https://repository.kopri.re.kr/handle/201206/5505 2026-04-17T07:05:15Z https://repository.kopri.re.kr/handle/201206/10610 Title: Paleoproductivity in the SW Pacific Ocean During the Early Holocene Climatic Optimum Authors: Bostock, H. C.; Prebble, J. G.; Cortese, G.; Hayward, B.; Calvo, E.; Quiros-Collazos, L.; Kienast, M.; Kim, Kitae Abstract: The oceans are warming, but it is unclear how marine productivity will be affected under future climate change. In this study we examined a wide range of paleoproductivity proxies along a latitudinal transect (36-58 degrees S) in the SW Pacific during the early Holocene climatic optimum, to explore regional patterns of productivity in a slightly warmer-than-present world. During the early Holocene there is a small increase in productivity in the subtropical waters, no change at the subtropical frontal zone, and conflicting evidence in records immediately south of the subtropical front, where an increase is inferred from one core site, but not at the other. Evidence for an increase in productivity in Antarctic Surface Waters, south of the polar front, is also equivocal. We infer a small increase in productivity in subtropical waters, and the ocean just south of the subtropical front was associated with changes in the ocean circulation of the SW Pacific, driven by changes in the Southern Hemisphere Westerly Winds split jet structure in this region. The relatively modest warming during the early Holocene climatic optimum in the SW Pacific indicates that this time period may provide an analog for future productivity for the midcentury (2055) under Intergovernmental Panel on Climate Change Representative Concentration Pathway 8.5 or for the end of the century (2100) under Representative Concentration Pathway 4.5. However, higher-resolution, downscaled models, with realistic Southern Hemisphere Westerly Winds, will be necessary to forecast future productivity for this oceanographically complex region. 2019-04-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/10974 Title: Clay Mineralogical Characteristics of Sediments Deposited during the Late Quaternary in the Larsen Ice Shelf B Embayment, Antarctica Authors: Jung, Jaewoo; Yoo, Kyu-Cheul; Lee, Kee-Hwan; Park, Young Kyu; Lee, Jae Il; Kim, Jinwook Abstract: Variations in grain size, clay mineral composition, and stable isotopes (delta C-13 and delta N-15) are closely linked to the sedimentary facies that reflect mineralogical and geochemical modification during the retreat and advance of the Larsen ice shelf. A whole round core of marine sediment (EAP13-GC17, 236 cm below the sea floor) was collected on the northwestern Larsen B embayment of the Antarctic Peninsula during a marine geological expedition (the ARA13 Cruise Expedition by the Korea Polar Research Institute, 2013). Four sedimentary facies (U1-U4) were clearly distinguishable: bioturbated sandy mud (open marine, U1), laminated sandy mud (sub-floating ice shelf, U2), sandy clay aggregates (deglacial, U3), and muddy diamictons (sub-glacial, U4), as well as interbedded silty. Clay minerals, including smectite, chlorite, illite, and kaolinite, were detected throughout the core. An increase in the clay mineral ratio of smectite/(illite + chlorite) was clearly observed in the open marine condition, which was strongly indicated by both a heavier isotopic composition of delta C-13 and delta N-15 (-24.4 parts per thousand and 4.3 parts per thousand, respectively), and an abrupt increase in Be-10 concentration (similar to 30 times). An increase in the average values of the crystal packet thickness of illite (similar to 1.5 times) in U1 also indicated sediments transported in open marine conditions. Based on the clay mineral composition in U1, the sediments are likely to have been transported from the Weddell Sea. The clay mineralogical assessments conducted in this region have significant implications for our understanding of paleodepositional environments. 2019-03-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/10972 Title: Glacial-interglacial records from sediments in Powell Basin, Antarctica Authors: Bak, Young-Suk; Yoo, Kyu-Cheul; Lee, Jae Il; Yoon, Ho Il Abstract: Palaeoenvironmental history is reconstructed from diatoms in two sediment cores, GC01-PW02 and GC03-PW02, recovered from Powell Basin, Antarctica. A total of 43 species belonging to 21 genera are identified from GC01-PW02. A total of 61 species belonging to 27 genera are identified from GC03-PW02. The number of diatom valves g-1 of dry sediment ranges from 0.1？48.3 ×106 valves g-1. Based on diatom abundance, six assemblage zones were identified from GC01-PW02, and five diatom zones were identified from GC03-PW02. Barren intervals represent glacial periods, while intervals with higher diatom abundances were deposited during interglacial periods and reduced sea ice cover. The occurrence of Rouxia leventerae only within the deepest zone of each of the cores indicates that the core sediments were deposited since marine isotope stage (MIS) 6. 2018-12-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/9530 Title: Genomic Insight Into the Predominance of Candidate Phylum Atribacteria JS1 Lineage in Marine Sediments Authors: Chun, Jongsik; Lee, Hong Kum; Shin, Seung Chul; Hong, Soon Gyu; Choi, Hakkyum; Noh, Hyun-Ju; Kim, Mincheol; Hwang, Chung Yeon; Lee, Jae Il; Hwang, Kyuin; Lee, Yung Mi Abstract: Candidate phylum Atribacteria JS1 lineage is one of the predominant bacterial groups in anoxic subseafloor sediments, especially in organic-rich or gas hydrate-containing sediments. However, due to the lack of axenic culture representatives, metabolic potential and biogeochemical roles of this phylum have remained elusive. Here, we examined the microbial communities of marine sediments of the Ross Sea, Antarctica, and found candidate phylum Atribacteria JS1 lineage was the most abundant candidate phylum accounting for 9.8？40.8% of the bacterial communities with a single dominant operational taxonomic unit (OTU). To elucidate the metabolic potential and ecological function of this species, we applied a single-cell genomic approach and obtained 18 single-cell amplified genomes presumably from a single species that was consistent with the dominant OTU throughout the sediment. The composite genome constructed by co-assembly showed the highest genome completeness among available Atribacteria JS1 genomes. Metabolic reconstruction suggested fermentative potential using various substrates and syntrophic acetate oxidation coupled with hydrogen or formate scavenging methanogens. This metabolic potential supports the predominance of Atribacteria JS1 in anoxic environments expanding our knowledge of the ecological function of this uncultivated group. 2018-11-29T00:00:00Z