https://repository.kopri.re.kr/handle/201206/9711 2026-04-21T15:56:29Z https://repository.kopri.re.kr/handle/201206/13007 Title: Spectral Characterization of Dissolved Organic Matter in Seawater and Sediment Pore Water from the Arctic Fjords (West Svalbard) in Summer Authors: Chen, Meilian; Kim, Ji-Hoon; Hong, Sungwook; Lee, Yun Kyung; Kang, Moo Hee; Jin, Young Keun; Hur, Jin Abstract: Fjords in the high Arctic, as aquatic critical zones at the interface of land-ocean continuum, are undergoing rapid changes due to glacier retreat and climate warming. Yet, little is known about the biogeochemical processes in the Arctic fjords. We measured the nutrients and the optical properties of dissolved organic matter (DOM) in both seawater and sediment pore water, along with the remote sensing data of the ocean surface, from three West Svalbard fjords. A cross-fjord comparison of fluorescence fingerprints together with downcore trends of salinity, Cl-, and PO43- revealed higher impact of terrestrial inputs (fluorescence index: similar to 1.2-1.5 in seawaters) and glaciofluvial runoffs (salinity: similar to 31.4 +/- 2.4 psu in pore waters) to the southern fjord of Hornsund as compared to the northern fjords of Isfjorden and Van Mijenfjorden, tallying with heavier annual runoff to the southern fjord of Hornsund. Extremely high levels of protein-like fluorescence (up to similar to 4.5 RU) were observed at the partially sea ice-covered fjords in summer, in line with near-ubiquity ice-edge blooms observed in the Arctic. The results reflect an ongoing or post-phytoplankton bloom, which is also supported by the higher levels of chlorophyll a fluorescence at the ocean surface, the very high apparent oxygen utilization through the water column, and the nutrient drawdown at the ocean surface. Meanwhile, a characteristic elongated fluorescence fingerprint was observed in the fjords, presumably produced by ice-edge blooms in the Arctic ecosystems. Furthermore, alkalinity and the humic-like peaks showed a general downcore accumulation trend, which implies the production of humic-like DOM via a biological pathway also in the glaciomarine sediments from the Arctic fjords. 2021-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/10966 Title: Seasonal differences in dissolved organic matter properties and sources in an Arctic fjord: Implications for future conditions Authors: Brogi, Simona Retelletti; Jung, Jinyoung; Ha, Sun-Yong; Hur, Jin Abstract: The Arctic Ocean is undergoing drastic changes due to the effects of climate change. Arctic fjords are preferred systems to study these changes as they respond quickly to variations in ocean, land and atmosphere conditions. In this study, we investigated for the first time the seasonal variability of dissolved organic matter (DOM) properties and its origin in an Arctic fjord, which allows for an assessment of the future potential effects of climate change in this environment. We conducted an integrated analysis of the concentrations, optical properties (absorption and fluorescence), and molecular size distributions of DOM in two seasons (October 2017 and April 2018) and in eight to ten stations in Kongsfjorden (Svalbard) along with the related environmental parameters such as chlorophyll-a, inorganic nutrients, particulate organic carbon (POC), temperature, and salinity. Our results showed that, in both seasons, the DOM in the fjord was predominately of autochthonous origin with a seasonally variable terrestrial input. The dissolved organic carbon (DOC) concentrations were consistently higher in October than in April at each station. Fluorescence spectroscopy revealed a marked seasonal variability depending on the DOM fluorophore types and size fractions. In October, humic-like and tryptophan-like substances were dominantwhereas in April, tyrosine-like compounds represented, on average, 58% of the DOMfluorescence. This study points out the key role of spring sea ice melting in determining the DOM properties of the fjord in spring. 2019-12-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/10965 Title: Discriminative biogeochemical signatures of methanotrophs in different chemosynthetic habitats at an active mud volcano in the Canadian Beaufort Sea Authors: Lee, Dong-Hun; Lee, Yung Mi; Kim, Junghyun; Jin, Young Keun; Paull, Charles; Niemann, Helge; Kim, Ji-Hoon; Shin, Kyung-Hoon Abstract: Several mud volcanoes are active in the Canadian Beaufort Sea. In this study, we investigated vertical variations in methanotrophic communities in sediments of the mud volcano MV420 (420 m water depth) by analyzing geochemical properties, microbial lipids, and nucleic acid signatures. Three push cores were collected with a remotely operated vehicle from visually discriminative habitats that were devoid of megafauna and/microbial mats (DM) to the naked eye, covered with bacterial mats (BM), or colonized by siboglinid tubeworms (ST). All MV420 sites showed the presence of aerobic methane oxidation (MOx)- and anaerobic methane oxidation (AOM)-related lipid biomarkers (4 alpha-methyl sterols and sn-2-hydroxyarchaeol, respectively), which were distinctly different in comparison with a reference site at which these compounds were not detected. Lipid biomarker results were in close agreement with 16S rRNA analyses, which revealed the presence of MOx-related bacteria (Methylococcales) and AOM-related archaea (ANME-2 and ANME-3) at the MV420 sites. 4 alpha-methyl sterols derived from Methylococcales predominated in the surface layer at the BM site, which showed a moderate methane flux (0.04 mmol cm(-2)y(-1)), while their occurrence was limited at the DM (0.06 mmol cm(-2)y(-1)) and ST (0.01 mmol cm(-2)y(-1)) sites. On the other hand, C-13-depleted sn-2-hydroxyarchaeol potentially derived from ANME-2 and/or ANME-3 was abundant in down-core sediments at the ST site. Our study indicates that a niche diversification within this mud volcano system has shaped distinct methanotrophic communities due to availability of electron acceptors in association with varying degrees of methane flux and bioirrigation activity. 2019-11-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/10903 Title: An observation of primary production enhanced by coastal upwelling in the southwest East/Japan Sea Authors: Hahm, Doshik; Rhee, Tae Siek; Kim, Hyun-cheol; Jang, Chan Joo; Kim, Yong Sun; Park, Jae-Hun Abstract: Coastal upwelling (CU) is an important process that causes changes in physical and chemical properties, resulting in variation of biological processes in a coastal area. In the southwestern part of the East/Japan Sea (SWES), CU has been alleged as one of the mechanisms responsible for higher net primary production (NPP) than the rest of the East/Japan Sea. We provide, for the first time, high spatial resolution underway observations of sea surface temperature, salinity, chlorophyll-a fluorescence and Delta(O-2/Ar), revealing the physical and biological characteristics of the upwelled waters in the SWES. The cold, upwelled waters retained high fluorescence and Delta(O-2/Ar), consistent with enhanced phytoplankton biomass and biological O-2 production by CU. The net community production (NCP) in the ambient and upwelled waters were 33 +/- 19 and 77 +/- 41 mmol O-2 m(-2) d(-1), respectively. The latter should be considered as a lower bound, containing a significant fraction of low O-2 waters from subsurface. Satellite observation indicated that NPP in the upwelled waters were higher than the ambient waters by 51%. This implies that up to half of higher NPP in the SWES than the rest of the East/Japan Sea can be ascribed to CU events. 2019-07-01T00:00:00Z