https://repository.kopri.re.kr/handle/201206/11926 2026-04-22T06:13:27Z https://repository.kopri.re.kr/handle/201206/13703 Title: Diel variations in chemical and isotopic compositions of a stream on King George Island, Antarctica: Implications for hydrologic pathways of meltwater Authors: Jung, Hyejung; Jeen, Sung-Wook; Lee, Hyoungseok; Lee, Jeonghoon Abstract: Antarctica is highly susceptible to climate and environmental change. In particular, climate change can lead to the warming of permafrost and the development of active layers in permafrost areas, resulting in variations in hydrological characteristics. This study investigated the hydrological process associated with a stream in a snow-dominated headwater catchment on King George Island, maritime Antarctica, during austral summer using the chemical and isotopic compositions. During the cold period, as the snowmelt rate decreased, the amount of new water also decreased. Hence, the electrical conductivity (EC) increased because the contribution of supra-permafrost groundwater ("old" water), which occurs in the active layer, increased more during the cold period than during the warm period. Moreover, diel variations in the stable isotopic compositions (delta O-18 and delta D) of snowmelt ("new" water) were clearly observed in the stream water, indicating that runoff was the dominant flow path of snowmelt during the cold period. In contrast, during the warm period, the amount of snowmelt increased and the EC value decreased as a result of the dilution effect. In addition, compared with the cold period, diel variations in the isotopic compositions of the stream water were attenuated during the warm period. This attenuation effect was not due to the increased contribution of old water; instead, it was due to the contribution of new water with a low-amplitude signal in the diel variations of the isotopic compositions. Thus, the observed diel variations in the isotopic compositions of the stream water during cold and warm periods suggest that this catchment is dominated by new water. These findings are helpful for improving our understanding of climate-related changes in the hydrological pathways and water-related ecosystems of polar catchments. 2022-06-15T00:00:00Z https://repository.kopri.re.kr/handle/201206/13542 Title: Measuring Phylogenetic Information of Incomplete Sequence Data Authors: Seo, Tae-Kun; Gascuel, Olivier; Thorne, Jeffrey L. Abstract: Widely used approaches for extracting phylogenetic information from aligned sets of molecular sequences rely upon probabilistic models of nucleotide substitution or amino-acid replacement. The phylogenetic information that can be extracted depends on the number of columns in the sequence alignment and will be decreased when the alignment contains gaps due to insertion or deletion events. Motivated by the measurement of information loss, we suggest assessment of the effective sequence length (ESL) of an aligned data set. The ESL can differ from the actual number of columns in a sequence alignment because of the presence of alignment gaps. Furthermore, the estimation of phylogenetic information is affected by model misspecification. Inevitably, the actual process of molecular evolution differs from the probabilistic models employed to describe this process. This disparity means the amount of phylogenetic information in an actual sequence alignment will differ from the amount in a simulated data set of equal size, which motivated us to develop a new test for model adequacy. Via theory and empirical data analysis, we show how to disentangle the effects of gaps and model misspecification. By comparing the Fisher information of actual and simulated sequences, we identify which alignment sites and tree branches are most affected by gaps and model misspecification. [Fisher information; gaps; insertion; deletion; indel; model adequacy; goodness-of-fit test; sequence alignment.] 2022-04-19T00:00:00Z https://repository.kopri.re.kr/handle/201206/13306 Title: Complete genome of Nocardioides aquaticus KCTC 9944T isolated from meromictic and hypersaline Ekho Lake, Antarctica Authors: Hwang, Kyuin; Choe, Hanna; Kim, Kyung Mo Abstract: Nocardioides aquaticus KCTC 9944(T) is an aerobic, non-motile, Gram-positive, psychrotolerant, non-spore-forming bacterium isolated from the surface water of Ekho Lake in the Vestfold Hills, East Antarctica. This meromictic lake separated from Antarctic seawater thousands of years ago exhibits steep gradients of salinity and temperature in the upper layer of the water column. The cells of N. aquaticus thriving in Ekho Lake are able to grow in wide ranges of temperature (3 to 43.5 degrees C) and salinity (0 to 15% NaCl). Here, we sequenced the complete genome of N. aquaticus KCTC 9944(T), aiming to better understand the adaptation of this bacterium to the strong environmental gradients at the molecular level. The genome consists of 4,580,814 bp (G + C content of 73.2%) with a single chromosome, 4432 protein-coding genes, 51 tRNAs and 2 rRNA operons. The genome possesses genes for the Entner-Doudoroff pathway, photoheterotrophy, the conversion of acetate to acetyl-CoA, gluconeogenesis, and energy storage that are all advantageous to oligotrophic bacteria. The presence of genes involved in osmotic balance, fatty acid desaturation, cold and heat shock responses, and the oxygen affinities of respiratory oxidases are likely associated with high tolerance to strong gradients of salinity, temperature and oxygen concentration. 2022-04-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/13826 Title: Statistical understanding for snow cover effects on near-surface ground temperature at the margin of maritime Antarctica, King George Island Authors: Lim, Hyoun Soo; Kim, Hyun-cheol; Kim, Ok-Sun; Jung, Hyejung; Lee, Jeonghoon; Hong, Soon Gyu Abstract: Snow cover plays an important role in water supply through melting of snow/ice in polar ecosystem and environments, in particular, Antarctica. Although a site access to Antarctica is high-priced, measurements of ground surface temperature (GST) using small self-recording temperature sensors (iButtons) can provide a powerful and relatively inexpensive approach to trace the spatial and temporal distributions of soil temperature and in addition, absence/presence of snow cover. In this study, principal component analysis (PCA) was utilized to explain major patterns of GST from 128 sites at King George Island in maritime Antarctica. Variations of GST were monitored between December 2011 and January 2013. The iButtons were initially installed in snow free areas in the austral summer of 2011. Principal components 1 and 2 were associated with air temperature and snow cover, respectively. Both PCs showed good correlations with the mean GST of JJA (June to August), not with that of DJF (December to January). Based on the results excluding an outlier, PCA divided the 127 GST observations into three groups effectively: absence of snow cover (Group 1), intermittent snow cover (Group 2), and presence of snow cover (Group 3). Snow cover can supply water to the ecosystem and the GST pattern of Group 2 may imply an abundance and high productivity of mosses in the study area. Using approaches suggested by previous studies, snow cover showed up nine days (days 317-326), and the melt-out date was day 326 (KG125 in Group 2). The GST data and statistical approaches used in this study can be useful in other GST studies, particularly, for both polar regions. 2022-03-15T00:00:00Z