https://repository.kopri.re.kr/handle/201206/5397 2026-04-21T15:37:09Z https://repository.kopri.re.kr/handle/201206/8458 Title: Fine-scale analysis of bacterial community structures in a sediment core of the Mendeleev Ridge in the western Arctic Ocean Authors: Nam, Seung-il; Han, Duk Ki; Lee, Yoo Kyung; Hwang, Chung Yeon; J. Matthiessen; R. Stein Abstract: Detailed sedimentological and organic-geochemical studies of marine sediments in high- latitude areas can yield important information on paleoenvironmental changes during the glacial-interglacial climate cycles. A sediment core (PS72/396-3GKG), taken from the Mendeleev Ridge in the western Arctic Ocean during the Polarstern Arctic expedition (ARK- 23/3) in 2008, was investigated to establish a precise chronostratigraphy using multi- proxies for reconstruction of glacial history and paleoenvironmental changes during the late Quaternary. Here, in a parallel study, we made an attempt to find if the change in bacterial communities within a relatively well-dated sediment core (spanning ca. 100 ka) could be used a proxy for drastic alterations in sedimentation conditions. Fine-scale distributions of bacterial community were examined using 454 pyrosequencing of the hypervariable regions of V1 to V3 of the 16S rRNA gene in a depth resolution of 1 cm from the surface to 33 cm. In 31 samples showing the success of polymerase chain reaction amplification, 87,015 sequence reads were obtained and clustered 2,532 different operational taxonomic units (OTUs) at the 97 % identity level. Four bacterial phyla including Firmicutes (31-49 %), Proteobacteria (10-39 %), Actinobacteria (20-34 %) and Bacteroidetes (3-7 %) were dominant near the surface (0-3 cm). In most samples below the surface, Firmicutes beca 2011-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8483 Title: Glacial history and paleoceanographic changes of the western Arctic Ocean (Mendeleev Ridge) using beryllium isotopes Authors: Nam, Seung-il; Kim, Kyeong J.; R. Stein; J. Matthiessen Abstract: Beryllium isotopes have been used as a proxy to understand paleoclimate signals which correspond well with oxygen isotope stages. Previous publications related with this aspect are well established in the science community related to paleoclimate change for both marine and lake environments [Aldahan et al., 1997]. In general, for warmer period, both the concentrations of beryllium isotopes were relatively higher than during colder period. Our recent investigation for the East Sea, Korea also shows this trend clearly although the characteristics of marine environmental setting and sediment accumulation are still revealed through the pattern of these isotopes as a proxy representing the regional climatic environment [Kim and Nam, 2010]. A new investigation of paleoclimate and environmental changes using beryllium isotopes for the Mendeleev Ridge of the western Arctic Ocean was accomplished using the 39 cm-long box core sediment (PS72/396-3 GKG) which was recovered during the Polarstern ARK23/3 Expedition in 2008. The age of core PS72/396-3 seems to be back to MIS 5.1 based on lithostratigarphy (well known brown- gray colour and pink layers), AMS 14C ages and oxygen and carbon isotopes of planktonic foraminifer N. pachyderma sin. 2011-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8482 Title: Multi-proxies from surface sediments in the western Arctic Ocean and its implications for oceanographic changes Authors: Nam, Seung-il; R. Stein; A. Mackensen; J. Matthiessen Abstract: During the ARK23/3 Expedition (2008) with the German icebreaker RV Polarstern, box core sediments were taken by using the GKG (Giant Box Corer) at 20 geological stations along two transects from the Canada Basin across the central Mendeleev Ridge towards the Makarov Basin and the Lomonosov Ridge in the Eurasian Arctic (northern transect along 80,30N, southern transect one along 77,30N). For this study a total of 20 surface sediment samples were collected on board from the box core sediments in order to investigate recent environmental changes related to global warming in the western Arctic Ocean, and to delineate associated paleoceanographic changes during the Holocene subatlantic period. 2011-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8481 Title: Glacial history and paleoenvironmental changes from the eastern Arctic Ocean (Yermak Plateau) during the last 200 ka Authors: Nam, Seung-il; R. Stein; Lee, H.-K.; J. Matthiessen Abstract: Late Quaternary glacial history and paleoenvironmental changes from the eastern continental margin of the Yermak Plateau were reconstructed by using two sediment cores taken during the Polarstern ARK-XX/3 Expedition (2004). Multi-proxies such as stable isotopes of planktonic foraminifera N. pachyderma sin., organic-geochemical parameters, opal, grain-size distribution (including IRD contents) were investigated in details for this study. Organic-geochemical proxies were used to assess characteristics and origin of organic matter (terrigenous vs. marine) deposited in the Eastern Arctic glaciomarine sediments associated with glacial history and productivity in surface water during seasonally ice-reduced warm periods. 2011-01-01T00:00:00Z