| Summary: | The sea-surface microlayer (SML) is the oceanic boundary to the atmosphere that mediates climate relevant processes like gas exchange and primary organic aerosols (POA) emission. In highly productive periods, POA can include marine gels that originate from phytoplankton exudates, and accumulate in the SML. During the 2012 sea ice minimum, total and dissolved organic carbon and amino acids, polysaccharidic and proteinaceous gels and their SML-enrichment were investigated in pack-ice melt ponds, at the ice edge and in open water north of 80°N. Based on carbon-normalized amino acids yields, more labile organic matter coincided with low-salinity ponds, where ice melting promoted a freshening of seawater. Higher salinities favored the abundance of bacteria and gels in the SML. Small particles (0.4–1.25 µm), largely proteinaceous and potentially relevant as POA precursors, dominated up to 85% of total gels abundance. We suggest that the organic composition of arctic microlayers, reflect the microbial turnover of organic matter and is likely to be affected by sea ice retreat. We discuss potential consequences on air-sea gas exchange and POA dynamics in the future Arctic Ocean.
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