Low photolability of yedoma permafrost dissolved organic carbon

Stubbins, Aron; Mann, P.; Powers, Leanne C.; Bittar, Thais B.; Dittmar, Thorsten; McIntyre, Cameron; Eglinton, T. I.; Zimov, N.; Spencer, Robert G. M.

doi:10.1002/2016jg003688

Cited by 60 publications

(81 citation statements)

References 47 publications

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“…The raw mass spectra for oak and cedar stemflow displayed molecular signatures consistent with those of whole river water DOM run on the same instrument, under the same conditions, during the same month (Kolyma River data in Figure 4; Stubbins et al, 2017). Looking at one representative mass to charge (343 m/z; Figure 4), DOM in oak stemflow and cedar stemflow has similar molecular diversities (i.e., there are a similar number of peaks).…”

Section: Molecular Signatures Of Tree-derived Dissolved Organic Mattermentioning

confidence: 64%

Molecular and Optical Properties of Tree-Derived Dissolved Organic Matter in Throughfall and Stemflow from Live Oaks and Eastern Red Cedar

et al. 2017

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Studies of dissolved organic matter (DOM) transport through terrestrial aquatic systems usually start at the stream. However, the interception of rainwater by vegetation marks the beginning of the terrestrial hydrological cycle making trees the headwaters of aquatic carbon cycling. Rainwater interacts with trees picking up tree-DOM, which is then exported from the tree in stemflow and throughfall. Stemflow denotes water flowing down the tree trunk, while throughfall is the water that drips through the leaves of the canopy. We report the concentrations, optical properties (light absorbance) and molecular signatures (ultrahigh resolution mass spectrometry) of tree-DOM in throughfall and stemflow from two tree species (live oak and eastern red cedar) with varying epiphyte cover on Skidaway Island, Savannah, Georgia, USA. Both stemflow and throughfall were enriched in DOM compared to rainwater, indicating trees were a significant source of DOM. The optical and molecular properties of tree-DOM were broadly consistent with those of DOM in other aquatic ecosystems. Stemflow was enriched in highly colored DOM compared to throughfall. Elemental formulas identified clustered the samples into three groups: oak stemflow, oak throughfall and cedar. The molecular properties of each cluster are consistent with an autochthonous aromatic-rich source associated with the trees, their epiphytes and the microhabitats they support. Elemental formulas enriched in oak stemflow were more diverse, enriched in aromatic formulas, and of higher molecular mass than for other tree-DOM classes, suggesting greater contributions from fresh and partially modified plant-derived organics. Oak throughfall was enriched in lower molecular weight, aliphatic and sugar formulas, suggesting greater contributions from foliar surfaces. While the optical properties and the majority of the elemental formulas within tree-DOM were consistent with vascular plant-derived organics, condensed aromatic formulas were also identified. As condensed aromatics are generally interpreted Stubbins et al.Optical and Molecular Signatures of Tree-DOM as deriving from partially combusted organics, some of the tree-DOM may have derived from the atmospheric deposition of thermogenic and other windblown organics. These initial findings should prove useful as future studies seek to track tree-DOM across the aquatic gradient from canopy roof, through soils and into fluvial networks.

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Section: Molecular Signatures Of Tree-derived Dissolved Organic Mattermentioning

confidence: 64%

Molecular and Optical Properties of Tree-Derived Dissolved Organic Matter in Throughfall and Stemflow from Live Oaks and Eastern Red Cedar

et al. 2017

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“…However, the analysis also implies that the overall contribution of photomineralization to the carbon balance of Arctic lakes could be limited due to the limitation of UV energy. Because of the low photolability of yedoma permafrost carbon [ Stubbins et al ., ], the absolute photomineralization rate of the yedoma lakes is smaller than that of Toolik Lake.…”

Section: Resultsmentioning

confidence: 99%

“…It should be noted that the AQY parameter fitted from the work of Cory et al . [] would yield low DOC photolability in yedoma lakes, which is consistent with other investigations [ Ward and Cory , ; Stubbins et al ., ]. In contrast, tundra and thermokarst lakes, which are mainly fed by terrigenous modern‐age DOC, would likely have much higher photochemical activities [ Cory et al ., ; Ward and Cory , ].…”

Section: Methodsmentioning

confidence: 99%

Modeling CO₂ emissions from Arctic lakes: Model development and site‐level study

Tan

Zhuang

Shurpali

et al. 2017

J Adv Model Earth Syst

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Recent studies indicated that Arctic lakes play an important role in receiving, processing, and storing organic carbon exported from terrestrial ecosystems. To quantify the contribution of Arctic lakes to the global carbon cycle, we developed a one‐dimensional process‐based Arctic Lake Biogeochemistry Model (ALBM) that explicitly simulates the dynamics of organic and inorganic carbon in Arctic lakes. By realistically modeling water mixing, carbon biogeochemistry, and permafrost carbon loading, the model can reproduce the seasonal variability of CO2 fluxes from the study Arctic lakes. The simulated area‐weighted CO2 fluxes from yedoma thermokarst lakes, nonyedoma thermokarst lakes, and glacial lakes are 29.5, 13.0, and 21.4 g C m−2 yr−1, respectively, close to the observed values (31.2, 17.2, and 16.5 ± 7.7 g C m−2 yr−1, respectively). The simulations show that the high CO2 fluxes from yedoma thermokarst lakes are stimulated by the biomineralization of mobilized labile organic carbon from thawing yedoma permafrost. The simulations also imply that the relative contribution of glacial lakes to the global carbon cycle could be the largest because of their much larger surface area and high biomineralization and carbon loading. According to the model, sunlight‐induced organic carbon degradation is more important for shallow nonyedoma thermokarst lakes but its overall contribution to the global carbon cycle could be limited. Overall, the ALBM can simulate the whole‐lake carbon balance of Arctic lakes, a difficult task for field and laboratory experiments and other biogeochemistry models.

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“…, Stubbins et al. ). Such photochemical effects on organic matter processing in streams and lakes will likely cause diel changes in oxygen consumption rates that confound the processes we have ascribed to oxidation of labile organic matter produced via aquatic photosynthesis in the model presented here.…”

Section: Discussionmentioning

confidence: 99%

Two‐stage metabolism inferred from diel oxygen dynamics in aquatic ecosystems

et al. 2017

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Abstract. Dynamics of dissolved oxygen in aquatic ecosystems reflect the biological, physical, and chemical processes that regulate ecosystem metabolism. Organic matter that supports ecosystem respiration (ER) is produced both by in situ photosynthesis and via loading from terrestrial ecosystems. Terrestrial-derived organic matter is relatively recalcitrant and its availability is stable at diel time scales relative to substrates produced through photosynthesis, which are more labile and often show distinct diel changes in availability. Here, we explored whether the contributions of these two sources of organic matter to ecosystem metabolism could be quantified by a process model of photosynthesis and ER fit to high-frequency observations of oxygen concentration in streams. We found that a two-stage model of respiration provided a better fit to diel oxygen dynamics in most streams than a model assuming that the substrates supporting ER were one temporally stable pool. Two-stage models estimated peak daytime respiration rates that were~2.99 higher on average than nighttime rates, but this increase was variable and ranged from 1.1 to 11.69. Estimates of gross primary production were 1.359 higher, on average, (range = 1.04-7.919) compared to estimates generated by a single-stage model. Streams draining watersheds with less than about 7% gradient exhibited oxygen dynamics that provided comparable statistical support for single-stage metabolism, likely due to the higher loading of allochthonous organic matter that swamped metabolism based on autochthonous production in these streams. Ecosystem metabolism in streams draining steeper watersheds was best characterized by two-stage metabolism, reflecting the greater importance of autochthonous contributions to labile organic carbon pools in these ecosystems.

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Low photolability of yedoma permafrost dissolved organic carbon

Cited by 60 publications

References 47 publications

Molecular and Optical Properties of Tree-Derived Dissolved Organic Matter in Throughfall and Stemflow from Live Oaks and Eastern Red Cedar

Molecular and Optical Properties of Tree-Derived Dissolved Organic Matter in Throughfall and Stemflow from Live Oaks and Eastern Red Cedar

Modeling CO₂ emissions from Arctic lakes: Model development and site‐level study

Two‐stage metabolism inferred from diel oxygen dynamics in aquatic ecosystems

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Low photolability of yedoma permafrost dissolved organic carbon

Cited by 60 publications

References 47 publications

Molecular and Optical Properties of Tree-Derived Dissolved Organic Matter in Throughfall and Stemflow from Live Oaks and Eastern Red Cedar

Molecular and Optical Properties of Tree-Derived Dissolved Organic Matter in Throughfall and Stemflow from Live Oaks and Eastern Red Cedar

Modeling CO2 emissions from Arctic lakes: Model development and site‐level study

Two‐stage metabolism inferred from diel oxygen dynamics in aquatic ecosystems

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Modeling CO₂ emissions from Arctic lakes: Model development and site‐level study