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

Gašparović, Blaženka; Penezić, Abra; Frka Milosavljević, Sanja; Kazazić, Saša; Lampitt, Richard S.; Holhuin, F.O.; Sudasinghe, Nilusha; 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 (1). pp. 12-22. ISSN 0967-0637

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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), sulphite and sulphate 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 to 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 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.

Item Type:	Article
Uncontrolled Keywords:	Sulfur-containing lipids ; lipid depth-related transformations ; FT-ICR MS, TLC/FID ; northeast Atlantic Ocean
Subjects:	NATURAL SCIENCES > Interdisciplinary Natural Sciences NATURAL SCIENCES > Interdisciplinary Natural Sciences > Marine Science
Divisions:	Division for Marine and Enviromental Research
Projects:	Project title Project leader Project code Project type Utjecaj okolišnog stresa na pojavnost i međudjelovanje biološki važnih organskih molekula i mikronutrijenata u morskom ekosustavu-AMBIOMERES Blaženka Gašparović IP-2013-11-8607 HRZZ
Depositing User:	Blaženka Gašparović
Date Deposited:	21 May 2018 09:53
URI:	http://fulir.irb.hr/id/eprint/4038
DOI:	10.1016/j.dsr.2018.03.007

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