Degradation of sterols and terrigenous organic matter in waters of the Mackenzie Shelf, Canadian Arctic

Jean François Rontani, Bruno Charrière, Richard Sempéré, David Doxaran, Frédéric Vaultier, Jorien E. Vonk, John K. Volkman

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Sterols and their biotic and abiotic degradation products were quantified in suspended particulate matter (SPM) from surface waters in the Mackenzie River mouth to the Beaufort Sea shelf (Canadian Arctic). 24-Ethylcholesterol (sitosterol) and 24-methylcholesterol (campesterol) appeared to be extensively degraded by bacterial and especially autoxidative degradation in the samples. Degradation was most extensive in some samples from the outer boundaries of the plume, which exhibited much higher sitosterol/campesterol ratio values than previously observed in studies of the Beaufort Sea. The lack of reactivity of specific planktonic sterols such as cholesterol, 24-methylcholesta-5,22. E-dien-3β-ol (epi-brassicasterol) and 24-methylenecholesterol and the good correlation between the abundances of sitosterol, campesterol and dehydroabietic acid (DHAA, a biomarker of Pinaceae resin) oxidation products allowed us to attribute the main origin of these two sterols to terrigenous vascular plants. A good correlation was observed between the extent of autoxidation and salinity, suggesting that the free radical oxidation is enhanced via contact with seawater. Laboratory incubation of Mackenzie River SPM in Milli-Q water and seawater confirmed this proposal. To explain the specific induction of autoxidation on vascular plant-derived material, a mechanism involving homolytic cleavage of photochemically produced hydroperoxides resulting from the senescence of higher plants on land is proposed. Cleavage could be catalyzed by redox-active metal ions released from SPM in the mixing zone of riverine water and marine water. The greatest extent of degradation observed at outer boundaries of the plume is attributed to preferential settling of lithic material relative to less dense higher plant debris increasing the proportion of highly degraded vascular plant material in the SPM. The results are important for this ecologically vulnerable region, where destabilization of permafrost by global warming is expected to increase the input of terrigenous C to coastal seas. Autoxidation, which until now has received little attention, plays a key role in the degradation of vascular plant-derived lipids in surface waters and should be taken into consideration during future studies of terrigenous organic matter degradation.

Original languageEnglish
Pages (from-to)61-73
Number of pages13
JournalOrganic Geochemistry
Volume75
DOIs
Publication statusPublished - 2014

Fingerprint

sterol
Sterols
Biological materials
suspended particulate matter
vascular plant
Particulate Matter
organic matter
Degradation
degradation
Water
cleavage
Surface waters
Seawater
water
plume
seawater
surface water
oxidation
Rivers
shelf sea

Keywords

  • Abiotic and biotic degradation
  • Autoxidation
  • Bacterial degradation
  • Dehydroabietic acid
  • Mackenzie River
  • Mackenzie shelf
  • SPM
  • Sterols
  • Terrigenous organic matter

Cite this

Rontani, Jean François ; Charrière, Bruno ; Sempéré, Richard ; Doxaran, David ; Vaultier, Frédéric ; Vonk, Jorien E. ; Volkman, John K. / Degradation of sterols and terrigenous organic matter in waters of the Mackenzie Shelf, Canadian Arctic. In: Organic Geochemistry. 2014 ; Vol. 75. pp. 61-73.
@article{6b63210942134ef39d0f90c20e94cc42,
title = "Degradation of sterols and terrigenous organic matter in waters of the Mackenzie Shelf, Canadian Arctic",
abstract = "Sterols and their biotic and abiotic degradation products were quantified in suspended particulate matter (SPM) from surface waters in the Mackenzie River mouth to the Beaufort Sea shelf (Canadian Arctic). 24-Ethylcholesterol (sitosterol) and 24-methylcholesterol (campesterol) appeared to be extensively degraded by bacterial and especially autoxidative degradation in the samples. Degradation was most extensive in some samples from the outer boundaries of the plume, which exhibited much higher sitosterol/campesterol ratio values than previously observed in studies of the Beaufort Sea. The lack of reactivity of specific planktonic sterols such as cholesterol, 24-methylcholesta-5,22. E-dien-3β-ol (epi-brassicasterol) and 24-methylenecholesterol and the good correlation between the abundances of sitosterol, campesterol and dehydroabietic acid (DHAA, a biomarker of Pinaceae resin) oxidation products allowed us to attribute the main origin of these two sterols to terrigenous vascular plants. A good correlation was observed between the extent of autoxidation and salinity, suggesting that the free radical oxidation is enhanced via contact with seawater. Laboratory incubation of Mackenzie River SPM in Milli-Q water and seawater confirmed this proposal. To explain the specific induction of autoxidation on vascular plant-derived material, a mechanism involving homolytic cleavage of photochemically produced hydroperoxides resulting from the senescence of higher plants on land is proposed. Cleavage could be catalyzed by redox-active metal ions released from SPM in the mixing zone of riverine water and marine water. The greatest extent of degradation observed at outer boundaries of the plume is attributed to preferential settling of lithic material relative to less dense higher plant debris increasing the proportion of highly degraded vascular plant material in the SPM. The results are important for this ecologically vulnerable region, where destabilization of permafrost by global warming is expected to increase the input of terrigenous C to coastal seas. Autoxidation, which until now has received little attention, plays a key role in the degradation of vascular plant-derived lipids in surface waters and should be taken into consideration during future studies of terrigenous organic matter degradation.",
keywords = "Abiotic and biotic degradation, Autoxidation, Bacterial degradation, Dehydroabietic acid, Mackenzie River, Mackenzie shelf, SPM, Sterols, Terrigenous organic matter",
author = "Rontani, {Jean Fran{\cc}ois} and Bruno Charri{\`e}re and Richard Semp{\'e}r{\'e} and David Doxaran and Fr{\'e}d{\'e}ric Vaultier and Vonk, {Jorien E.} and Volkman, {John K.}",
year = "2014",
doi = "10.1016/j.orggeochem.2014.06.002",
language = "English",
volume = "75",
pages = "61--73",
journal = "Organic Geochemistry",
issn = "0146-6380",
publisher = "Elsevier Limited",

}

Degradation of sterols and terrigenous organic matter in waters of the Mackenzie Shelf, Canadian Arctic. / Rontani, Jean François; Charrière, Bruno; Sempéré, Richard; Doxaran, David; Vaultier, Frédéric; Vonk, Jorien E.; Volkman, John K.

In: Organic Geochemistry, Vol. 75, 2014, p. 61-73.

Research output: Contribution to JournalArticleAcademicpeer-review

TY - JOUR

T1 - Degradation of sterols and terrigenous organic matter in waters of the Mackenzie Shelf, Canadian Arctic

AU - Rontani, Jean François

AU - Charrière, Bruno

AU - Sempéré, Richard

AU - Doxaran, David

AU - Vaultier, Frédéric

AU - Vonk, Jorien E.

AU - Volkman, John K.

PY - 2014

Y1 - 2014

N2 - Sterols and their biotic and abiotic degradation products were quantified in suspended particulate matter (SPM) from surface waters in the Mackenzie River mouth to the Beaufort Sea shelf (Canadian Arctic). 24-Ethylcholesterol (sitosterol) and 24-methylcholesterol (campesterol) appeared to be extensively degraded by bacterial and especially autoxidative degradation in the samples. Degradation was most extensive in some samples from the outer boundaries of the plume, which exhibited much higher sitosterol/campesterol ratio values than previously observed in studies of the Beaufort Sea. The lack of reactivity of specific planktonic sterols such as cholesterol, 24-methylcholesta-5,22. E-dien-3β-ol (epi-brassicasterol) and 24-methylenecholesterol and the good correlation between the abundances of sitosterol, campesterol and dehydroabietic acid (DHAA, a biomarker of Pinaceae resin) oxidation products allowed us to attribute the main origin of these two sterols to terrigenous vascular plants. A good correlation was observed between the extent of autoxidation and salinity, suggesting that the free radical oxidation is enhanced via contact with seawater. Laboratory incubation of Mackenzie River SPM in Milli-Q water and seawater confirmed this proposal. To explain the specific induction of autoxidation on vascular plant-derived material, a mechanism involving homolytic cleavage of photochemically produced hydroperoxides resulting from the senescence of higher plants on land is proposed. Cleavage could be catalyzed by redox-active metal ions released from SPM in the mixing zone of riverine water and marine water. The greatest extent of degradation observed at outer boundaries of the plume is attributed to preferential settling of lithic material relative to less dense higher plant debris increasing the proportion of highly degraded vascular plant material in the SPM. The results are important for this ecologically vulnerable region, where destabilization of permafrost by global warming is expected to increase the input of terrigenous C to coastal seas. Autoxidation, which until now has received little attention, plays a key role in the degradation of vascular plant-derived lipids in surface waters and should be taken into consideration during future studies of terrigenous organic matter degradation.

AB - Sterols and their biotic and abiotic degradation products were quantified in suspended particulate matter (SPM) from surface waters in the Mackenzie River mouth to the Beaufort Sea shelf (Canadian Arctic). 24-Ethylcholesterol (sitosterol) and 24-methylcholesterol (campesterol) appeared to be extensively degraded by bacterial and especially autoxidative degradation in the samples. Degradation was most extensive in some samples from the outer boundaries of the plume, which exhibited much higher sitosterol/campesterol ratio values than previously observed in studies of the Beaufort Sea. The lack of reactivity of specific planktonic sterols such as cholesterol, 24-methylcholesta-5,22. E-dien-3β-ol (epi-brassicasterol) and 24-methylenecholesterol and the good correlation between the abundances of sitosterol, campesterol and dehydroabietic acid (DHAA, a biomarker of Pinaceae resin) oxidation products allowed us to attribute the main origin of these two sterols to terrigenous vascular plants. A good correlation was observed between the extent of autoxidation and salinity, suggesting that the free radical oxidation is enhanced via contact with seawater. Laboratory incubation of Mackenzie River SPM in Milli-Q water and seawater confirmed this proposal. To explain the specific induction of autoxidation on vascular plant-derived material, a mechanism involving homolytic cleavage of photochemically produced hydroperoxides resulting from the senescence of higher plants on land is proposed. Cleavage could be catalyzed by redox-active metal ions released from SPM in the mixing zone of riverine water and marine water. The greatest extent of degradation observed at outer boundaries of the plume is attributed to preferential settling of lithic material relative to less dense higher plant debris increasing the proportion of highly degraded vascular plant material in the SPM. The results are important for this ecologically vulnerable region, where destabilization of permafrost by global warming is expected to increase the input of terrigenous C to coastal seas. Autoxidation, which until now has received little attention, plays a key role in the degradation of vascular plant-derived lipids in surface waters and should be taken into consideration during future studies of terrigenous organic matter degradation.

KW - Abiotic and biotic degradation

KW - Autoxidation

KW - Bacterial degradation

KW - Dehydroabietic acid

KW - Mackenzie River

KW - Mackenzie shelf

KW - SPM

KW - Sterols

KW - Terrigenous organic matter

UR - http://www.scopus.com/inward/record.url?scp=84904676553&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84904676553&partnerID=8YFLogxK

U2 - 10.1016/j.orggeochem.2014.06.002

DO - 10.1016/j.orggeochem.2014.06.002

M3 - Article

VL - 75

SP - 61

EP - 73

JO - Organic Geochemistry

JF - Organic Geochemistry

SN - 0146-6380

ER -