Monitoring photo-oxidative and salinity-induced bacterial stress in the Canadian Arctic using specific lipid tracers

Amiraux, Rémi; Belt, Simon T.; Vaultier, Frédéric; Galindo, Virginie; Gosselin, Michel; Bonin, Patricia; Rontani, Jean‐François

doi:10.1016/j.marchem.2017.05.006

Cited by 20 publications

(55 citation statements)

References 75 publications

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“…The propensity of ice algae to form aggregates, facilitated by microbial exopolymeric substances and the rapid sinking of the pennate diatom N. frigida, may indicate greater relative pulses of ice algae to the seafloor despite a larger relative proportion of pelagic productivity [79,80]. These processes have also been suggested to support the greater burial potential of sympagic lipid biomarkers [66,81]. The H-Print values also suggest there is a greater source of ice algae lipids available to the benthic infaunal communities that occupy these sediment horizons.…”

Section: Plos Onementioning

confidence: 99%

Seasonal and latitudinal variations in sea ice algae deposition in the Northern Bering and Chukchi Seas determined by algal biomarkers

et al. 2020

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An assessment of the production, distribution and fate of highly branched isoprenoid (HBI) biomarkers produced by sea ice and pelagic diatoms is necessary to interpret their detection and proportions in the northern Bering and Chukchi Seas. HBIs measured in surface sediments collected from 2012 to 2017 were used to determine the distribution and seasonality of the biomarkers relative to sea ice patterns. A northward gradient of increasing ice algae deposition was observed with localized occurrences of elevated IP 25 (sympagic HBI) concentrations from 68-70˚N and consistently strong sympagic signatures from 71-72.5˚N. A declining sympagic signature was observed from 2012 to 2017 in the northeast Chukchi Sea, coincident with declining sea ice concentrations. HBI fluxes were investigated on the northeast Chukchi shelf with a moored sediment trap deployed from August 2015 to July 2016. Fluxes of sea ice exclusive diatoms (Nitzschia frigida and Melosira arctica) and HBIproducing taxa (Pleurosigma, Haslea and Rhizosolenia spp.) were measured to confirm HBI sources and ice associations. IP 25 was detected year-round, increasing in March 2016 (10 ng m-2 d-1) and reaching a maximum in July 2016 (1331 ng m-2 d-1). Snowmelt triggered the release of sea ice algae into the water column in May 2016, while under-ice pelagic production contributed to the diatom export in June and July 2016. Sea ice diatom fluxes were strongly correlated with the IP 25 flux, however associations between pelagic diatoms and HBI fluxes were inconclusive. Bioturbation likely facilitates sustained burial of sympagic organic matter on the shelf despite the occurrence of pelagic diatom blooms. These results suggest that sympagic diatoms may sustain the food web through winter on the northeast Chukchi shelf. The reduced relative proportions of sympagic HBIs in the northern Bering Sea are likely driven by sea ice persistence in the region.

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Section: Plos Onementioning

confidence: 99%

Seasonal and latitudinal variations in sea ice algae deposition in the Northern Bering and Chukchi Seas determined by algal biomarkers

et al. 2020

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“…However, here we show that autoxidative degradation of IP 25 may occur under more 'forced' conditions and such processes may also take place in Arctic surface sediments. Indeed, due to recent evidence of strong lipoxygenase activity (a well-known source of radicals; Fuchs and Spiteller, 2014) in bacteria associated with ice algae (Amiraux et al, 2017) and in terrestrial particulate organic matter discharged from Arctic rivers (Galeron et al, 2018), autoxidative degradation reactions can even be dominant in Arctic sediments (Rontani et al, 2012(Rontani et al, , 2017, despite the low temperatures. The autoxidation of IP 25 in sediments possessing a thick oxic layer, where the contact of ice algal detritus with oxygen may be relatively long, therefore represents a viable degradation pathway of this biomarker in near-surface sediments.…”

Section: Degradation Of Ip 25 Epi-brassicasterol and 24methylenechomentioning

confidence: 99%

“…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). Indeed, the latter mechanism has recently been observed in sinking particles dominated by ice algae (Amiraux et al, 2017) and in particles discharged from the Mackenzie River (Galeron et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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

Rontani

Belt

Amiraux

2018

Organic Geochemistry

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The organic geochemical IP 25 (Ice Proxy with 25 carbon atoms) has been used as a proxy for Arctic sea ice in recent years. To date, however, the role of degradation of IP 25 in Arctic marine sediments and the impact that this may have on palaeo sea ice reconstruction based on this biomarker have not been investigated in any detail. Here, we show that IP 25 may be susceptible to autoxidation in near-surface oxic sediments. To arrive at these conclusions, we first subjected a purified sample of IP 25 to autoxidation in the laboratory and characterised the oxidation products using high resolution gas chromatography-mass spectrometric methods. Most of these IP 25 oxidation products were also detected in near-surface sediments collected from Barrow Strait in the Canadian Arctic, although their proposed secondary oxidation and the relatively lower abundances of IP 25 in other sediments probably explain why we were not able to detect them in material from other parts of the region. A rapid decrease in IP 25 concentration in some near-surface Arctic marine sediments, including examples presented here, may potentially be attributed to at least partial degradation, especially for sediment cores containing relatively thick oxic layers representing decades or centuries of deposition. An increase in the ratio of two common phytoplanktonic sterols-epi-brassicasterol and 24-methylenecholesterol-provides further evidence for such autoxidation reactions given the known enhanced reactivity of the latter to such processes reported previously. In addition, we provide some evidence that biodegradation processes also act on IP 25 in Arctic sediments. The oxidation products identified in the present study will need to be quantified more precisely in downcore records in the future before the effects of degradation processes on IP 25-based palaeo sea ice reconstruction can be fully understood. In the meantime, a brief overview of some previous investigations of IP 25 in relatively shallow Arctic marine sediments suggests that overlying climate conditions were likely dominant over degradation processes, as evidenced from often increasing IP 25 concentration downcore, together with positive relationships to known sea ice conditions.

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“…A climate-change-mediated shift in primary producers would thus impact the structure and function of the sea floor community, which is strongly dependent upon the deposition of organic material from the overlying water column for its energy requirements (McMahon et al, 2006). Moreover, under the effect of global warming the carbon sink potential of ice algae (resulting from their strong aggregation and the stress state of their associated bacteria, should be gradually replaced by the carbon source potential of open water phytoplankton (weakly aggregated and mineralized before the bottom) (Amiraux et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Use of palmitoleic acid and its oxidation products for monitoring the degradation of ice algae in Arctic waters and bottom sediments

Rontani

Amiraux

Lalande

et al. 2018

Organic Geochemistry

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Degradation of palmitoleic acid (C 16:1x7), the main fatty acid component of sea ice-associated (sympagic) diatoms, was monitored in Arctic sea ice at the beginning of ice melting and in the underlying sinking particles and superficial bottom sediments. In sea ice, degradation of sympagic algae involved biotic oxidation induced by 10S-DOX-like lipoxygenase of unknown salinity-stressed attached bacteria, while photo-and autoxidation were limited. In the water column, strong hydratase and Z/E isomerase activity were observed. Hydration of unsaturated fatty acids seems to be a detoxification strategy, which is essential for bacterial survival when associated with free fatty acid-rich environments such as ice algae. In contrast, Z/E isomerisation of palmitoleic acid was attributed to the release of Fe 2+ ions during radicalinduced damage of the active site of the bacterial 10S-DOX-like lipoxygenase and Z/E isomerases. Due to the poor physiological state of their attached bacteria resulting from salinity stress in brine channels or toxicity of free ice algae fatty acids, sympagic algae appeared to be only very weakly biotically degraded within the water column. In bottom sediments, free radicals resulting from 10S-DOX-like lipoxygenase activity induced a strong autoxidation of the ice algal material. The presence in bottom sediments of a significant proportion of oxidation products resulting from 10S-DOX-like lipoxygenase activity attested to the strong contribution of sea ice-derived OM released during the early stages of ice melt prior to deposition in the sediments. However, on the basis of the highest fatty acid photooxidation state observed in these sediments, an additional contribution of highly photooxidized material (ice algal material released at the end of ice melting or open water phytoplankton) seems likely. The degradation of hydroperoxides, resulting from biotic and abiotic degradation of palmitoleic acid, appeared to involve: (i) homolytic cleavage of the peroxyl group affording the corresponding hydroxy-and oxoacids, (ii) reduction to the corresponding hydroxyacids by peroxygenases, (iii) heterolytic proton-catalysed cleavage and (iv) conversion to allylic 1,4-diols by diol synthases and hydroperoxide isomerases.

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Monitoring photo-oxidative and salinity-induced bacterial stress in the Canadian Arctic using specific lipid tracers

Abstract: Monitoring photooxidative and salinity-induced bacterial stress in the Canadian Arctic using specific lipid tracers,

Cited by 20 publications

References 75 publications

Seasonal and latitudinal variations in sea ice algae deposition in the Northern Bering and Chukchi Seas determined by algal biomarkers

Seasonal and latitudinal variations in sea ice algae deposition in the Northern Bering and Chukchi Seas determined by algal biomarkers

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

Use of palmitoleic acid and its oxidation products for monitoring the degradation of ice algae in Arctic waters and bottom sediments

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