Effect of permafrost thawing on the organic carbon and trace element colloidal speciation and microbial activity in thermokarst lakes of Western Siberia

Abstract. In order to understand the mechanisms of carbon mobilization and biodegradation during permafrost thawing and to establish the link between the organic carbon (OC), and other chemical and microbiological parameters in forming thermokarstic (thaw) lakes, we studied biogeochemistry of OC and trace elements (TE) in a chronosequence of small lakes that are being formed due to permafrost thawing in the northern part of Western Siberia. About 20 lakes and small ponds of various sizes and ages were sampled for dissolved and colloidal organic carbon and metals and culturable heterotrophic bacterial cell number. We observed a sequence of ecosystem stages corresponding to the evolution from peat thawing and palsa degradation due to permafrost subsidence in small ponds to large, km – size lakes subject to drainage and, finally, the khasyrey (drained lake) formation. There is a systematic evolution of both total dissolved and colloidal concentration of OC and TE in the lake water along the chronosequence of lake development that may be directly linked to microbial mineralization of dissolved organic matter and liberation of the mineral part (Fe, Al, TE) from organo-mineral colloids. In this chronosequence of lake development, we observe a clear decrease of the relative proportion of <1 kDa (1 kDa~1 nm) OC concentration along with concentration of total dissolved (<0.45 μm) OC. This is accompanied by an increase of the small size organic ligands (probably autochtonous exometabolites produced by the phytoplankton) and a concomitant decrease of the proportion of large-size organic (humic) complexes having allochtonous (soil) origin. This evolution may be due to the activity of heterotrophic bacterioplancton that uses allochtonous organic matter and dissolved nutrients originated from the peat lixiviation. Most insoluble TE demonstrate a systematic decrease of concentration during filtration (5 μm, 0.45 μm) exhibiting a similar pattern among different samples. At the same time, there is an increase of the relative proportion of large size particles over <1 kDa fraction for most insoluble elements along the chronosequence of lake evolution. TE are likely to be bound to colloidal OC but also coprecipitated with the mineral (Fe, Al) part of colloids. Upon progressive consumption of dissolved OC by heterotrophic bacteria, there is a liberation of Fe, Al, and insoluble TE in the water column that may be subjected to coagulation in the form of particles or large-size mineral colloids.

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Effect of permafrost thawing on organic carbon and trace element colloidal speciation in the thermokarst lakes of western Siberia

Biogeosciences ◽

10.5194/bg-8-565-2011 ◽

2011 ◽

Vol 8 (3) ◽

pp. 565-583 ◽

Cited By ~ 83

Author(s):

O. S. Pokrovsky ◽

L. S. Shirokova ◽

S. N. Kirpotin ◽

S. Audry ◽

J. Viers ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Western Siberia ◽

Heterotrophic Bacteria ◽

Relative Proportion ◽

Cell Number ◽

Lake Development ◽

Large Size ◽

Lake Formation ◽

Permafrost Thawing

Abstract. To examine the mechanisms of carbon mobilization and biodegradation during permafrost thawing and to establish a link between organic carbon (OC) and other chemical and microbiological parameters in forming thermokarst (thaw) lakes, we studied the biogeochemistry of OC and trace elements (TEs) in a chronosequence of small lakes that are being formed due to permafrost thawing in the northern part of western Siberia. Twenty lakes and small ponds of various sizes and ages were sampled for dissolved and colloidal organic carbon, metals and culturable heterotrophic bacterial cell number. We observed a sequence of ecosystems from peat thawing and palsa degradation due to permafrost subsidence in small ponds to large, km-size lakes that are subject to drainage to, finally, the khasyrey (drained lake) formation. There is a systematic evolution of both total dissolved and colloidal concentration of OC and TEs in the lake water along with the chronosequence of lake development that may be directly linked to the microbial mineralization of dissolved organic matter and the liberation of the inorganic components (Fe, Al, and TEs) from the organo-mineral colloids. In this chronosequence of lake development, we observed an apparent decrease in the relative proportion of low molecular weight <1 kDa (1 kDa ~ 1 nm) OC concentration along with a decrease in the concentration of total dissolved (<0.45 μm) OC. This decrease was accompanied by an increase in the small size organic ligands (probably autochthonous exometabolites produced by the phytoplankton) and a simultaneous decrease in the proportion of large-size organic (humic) complexes of allochthonous (soil) origin. This evolution may be due to the activity of heterotrophic bacterioplankton that use allochthonous organic matter and dissolved nutrients originating from peat lixiviation. Most insoluble TEs demonstrate a systematic decrease in concentration during filtration (5 μm, 0.45 μm) exhibiting a similar pattern among different samples. At the same time, there is an increase in the relative proportion of large size particles over the <1 kDa fraction for most insoluble elements along the chronosequence of lake evolution. TEs are likely to be bound to colloidal OC and coprecipitate with the mineral (Fe, Al) part of the colloids. Upon progressive consumption of dissolved OC by the heterotrophic bacteria, there is liberation of Fe, Al, and insoluble TEs in the water column that may be subjected to coagulation in the form of particles or large-size mineral colloids.

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Organic matter mineralization and trace element post-depositional redistribution in Western Siberia thermokarst lake sediments

Biogeosciences ◽

10.5194/bg-8-3341-2011 ◽

2011 ◽

Vol 8 (11) ◽

pp. 3341-3358 ◽

Cited By ~ 48

Author(s):

S. Audry ◽

O. S. Pokrovsky ◽

L. S. Shirokova ◽

S. N. Kirpotin ◽

B. Dupré

Keyword(s):

Trace Elements ◽

Organic Matter ◽

Organic Carbon ◽

Lake Sediments ◽

Water Column ◽

Western Siberia ◽

Ecosystem Development ◽

Thermokarst Lake ◽

Fe And Mn ◽

The Impact

Abstract. This study reports the very first results on high-resolution sampling of sediments and their porewaters from three thermokarst (thaw) lakes representing different stages of ecosystem development located within the Nadym-Pur interfluve of the Western Siberia plain. Up to present time, the lake sediments of this and other permafrost-affected regions remain unexplored regarding their biogeochemical behavior. The aim of this study was to (i) document the early diagenesic processes in order to assess their impact on the organic carbon stored in the underlying permafrost, and (ii) characterize the post-depositional redistribution of trace elements and their impact on the water column. The estimated organic carbon (OC) stock in thermokarst lake sediments of 14 ± 2 kg m−2 is low compared to that reported for peat soils from the same region and denotes intense organic matter (OM) mineralization. Mineralization of OM in the thermokarst lake sediments proceeds under anoxic conditions in all the three lakes. In the course of the lake development, a shift in mineralization pathways from nitrate and sulfate to Fe- and Mn-oxyhydroxides as the main terminal electron acceptors in the early diagenetic reactions was suggested. This shift was likely promoted by the diagenetic consumption of nitrate and sulfate and their gradual depletion in the water column due to progressively decreasing frozen peat lixiviation occurring at the lake's borders. Trace elements were mobilized from host phases (OM and Fe- and Mn-oxyhydroxides) and partly sequestered in the sediment in the form of authigenic Fe-sulfides. Arsenic and Sb cycling was also closely linked to that of OM and Fe- and Mn-oxyhydroxides. Shallow diagenetic enrichment of particulate Sb was observed in the less mature stages. As a result of authigenic sulfide precipitation, the sediments of the early stage of ecosystem development were a sink for water column Cu, Zn, Cd, Pb and Sb. In contrast, at all stages of ecosystem development, the sediments were a source of dissolved Co, Ni and As to the water column. However, the concentrations of these trace elements remained low in the bottom waters, indicating that sorption processes on Fe-bounding particles and/or large-size organo-mineral colloids could mitigate the impact of post-depositional redistribution of toxic elements on the water column.

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Comparative Assessment of the Bioremediation Potential of Polychaetes (Lug worm-Arenicola marina sp and Syllidae Worm-Syllis prolifera sp) in Aquaculture Pond Sediment

Asian Journal of Applied Chemistry Research ◽

10.9734/ajacr/2021/v10i130225 ◽

2021 ◽

pp. 1-13

Author(s):

I. O. Oyo-Ita ◽

U. A. Ugbaja ◽

E. E. Oyo-Ita ◽

C. Oge ◽

B. B. Asuquo ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Feeding Habits ◽

Sediment Quality ◽

Arenicola Marina ◽

Aquaculture Pond ◽

Pond Sediment ◽

Large Size ◽

Set Up ◽

Aquaculture Waste

Polychaetes play an important role in nutrient cycling and remediation of coastal ecosystems. Large quantities of organic matter that could lead to pollution of pond and coastal waters are generated by aquaculture waste. To assess the remediation prospects of Arenicola marina and Syllis prolifera species, laboratory sediment microcosm experiments were conducted where large size Arenicola marina and Syllis prolifera were introduced to sediment in microcosm A, large size Arenicola marina to sediment in microcosm B, large sized Syllis prolifera to sediment in microcosm C and no polychaetes to sediment in microcosm D. Microcosm A′, B′ and C′ as replicates for small size polychaetes were also set up, respectively. After 30 days, microcosm A, B and C had significant decrease in organic carbon levels with microcosm B being the highest (Total organic carbon (TOC); 27.87%; p< 0.05). Both large and small polychaetes promoted significant decrease in sulphur (S) content (mean=62.76±0.21; 62.81±0.21%) and iron(Fe) (mean=49.43±1.47; 36.28±5.90%) respectively. Increase in pH by 31.15±0.13% was found in the presence of large size polychaetes, most likely associated with the burrowing process involving oxidation of Fe to Fe2O3. Large size polychaetes had better survival (mean=92±0.82%) than their small size counterpart (mean=55±4.08%). The extent of biodegradation B>A>C>D observed revealed that large size Arenicola marina was a better bioremediator of organic matter (OM), Fe and S enriched aquaculture pond sediment, probably due to its biological characteristics, well suited for the aquaculture than other species of sea worms that produce free swimming larvae. Therefore, large size Arenicola marina significantly improved sediment quality as well as increased its pH without compromising their survival. As the search for a better bioremediator of organically enriched sediment continues, our result revealed large size Arenicola marina as a more promising candidate compared to other species documented elsewhere in the world. Hence, rearing of large size Arenicola marina sp is recommended as their feeding habits are well suited for aquaculture.

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Freeze-thaw dynamics in synthetic permafrost soil columns with variable organic carbon content

10.5194/egusphere-egu2020-7532 ◽

2020 ◽

Author(s):

Jelte de Bruin ◽

Victor Bense ◽

Martine van der Ploeg

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Physical Properties ◽

Groundwater Flow ◽

Soil Column ◽

Soil Physical Properties ◽

Soil Columns ◽

Cold Regions ◽

Warming Climate ◽

Permafrost Thawing

Cold-regions hold a pool of organic carbon that has accumulated over many thousands to millions of years and which is currently kept immobile by permafrost. However, in a warming climate, a deepening of the active layer results in the release of greenhouse gasses CO2 and CH4 into the atmosphere from this carbon pool. Additionally, due to the degradation of deeper permafost, soil hydraulic properties and associated groundwater flow paths are shifting rapidly as a result of which also organic carbon in deeper permafrost is being dissolved into groundwater, which can then reach the surface environment via groundwater flow. &#160;This provides an additional mechanism by which permafrost carbon can be mobilized in &#160;a warming climate, and one which is likely increasingly important for progressive surface warming.Although the process of carbon leaching from thawing organic rich permafrost layers into the groundwater is an increasingly important part of the carbon cycle of cold-regions, it is notoriously difficult to measure in situ or incorporate into numerical model assessments due to the highly heterogeneous properties of the permafrost, and lack of process knowledge. In particular, the crucial understanding of the influence of different soil physical properties such as soil grain size and organic matter content on permafrost thawing processes is missing, as well the precise release mechanisms&#160; of organic matter into pore waters in thawing soils.This study employs lab soil column experiments to investigate the interplay between soil physical properties and thawing dynamics of permafrost. One meter high soil columns are frozen to create controlled permafrost conditions. A range of sand grain sizes (0.1 to 0.8mm) and organic matter contents (1 to 10 wt%) representative for sedimentary permafrost are used. The column is thermally insulated on the sides and top, exposing only one face to ambient temperature in the climate chamber. In this way one-dimensional heat flow conditions are created. So far, the columns are equipped with arrays of temperature sensors. Experiments consist of a cycle of freezing and thawing. Our initial data and analysis illustrate how a fast evolving thawing front develops through the frozen soil column &#160;including the effects of latent heat at the thawing front. Numerical modeling allows to infer the soil thermal properties relevant to model the permafrost thawing process.

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Potential bioavailability of organic matter from atmospheric particles to marine heterotrophic bacteria

Biogeosciences ◽

10.5194/bg-17-6271-2020 ◽

2020 ◽

Vol 17 (24) ◽

pp. 6271-6285

Author(s):

Kahina Djaoudi ◽

France Van Wambeke ◽

Aude Barani ◽

Nagib Bhairy ◽

Servanne Chevaillier ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Incubation Period ◽

Bacterial Growth ◽

Heterotrophic Bacteria ◽

Water Soluble ◽

Bacterial Growth Efficiency ◽

Anthropogenic Aerosols ◽

Biogeochemical Models ◽

Marine Heterotrophic Bacteria

Abstract. The surface ocean receives important amounts of organic carbon from atmospheric deposition. The degree of bioavailability of this source of organic carbon will determine its impact on the marine carbon cycle. In this study, the potential availability of dissolved organic carbon (DOC) leached from both desert dust and anthropogenic aerosols to marine heterotrophic bacteria was investigated. The experimental design was based on 16 d incubations, in the dark, of a marine bacterial inoculum into artificial seawater amended with water-soluble Saharan dust (D treatment) and anthropogenic (A treatment) aerosols, so that the initial DOC concentration was similar between treatments. Glucose-amended (G) and non-amended (control) treatments were run in parallel. Over the incubation period, an increase in bacterial abundance (BA) and bacterial production (BP) was observed first in the G treatment, followed then by the D and finally A treatments, with bacterial growth rates significantly higher in the G and D treatments than the A treatment. Following this growth, maxima of BP reached were similar in the D (879 ± 64 ng C L−1 h−1; n=3) and G (648 ± 156 ng C L−1 h−1; n=3) treatments and were significantly higher than in the A treatment (124 ng C L−1 h−1; n=2). The DOC consumed over the incubation period was similar in the A (9 µM; n=2) and D (9 ± 2 µM; n=3) treatments and was significantly lower than in the G treatment (22 ± 3 µM; n=3). Nevertheless, the bacterial growth efficiency (BGE) in the D treatment (14.2 ± 5.5 %; n=3) compared well with the G treatment (7.6 ± 2 %; n=3), suggesting that the metabolic use of the labile DOC fraction in both conditions was energetically equivalent. In contrast, the BGE in the A treatment was lower (1.7 %; n=2), suggesting that most of the used labile DOC was catabolized. The results obtained in this study highlight the potential of aerosol organic matter to sustain the metabolism of marine heterotrophs and stress the need to include this external source of organic carbon in biogeochemical models for a better constraining of the carbon budget.

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Experimental evidence of the potential bioavailability for marine heterotrophic bacteria of aerosols organic matter

10.5194/bg-2020-187 ◽

2020 ◽

Author(s):

Kahina Djaoudi ◽

France Van Wambeke ◽

Aude Barani ◽

Najib Bhairy ◽

Servanne Chevaillier ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Incubation Period ◽

Bacterial Growth ◽

Heterotrophic Bacteria ◽

Water Soluble ◽

Bacterial Growth Efficiency ◽

Anthropogenic Aerosols ◽

Biogeochemical Models ◽

Marine Heterotrophic Bacteria

Abstract. The surface ocean receives important amounts of organic carbon from atmospheric deposition. The degree of bioavailability of this source of organic carbon will determine its impact on the marine carbon cycle. In this study, the potential availability of dissolved organic carbon (DOC) leached from both desert dust and anthropogenic aerosols to marine heterotrophic bacteria was investigated. The experimental design was based on 16-days incubation, in the dark, of a marine bacterial inoculum into artificial seawater amended with water-soluble Saharan dust (D-treatment) and anthropogenic (A-treatment) aerosols, so that the initial DOC concentration leachate from aerosols is 36 µM C. Glucose-amended (G) and non-amended (control) treatments were run in parallel. Over the incubation period, an increase in bacterial abundance (BA) and bacterial production (BP) was observed first in the G-treatment, followed then by D and finally A treatments, with bacterial growth rates significantly higher in the G and D treatments than the A treatment. Following this growth, maxima of BP reached were similar in D (879 ± 64 ng C L−1 h−1; n = 3) and G (648 ± 156 ng C L−1 h−1; n = 3) treatments and were significantly higher than in A-treatment (124 ± 39 ng C L−1 h−1; n = 2). The DOC consumed over the incubation period was similar in A (9 ± 4 µM; n = 2) and D (9 ± 2 µM; n = 3) treatments and was significantly lower than that consumed in the G-treatment (22 ± 3 µM). Nevertheless, the bacterial growth efficiency (BGE) in the D treatment (14.2 ± 5.5 %; n = 3) compared well with the G treatment (7.6 ± 2 %; n = 3), suggesting that the metabolic use of the labile DOC fraction in both conditions was energetically equivalent. In contrast, the BGE in the A-treatment was lower (1.7 ± 0.1 %; n = 2), suggesting that the most part of used labile DOC was catabolized. The results obtained in this study highlight the potential of aerosol organic matter to sustain the metabolism of marine heterotrophs and stress the need to include this external source of organic carbon into biogeochemical models, for a better constraining of the carbon budget.

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Organic matter mineralization and trace element post-depositional redistribution in Western Siberia thermokarst lake sediments

Biogeosciences Discussions ◽

10.5194/bgd-8-8845-2011 ◽

2011 ◽

Vol 8 (4) ◽

pp. 8845-8894

Author(s):

S. Audry ◽

O. S. Pokrovsky ◽

L. S. Shirokova ◽

S. N. Kirpotin ◽

B. Dupré

Keyword(s):

Trace Elements ◽

Organic Matter ◽

Organic Carbon ◽

Lake Sediments ◽

Water Column ◽

Western Siberia ◽

Ecosystem Development ◽

Thermokarst Lake ◽

Fe And Mn ◽

The Impact

Abstract. This study reports the very first results on high-resolution sampling of sediments and their porewaters from three thermokarst (thaw) lakes representing different stages of ecosystem development located within the Nadym-Pur interfluve of the Western Siberia plain. Up to present time, the lake sediments of this and other permafrost-affected regions remain unexplored regarding their biogeochemical behavior. The aim of this study was to (i) document the early diagenesic processes in order to assess their impact on the organic carbon stored in the underlying permafrost, and (ii) characterize the post-depositional redistribution of trace elements and their impact on the water column. The estimated organic carbon (OC) stock in thermokarst lake sediments of 14 ± 2 kg m−2 is low compared to that reported for peat soils from the same region and denotes intense organic matter (OM) mineralization. Mineralization of OM in the thermokarst lake sediments proceeds under anoxic conditions in all the three lakes. In the course of the lake development, a shift in mineralization pathways was evidenced from nitrate and sulfate to Fe- and Mn-oxyhydroxides as the main terminal electron acceptors in the early diagenetic reactions. This shift was promoted by the diagenetic consumption of nitrate and sulfate and their gradual depletion in the water column due to progressively decreasing frozen peat lixiviation occurring at the lake's borders. Trace elements were mobilized from host phases (OM and Fe- and Mn-oxyhydroxides) and partly sequestered in the sediment in the form of authigenic Fe-sulfides. Arsenic and Sb cycling was also closely linked to that of OM and Fe- and Mn-oxyhydroxides. Shallow diagenetic enrichment of particulate Sb was observed in the less mature stages. As a result of authigenic sulfide precipitation, the sediments of the early stage of ecosystem development were a sink for water column Cu, Zn, Cd, Pb and Sb. In contrast, at all stages of ecosystem development, the sediments were a source of dissolved Co, Ni and As to the water column. However, the concentrations of these trace elements remained low in the bottom waters, indicating that sorption processes on Fe-bounding particles and/or large-size organo-mineral colloids could mitigate the impact of post-depositional redistribution of toxic elements on the water column.

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Earth’s Middle Ages: What Came after the GOE

10.23943/princeton/9780691145020.003.0009 ◽

2017 ◽

Author(s):

Donald Eugene Canfield

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Middle Ages ◽

Atmospheric Oxygen ◽

Iron Formation ◽

Banded Iron Formation ◽

Dissolved Iron ◽

Great Oxidation Event ◽

Low Levels ◽

Substantial Rise

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.

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Application of a fractionation technique for better understanding of the removal of natural organic matter by alum coagulation

Water Science & Technology Water Supply ◽

10.2166/ws.2002.0200 ◽

2002 ◽

Vol 2 (5-6) ◽

pp. 427-433 ◽

Cited By ~ 4

Author(s):

J. van Leeuwen ◽

C. Chow ◽

R. Fabris ◽

N. Withers ◽

D. Page ◽

...

Keyword(s):

Organic Matter ◽

Natural Organic Matter ◽

High Performance ◽

Relative Proportion ◽

Water Source ◽

Size Exclusion ◽

Gas Chromatography Mass Spectrometry ◽

Pyrolysis Gas ◽

Alum Treatment ◽

Hydrophobic Acids

To gain an improved understanding of the types of organic compounds that are recalcitrant to water treatment, natural organic matter (NOM) isolates from two drinking water sources (Mt. Zero and Moorabool reservoirs, Victoria, Australia) were separated into fractions of distinct chemical behaviour using resins. Four fractions were obtained from each water source and were organics absorbed to: (1) XAD-8 (very hydrophobic acids, VHA); (2) DAX-4 (slightly hydrophobic acids, SHA); (3) bound to an anion exchange resin (charged organics, CHAR); and (4) not absorbed or bound to resins (neutrals, NEUT). These fractions were then tested to determine the capacity of alum to remove them from water and to correlate this with the character of each isolate. The fractions were characterised by the application of high performance size exclusion chromatography (HPSEC), bacterial regrowth potential (BRP), trihalomethane formation potential (THMFP), pyrolysis gas-chromatography mass spectrometry (Py-GC-MS) and thermochemolysis. The highest removals of dissolved organic carbon (DOC) by alum treatment were in waters spiked with the CHAR fractions while the NEUT fractions were the most recalcitrant. The number average molecular weights (Mn) of DOC of the CHAR fractions before treatment were the highest, whilst those of the NEUT fractions were the lowest. After alum treatment, the Mn of the NEUT fractions were only slightly reduced. Results from Py-GC-MS and thermochemolysis indicate that the NEUT fractions had the highest relative proportion of saccharide derived organic material. Nonetheless, the BRP of waters spiked with the NEUT fractions differed markedly, indicating that organics recalcitrant to alum treatment can vary substantially in their chemical composition and capacity to support microbial growth.

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Impact of aquaculture on distribution of dissolved organic matter in coastal Jeju Island, Korea, based on absorption and fluorescence spectroscopy

Environmental Science and Pollution Research ◽

10.1007/s11356-021-15553-3 ◽

2021 ◽

Author(s):

Jeonghyun Kim ◽

Yeseul Kim ◽

Sung Eun Park ◽

Tae-Hoon Kim ◽

Bong-Guk Kim ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Fluorescence Spectroscopy ◽

Dissolved Organic Matter ◽

Coastal Water ◽

Coastal Region ◽

Principal Component ◽

Distribution Patterns ◽

Organic Pollution ◽

Jeju Island

AbstractIn Jeju Island, multiple land-based aquafarms were fully operational along most coastal region. However, the effect of effluent on distribution and behaviours of dissolved organic matter (DOM) in the coastal water are still unknown. To decipher characteristics of organic pollution, we compared physicochemical parameters with spectral optical properties near the coastal aquafarms in Jeju Island. Absorption spectra were measured to calculate the absorption coefficient, spectral slope coefficient, and specific UV absorbance. Fluorescent DOM was analysed using fluorescence spectroscopy coupled with parallel factor analysis. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were measured using high-temperature catalytic oxidation. The DOC concentration near the discharge outlet was twice higher than that in natural groundwater, and the TDN concentration exponentially increased close to the outlet. These distribution patterns indicate that aquafarms are a significant source of DOM. Herein, principal component analysis was applied to categorise the DOM origins. There were two distinct groups, namely, aquaculture activity for TDN with humic-like and high molecular weights DOM (PC1: 48.1%) and natural biological activity in the coastal water for DOC enrichment and protein-like DOM (PC2: 18.8%). We conclude that the aquafarms significantly discharge organic nitrogen pollutants and provoke in situ production of organic carbon. Furthermore, these findings indicate the potential of optical techniques for the efficient monitoring of anthropogenic organic pollutants from aquafarms worldwide.

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