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Phospholipid characterization as a component of the oceanic phosphorus and carbon cycle

We report on the production and cycling of oceanic phosphorus-containing lipids (PL) in the Northeast Atlantic. We have analysed PL by Iatroscan thin layer chromatography and high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Phospholipids are a small but significant fraction of the pool of particulate organic carbon (POC) (1.5%). We monitor 1, 862 PL species in total, including 27.4% that match those in the Nature Lipidomics Gateway database and the rest are unassigned PL (unsaturated and saturated), which we termed “novel”. The highest relative concentration in the epipelagic indicate on their main production in this layer, while depth related removal was the strongest for the database-matched PL and the least removal is detected for the saturated novel PL. The depth transformation of database- matched PL is marked by loss of unsaturation with phosphatidic acid that is assumed to be generated as the earliest transformation of PL. Novel PL are dominated by unsaturated compounds for which unsaturation increased between the epipelagic (average DBE=5) and the abyssopelagic (average DBE=6.7) zones together with increase of the average molecular weight and their molecular contribution to all lipid molecules. Possible explanation for this observation would be cross-linking of unsaturated compounds that may lead to the formation of higher molecular weight PL with higher degrees of unsaturation (as observed). Our data indicate that novel PL are selectively preserved with depth and therefore are P and C carriers to deep Atlantic.

phospholipids ; production ; cycling ; Atlantic Ocean

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