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Sanial V, van Beek P, Lansard B, Souhaut M, Kestenare E, d'Ovidio F, Zhou M, Blain S, . (2015). Use of Ra isotopes to deduce rapid transfer of sediment-derived inputs off Kerguelen
. Biogeosciences, 12(5), 1415–1430.
Abstract: KEOPS-2 Special Issue
Programme: 1077
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Jean-François Rontani, Rémi Amiraux, Catherine Lalande, Marcel Babin, Hak-Ryul Kim, Simon T. Belt. (2018). Use of palmitoleic acid and its oxidation products for monitoring the degradation of ice algae in Arctic waters and bottom sediments (Vol. 124).
Abstract: Degradation of palmitoleic acid (C16:1ω7), 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 Fe2+ ions during radical-induced 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.
Keywords: Arctic Biotic and abiotic degradation Palmitoleic acid Sea ice Sinking particles Superficial bottom sediments Sympagic algae
Programme: 1164
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Dobson S. & Jouventin P. (2003). Use of nest-site as a rendezvous in Pinguins. Colonial waterbirds, 26, 409–415.
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Collins, T., Hoyoux, A., Dutron, A., Georis, J., Genot, B., Dauvrin, T., Arnaut, F., Gerday, C. & Feller G. (2006). Use of glycoside hydrolase family 8 xylanases in baking. J. Cereal Sci, 43, 79–84.
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Buguet A., Couturier P., Martin J.Y., Montmayeur A., Fidier N., Roux A., Argentier A.M., Revillon G., Heyward B. & Franco A. (1995). Use of an actigraphic over-mattress to record body movements. JOURNAL OF SLEEP RESEARCH, 24A, 464.
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Barraclough D.R., Williams L. & Quinn J.M. (1992). US/UK candidates for the definitive geomagnetic reference field modelDGRF-85 and the predictive geomagnetic reference field model IGRF-90. J. geomag. geoelectr., 44, 719–734.
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Margaux Gourdal, Odile Crabeck, Martine Lizotte, Virginie Galindo, Michel Gosselin, Marcel Babin, Michael Scarratt, Maurice Levasseur. (2019). Upward transport of bottom-ice dimethyl sulfide during advanced melting of arctic first-year sea ice (Vol. 7).
Abstract: This paper presents the first empirical estimates of dimethyl sulfide (DMS) gas fluxes across permeable sea ice in the Arctic. DMS is known to act as a major potential source of aerosols that strongly influence the Earth’s radiative balance in remote marine regions during the ice-free season. Results from a sampling campaign, undertaken in 2015 between June 2 and June 28 in the ice-covered Western Baffin Bay, revealed the presence of high algal biomass in the bottom 0.1-m section of sea ice (21 to 380 µg Chl a L–1) combined with the presence of high DMS concentrations (212–840 nmol L–1). While ice algae acted as local sources of DMS in bottom sea ice, thermohaline changes within the brine network, from gravity drainage to vertical stabilization, exerted strong control on the distribution of DMS within the interior of the ice. We estimated both the mean DMS molecular diffusion coefficient in brine (5.2 × 10–5 cm2 s–1 ± 51% relative S.D., n = 10) and the mean bulk transport coefficient within sea ice (33 × 10–5 cm2 s–1 ± 41% relative S.D., n = 10). The estimated DMS fluxes ± S.D. from the bottom ice to the atmosphere ranged between 0.47 ± 0.08 µmol m–2 d–1 (n = 5, diffusion) and 0.40 ± 0.15 µmol m–2 d–1 (n = 5, bulk transport) during the vertically stable phase. These fluxes fall within the lower range of direct summer sea-to-air DMS fluxes reported in the Arctic. Our results indicate that upward transport of DMS, from the algal-rich bottom of first-year sea ice through the permeable sea ice, may represent an important pathway for this biogenic gas toward the atmosphere in ice-covered oceans in spring and summer.
Programme: 1164
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C.P. Legendre, L. Zhao and Q.-F. Chen. (2015). Upper-mantle shear-wave structure under East and Southeast Asia from Automated Multimode Inversion of waveforms. Geophys J Int, 203(1), 707–719 .
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Sieminski A., Debayle E. & Lévêque J.J. (2002). Upper-Mantle Shear-Velocity Structure Beneath Antarctica and Surrounding Regions From Waveform Inversion of Rayleigh Waves..
Abstract: AGU San Francisco
Programme: 906
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Williams G D, Hindell M, Houssais M-N, Tamura T, Field I C, . (2011). Upper ocean stratification and sea ice growth rates during the summer-fall transition, as revealed by Elephant seal foraging in the Adélie Depression, East Antarctica
. 1812-0784, 7(2), 185–202.
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