scholarly journals Dissolved organic carbon from cultured kelp Saccharina japonica: production, bioavailability, and bacterial degradation rates

2021 ◽  
Author(s):  
Y Gao ◽  
Y Zhang ◽  
M Du ◽  
F Lin ◽  
W Jiang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Saccharina Japonica ◽  
Bacterial Degradation ◽  
Degradation Rates

scholarly journals Characterizing the origins of dissolved organic carbon in coastal seawater using stable carbon isotope and light absorption characteristics

2021 ◽  
Vol 18 (5) ◽  
pp. 1793-1801
Author(s):  
Heejun Han ◽  
Jeomshik Hwang ◽  
Guebuem Kim
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Carbon Isotope ◽  
Stable Carbon Isotope ◽  
The Yellow Sea ◽  
Bacterial Degradation ◽  
Western Coast ◽  
Stable Carbon ◽  
Δ13c Values ◽  
Lower Salinity

Abstract. In order to determine the origins of dissolved organic matter (DOM) occurring in the seawater of Sihwa Lake, we measured the stable carbon isotope ratios of dissolved organic carbon (DOC-δ13C) and the optical properties (absorbance and fluorescence) of DOM in two different seasons (March 2017 and September 2018). Sihwa Lake is enclosed by a dike along the western coast of South Korea, and the water is exchanged with the Yellow Sea twice a day through the sluice gates. The DOC concentrations were generally higher in lower-salinity waters in both periods, and excess of DOC was also observed in 2017 in high-salinity waters. Here, the excess DOC represents any DOC concentrations higher than those in the incoming open-ocean seawater. The excess DOC occurring in the lower-salinity waters originated mainly from marine sediments of tidal flats, based on the DOC-δ13C values (-20.7±1.2 ‰) and good correlations among the DOC, humic-like fluorescent DOM (FDOMH), and NH4+ concentrations. However, the origins of the excess DOC observed in 2017 appear to be from two different sources: one mainly from marine sources such as biological production based on the DOC-δ13C values (−19.1 ‰ to −20.5 ‰) and the other mainly from terrestrial sources by land–seawater interactions based on its depleted DOC-δ13C values (−21.5 ‰ to −27.8 ‰). This terrestrial DOM source observed in 2017 was likely associated with DOM on the reclaimed land, which experienced extended exposure to light and bacterial degradation as indicated by the higher spectral slope ratio (SR) of light absorbance and no concurrent increases in the FDOMH and NH4+ concentrations. Our study demonstrates that the combination of these biogeochemical tools can be a powerful tracer of DOM sources and characteristics in coastal environments.

scholarly journals Characterizing the origin of excess dissolved organic carbon in coastal seawater using stable carbon isotope and light absorption characteristics

2020 ◽  
Author(s):  
Heejun Han ◽  
Jeomshik Hwang ◽  
Guebuem Kim
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Isotopic Ratio ◽  
Stable Carbon Isotope ◽  
Bacterial Degradation ◽  
Salinity Range ◽  
Stable Carbon ◽  
Reclaimed Land ◽  
Δ13c Values ◽  
Coastal Seawater

Abstract. In order to determine the origins of dissolved organic matter (DOM) occurring in coastal seawater of the Sihwa Lake, South Korea, which is semi-enclosed by a dyke, we measured the stable carbon isotopic ratio of dissolved organic carbon (DOC-δ13C) and optical properties (absorbance and fluorescence) of the DOM in two different seasons (March 2017 and September 2018). The concentrations of DOC were generally higher in lower-salinity waters in both periods, while a significant excess of DOC was observed in 2017 in the same salinity range. The main source of DOC, dependent on salinity, was found to be from marine sediments in the freshwater-seawater mixing zone rather than from terrestrial sources based on the DOC-δ13C values (−20.7±1.2 ‰) and good correlations among DOC, humic-like fluorescent DOM (FDOMH), and NH4+ concentrations. However, the excess DOC observed in 2017 seems to originate from terrestrial sources by direct land-seawater interactions rather than from in-situ biological production, considering the lower DOC-δ13C values (−27.8 ‰ to −22.6 ‰) and higher spectral slope ratio (SR) of light absorbance, without increases in FDOMH and NH4+ concentrations. This terrestrial DOM source could have been exposed to light and bacterial degradation for a long time, resulting in nonfluorescent and low-molecular-weight DOM, as this study area is surrounded by the reclaimed land. Our results suggest that the combination of these biogeochemical tools can be a powerful tracer of coastal DOM sources.

scholarly journals Remineralization rate of terrestrial DOC as inferred from CO<sub>2</sub> supersaturated coastal waters

2018 ◽  
Author(s):  
Filippa Fransner ◽  
Agneta Fransson ◽  
Christoph Humborg ◽  
Erik Gustafsson ◽  
Letizia Tedesco ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Removal Rate ◽  
Light Attenuation ◽  
Bacterial Degradation ◽  
High Pco2 ◽  
Photochemical Degradation ◽  
Co2 Partial Pressure ◽  
Degradation Rates ◽  
Gulf Of Bothnia ◽  
One Year

Abstract. Coastal seas receive large amounts of terrestrially derived organic carbon (OC). The fate of this carbon, and its impact on the marine environment, is however poorly understood. Here we combine underway CO2 partial pressure (pCO2) measurements with coupled 3D hydrodynamical-biogeochemical modelling to investigate whether remineralization of terrestrial dissolved organic carbon (tDOC) can explain CO2 supersaturated surface waters in the Gulf of Bothnia, a subarctic estuary. We find that a substantial remineralization of tDOC, and that a strong tDOC induced light attenuation dampening the primary production, is required to reproduce the observed CO2 supersaturated waters in the nearshore areas. A removal rate of tDOC of the order of one year, estimated in a previous modelling study in the same area, gives a good agreement between modelled and observed pCO2. The remineralization rate is on the same order as bacterial degradation rates calculated from published incubation experiments, suggesting that this remineralization could be caused by bacterial degradation. Furthermore, the observed high pCO2 values during the ice covered season argues against photochemical degradation as the main removal mechanism. All of the remineralized tDOC is outgassed to the atmosphere in the model, turning the northernmost part of the Gulf of Bothnia to a source of atmospheric CO2.

scholarly journals Degradation of permafrost carbon in the Kolyma River

2020 ◽  
Author(s):  
Kirsi Keskitalo ◽  
Lisa Bröder ◽  
Dirk Jong ◽  
Nikita Zimov ◽  
Anya Davydova ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Climate Impacts ◽  
Frozen Ground ◽  
River Bank ◽  
Permafrost Thaw ◽  
Degradation Rates ◽  
Kolyma River

&lt;p&gt;Soil temperatures in permafrost (i.e. perennially frozen ground) are rising globally. The increasing temperatures accelerate permafrost thaw and release of organic carbon, that has been locked in permafrost soils since the last glacial period, to the contemporary carbon cycle. The potential remineralisation of organic carbon to greenhouse gases can contribute to further climate warming. Particulate organic carbon (POC) in the Kolyma River is older than dissolved organic carbon (DOC) thus serves as a good tracer for abrupt permafrost thaw (i.e. river bank erosion and thermokarst) that dominantly releases old POC. While dissolved organic carbon (DOC) mobilised from the old Yedoma outcrops on the banks of the Kolyma River is shown to be highly labile, vulnerability of POC to biodegradation is not yet known. In this study we aim to constrain degradation rates for POC in the Kolyma River. To capture seasonal variability of the POC pool and its degradation rate the incubation was conducted both during the spring freshet and in late summer (2019 and 2018, respectively). We incubated whole-water samples over 9 to 15 days and quantified POC (and DOC) loss over time, as well as dissolved inorganic carbon (DIC). The incubation was carried out in the dark. We also tracked changes in POC composition and age with carbon isotopes (d&lt;sup&gt;13&lt;/sup&gt;C-OC, d&lt;sup&gt;13&lt;/sup&gt;C-DIC, &amp;#8710;&lt;sup&gt;14&lt;/sup&gt;C). Preliminary results from 2018 suggest a decrease in POC concentrations of up to 30 % while those of DOC decrease by up to 11 %. The rate of POC degradation is nearly three times faster than DOC though the absolute amounts of DOC are in turn higher than those of POC (&lt; 1 mg L&lt;sup&gt;-1&lt;/sup&gt; for POC and ~3 mg L&lt;sup&gt;-1&lt;/sup&gt; for DOC). Furthermore, the changes in d&lt;sup&gt;13&lt;/sup&gt;C of POC, DOC and DIC suggest ongoing microbial degradation and conversion of organic carbon into inorganic carbon. These first estimates show that POC degrades fairly rapidly while transported in the Kolyma River. A better understanding of POC degradation along lateral flow paths is critical for improving our knowledge of permafrost thaw and its possible climate impacts in the future.&lt;/p&gt;

scholarly journals Remineralization rate of terrestrial DOC as inferred from CO<sub>2</sub> supersaturated coastal waters

2019 ◽  
Vol 16 (4) ◽  
pp. 863-879 ◽  
Author(s):  
Filippa Fransner ◽  
Agneta Fransson ◽  
Christoph Humborg ◽  
Erik Gustafsson ◽  
Letizia Tedesco ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Removal Rate ◽  
Light Attenuation ◽  
Bacterial Degradation ◽  
High Pco2 ◽  
Photochemical Degradation ◽  
Co2 Partial Pressure ◽  
Incubation Experiments ◽  
Degradation Rates ◽  
Gulf Of Bothnia

Abstract. Coastal seas receive large amounts of terrestrially derived organic carbon (OC). The fate of this carbon, and its impact on the marine environment, is however poorly understood. Here we combine underway CO2 partial pressure (pCO2) measurements with coupled 3-D hydrodynamical–biogeochemical modelling to investigate whether remineralization of terrestrial dissolved organic carbon (tDOC) can explain CO2 supersaturated surface waters in the Gulf of Bothnia, a subarctic estuary. We find that a substantial remineralization of tDOC and a strong tDOC-induced light attenuation dampening the primary production are required to reproduce the observed CO2 supersaturated waters in the nearshore areas. A removal rate of tDOC of the order of 1 year, estimated in a previous modelling study in the same area, gives a good agreement between modelled and observed pCO2. The remineralization rate is on the same order as bacterial degradation rates calculated from published incubation experiments, suggesting that bacteria has the potential to cause this degradation. Furthermore, the observed high pCO2 values during the ice-covered season argue against photochemical degradation as the main removal mechanism. All of the remineralized tDOC is outgassed to the atmosphere in the model, turning the northernmost part of the Gulf of Bothnia into a source of CO2 to the atmosphere.

CHARACTERISATION OF DISSOLVED ORGANIC CARBON (DOC) LEACHED FROM LEAVES IN WATER

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Markus Heryanto Langsa
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Total Organic Carbon ◽  
Gas Chromatography Mass Spectrometry ◽  
Pyrolysis Gas ◽  
Pyrolysis Gas Chromatography ◽  
Chromatography Mass Spectrometry ◽  
Pinus Radiate

<p>Penelitian ini bertujuan untuk menentukan senyawa organik khususnya organic karbon terlarut (DOC) dari dua spesies daun tumbuhan (<em>wandoo eucalyptus </em>and <em>pinus radiate, conifer</em>) yang larut dalam air selama periode 5 bulan leaching eksperimen. Kecepatan melarutnya senyawa organic ditentukan secara kuantitatif dan kualitatif menggunakan kombinasi dari beberapa teknik diantaranya Total Organic Carbon (TOC) analyser, Ultraviolet-Visible (UV-VIS) spektrokopi dan pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS).</p><p>Hasil analisis DOC dan UV menunjukkan peningkatan yang tajam dari kelarutan senyawa organic di awal periode pengamatan yang selanjutnya berkurang seiring dengan waktu secara eksponensial. Jumlah relatif senyawa organic yang terlarut tergantung pada luas permukaan, aktifitas mikrobiologi dan jenis sampel tumbuhan (segar atau kering) yang digunakan. Fluktuasi profil DOC dan UV<sub>254</sub> disebabkan oleh aktifitas mikrobiologi. Diperoleh bahwa daun kering lebih mudah terdegradasi menghasilkan senyawa organic dalam air dibandingkan dengan daun segar. Hasil pyrolysis secara umum menunjukkan bahwa senyawa hidrokarbon aromatic dan fenol (dan turunannya) lebih banyak ditemukan pada residue sampel setelah proses leaching kemungkinan karena adanya senyawa lignin atau aktifitas humifikasi mikrobiologi membuktikan bahwa senyawa-senyawa tersebut merupakan komponen penting dalam proses karakterisasi DOC.</p>

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