scholarly journals Optical properties and bioavailability of dissolved organic matter along a flow-path continuum from soil pore waters to the Kolyma River, Siberia

2015 ◽  
Vol 12 (15) ◽  
pp. 12321-12347 ◽  
Author(s):  
K. E. Frey ◽  
W. V. Sobczak ◽  
P. J. Mann ◽  
R. M. Holmes
Keyword(s):  
Organic Matter ◽  
Optical Properties ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
River Basin ◽  
Flow Path ◽  
The Arctic ◽  
Pore Waters ◽  
Water Types ◽  
Kolyma River

Abstract. The Kolyma River in Northeast Siberia is among the six largest arctic rivers and drains a region underlain by vast deposits of Holocene-aged peat and Pleistocene-aged loess known as yedoma, most of which is currently stored in ice-rich permafrost throughout the region. These peat and yedoma deposits are important sources of dissolved organic matter (DOM) to inland waters that in turn play a significant role in the transport and ultimate remineralization of organic carbon to CO2 and CH4 along the terrestrial flow-path continuum. The turnover and fate of terrigenous DOM during offshore transport will largely depend upon the composition and amount of carbon released to inland and coastal waters. Here, we measured the optical properties of chromophoric DOM (CDOM) from a geographically extensive collection of waters spanning soil pore waters, streams, rivers, and the Kolyma River mainstem throughout a ∼ 250 km transect of the northern Kolyma River basin. During the period of study, CDOM absorbance values were found to be robust proxies for the concentration of DOM, whereas additional CDOM parameters such as spectral slopes (S) were found to be useful indicators of DOM quality along the flow-path. In particular, CDOM absorption at 254 nm showed a strong relationship with dissolved organic carbon (DOC) concentrations across all water types (r2 = 0.958, p < 0.01). The spectral slope ratio (SR) of CDOM demonstrated statistically significant differences between all four water types and tracked changes in the concentration of bioavailable DOC, suggesting that this parameter may be suitable for clearly discriminating shifts in organic matter characteristics among water types along the full flow-path continuum across this landscape. The heterogeneity of environmental characteristics and extensive continuous permafrost of the Kolyma River basin combine to make this a critical region to investigate and monitor. With ongoing and future permafrost degradation, peat and yedoma deposits throughout the Northeast Siberian region will become more hydrologically active, providing greater amounts of DOM to fluvial networks and ultimately to the Arctic Ocean. The ability to rapidly and comprehensively monitor shifts in the quantity and quality of DOM across the landscape is therefore critical for understanding potential future feedbacks on the arctic carbon cycle.

scholarly journals Optical properties and bioavailability of dissolved organic matter along a flow-path continuum from soil pore waters to the Kolyma River mainstem, East Siberia

2016 ◽  
Vol 13 (8) ◽  
pp. 2279-2290 ◽  
Author(s):  
Karen E. Frey ◽  
William V. Sobczak ◽  
Paul J. Mann ◽  
Robert M. Holmes
Keyword(s):  
Organic Matter ◽  
Optical Properties ◽  
Dissolved Organic Matter ◽  
Residence Time ◽  
Flow Path ◽  
The Arctic ◽  
Pore Waters ◽  
Water Types ◽  
Kolyma River ◽  
Dom Composition

Abstract. The Kolyma River in northeast Siberia is among the six largest Arctic rivers and drains a region underlain by vast deposits of Holocene-aged peat and Pleistocene-aged loess known as yedoma, most of which is currently stored in ice-rich permafrost throughout the region. These peat and yedoma deposits are important sources of dissolved organic matter (DOM) to inland waters that in turn play a significant role in the transport and ultimate remineralization of organic carbon to CO2 and CH4 along the terrestrial flow-path continuum. The turnover and fate of terrigenous DOM during offshore transport largely depends upon the composition and amount of carbon released to inland and coastal waters. Here, we measured the ultraviolet-visible optical properties of chromophoric DOM (CDOM) from a geographically extensive collection of waters spanning soil pore waters, streams, rivers, and the Kolyma River mainstem throughout a  ∼  250 km transect of the northern Kolyma River basin. During the period of study, CDOM absorption coefficients were found to be robust proxies for the concentration of DOM, whereas additional CDOM parameters such as spectral slopes (S) were found to be useful indicators of DOM quality along the flow path. In particular, the spectral slope ratio (SR) of CDOM demonstrated statistically significant differences between all four water types and tracked changes in the concentration of bioavailable DOC, suggesting that this parameter may be suitable for clearly discriminating shifts in organic matter characteristics among water types along the full flow-path continuum across this landscape. However, despite our observations of downstream shifts in DOM composition, we found a relatively constant proportion of DOC that was bioavailable ( ∼  3–6 % of total DOC) regardless of relative water residence time along the flow path. This may be a consequence of two potential scenarios allowing for continual processing of organic material within the system, namely (a) aquatic microorganisms are acclimating to a downstream shift in DOM composition and/or (b) photodegradation is continually generating labile DOM for continued microbial processing of DOM along the flow-path continuum. Without such processes, we would otherwise expect to see a declining fraction of bioavailable DOC downstream with increasing residence time of water in the system. With ongoing and future permafrost degradation, peat and yedoma deposits throughout the northeast Siberian region will become more hydrologically active, providing greater amounts of DOM to fluvial networks and ultimately to the Arctic Ocean. The ability to rapidly and comprehensively monitor shifts in the quantity and quality of DOM across the landscape is therefore critical for understanding potential future feedbacks within the Arctic carbon cycle.

scholarly journals Controls on the composition and lability of dissolved organic matter in Siberia's Kolyma River basin

2012 ◽  
Vol 117 (G1) ◽  
Author(s):  
P. J. Mann ◽  
A. Davydova ◽  
N. Zimov ◽  
R. G. M. Spencer ◽  
S. Davydov ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
River Basin ◽  
Kolyma River

scholarly journals Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments

2019 ◽  
Vol 16 (23) ◽  
pp. 4535-4553 ◽  
Author(s):  
Caroline Coch ◽  
Bennet Juhls ◽  
Scott F. Lamoureux ◽  
Melissa J. Lafrenière ◽  
Michael Fritz ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
High Arctic ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Low Arctic ◽  
Arctic Rivers ◽  
Flow Pathways ◽  
Small Catchments

Abstract. Climate change is affecting the rate of carbon cycling, particularly in the Arctic. Permafrost degradation through deeper thaw and physical disturbances results in the release of carbon dioxide and methane to the atmosphere and to an increase in lateral dissolved organic matter (DOM) fluxes. Whereas riverine DOM fluxes of the large Arctic rivers are well assessed, knowledge is limited with regard to small catchments that cover more than 40 % of the Arctic drainage basin. Here, we use absorption measurements to characterize changes in DOM quantity and quality in a low Arctic (Herschel Island, Yukon, Canada) and a high Arctic (Cape Bounty, Melville Island, Nunavut, Canada) setting with regard to geographical differences, impacts of permafrost degradation, and rainfall events. We find that DOM quantity and quality is controlled by differences in vegetation cover and soil organic carbon content (SOCC). The low Arctic site has higher SOCC and greater abundance of plant material resulting in higher chromophoric dissolved organic matter (cDOM) and dissolved organic carbon (DOC) than in the high Arctic. DOC concentration and cDOM in surface waters at both sites show strong linear relationships similar to the one for the great Arctic rivers. We used the optical characteristics of DOM such as cDOM absorption, specific ultraviolet absorbance (SUVA), ultraviolet (UV) spectral slopes (S275–295), and slope ratio (SR) for assessing quality changes downstream, at base flow and storm flow conditions, and in relation to permafrost disturbance. DOM in streams at both sites demonstrated optical signatures indicative of photodegradation downstream processes, even over short distances of 2000 m. Flow pathways and the connected hydrological residence time control DOM quality. Deeper flow pathways allow the export of permafrost-derived DOM (i.e. from deeper in the active layer), whereas shallow pathways with shorter residence times lead to the export of fresh surface- and near-surface-derived DOM. Compared to the large Arctic rivers, DOM quality exported from the small catchments studied here is much fresher and therefore prone to degradation. Assessing optical properties of DOM and linking them to catchment properties will be a useful tool for understanding changing DOM fluxes and quality at a pan-Arctic scale.

scholarly journals Characterizing organic matter composition in small Low and High Arctic catchments using terrestrial colored dissolved organic matter (cDOM)

2019 ◽  
Author(s):  
Caroline Coch ◽  
Bennet Juhls ◽  
Scott F. Lamoureux ◽  
Melissa Lafrenière ◽  
Michael Fritz ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
High Arctic ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Low Arctic ◽  
Arctic Rivers ◽  
Flow Pathways ◽  
Small Catchments

Abstract. Climate change is an important control of carbon cycling, particularly in the Arctic. Permafrost degradation through deeper thaw and physical disturbances result in the release of carbon dioxide and methane to the atmosphere and to an increase in riverine dissolved organic matter (DOM) fluxes. Whereas riverine DOM fluxes of the large Arctic rivers are well assessed, knowledge is limited with regard to small catchments that cover more than 40 % of the Arctic drainage basin. Here, we use absorption measurements to characterize changes in DOM quantity and quality in a Low Arctic (Herschel Island, Yukon, Canada) and a High Arctic (Cape Bounty, Melville Island, Nunavut, Canada) setting with regard to geographical differences, impacts of permafrost degradation and rainfall events. We find that DOM quantity and quality is controlled by differences in vegetation cover and soil organic carbon content. The Low Arctic site has higher SOCC and greater abundance of plant material introducing higher lignin concentrations into the aquatic system and resulting in a stronger color of DOM than in the High Arctic. There is a strong relationship between dissolved organic carbon (DOC) concentration and absorption characteristics (cDOM) for surface waters at both sites similar to the one for the great Arctic rivers. We used the optical characteristics of DOM such as cDOM absorption, Specific UltraViolet Absorbance SUVA, UltraViolet UV Slope, Slope Ratio for assessing quality changes downstream, at baseflow and stormflow conditions and in relation to permafrost disturbance. DOM in streams at both sites demonstrated optical signatures indicative of photodegradation downstream processes, even over short distances of 2000 m. It was determined that flow pathways and the connected hydrological residence time control DOM quality. Deeper flow pathways allow the export of permafrost-derived DOM, whereas shallow pathways with shorter residence times lead to the export of fresh near-surface derived DOM. Compared to the large Arctic rivers, DOM quality exported from the small catchments studied here is much fresher and therefore prone to degradation. This work shows that optical properties of DOM will be a useful tool for understanding DOM sources and quality at a pan-Arctic scale.

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

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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