On the chemical dynamics of extracellular polysaccharides in the high Arctic surface microlayer

• Published in: Ocean Science
• Main Authors: Gao, Qiuju, Leck, Caroline, Rauschenberg, Carlton, Matrai, Patricia A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Meteorologiska institutionen (MISU) 2012
• Subjects: Surface microlayer; Biogenic microcolloids; Extracellular polymeric secretions (EPS); Polymer microgels; Polysaccharides; Carbohydrates; central Arctic Ocean; Meteorology and Atmospheric Sciences; Meteorologi och atmosfärforskning; Arctic; Arctic Ocean
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-72513; https://doi.org/10.5194/os-8-401-2012

The surface microlayer (SML) represents a unique system of which the physicochemical characteristics may differ from those of the underlying subsurface seawater (SSW). Within the Arctic pack ice area, the SML has been characterized as enriched in small colloids of biological origin, resulting from extracellular polymeric secretions (EPS). During the Arctic Summer Cloud-Ocean Study (ASCOS) in August 2008, particulate and dissolved organic matter (POM, DOM) samples were collected and chemically characterized from the SML and the corresponding SSW at an open lead centered at 87.5° N and 5°E. Total organic carbon was persistently enriched in the SML with a mean enrichment factor (EF) of 1.45 ± 0.41, whereas sporadic depletions of dissolved carbohydrates and amino acids were observed. Monosaccharide compositional analysis reveals that EPS in the Arctic lead was formed mainly of distinctive heteropolysaccharides, enriched in xylose, fucose and glucose. The mean concentrations of total hydrolysable neutral sugars in SSW were 94.9 ± 37.5 nM in high molecular weight (HMW) DOM and 64.4 ± 14.5 nM in POM. The enrichment of polysaccharides in the SML appeared to be a common feature, with EFs ranging from 1.7 to 7.0 for particulate polysaccharides and 3.5 to 12.1 for polysaccharides in the HMW DOM fraction. A calculated monosaccharide yield suggests that polymers in the HMW DOM fraction were scavenged, without substantial degradation, into the SML. Bubble scavenging experiments showed that newly aggregated particles could be formed abiotically by coagulation of low molecular weight nanometer-sized gels. Experimentally-generated aerosol particles were enriched in polysaccharides by factors of 22-70, relative to the source seawater. We propose that bubble scavenging of surface-active polysaccharides was one of the possible mechanisms for the enrichment of polysaccharides in the SML. First published in Ocean Sci. Discuss., 9, 215–259, 2012, www.ocean-sci-discuss.net/9/215/2012/, doi:10.5194/osd-9-215-2012