The oceans are the largest carbon sink on Earth. As such, they play an essential role in mitigating the effects of global change. One of the many disciplines involved in the search for the mechanisms underlying the formation, composition, and cycling of organic matter is ocean organic geochemistry.

In the water column, the amount of molecularly uncharacterized organic carbon percentages rise steadily until they reach nearly 80 percent in the underlying sediments.

Lipids are one of the most important biochemical classes in seawater. The processes of lipid transformation are still largely unknown due to the lack of analytical methods and standards that would allow these studies.

Using novel direct-infusion Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), the researchers are able to study the elemental composition of thousands of lipids in a single sample.

''In our work, we have provided insights into the molecular-level changes that occur during lipid transformation in the NE Atlantic Ocean water column as to better understand early lipid transformation processes and the formation of decomposition intermediates,'' explains Dr. Gašparović.

Considering the H/C and O/C ratios, the distribution of molecular rings and/or double bonds, molecular diversity based on the number of mass spectral signals for monoisotopic species, and carbon number in molecules it was concluded that lipid transformation mechanisms include crosslinking (condensation), partial degradation or fragmentation, double bond reduction, oxidation, hydrogenation, dehydrogenation and cyclization.

''The results show low unsaturation and rapid transport to depth promote the preservation of lipid transformation products in the water column. Such compounds contribute to the export of carbon from the atmosphere to the deep ocean and thus participate in the mitigation of global change", authors concluded.