A quantitative study of the degradation of whale bone lipids: Implications for the preservation of fatty acids in marine sediments

• Published in: Organic Geochemistry
• Main Authors: Liebenau, Katharina, Kiel, Steffen, Vardeh, David, Treude, Tina, Thiel, Volker
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2015
• Subjects: Phocoena phocoena
• Online Access: https://oceanrep.geomar.de/id/eprint/30666/; https://oceanrep.geomar.de/id/eprint/30666/1/1-s2.0-S0146638015001783-main.pdf; https://doi.org/10.1016/j.orggeochem.2015.09.005

The degradation and preservation affecting the biomarker record of ancient metazoa are not fully understood. We report on a five month experiment on the fate of fatty acids (FAs) during the degradation of recent whale vertebrae (Phocoena phocoena). Whale bones were analysed for extractable FAs and macromolecularly bound n-acyl compounds. Fresh bone showed extractable FAs dominated by 16: 1 omega 7c, 16:0, 18:1 omega 9c and 18:0. Calculated degradation rate constant (k) values showed a rapid decrease in FA concentration, with k values higher for unsaturated than for saturated compounds (0.08/day for 18: 1 omega 9c, 0.05/day for 16:0). The appearance or increased abundance of distinctive methyl branched (e.g. i/ai-15:0 and -17:0, 10Me-16:0) and hydroxy FAs (e.g. 10OH-16:0 and 10OH-18:0) were observed, providing clear evidence for the microbial degradation of bone organic matter and an input of lipids from specialised bacteria. Catalytic hydropyrolysis (HyPy) of demineralised extraction residues released up to 0.13% of the total n-C-16 and n-C-18 moieties in the degraded bones. This revealed that only a small, yet sizeable, portion of bone-derived fatty acyl units was sequestered into (proto)kerogen during the earliest stages of degradation.