived Biogeochemical Indicators Of Organic Matter Origin and Degradationmentioning

confidence: 99%

“…Differences of hydrolysis conditions can explain the large range of AA contribution to dissolved organic carbon found in different experiments. Mild acid hydrolysis of AA resulted in amino acid carbon contributions to total dissolved carbon (AAC/C) between 0.4 and 4 % with a reduction from 1-4 % AAC/C % in surface waters to 0.4-0.8 % in waters >1.000 m (Guo et al, 2018;Davis and Benner, 2005). Moreover, this reduction was associated with a progressive AA degradation (Kim et al, 2017;Davis and Benner, 2005).…”

Section: Introductionmentioning

confidence: 99%

What can we learn from amino acids about oceanic organic matter cycling and degradation?

Gaye

Lahajnar

Harms

et al. 2021

Preprint

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Abstract. Amino acids (AA) mainly bound in proteins are major constituents of living biomass and non-living organic material in the oceanic particulate and dissolved organic matter pool. Uptake and cycling by heterotrophic organisms lead to characteristic changes in AA composition so that AA based biogeochemical indicators are often used to elucidate processes of organic matter cycling and degradation. We analyzed particulate AA in a large sample set collected in various oceanic regions covering sinking and suspended particles in the water column, sediment samples as well as dissolved AA from water column and pore water samples. The aim of this study was to test and improve the use of AA derived biogeochemical indicators as proxies for organic matter sources and degradation, and to better understand particle dynamics and interaction between the dissolved and particulate organic matter pools. A principal component analysis (PCA) of all data delineates diverging AA compositions of sinking and suspended particles with increasing water depth. A new sinking particle and sediment degradation indicator (SDI) allows a fine-tuned classification of sinking particles and sediments with respect to the intensity of degradation, which is associated with changes of bulk δ15N ratios. This new indicator furthermore is sensitive to sedimentary redox conditions and can be used to detect past anoxic early diagenesis. A second indicator emerges from the AA spectra of suspended particulate matter (SPM) in the epipelagic and that of the meso- and bathypelagic ocean and is a residence time indicator (RTI). The characteristic changes in AA patterns from shallow to deep SPM are recapitulated in the AA spectra of the dissolved organic matter (DOM) pool, so that deep SPM is more similar to DOM than to any of the other organic matter pools. This implies that there is equilibration between finely dispersed SPM and DOM in the deep sea, which may be driven by microbial activity combined with annealing and fragmentation of gels. As these processes strongly depend on physico-chemical conditions in the deep ocean, changes in quality and degradability of DOM may strongly affect the relatively large pool of suspended and dissolved AA in the ocean that amounts to 15 Pg amino acid carbon (AAC) and 89 ± 29 Pg AAC, respectively.

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“…Several studies have looked into the behavior of terrestrial organic matter in the Changjiang Estuary and monitored seasonal differences in organic matter distributions. However, the removal processes and fates of DOM in the Changjiang Estuary and the adjacent sea remain unclear (Chen et al., 2016; Guo et al., 2018; Hung et al., 2003; Wu et al., 2003, 2007, 2016; Z. Y. Zhu et al., 2014). The aims of this study were to: (1) investigate the temporal and spatial distributions and compositions of DOC and total hydrolyzable amino acids (THAA); (2) discuss the possible relationships of DOM with salinity and chlorophyll a (Chl‐ a ); (3) evaluate the bioavailability of DOM based on DI and THAA‐C%; and (4) investigate the removal mechanisms of DOM via seawater photochemical and microbial incubation experiments.…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Seasonal Variation, Degradation, and Bioavailability of Dissolved Organic Matter in the Changjiang Estuary and its Adjacent East China Sea

Yang

2021

JGR Oceans

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Dissolved organic carbon (DOC) in the sea is primarily removed by heterotrophic prokaryotes (Azam, 1998). However, Hansell and Carlson (1998) estimated that 17% of global new production escapes rapid utilization by microbes and accumulates as DOC in surface waters. Previous field observations from the Bermuda Atlantic Time-Series Study (BATS) site demonstrated that semilabile DOC in the upper euphotic zone was less available to microorganisms and remained at constant concentrations in stratified water column (Carlson et al., 2002; Hansell & Carlson, 2001). Depending on the marine system, temperature, grazing, and competition for limited nutrients might restrict bacterial production (Rivkin & Anderson, 1997; Shiah &

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Composition and bioavailability of dissolved organic matter in different water masses of the East China sea

Cited by 23 publications

References 68 publications

Factors controlling the distributions of dissolved organic matter in the East China Sea during summer

Factors controlling the distributions of dissolved organic matter in the East China Sea during summer

What can we learn from amino acids about oceanic organic matter cycling and degradation?

Seasonal Variation, Degradation, and Bioavailability of Dissolved Organic Matter in the Changjiang Estuary and its Adjacent East China Sea

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