Evidence for significant protein-like dissolved organic matter accumulation in Sea of Okhotsk sea ice

• Published in: Annals of Glaciology
• Main Authors: Granskog, Mats A., Nomura, Daiki, Müller, Susann, Krell, Andreas, Toyota, Takenobu, Hattori, Hiroshi
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press
• Subjects: sea ice; sea-ice ecology; 660; Okhotsk; Annals of Glaciology; okhotsk sea; Sea ice
• Online Access: http://hdl.handle.net/2115/70587; https://doi.org/10.3189/2015AoG69A002

Absorption and fluorescence of chromophoric dissolved organic matter (CDOM) in sea ice and surface waters in the southern Sea of Okhotsk was examined. Sea-water CDOM had featureless absorption increasing exponentially with shorter wavelengths. Sea ice showed distinct absorption peaks in the ultraviolet, especially in younger ice. Older first-year sea ice had relatively flat absorption spectra in the ultraviolet range. Parallel factor analysis (PARAFAC) identified five fluorescent CDOM components, two humic-like and three protein-like. Sea water was largely governed by humic-like fluorescence. In sea ice, protein-like fluorescence was found in considerable excess relative to sea water. The accumulation of protein-like CDOM fluorescence in sea ice is likely a result of biological activity within the ice. Nevertheless, sea ice does not contribute excess CDOM during melt, but the material released will be of different composition than that present in the underlying waters. Thus, at least transiently, the CDOM introduced during sea-ice melt might provide a more labile source of fresher protein-like DOM to surface waters in the southern Sea of Okhotsk.