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Particulate sulfur-containing lipids: Production and cycling from the epipelagic to the abyssopelagic zone

Particulate sulfur-containing lipids: Production and cycling from the epipelagic to the abyssopelagic zone
Particulate sulfur-containing lipids: Production and cycling from the epipelagic to the abyssopelagic zone
There are major gaps in our understanding of the distribution and role of lipids in the open ocean especially with regard to sulfur-containing lipids (S-lipids). Here, we employ a powerful analytical approach based on high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to elucidate depth-related S-lipid production and molecular transformations in suspended particulate matter from the Northeast Atlantic Ocean in this depth range. We show that within the open-ocean environment S-lipids contribute up to 4.2% of the particulate organic carbon, and that up to 95% of these compounds have elemental compositions that do not match those found in the Nature Lipidomics Gateway database (termed “novel”). Among the remaining 5% of lipids that match the database, we find that sulphoquinovosyldiacylglycerol (SQDG) are efficiently removed while sinking through the mesopelagic zone. The relative abundance of other assigned lipids (sulphoquinovosylmonoacylglycerol (SQMG), sulfite and sulfate lipids, Vitamin D2 and D3 derivatives, and sphingolipids) did not change substantially with depth. The novel S-lipids, represented by hundreds of distinct elemental compositions (160–300 molecules at any one depth), contribute increasingly to the lipid and particulate organic matter pools with increased depth. Depth-related transformations cause (i) incomplete degradation/transformation of unsaturated S-lipids which leads to the depth-related accumulation of the refractory saturated compounds with reduced molecular weight (average 455 Da) and (ii) formation of highly unsaturated S-lipids (average abyssopelagic molecular double bond equivalents, DBE=7.8) with lower molecular weight (average 567 Da) than surface S-lipids (average 592 Da). A depth-related increase in molecular oxygen content is observed for all novel S-lipids and indicates that oxidation has a significant role in their transformation while (bio)hydrogenation possibly impacts the formation of saturated compounds. The instrumentation approach applied here represents a step change in our comprehension of marine S-lipid diversity and the potential role of these compounds in the oceanic carbon cycle. We describe a very much higher number of compounds than previously reported, albeit at the level of elemental composition and fold-change quantitation with depth, rather than isomeric confirmation and absolute quantitation of individual lipids. We emphasize that saturated S-lipids have the potential to transfer carbon from the upper ocean to depth and hence are significant vectors for carbon sequestration.
0967-0637
12-22
Gašparović, Blaženka
0627e543-b4cc-4576-ad54-bb6440a5b86b
Penezić, Abra
714032c0-6837-4187-8738-d9402666f562
Frka, Sanja
65bd8ac8-ab93-48c4-b3be-73fe0fc47aa1
Kazazić, Saša
8cb04c17-8dae-4d2d-b35a-7dea217d8983
Lampitt, Richard S.
dfc3785c-fc7d-41fa-89ee-d0c6e27503ad
Holguin, F. Omar
b4963c9e-08ab-4738-9bf7-baab1b4a2468
Sudasinghe, Nilusha
eb6d451d-0033-47dc-8066-a626cbdd3959
Schaub, Tanner
9e4127d3-01f1-4923-8da6-65218f3fb96b
Gašparović, Blaženka
0627e543-b4cc-4576-ad54-bb6440a5b86b
Penezić, Abra
714032c0-6837-4187-8738-d9402666f562
Frka, Sanja
65bd8ac8-ab93-48c4-b3be-73fe0fc47aa1
Kazazić, Saša
8cb04c17-8dae-4d2d-b35a-7dea217d8983
Lampitt, Richard S.
dfc3785c-fc7d-41fa-89ee-d0c6e27503ad
Holguin, F. Omar
b4963c9e-08ab-4738-9bf7-baab1b4a2468
Sudasinghe, Nilusha
eb6d451d-0033-47dc-8066-a626cbdd3959
Schaub, Tanner
9e4127d3-01f1-4923-8da6-65218f3fb96b

Gašparović, Blaženka, Penezić, Abra, Frka, Sanja, Kazazić, Saša, Lampitt, Richard S., Holguin, F. Omar, Sudasinghe, Nilusha and Schaub, Tanner (2018) Particulate sulfur-containing lipids: Production and cycling from the epipelagic to the abyssopelagic zone. Deep Sea Research Part I: Oceanographic Research Papers, 134, 12-22. (doi:10.1016/j.dsr.2018.03.007).

Record type: Article

Abstract

There are major gaps in our understanding of the distribution and role of lipids in the open ocean especially with regard to sulfur-containing lipids (S-lipids). Here, we employ a powerful analytical approach based on high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to elucidate depth-related S-lipid production and molecular transformations in suspended particulate matter from the Northeast Atlantic Ocean in this depth range. We show that within the open-ocean environment S-lipids contribute up to 4.2% of the particulate organic carbon, and that up to 95% of these compounds have elemental compositions that do not match those found in the Nature Lipidomics Gateway database (termed “novel”). Among the remaining 5% of lipids that match the database, we find that sulphoquinovosyldiacylglycerol (SQDG) are efficiently removed while sinking through the mesopelagic zone. The relative abundance of other assigned lipids (sulphoquinovosylmonoacylglycerol (SQMG), sulfite and sulfate lipids, Vitamin D2 and D3 derivatives, and sphingolipids) did not change substantially with depth. The novel S-lipids, represented by hundreds of distinct elemental compositions (160–300 molecules at any one depth), contribute increasingly to the lipid and particulate organic matter pools with increased depth. Depth-related transformations cause (i) incomplete degradation/transformation of unsaturated S-lipids which leads to the depth-related accumulation of the refractory saturated compounds with reduced molecular weight (average 455 Da) and (ii) formation of highly unsaturated S-lipids (average abyssopelagic molecular double bond equivalents, DBE=7.8) with lower molecular weight (average 567 Da) than surface S-lipids (average 592 Da). A depth-related increase in molecular oxygen content is observed for all novel S-lipids and indicates that oxidation has a significant role in their transformation while (bio)hydrogenation possibly impacts the formation of saturated compounds. The instrumentation approach applied here represents a step change in our comprehension of marine S-lipid diversity and the potential role of these compounds in the oceanic carbon cycle. We describe a very much higher number of compounds than previously reported, albeit at the level of elemental composition and fold-change quantitation with depth, rather than isomeric confirmation and absolute quantitation of individual lipids. We emphasize that saturated S-lipids have the potential to transfer carbon from the upper ocean to depth and hence are significant vectors for carbon sequestration.

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More information

Accepted/In Press date: 14 March 2018
e-pub ahead of print date: 15 March 2018
Published date: April 2018

Identifiers

Local EPrints ID: 421592
URI: http://eprints.soton.ac.uk/id/eprint/421592
ISSN: 0967-0637
PURE UUID: 3e1430f2-caee-4385-a450-ba1e09f26e3c

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Date deposited: 15 Jun 2018 16:30
Last modified: 26 Apr 2022 18:50

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Contributors

Author: Blaženka Gašparović
Author: Abra Penezić
Author: Sanja Frka
Author: Saša Kazazić
Author: Richard S. Lampitt
Author: F. Omar Holguin
Author: Nilusha Sudasinghe
Author: Tanner Schaub

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