The molecular distribution of combined aldoses in sinking particles in various oceanic conditions

Abstract : Sinking particles were collected from different marine locations in the Southern Indian Ocean, Mediterranean Sea, and the upwelling (UPW) zone of Agadir Morocco using free-floating sediment traps set from 50 to 300 m. Aldose composition was determined using high-performance anion-exchange chromatography with pulsed amperometric detection following hydrolysis in 0.1 M HCl. Carbohydrate yields (PCHO-C/POC%) and C:N ratios were higher in the Mediterranean Sea samples (PCHO-C/ POC= 12.9 +/- 8.4%; C:N ratios=8.3 +/- 1.6; n=11) than in samples from the Southern Indian Ocean (PCHO-C/POC=3.6 +/-0.94%; C:N ratios=5.7 +/-0.59, n=7), indicating compositional differences in the bulk and sugar content of the collected particles. The molecular composition revealed that glucose was the most abundant monosaccharide in the Mediterranean Sea and upwelling zone samples (22-51 wt.% of the total aldoses), whereas ribose (17-39 wt.%) and galactose (10-27 wt.%) were the predominant aldoses in the Southern Indian Ocean samples. Similarly, deoxysugars (fucose+rhamnose) calculated on glucose-free basis were more abundant in particles from the Mediterranean Sea (18.8 +/- 5.6 wt.%, n=12) than those from the Southern Ocean samples (8.4 +/- 3.5 wt.%, n=7). These results suggest a non-uniform chemical composition of upper ocean sinking particles among oceanic provinces in terms of carbon, nitrogen, and sugar content. Such differences might be due to various biological species encountered in surface waters and/or to different status of degradation of recently produced sinking particles between Southern Ocean and Mediterranean Sea during the sampling periods. These results suggest that both high PCHO-C yields and high relative abundance of glucose do not necessarily reflect the presence of fresh material as hitherto assumed. A more extensive study at the molecular level is necessary in order to understand the distribution of sugars in different oceanic regimes.
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Christos Panagiotopoulos, Richard Sempere. The molecular distribution of combined aldoses in sinking particles in various oceanic conditions. Marine Chemistry, Elsevier, 2005, 95 (1-2), pp.31-49. ⟨10.1016/j.marchem.2004.07.005⟩. ⟨hal-00812050⟩



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