Organic carbon flux and particulate organic matter composition in Arctic  valley glaciers: examples from the Bayelva River and adjacent Kongsfjorden

Zhu, Zhuoyi; Wu, Ying; Liu, Sumei; Wenger, Fred; Hu, Jun; Zhang, Jing; Zhang, Ruifeng

doi:10.5194/bg-13-975-2016

Cited by 48 publications

(26 citation statements)

References 51 publications

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“…Sipler and colleagues used seven times higher DOC concentrations (400-500 µM) than in their control to stimulate a community response, while the DOC concentrations (128 µM) in our study were only 1.5 times higher than in the control incubations. Pulses of tDOM released via Arctic rivers can reach the DOC concentrations used by Sipler and colleagues (Benner et al, 2005), but at our sampling site in Kongsfjorden the DOC concentration is on average 109 µM (Zhu et al, 2016). Despite the relatively small increase in tDOM concentration in our study, we here stimulated faster growth of certain taxa than the change reported by Sipler and colleagues.…”

Section: Tdom Addition Induced Changes In Bacterial Community Composicontrasting

confidence: 55%

“…The final DOC concentration was 1.5 times higher in the tDOM treatment incubations (128 µM) than in the control incubations (83 µM). The elevated DOC concentration in the tDOM treatment reflects ranges of natural, elevated concentrations near the sample site in Kongsfjorden (Zhu et al, 2016). The 16 bottles, 8 treatment and 8 controls were incubated in the dark at 2 • C. Samples for bacterial community composition were obtained after 0, 0.5, 1, 2, 3, 4, 5, and 9 days of incubation by harvesting one treatment and one control bottle, each representing an independent incubation, as described below.…”

Section: Study Site and Experimental Set-upmentioning

confidence: 95%

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Bacterial Response to Permafrost Derived Organic Matter Input in an Arctic Fjord

et al. 2018

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The warming of the Arctic causes increased riverine discharge, coastal erosion, and the thawing of permafrost. Together, this is leading to an increased wash out of terrestrial dissolved organic matter (tDOM) into the coastal Arctic ecosystems. This tDOM may be anticipated to affect both carbon and nutrient flow in the microbial food web and microbial community composition, but there are few studies detailing this in Arctic marine ecosystems. We tested the effects of tDOM on the bacterial community composition and net-growth by extracting DOM from the active layer of permafrost soil and adding the aged tDOM concentrate to a natural microbial fjord community (Kongsfjorden, NW Svalbard). This resulted in an increased carbon load of 128 µM DOC in the tDOM treatment relative to the control of 83 µM DOC. We observed changes in community composition and activity in incubations already within 12 h where tDOM was added. Flow cytometry revealed that predominantly large bacteria increased in the tDOM treated incubations. The increase of this group correlated with the increase in relative abundance of the genus Glaciecola (Gammaproteobacteria). Glaciecola were initially not abundant in the bacterial community (0.6%), but their subsequent increase up to 47% after 4 days upon tDOM addition compared to 8% in control incubations indicates that they are likely capable of degrading permafrost derived DOM. Further, according to our experimental results we hypothesize that the tDOM addition increased bacterivorous grazing by small protists and thus tDOM might indirectly also effect higher trophic levels of the microbial food web.

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Section: Tdom Addition Induced Changes In Bacterial Community Composicontrasting

confidence: 55%

Section: Study Site and Experimental Set-upmentioning

confidence: 95%

Bacterial Response to Permafrost Derived Organic Matter Input in an Arctic Fjord

et al. 2018

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“…Total release of DOC from ASG, SJG, CUG, ALG, ACG, and CEG is 577 Gg C/a of DOC, which can be compared with global mountain glacier DOC release (Table ). In addition, the area‐weighted flux of DOC from ASG is higher than those from ALG, CUG, ACG, and CEG (Table ) as well as from European Alps (70 kg·km −2 ·a −1 ; Singer et al, ) and Svalbard Archipelago (550 kg·km −2 ·a −1 ; Zhu et al, ). Given the high bioavailability of glacially derived DOC, this underscores the regional relevance of Asian mountain glaciers for downstream biogeochemistry.…”

Section: Discussionmentioning

confidence: 97%

Importance of Mountain Glaciers as a Source of Dissolved Organic Carbon

Ding

et al. 2018

JGR Earth Surface

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Ice sheets and glaciers have been shown to deliver large amounts of labile dissolved organic carbon (DOC) to downstream aquatic ecosystems, but recent studies may underestimate the release of DOC from mountain glaciers. To date, continuous measurements of DOC from mountain glaciers throughout entire glacier melt season are very limited. Here we present high-density data on DOC from two Asian mountain glaciers over a full melt season in 2013 and compile a global data set of DOC from 42 mountain glaciers. Based on our study and previously published DOC data, we estimate the storage and release of DOC associated with Asian mountain glaciers to be 8.8 to 13.8 Tg C and 0.19 Tg C/a, respectively. Rough extrapolation of glacier runoff to a global scale suggests that DOC release from mountain glaciers is on the order of 0.8 Tg C/a, which is 1.4 times higher than the most current estimates. The current release of DOC from mountain glaciers is therefore far more significant than previously thought and should be considered in future evaluation of the global carbon cycle.

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“…Glacial runoff is an important mechanism for the export of organic C to the oceans (e.g., Bhatia et al, ; Hood et al, ; Lawson et al, ; Zhu et al, ). Sources of this glacial C are the deposition of aerosols, including pyrogenic C (e.g., McConnell et al, ; Mouteva et al, ; Stubbins et al, ; Tedesco et al, ), the drainage and erosion of subglacial C reservoirs (Bhatia et al, ), and in situ microbial activety on, within, and below the GIS (Bhatia et al, , ; Hood et al, , ).…”

Section: Introductionmentioning

confidence: 99%

Seasonal Patterns of Riverine Carbon Sources and Export in NW Greenland

Csank

Czimczik

et al. 2019

JGR Biogeosciences

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Glacial runoff exports large amounts of carbon (C) to the oceans, but major uncertainty remains regarding sources, seasonality, and magnitude. We apportioned C exported by five rivers from glacial and periglacial sources in northwest Greenland by monitoring discharge, water sources (δ 18 O), concentration and composition of dissolved organic carbon (DOC), and ages ( 14 C) of DOC and particulate organic C over three summers (2010)(2011)(2012). We found that particulate organic C (F = 1.0366-0.2506) was generally older than DOC in glacial sourced rivers and likely sourced from the physical erosion of aged C pools. Most exported DOC showed strong seasonal variations in sources and discharge. In summer, mean DOC ages ranged from modern to 4,750 cal years BP (F = 1.0022-0.6291); however, the annual C flux from glacially sourced rivers was dominated by young, plant-derived DOC (F = 0.9667-1.002) exported during the spring freshet. The most aged DOC (F = 0.6891-0.8297) was exported in middle to late summer at lower concentrations and was glacial in origin. Scaled to the whole of Greenland using model-estimated runoff, we estimate a total riverine DOC flux of 0.29% to 0.45% ± 20% Tg C/year. Our flux results indicate that the highest C fluxes occur during the time of year when the majority of C is modern in age. However, higher melt rates from the Greenland ice sheet and longer growing seasons could result in increasing amounts of ancient C from the Greenland ice sheet and from the periglacial landscape to the ocean. Key Points:• Rivers in NW Greenland transport 4.5-8.2 × 10 −5 Tg C/year of dissolved organic carbon with the majority exported early in the melt season • Seasonally, sources shift from young, plant-like carbon from forelands to older, more processed carbon from glaciers, soils, and sediments • Based on modeled discharge, we estimate a carbon flux of 0.29% to 0.45% ± 20% Tg C/year for Greenland, 35-40% higher than previous estimates

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Organic carbon flux and particulate organic matter composition in Arctic valley glaciers: examples from the Bayelva River and adjacent Kongsfjorden

Cited by 48 publications

References 51 publications

Bacterial Response to Permafrost Derived Organic Matter Input in an Arctic Fjord

Bacterial Response to Permafrost Derived Organic Matter Input in an Arctic Fjord

Importance of Mountain Glaciers as a Source of Dissolved Organic Carbon

Seasonal Patterns of Riverine Carbon Sources and Export in NW Greenland

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