A004-0008
Geographic distribution of marine bioaerosols and roles of biological gel particles over the Arctic Ocean

Monday, 7 December 2020
Poster
Kaori Kawana1, Fumikazu Taketani2, Kazuhiko Matsumoto1, Takuma Miyakawa1, Yutaka Tobo3, Yoko Iwamoto4, Akinori Ito1 and Yugo Kanaya2, (1)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan, (2)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Research Institute for Global Change, Kanagawa, Japan, (3)NIPR National Institute of Polar Research, Meteorology and Glaciology Group, Tokyo, Japan, (4)Hiroshima University, Graduate School of Integrated Sciences for Life, Higashi-Hiroshima, Japan
Abstract:
Marine bioaerosols are uplifted from the sea surface to the atmosphere by wind and they could drive climate change via cloud processes by acting as cloud condensation nuclei (CCN) and ice-nucleating particles (INP). Nevertheless, distribution of biological particles over the ocean surface, air-sea interaction, and roles in the cloud system are still unknown.

Cruise observation was conducted on R/V MIRAI from 28 Sep to 10 Nov, 2019, over the Arctic Ocean, Bering Sea and North Pacific. During the cruise, bioaerosol particles were identified with an online waveband integrated bioaerosol sensor (WIBS-4). An offline method based on DNA stained fluorescence was also utilized for the sampled seawater and ambient air. Additionally, gel particles originating from marine biota, i.e., the polysaccharidic transparent exopolymer particles (TEP) and the proteinaceous Coomassie stainable particles (CSP), were extracted from surface seawater and quantified. Using these comprehensive data, we discuss (1) relationship between bioaerosols and oceanic biological activity underlining air-sea interaction and (2) geographic distribution of number concentrations of marine bioaerosols and their florescence pattern.

TEP and CSP both increased in the Bering Sea and decreased in the Arctic Ocean, having positive correlations to each other (R: 0.75) and also with the Chl-a concentrations (R: 0.86 and 0.59 for TEP and CSP, respectively). The number concentration of ambient florescence particles was ~20-30 in the Bering Sea and also was low in the Arctic Ocean. The chemical analysis of ambient particles collected with a high-volume air sampler revealed that the mass fraction of Inorganic salts (sodium chloride, sulfate) was dominant (>0.7), especially in the Arctic Ocean (~0.9), while the rest portion was organics. The mass fraction of insoluble OC was elevated to ～6% in the Bering sea and Arctic Ocean when the abundance of TEP and CSP were large. The ambient fluorescence particles increased with the large wind speed, suggesting that insoluble biological particles present in the surface seawater were uplifted by wind to form ambient bioaerosols, acting as CCN and INPs. In the presentation, the role of bioaerosols for activation in the cloud processes will be discussed based on the observed CCN and INP properties.

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