Sources, Sinks, and Subsidies: Terrestrial Carbon Storage in Mid‐latitude Fjords

Smeaton, Craig; Austin, William E. N.

doi:10.1002/2017jg003952

Cited by 26 publications

(39 citation statements)

References 60 publications

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“…By comparing the C/N ratios and δ 13 C org values of the saltmarsh soils to known Scottish values (Smeaton & Austin, 2017;Thornton et al, 2015), we find that the sources of OC to these marshes differ. The back-barrier marsh is characterized by high C/N ratios and depleted δ 13 C org values suggesting that the OC mainly originates from in situ C3 production or the terrestrial environment.…”

Section: Soil Characteristicsmentioning

confidence: 92%

An Assessment of the Tea Bag Index Method as a Proxy for Organic Matter Decomposition in Intertidal Environments

2019

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Intertidal wetlands capture and store carbon (C) for long periods of time, helping to reduce the concentration of CO2 in the atmosphere. Yet the processes, which govern the decomposition and subsequent long‐term storage of organic matter (OM) and C in these habitats, remain poorly understood. The Tea Bag Index (TBI) uses a standardized OM (green and Rooibos tea) and has the potential to shed light on OM decomposition across habitats, including saltmarshes. Here, we apply the TBI method at two saltmarshes within the same estuary with the aim of (i) reducing the influence of climatic variables and (ii) determining the role of the environment, including the soil characteristics, in the decomposition of OM. We extended the standard (3 months) incubation period over a full year in order to investigate the longer‐term decomposition processes at each site. The initial results partially support previous studies that the early stages of decomposition (leaching of the water‐soluble fraction) is governed by climatic conditions, but may be further enhanced by tidal flushing in saltmarshes. By extending the incubation period, we observed the initiation of midstage OM decomposition (cellulose degradation) upon which the soil characteristics appear to be the dominant control. These results highlight the importance of long‐term TBI incubations to understand early‐stage OM decomposition. The relationship between tea mass (OM) loss and C loss in these intertidal environments is not straightforward, and we would caution the use of the TBI as a direct universal proxy for soil C degradation in such intertidal wetlands.

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Section: Soil Characteristicsmentioning

confidence: 92%

An Assessment of the Tea Bag Index Method as a Proxy for Organic Matter Decomposition in Intertidal Environments

2019

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“…These results suggest that low oxygen conditions inhibit the reworking and remineralisation of organics and the production of carbonate fauna (Woulds et al, 2016). Loch Sunart has large sills (Smeaton et al, 2016) and is one of the largest fjords in Scotland; these features favour the capture of terrestrial OC (Smeaton and Austin, 2017) and the storage of large quantities of postglacial OC (9.4 ± 0.2 Mt) and IC (10.1 ± 0.2 Mt). The quantities of C stored in the sediment of the smaller fjords are strongly linked to how restrictive the geomorphology of the fjord is.…”

Section: Fjord-specific Sedimentary Carbon Inventoriesmentioning

confidence: 99%

“…This suggests that these systems have the capacity to adapt to future environmental change. Intriguingly, there is also the possibility that this process may have aided the capture of terrestrial C during the late Holocene and recent past (Smeaton and Austin, 2017).…”

Section: A National Fjordic Sedimentary C Inventorymentioning

confidence: 99%

Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

et al. 2017

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Abstract. Fjords are recognised as hotspots for the burial and long-term storage of carbon (C) and potentially provide a significant climate regulation service over multiple timescales. Understanding the magnitude of marine sedimentary C stores and the processes which govern their development is fundamental to understanding the role of the coastal ocean in the global C cycle. In this study, we use the mid-latitude fjords of Scotland as a natural laboratory to further develop methods to quantify these marine sedimentary C stores on both the individual fjord and national scale. Targeted geophysical and geochemical analysis has allowed the quantification of sedimentary C stocks for a number of mid-latitude fjords and, coupled with upscaling techniques based on fjord classification, has generated the first full national sedimentary C inventory for a fjordic system. The sediments within these mid-latitude fjords hold 640.7 ± 46 Mt of C split between 295.6±52 and 345.1 ± 39 Mt of organic and inorganic C, respectively. When compared, these marine mid-latitude sedimentary C stores are of similar magnitude to their terrestrial equivalents, with the exception of the Scottish peatlands, which hold significantly more C. However, when areanormalised comparisons are made, these mid-latitude fjords are significantly more effective as C stores than their terrestrial counterparts, including Scottish peatlands. The C held within Scotland's coastal marine sediments has been largely overlooked as a significant component of the nation's natural capital; such coastal C stores are likely to be key to understanding and constraining improved global C budgets. Highlights-Scottish fjords are a more effective store of C than the terrestrial environment.-A total of 640.7 ± 46 Mt of C is stored in the sediment of Scotland's 111 fjords.-An estimated 31 139-40 615 t yr −1 of C is buried in the sediment of Scotland's fjords.-Fjord sediments are potentially the most effective store of C globally.

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“…δ 15 N in Arctic shelf sediments has been successfully applied as tool for tracing allochthonous versus autochthonous OM (Knies et al, 2007;Schubert & Calvert, 2001). Also, in fjord surface sediments from Patagonia, New Zealand, and Scotland δ 15 N variations are interpreted as an indicator of OM source, which often shows an inside-outside trend with lower (terrigenous) values in the inner fjord and higher values (marine) at the fjord entrance (Hinojosa et al, 2014;Sepúlveda et al, 2011;Smeaton & Austin, 2017). In the Ofotfjord, Tysfjord, and Vestfjord surface sediments δ 15 N content ranges between 4.69‰ and 6.90‰.…”

Section: δ 15 N Of Sedimentary Ommentioning

confidence: 99%

Organic Matter Sources in North Atlantic Fjord Sediments

Faust

Knies

2019

Geochem Geophys Geosyst

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To better constrain the global carbon cycle fundamental knowledge of the role of carbon cycling on continental margins is crucial. Fjords are particularly important shelf areas for carbon burial due to relatively high sedimentation rates and high organic matter fluxes. As terrigenous organic matter is more resistant to remineralization than marine organic matter, a comprehensive knowledge of the carbon source is critical to better constrain the efficiency of organic carbon burial in fjord sediments. Here we investigated highly productive fjords in northern Norway and compare our results with both existing and new organic carbon to organic nitrogen ratios and carbon stable isotope compositions from fjords in mid‐Norway, west Svalbard, and east Greenland. The marine organic carbon contribution varies significantly between these fjords, and the contribution of marine organic carbon in Norwegian fjords is much larger than previously suggested for fjords in NW Europe and also globally. Additionally, northern Norwegian fjords show very high marine carbon burial rates (73.6 gC · m‐2 · year‐1) suggesting that these fjords are probably very distinct carbon burial hotspots. We argue that the North Atlantic Current inflow sustains these high burial rates and changes in the current strength due to ongoing climate change are likely to have a pronounced effect on carbon burial in North Atlantic fjords.

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Sources, Sinks, and Subsidies: Terrestrial Carbon Storage in Mid‐latitude Fjords

Cited by 26 publications

References 60 publications

An Assessment of the Tea Bag Index Method as a Proxy for Organic Matter Decomposition in Intertidal Environments

An Assessment of the Tea Bag Index Method as a Proxy for Organic Matter Decomposition in Intertidal Environments

Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

Organic Matter Sources in North Atlantic Fjord Sediments

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