Kim Jung-Hyun

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Kim
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Jung-Hyun
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  • Article
    Diversity of Archaea and detection of crenarchaeotal amoA genes in the rivers Rhine and Têt
    (Inter-Research, 2009-04-28) Herfort, Lydie ; Kim, Jung-Hyun ; Coolen, Marco J. L. ; Abbas, Ben ; Schouten, Stefan ; Herndl, Gerhard J. ; Sinninghe Damste, Jaap S.
    Pelagic archaeal phylogenetic diversity and the potential for crenarchaeotal nitrification of Group 1.1a were determined in the rivers Rhine and Têt by 16S rRNA sequencing, catalyzed reported deposition-fluorescence in situ hybridization (CARD–FISH) and quantification of 16S rRNA and functional genes. Euryarchaeota were, for the first time, detected in temperate river water even though a net predominance of crenarchaeotal phylotypes was found. Differences in phylogenic distribution were observed between rivers and seasons. Our data suggest that a few archaeal phylotypes (Euryarchaeota Groups RC-V and LDS, Crenarchaeota Group 1.1a) are widely distributed in pelagic riverine environments whilst others (Euryarchaeota Cluster Sagma-1) may only occur seasonally in river water. Crenarchaeota Group 1.1a has recently been identified as a major nitrifier in the marine environment and phylotypes of this group were also present in both rivers, where they represented 0.3% of the total pelagic microbial community. Interestingly, a generally higher abundance of Crenarchaeota Group 1.1a was found in the Rhine than in the Têt, and crenarchaeotal ammonia monooxygenase gene (amoA) was also detected in the Rhine, with higher amoA copy numbers measured in February than in September. This suggests that some of the Crenarchaeota present in river waters have the ability to oxidize ammonia and that riverine crenarchaeotal nitrification of Group 1.1a may vary seasonally.
  • Article
    Unraveling Environmental Forces Shaping Surface Sediment Geochemical “Isodrapes” in the East Asian Marginal Seas
    (American Geophysical Union, 2024-04-04) Paradis, Sarah ; Diesing, Markus ; Gies, Hannah ; Haghipour, Negar ; Narman, Lena ; Magill, Clayton ; Wagner, Thomas ; Galy, Valier V. ; Hou, Pengfei ; Zhao, Meixun ; Kim, Jung-Hyun ; Shin, Kyung-Hoon ; Lin, Baozhi ; Liu, Zhifei ; Wiesner, Martin G. ; Stattegger, Karl ; Chen, Jianfang ; Zhang, Jingjing ; Eglinton, Timothy I.
    As major sites of carbon burial and remineralization, continental margins are key components of the global carbon cycle. However, heterogeneous sources of organic matter (OM) and depositional environments lead to complex spatial patterns in sedimentary organic carbon (OC) content and composition. To better constrain the processes that control OM cycling, we focus on the East Asian marginal seas as a model system, where we compiled extensive data on the OC content, bulk isotopic composition (δ13C and Δ14C), total nitrogen, and mineral surface area of surficial sediments from previous studies and new measurements. We developed a spatial machine learning modeling framework to predict the spatial distribution of these parameters and identify regions where sediments with similar geochemical signatures drape the seafloor (i.e., “isodrapes”). We demonstrate that both provenance (44%–77%) and hydrodynamic processes (22%–53%) govern the fate of OM in this margin. Hydrodynamic processes can either promote the degradation of OM in mobile mud-belts or preserve it in stable mud-deposits. The distinct isotopic composition of OC sources from marine productivity and individual rivers regulates the age and reactivity of OM deposited on the sea-floor. The East Asian marginal seas can be separated into three main isodrapes: hydrodynamically energetic shelves with coarser-grained sediment depleted in OC, OM-enriched mud deposits, and a deep basin with fine-grained sediments and aged OC affected by long oxygen exposure times and petrogenic input from rivers. This study confirms that both hydrodynamic processes and provenance should be accounted for to understand the fate of OC in continental margins.