Efficient burial of labile organic carbon in sediments of oxygenated Icelandic fjords

Emily G. Watts; Kira  Zautcke; Isaac  Santos; Craig Smeaton; Wilma  Ljungberg; Henry L. S. Cheung; Stefano  Bonaglia; Tobia  Politi; Zhanfei  Liu; Thomas S. Bianchi

doi:10.1007/s12237-025-01582-5

Efficient burial of labile organic carbon in sediments of oxygenated Icelandic fjords

Emily G. Watts^*, Kira Zautcke, Isaac Santos, Craig Smeaton, Wilma Ljungberg, Henry L. S. Cheung, Stefano Bonaglia, Tobia Politi, Zhanfei Liu, Thomas S. Bianchi

^*Corresponding author for this work

School of Geography & Sustainable Development

Research output: Contribution to journal › Article › peer-review

Abstract

Fjords are hotspots of organic carbon (OC) burial, making them key components in the global carbon cycle. Recent research shows high marine OC burial even under oxic fjord water columns, broadening the scope of key drivers of OC burial therein. Here, we investigate the fate of marine OC in fjord sediments underlying oxic bottom waters in East Iceland. We estimate OC sources using stable isotopes, degradation using chemical biomarkers, and burial using 210Pb and 137Cs profiles. The average OC accumulation rates in East Iceland fjords was ~15 g OC m-2 yr-1, lower than the fjord global average of 54 g OC m-2 yr-1. Marine OC was the overwhelming source of OC to sediments and accounted for 91% of the OC buried in Iceland. The gradient in OC source from the head-to-mouth of the fjords was minimal, due to limited terrestrial vegetation and soil cover, low riverine inputs, and effective exchange with coastal waters. Lignin and total hydrolyzable amino acid biomarkers suggest negligible degradation of terrestrial OC and minor degradation of marine OC. Although a portion of marine OC was prone to remineralization in sediments, it represented only a small fraction of the total OC resulting in high OC transfer (burial) efficiencies of 68-96% within the top 25 cm of sediments. Overall, Icelandic fjords efficiently bury labile marine OC despite oxic water columns.

Original language	English
Article number	167
Pages (from-to)	1-20
Number of pages	20
Journal	Estuaries and Coasts
Volume	48
Issue number	6
Early online date	19 Aug 2025
DOIs	https://doi.org/10.1007/s12237-025-01582-5
Publication status	Published - Nov 2025

Keywords

Fjords
Organic carbon
Coastal
Sediment
210Pb sediment dating
Geochronology
Lignin
Burial
Land-sea
Accumulation
Iceland
North Atlantic
Sills
Stable isotope
Biomarkers
Chemical biomarkers

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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Cite this

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title = "Efficient burial of labile organic carbon in sediments of oxygenated Icelandic fjords",

abstract = "Fjords are hotspots of organic carbon (OC) burial, making them key components in the global carbon cycle. Recent research shows high marine OC burial even under oxic fjord water columns, broadening the scope of key drivers of OC burial therein. Here, we investigate the fate of marine OC in fjord sediments underlying oxic bottom waters in East Iceland. We estimate OC sources using stable isotopes, degradation using chemical biomarkers, and burial using 210Pb and 137Cs profiles. The average OC accumulation rates in East Iceland fjords was ~15 g OC m-2 yr-1, lower than the fjord global average of 54 g OC m-2 yr-1. Marine OC was the overwhelming source of OC to sediments and accounted for 91% of the OC buried in Iceland. The gradient in OC source from the head-to-mouth of the fjords was minimal, due to limited terrestrial vegetation and soil cover, low riverine inputs, and effective exchange with coastal waters. Lignin and total hydrolyzable amino acid biomarkers suggest negligible degradation of terrestrial OC and minor degradation of marine OC. Although a portion of marine OC was prone to remineralization in sediments, it represented only a small fraction of the total OC resulting in high OC transfer (burial) efficiencies of 68-96% within the top 25 cm of sediments. Overall, Icelandic fjords efficiently bury labile marine OC despite oxic water columns. ",

keywords = "Fjords, Organic carbon, Coastal, Sediment, 210Pb sediment dating, Geochronology, Lignin, Burial, Land-sea, Accumulation, Iceland, North Atlantic, Sills, Stable isotope, Biomarkers, Chemical biomarkers",

author = "Watts, {Emily G.} and Kira Zautcke and Isaac Santos and Craig Smeaton and Wilma Ljungberg and Cheung, {Henry L. S.} and Stefano Bonaglia and Tobia Politi and Zhanfei Liu and Bianchi, {Thomas S.}",

note = "Funding: T. S. Bianchi was funded by the Jon and Beverly Thompson Endowed Chair in the Department of Geological Sciences at Univ. of Florida. We thank the crew of the R/V Skagerak at the University of Gothenburg and funding from the Swedish Research Council (VR 2020-00457). S. B. and T. P. were additionally supported by the Swedish Research Council (VR 2022-04710). ",

year = "2025",

month = nov,

doi = "10.1007/s12237-025-01582-5",

language = "English",

volume = "48",

pages = "1--20",

journal = "Estuaries and Coasts",

issn = "1559-2723",

publisher = "Springer",

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TY - JOUR

T1 - Efficient burial of labile organic carbon in sediments of oxygenated Icelandic fjords

AU - Watts, Emily G.

AU - Zautcke, Kira

AU - Santos, Isaac

AU - Smeaton, Craig

AU - Ljungberg, Wilma

AU - Cheung, Henry L. S.

AU - Bonaglia, Stefano

AU - Politi, Tobia

AU - Liu, Zhanfei

AU - Bianchi, Thomas S.

N1 - Funding: T. S. Bianchi was funded by the Jon and Beverly Thompson Endowed Chair in the Department of Geological Sciences at Univ. of Florida. We thank the crew of the R/V Skagerak at the University of Gothenburg and funding from the Swedish Research Council (VR 2020-00457). S. B. and T. P. were additionally supported by the Swedish Research Council (VR 2022-04710).

PY - 2025/11

Y1 - 2025/11

N2 - Fjords are hotspots of organic carbon (OC) burial, making them key components in the global carbon cycle. Recent research shows high marine OC burial even under oxic fjord water columns, broadening the scope of key drivers of OC burial therein. Here, we investigate the fate of marine OC in fjord sediments underlying oxic bottom waters in East Iceland. We estimate OC sources using stable isotopes, degradation using chemical biomarkers, and burial using 210Pb and 137Cs profiles. The average OC accumulation rates in East Iceland fjords was ~15 g OC m-2 yr-1, lower than the fjord global average of 54 g OC m-2 yr-1. Marine OC was the overwhelming source of OC to sediments and accounted for 91% of the OC buried in Iceland. The gradient in OC source from the head-to-mouth of the fjords was minimal, due to limited terrestrial vegetation and soil cover, low riverine inputs, and effective exchange with coastal waters. Lignin and total hydrolyzable amino acid biomarkers suggest negligible degradation of terrestrial OC and minor degradation of marine OC. Although a portion of marine OC was prone to remineralization in sediments, it represented only a small fraction of the total OC resulting in high OC transfer (burial) efficiencies of 68-96% within the top 25 cm of sediments. Overall, Icelandic fjords efficiently bury labile marine OC despite oxic water columns.

AB - Fjords are hotspots of organic carbon (OC) burial, making them key components in the global carbon cycle. Recent research shows high marine OC burial even under oxic fjord water columns, broadening the scope of key drivers of OC burial therein. Here, we investigate the fate of marine OC in fjord sediments underlying oxic bottom waters in East Iceland. We estimate OC sources using stable isotopes, degradation using chemical biomarkers, and burial using 210Pb and 137Cs profiles. The average OC accumulation rates in East Iceland fjords was ~15 g OC m-2 yr-1, lower than the fjord global average of 54 g OC m-2 yr-1. Marine OC was the overwhelming source of OC to sediments and accounted for 91% of the OC buried in Iceland. The gradient in OC source from the head-to-mouth of the fjords was minimal, due to limited terrestrial vegetation and soil cover, low riverine inputs, and effective exchange with coastal waters. Lignin and total hydrolyzable amino acid biomarkers suggest negligible degradation of terrestrial OC and minor degradation of marine OC. Although a portion of marine OC was prone to remineralization in sediments, it represented only a small fraction of the total OC resulting in high OC transfer (burial) efficiencies of 68-96% within the top 25 cm of sediments. Overall, Icelandic fjords efficiently bury labile marine OC despite oxic water columns.

KW - Fjords

KW - Organic carbon

KW - Coastal

KW - Sediment

KW - 210Pb sediment dating

KW - Geochronology

KW - Lignin

KW - Burial

KW - Land-sea

KW - Accumulation

KW - Iceland

KW - North Atlantic

KW - Sills

KW - Stable isotope

KW - Biomarkers

KW - Chemical biomarkers

U2 - 10.1007/s12237-025-01582-5

DO - 10.1007/s12237-025-01582-5

M3 - Article

SN - 1559-2723

VL - 48

SP - 1

EP - 20

JO - Estuaries and Coasts

JF - Estuaries and Coasts

IS - 6

M1 - 167

ER -

Efficient burial of labile organic carbon in sediments of oxygenated Icelandic fjords

Abstract

Keywords

UN SDGs

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