The impact of oxic degradation on long chain alkyl diol distributions in Arabian Sea surface sediments
Rodrigo-Gámiz, M.; Rampen, S.W.; Schouten, S.; Sinninghe Damsté, J.S. (2016). The impact of oxic degradation on long chain alkyl diol distributions in Arabian Sea surface sediments. Org. Geochem. 100: 1-9. dx.doi.org/10.1016/j.orggeochem.2016.07.003Additional data: In: Organic Geochemistry. Elsevier: Oxford; New York. ISSN 0146-6380; e-ISSN 1873-5290, more |   |
| Author keywords | Long chain alkyl diols; Keto-ols; LDI; UK’37; Upwelling indices; DOXI; Oxygen minimum zone; Arabian Sea; Surface sediments; Oxic degradation |
| Authors | | Top | - Rodrigo-Gámiz, M., more
- Rampen, S.W., more
- Schouten, S., more
- Sinninghe Damsté, J.S., more
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| Abstract | Oxygen exposure has a large impact on lipid biomarker preservation in surface sediments and may affectthe application of organic proxies used for reconstructing past environmental conditions. To determineits effect on long chain alkyl diol and keto-ol based proxies, the distributions of these lipids was studiedin nine surface sediments from the Murray Ridge in the Arabian Sea obtained from varying water depths(900–3000 m) but in close lateral proximity and, therefore, likely receiving a similar particle flux. Due tosubstantial differences in bottom water oxygen concentration (<3–77 lmol/L) and sedimentation rate,substantial differences exist in the time the biomarker lipids are exposed to oxygen in the sediment.Long chain alkyl diol and keto-ol concentrations in the surface sediments (0–0.5 cm) decreased progressivelywith increasing oxygen exposure time, suggesting increased oxic degradation. The 1,15-keto-ol/diol ratio (DOXI) increased slightly with oxygen exposure time as diols had apparently slightly higherdegradation rates than keto-ols. The ratio of 1,14- vs. 1,13- or 1,15-diols, used as upwelling proxies,did not show substantial changes. However, the C30 1,15-diol exhibited a slightly higher degradation ratethan C28 and C30 1,13-diols, and thus the Long chain Diol Index (LDI), used as sea surface temperatureproxy, showed a negative correlation with the maximum residence time in the oxic zone of the sediment,resulting in ca. 2–3.5 °C change, when translated to temperature. The UK037 index did not show significantchanges with increasing oxygen exposure. This suggests that oxic degradation may affect temperaturereconstructions using the LDI in oxic settings and where oxygen concentrations have varied substantiallyover time. |
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