https://repository.kopri.re.kr/handle/201206/13386 2026-03-05T19:33:49Z https://repository.kopri.re.kr/handle/201206/16187 Title: Microbially-mediated reductive dissolution of Fe-bearing minerals during freeze-thaw cycles Authors: Kim Jinwook; Park Young Kyu; Koo Tae-hee; Jung Jaewoo; Kang Insung; Kim, Kitae; Park Hanbeom; Yoo, Kyu-Cheul; Rosenheim Brad E.; Conway Tim M. Abstract: Constraining the role of microbes in the structural iron (Fe) reduction of iron-bearing minerals improves our understanding of sediments and ice sheets as a source of dissolved Fe (dFe) to the oceans. However, bio-mediated structural Fe-reduction has yet to be studied in cryospheric environments. Here, we show that the Fe reducing psychrophile bacterium Shewanella vesiculosa, isolated from sea ice in Antarctica, reduced structural Fe in nontronite (NAu-2) and maghemite (gamma-Fe 2 O 3 ), common mineral phases in glacial ice, and marine sediments in Antarctica, during two freeze-thaw cycles (-10 degrees C to +15 degrees C), resulting in the release of dFe. The modification of turbostratically disordered nontronite (ferric iron dominant phase) to discrete ordered illite-like structure (ferrous iron dominant phase), and the aggregation of altered small maghemite particles with neoformation of vivianite (Fe 3 (PO 4 ) 2 & sdot;nH 2 O) indicated the microbially induced reductive dissolution of nontronite and maghemite, respectively. The biotic Fe-reduction gradually decreased and ceased as the temperature approached freezing (-8 degrees C), however the rection reactivated in the thawing cycle (-7 to +15 degrees C). No discernable biotic Fereduction was measured for either mineral under freezing conditions, suggesting that temperature limits the activity of the microbes. Further, and regardless of temperatures during two freeze-thaw cycles, Fe-reduction was not observed in abiotic control. Overall, these results highlight the importance of microbially induced Fe reduction during seasonal freeze-thaw cycles of ice and sediments in continuous supplying bioavailable dFe to cryospheric environments and the often Fe-limited polar oceans. 2024-05-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/16221 Title: Elemental composition of smectite minerals in continental rise sediments from the Amundsen Sea, West Antarctica, as a tool to identify detrital input from various sources throughout late Quaternary glacial-interglacial cycles Authors: Park,Young Kyu; Claus-Dieter Hillenbrand; Werner Ehrmann; Park, Hanbeom; Julia S. Wellner; Jennifer R. Horrocks; Kim, Jinwook Abstract: Detrital smectite is a ubiquitous clay mineral in marine sediments and has a variable total Fe, Al, and Mg composition depending on the source, i.e., bedrock or unconsolidated sedimentary strata, the smectite is derived from. Analyses of elemental composition of smectite minerals in marine sediments can help to differentiate the smectite sources and, thus, sediment provenance, with potentially far-reaching paleo-environmental implications. In this study, we investigated the smectite compositions of modern-latest Holocene seafloor surface sediments deposited offshore from the Amundsen Sea drainage sector, where the West Antarctic Ice Sheet is currently unstable and losing mass due to ocean-forced melting, to detect and understand the variabilities of their elemental composition and geographical distribution. The smectite composition in continental rise sediments was compared to that of potential source areas on the Amundsen Sea continental shelf and in the sub-Antarctic South Pacific basin. Furthermore, we analyzed the smectite composition of sediments in continental rise cores deposited during the last glacial and last interglacial periods to reconstruct source variations over glacialinterglacial cycles. In particular, high contents of Al？Fe-rich smectite indicate that the glacial sediments had been supplied from the coastal region around Pine Island Bay by the cross-shelf advance of the West Antarctic Ice Sheet during the last glacial period. This clearly contrasts with the smectite minerals in rise sediments deposited during the present and the last interglacial periods that are composed of two distinct smectite types (Mg-rich and Al-rich, respectively), indicating their supply from multiple sources. During interglacials, Mg-rich smectite is probably transported by Circumpolar Deep Water from the sub-Antarctic South Pacific basin to the continental rise, while Al-rich smectite is supplied as part of ice rafted debris and by marine currents from the coasts around the Amundsen Sea embayment. Our research demonstrates that analysis of the elemental composition of smectite minerals on the Amundsen Sea continental margin provides a valuable tool to trace variations in sources for detrital sediment components and their pathways throughout glacial-interglacial cycles. 2024-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/14504 Title: Ice sheet retreat and ocean circulation in West Antarctica during the past warm periods Authors: Yoo, Kyu-Cheul 2023-07-26T00:00:00Z https://repository.kopri.re.kr/handle/201206/14531 Title: The study of reconstruction of paleo-depositional condition and biogeochemical alteration using clay minerals in marine sediments distributed in glacial retreating area West Antarctica Authors: Kim, Jinwook 2023-07-26T00:00:00Z