Abstract
Antarctic shelf systems play an important role in organic matter circulation on Earth; hence, identifying the characteristics of dissolved organic matter (DOM) can be a good indicator for understanding its origin, as well as climate change. In this study, to identify the characteristics of DOM in the ice shelf systems, surface water was collected from the open sea (OS) and Marian cove (Fjord; FJ). Although there were no differences in DOM characteristics between sampling sites in quantitative analyses, the DOM in surface water of each region seemed to be more affected by terrestrial than marine biological sources in optical and molecular properties. This finding indicates that the terrestrial DOM related to mosses based on the molecular properties results; high levels of lipid-like (35–39%) and unsaturated hydrocarbon-like (UH; 27–34%) in both the OS and FJ regions, and significantly higher tannin-like substance and condensed aromatic structures (CAS) in the FJ than the OS region. When comparing the FJ transect samples, those nearest to a glacier (FJ1; 0.93 km from the glacier) showed relatively low salinity, high dissolved organic carbon (DOC), and high chromophoric DOM (CDOM), indicating that terrestrial DOM (possibly produced by moss) inflow occurred with the runoff from the freshly melting land ice and glacier. However, no significant differences in molecular composition were detected, suggesting that terrestrial DOM introduced into the ice shelf systems by melting land ice and glacier runoff could be a major source of DOM-rich seawater during austral fall, when low marine biological activity occurs. This study has a great significance as background data for DOM characteristics in the ice shelf systems due to the enhanced biological activity during the austral summer.
Highlights
The ice shelf systems in Antarctica are one of the important organic carbon reservoirs on Earth
We investigated the characteristics of dissolved organic matter (DOM) from the Antarctic surface seawaters using optical spectrometry and Orbitrap-mass spectrometry (MS) and obtained the following results:
The DOM in the Antarctic seawater was more affected by terrestrial than marine biological sources due to the lower marine biological activities in the austral fall. Both lipid-like and unsaturated hydrocarbon-like (UH)-like substances were dominant in the ice shelf systems of King George Island, which is believed to be the result of non-algal and terrestrial organisms such as cryptogams spread across Antarctica
Summary
The ice shelf systems in Antarctica are one of the important organic carbon reservoirs on Earth. Dissolved organic matter (DOM) in seawater is directly emitted from the seawater surface into the atmosphere via bubble bursting (i.e., primary marine aerosols or sea spray aerosols), leading to the production of organicrich particles in the atmosphere over the Antarctica and the Arctic (O’Dowd and De Leeuw, 2007; Rastelli et al, 2017; Park J. et al, 2019). These organic aerosols can constitute large fractions (approximately 80%) of the submicron particle mass during a phytoplankton bloom (Park et al, 2014; Park J. et al, 2019). The characterization of DOM in the Antarctic seawater can be a good indicator for understanding its origin as well as contribute to the understanding of marine ecosystem changes and climate change
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