14 Jul 2022
14 Jul 2022
Status: this preprint is currently under review for the journal BG.

Spatial‐temporal distribution, photoreactivity and environmental control of dissolved organic matter in the sea-surface microlayer of the eastern marginal seas of China

Lin Yang1, Jing Zhang1,3, Anja Engel4, and Gui-Peng Yang1,2,3 Lin Yang et al.
  • 1Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China
  • 2Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China
  • 3Institute of Marine Chemistry, Ocean University of China, Qingdao 266100, China
  • 4GEOMAR Helmholtz Centre for Ocean Research, 24105 Kiel, Germany

Abstract. As the boundary interface between the atmosphere and ocean, the sea-surface microlayer (SML) plays a significant role in the biogeochemical cycles of dissolved organic matter (DOM) and macronutrients in marine environments. In our study, chromophoric DOM (CDOM), fluorescent DOM, dissolved organic carbon, chlorophyll a, picoplankton, nutrients, and bacteria were frequently enriched in the SML. We focus specifically on the optical properties in the SML, and we find that the enrichment factors (EFs) of tryptophan-like component 4 was significantly higher than other fluorescence components; the longer wavelength absorption values of CDOM showed higher EFs in the SML, and the more significant relationship between CDOM and Chl-a in the SML, indicating that autochthonous DOM was more frequently enriched in the SML than the terrestrial DOM. We find that higher EFs were generally observed in the SML in the off-shore regions than in the coastal regions, and CDOM in the SML is photobleached less after relatively strong irradiation, as also indicated by the lower percentages of humic-like DOM and lower specific UV absorbance values (SUVA254) in the SML than the subsurface water (SSW). In combination with the SSW, the elevated nutrients may stimulate phytoplankton growth, biological activity and then production of abundant fresh autochthonous DOM in the SML. Our results revealed a general enrichment model and the more autochthonous properties of DOM in the SML than the SSW for exploring the oceanic air-sea layer environment.

Lin Yang et al.

Status: open (until 01 Sep 2022)

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  • RC1: 'Comment on bg-2022-140', Liyang Yang, 13 Aug 2022 reply

Lin Yang et al.

Lin Yang et al.


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Short summary
EFs of DOM in the eastern marginal seas of China exhibited a significant spatiotemporal variation. Photochemical and enrichment processes co-regulated DOM enrichment in the SML. Autochthonous DOM was more frequently enriched in the SML than terrestrial DOM. DOM in the SSW exhibited higher aromaticity than that in the SML.