Physical Process Controlling the Surface Bacterial Community Composition in the Ulleung Basin of East Sea

Abstract

Although environmental drivers are known to shape the abundance and distribution of bacterial communities in the East Sea, the effects of physical processes have not been directly studied. Here, we aimed to examine the influences of water mass mixing (summer) and eddy circulation (winter) on the surface bacterial communities of the Ulleung Basin (UB), East Sea, based on the metagenomic approach. Overall, 490,087 operational taxonomic units (OTUs) were identified from five stations, and prokaryotic abundance was dominant at all stations in both seasons. Among the prokaryotes, most OTUs were affiliated with Proteobacteria, Cyanobacteria, Flavobacteria, and Actinobacteria during summer and winter. Bacterial communities were found to differ with water masses (Changjiang, Tsushima, and North Korea surface water) and eddy circulation, and were strongly correlated with environmental variables, suggesting specific bacterial community responses with specific seasonal physicochemical parameters. Our investigation indicates that together with distance and environment, advection shapes the UB bacterial community composition, helping us better understand the physical cues related to biological composition in the East Sea. However, further studies are needed to ascertain the role of microbial functional genes along with the advection of oceanographic processes in the East Sea to better understand the regional biogeochemical processes.

Water mass structure determine the prokaryotic community and metabolic pattern in the Korea Strait during fall 2018 and 2019

“…Unlike in 2018, stations 1 and 2 in the UL of 2019 showed the different temperature (Figure 2E) and lower range of S (<32 PSU) than those observed at the same stations in 2018 (>33 PSU) (Figures 2B, F). This low-S water indicates FW influence from the Changjiang Diluted Water (CDW) from the East China Sea (ECS) (Figure S1) (Chang and Isobe, 2003;Gomes et al, 2018;Kim et al, 2022;Yoon et al, 2022). Similar to the S variation, the UL T in the fall of 2019 was higher (21.76-24.26°C) than that observed in the fall of 2018.…”

“…Compared to UL 2018, the UL 2019 (Sts. 1-2) exhibited low-S waters (S<32.0 PSU), indicating a FW effect from the CDW from the ECS (Chang and Isobe, 2003;Gomes et al, 2018;Kim et al, 2022). The Changjiang River has the world's third largest and the fifthlargest in FW discharge (Beardsley et al, 1985).…”

“…Regarding bacterial dynamics in KS, there have been few studies on organic matter production as a result of changes in hydrographic conditions (Chung and Kang, 1995;Kang and Kang, 2002). Lee and Choi (2021) and Kim et al (2022) showed that the composition of distinct water masses in the East Sea's Ulleung basin, i.e., TWW, has a major impact on bacterial production and diversity. Similarly, Ichinomiya et al (2019) found that fluctuations in T and S of the TWW in the northern Japan basin significantly influence microbial abundance and diversity.…”

Metagenomic data from surface seawater of the east coast of South Korea

“…Previous microbial investigations in the East Sea have primarily concentrated on the deep-sea sediments or methane hydrate-containing sediments 26 – 29 . In addition, a metagenomic study has been undertaken to assess the influence of environmental determinants on the spatial distribution of pelagic bacteria in the East Sea, albeit limited to a bimonthly scale during the summer and winter months 30 .…”