Phospholipids as a component of the oceanic phosphorus cycle

Abstract

We characterize the distribution of oceanic phosphorus-containing lipids (PL) in the Northeast Atlantic by Iatroscan thin layer chromatography and high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Phospholipids are a small but significant fraction of oceanic particulate organic carbon (POC) (1.5%). We describe the distribution of 1,862 PL compounds in total, of which only ~27% have elemental compositions that match those found in the Nature Lipidomics Gateway database (e.g., phosphatidylglycerol (PG), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidic acid (PA), phosphatidyl serine (PS), and phosphatidylinositol (PI)). The highest phospholipid concentration is found in the epipelagic, which reflects primary production in that depth horizon. Depthrelated PL removal was the strongest for PL signals that match database-reported (known) lipids and was lower for saturated non-database (novel) matched PL. The transformation of known PL is marked by depth-related increase in saturation with PA that is assumed to be generated as the earliest transformation product of PL. Novel unsaturated P-lipids likely originate from both PL transformation processes and insitu biological production at the surface layer. Novel PL are dominated by unsaturated compounds for which unsaturation increased between the epipelagic (average molecular double bond equivalents, DBE=5) and the abyssopelagic (average DBE=6.7) zones. Additionally, those compounds increase in both average molecular weight and contribution to all lipid content with increasing depth, likely from crosslinking of unsaturated compounds. Our data indicate that novel PL are selectively preserved with depth and therefore are P and C carriers to the deep Atlantic. We demonstrate that a full appreciation of

Concerted measurements of lipids in seawater and on submicrometer aerosol particles at the Cabo Verde islands: biogenic sources, selective transfer and high enrichments

“…Furthermore, the degradation lipid class FFA showed high enrichments in the SML (averaged EF SML(FFA) : of 3.1 (PL) and 1.5 (DL)). These high concentrations and enrichments point to an enhanced biodegradation in the SML, which is consistent with previous observations (Frka et al, 2011;Gašparović et al, 2018) that lipids are more degraded in the SML (high LI) than in the ULW. Besides the increased abundance of microbial cells, this may also be due to a different microbial community composition between the SML and the ULW and thus to different functional diversity (Cunliffe et al, 2011).…”

“…S9b). The contri-bution of bacteria to the PE pool most likely results from the fact that PE is part of the bacterial membrane (Stillwell, 2016;Gašparović et al, 2018). Additional indications for bacteria influencing the lipid pool result from a negative correlation between the lipolysis index of total particulate lipids (LI PL ) and TCN in the ULW and the SML samples.…”

Molecular-level evidence of early lipid transformations throughout oceanic depths

“…Particulate-derived lipid material was analyzed by directinfusion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) in both positive and negative ionization modes, with a hybrid linear ion trap 7T FT-ICR mass spectrometer (LTQ FT, Thermo Fisher, San Jose, CA) equipped with an Advion Triversa NanoMate (Advion Biosystems, Inc.) as previously described (Holguin and Schaub, 2013;Gašparovic ´et al, 2018b). The electrospray solutions for positive ion mode include 1 mM sodium acetate, which facilitates formation of predominantly sodium-adducted ions.…”

“…Among these unidentified lipids, the compounds containing carbon, hydrogen, and oxygen in the molecular formula are termed CHO compounds. Previously, we studied other unidentified lipids that contain heteroatoms, nitrogen, phosphorus, and sulfur (Gašparovic ´et al, 2017;2018a, 2018b. We combined CHO compound data with environmental data, including oxygen content, photosynthetically active radiation (PAR), and bacterial hopanoid biomarkers, to identify possible factors affecting lipid transformation.…”

Concerted measurements of lipids in seawater and on submicron aerosol particles at the Cape Verde Islands: biogenic sources, selective transfer and high enrichments

“…S10b). The contribution of bacteria to the PE pool most likely results from the fact, that PE is part of the bacterial membrane (Stillwell, 2016;Gašparović et al, 2018). Additional indications for bacteria influencing the lipid pool results from a negative correlation between the lipolysis index of total particulate lipids (LIPL) and TCN in ULW and SML samples.…”