Identification of di- and triterpenoid lipid tracers confirms the significant role of autoxidation in the degradation of terrestrial vascular plant material in the Canadian Arctic

Abstract

Identification of di-and triterpenoid lipid tracers confirms the significant role of autoxidation in the degradation of terrestrial vascular plant material in the Canadian Arctic

Lipoxygenase-induced autoxidative degradation of terrestrial particulate organic matter in estuaries: A widespread process enhanced at high and low latitude

“…and -Amyrins and betulin (unambiguous tracers of angiosperms; Otto et al, 2005) showed a clear increase in autoxidation state from the Amazon River to the sea (Table 4). It is interesting to note that the high extent of autoxidation observed in the Amazon shelf sediment samples (Table 4) was comparable with that recently observed in Arctic sediments (Rontani et al, 2017). The net increase in autoxidation state (Table 4) in SPM samples from A10 (S 0 g/kg) to 8 (S 29.6 g/kg) confirmed the key role played by the increase in salinity in the induction of autoxidation.…”

“…To compare the efficiency of autoxidation in vascular plant debris discharged by temperate and tropical rivers with that previously measured in Arctic sediments (Rontani et al, 2017), oxidation products of specific tracers of vascular plants (-and -amyrins and betulin) were quantified in surface sediment (0-1 cm) and SPM samples from the Amazon River, fan and shelf and surface sediment (0-1 cm) from the Rhône Shelf. The extent of autoxidation of vascular plant debris appeared to be considerably higher in the Amazon Shelf than in the Rhône Shelf (Table 4).…”

“…For example, autoxidation of 24-ethylcholest-5-en-3-ol (sitosterol) can reach 98% in SPM from surface waters of the Beaufort Sea shelf (Rontani et al, 2014a), compared with only 10% of similar material in the Mediterranean Sea (Galeron et al, 2017). Moreover, autoxidation of specific biomarkers of vascular plants (-and -amyrins and betulin) reached 99.8, 99.7 and 93.5%, respectively in surface sediments from different regions of the Canadian Arctic (Rontani et al, 2017), while they appeared to be considerably lower in similar material collected from the Rhône Shelf (Table 4). In order to explain the high level of autoxidation in the Arctic, we compared several parameters (efficiency of photooxidation in terrestrial higher plant debris, hydroperoxide concentrations and LOX activity in river SPM) in the Mackenzie and Rhône rivers.…”

Biotic and abiotic degradation of the sea ice diatom biomarker IP25 and selected algal sterols in near-surface Arctic sediments

“…Numerous organisms, including bacteria, fungi and micro-and macrofauna, are responsible for the aerobic biodegradation of organic carbon in sediments (Fenchel et al, 1998) and almost all of these organisms have the enzymatic capacity to perform a total mineralization of numerous organic substrates (Kristensen, 2000). Although autoxidation of organic matter involving spontaneous free radical reaction of organic compounds with O 2 has been rather under-considered in the marine realm, it is now known that autoxidative processes can act very intensively on vascular plant debris in Arctic sediments (Rontani et al, 2017). This high autoxidation efficiency likely reflects the enhanced photooxidation of senescent vascular plants in the region (thus yielding high amounts of hydroperoxides), together with high lipoxygenase activity (a potential source of radicals; Fuchs and Spiteller, 2014).…”

Electron ionization mass spectrometry fragmentation and multiple reaction monitoring quantification of autoxidation products of α‐ and β‐amyrins in natural samples

“…The ketones 7 and 8 were thus proposed as tracers of abiotic degradation (autoxidation) of terrestrial higher plants in the marine realm . Although very high proportions of these tracers could be easily detected by GC/MS operating in selected ion monitoring (SIM) mode in particulate matter and sediment samples collected in the Arctic and tropical zones, their quantification in samples where terrestrial organic matter is present in lesser proportions remains more problematic.…”