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Abiotic degradation of highly branched isoprenoid alkenes and other lipids in the water column off East Antarctica

Citation

Rontani, J-F and Smik, L and Belt, ST and Vaultier, F and Armbrecht, L and Leventer, A and Armand, LK, Abiotic degradation of highly branched isoprenoid alkenes and other lipids in the water column off East Antarctica, Marine Chemistry, 210 pp. 34-47. ISSN 0304-4203 (2019) [Refereed Article]

Copyright Statement

Crown Copyright 2019 Published by Elsevier B.V. All rights reserved.

DOI: doi:10.1016/j.marchem.2019.02.004

Abstract

In some previous studies, the ratio between a di-unsaturated highly branched isoprenoid (HBI) lipid termed IPSO25 and a structurally related tri-unsaturated counterpart (HBI III) (viz. IPSO25/HBI III) has been used as a proxy measure of variable sea ice cover in the Antarctic owing to their production by certain sea ice algae and open water diatoms, respectively. To investigate this further, we quantified selected lipids and their photo- and autoxidation products in samples of suspended particulate matter (SPM) collected at different water depths in the polynya region west of the Dalton Iceberg Tongue (East Antarctica). The results obtained confirm the high efficiency of photo- and autoxidation processes in diatoms from the region. The systematic increase of the ratio IPSO25/HBI III with water depth in the current samples appeared to be dependent on the sampling site and was due to both (i) a relatively higher contribution of ice algae to the deeper samples resulting from their increased aggregation and therefore higher sinking rate, or (ii) a stronger abiotic degradation of HBI III during settling through the water column. Analyses of samples taken from the water-sediment interface and some underlying near-surface sediments revealed a further increase of the ratio IPSO25/HBI III, indicative of further differential oxidation of the more unsaturated HBI. Unfortunately, specific oxidation products of HBI III could not be detected in the strongly oxidized SPM and sediment samples, likely due to their lability towards further oxidation. In contrast, oxidation products of HBI III were detected in weakly oxidized samples of phytoplanktonic cells collected from Commonwealth Bay (also East Antarctica), thus providing more direct evidence for the involvement of photo- and/or autoxidation of HBI III in the region. This oxidative alteration of the ratio IPSO25/HBI III between their source and sedimentary environments might need to be considered more carefully when using this parameter for palaeo sea ice reconstruction purposes in the Antarctic.

Item Details

Item Type:Refereed Article
Keywords:HBI, Antarctica, diatoms, sea-ice, degradation
Research Division:Earth Sciences
Research Group:Geochemistry
Research Field:Organic geochemistry
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean ice dynamics
UTAS Author:Armbrecht, L (Dr Linda Armbrecht)
ID Code:146479
Year Published:2019
Web of Science® Times Cited:6
Deposited By:Ecology and Biodiversity
Deposited On:2021-09-08
Last Modified:2021-10-12
Downloads:0

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