• Ocean and Polar Research
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• v.27 no.2
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• pp.197-203
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• 2005

Dimethylsulfide (DMS) is the most abundant form of volatile sulfurs in the ocean. Many biogeochemical studies have been conducted in the past several decades to unveil the processes driving the production, transformation and removal of DMS. They have shown that the Southern Ocean is an area with one of the highest levels of DMS concentrations during the austral summer in the global oceans. It has recently been observed that Antarctic krill, Euphausia superba, produces DMS and dissolved dimethyl-sulfoniopropionate (DMSP) in its gazing process. Copepods also produce DMS, and the potential production rates of DMS in the Southern Ocean by krill and copepods are estimated to be as much as $21{\mu}mol\;m^{-2}d^{-1}$ and $0.6{\mu}mol\;m^{-2}d^{-1}$, respectively. These production rates of zooplankton and the presence of phytoplanktot which have high DMSP contents in their cells, might facilitate in situ DMS production in the Southern Ocean.

• Ocean and Polar Research
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• v.21 no.2
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• pp.127-136
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• 1999

Radiolarian assemblages from KODOS area were analyzed in order to understand the biostratigraphy and paleoceanography of deep-sea sediment from the Northeast Equatorial Pacific. The sediment core was divided into two or three units on the basis of the chemical and physical properties. In the upper sediment, mixtures of Quaternary and Tertiary radiolarians are found indicating active reworking processes. Dissolution of radiolarians seem to increase with depth. Radiolarians are seldom in Unit III presumably due to dissolution and corrosion. The middle part of unit I appears to correspond to Collosphaera invaginata Zone (0.21 Ma). Unit II belongs to Collosphaera tuberosa Zone. Based on the absence of Stylatractus universus, we estimate its age to be younger than 0.42 Ma. Based on our analyses of radiolarians in Unit I and II, we estimated the age of unit III as Tertiary, particularly from Oligocene to Miocene. There may to be hiatuses of more than 3 My from late Miocene to Pliocene, which probably resulted from erosion and dissolution by the Antarctic Bottom Water Sedimentation rates during Quaternary range from 0.15 to 0.50 mm/ky with significant variabilities among stations. Radiolarians in the study area were mostly warm-water species.

• Ocean and Polar Research
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• v.44 no.1
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• pp.69-82
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• 2022

The Ross Sea, Antarctica plays an important role in the formation of Antarctic Bottom Water (AABW) which is the densest water mass in global thermohaline circulation. Of the AABW, 25% is formed in the Ross Sea, and sea ice formation at the polynya (ice-free area) developed in front of ice shelves of the Ross Sea is considered as a pivotal mechanism for AABW production. For this reason, monitoring the Ross Sea variations is very important to understand changes of global thermohaline circulation influenced by climate change. In addition, the Ross Sea is also regarded as a natural laboratory in investigating ice-ocean interactions owing to the development of the polynya. In this article, I introduce characteristics of the Ross Sea described in previous observational studies, and investigate variations that have occurred in the Ross Sea in the past and those taking place in the present. Furthermore, based on these observational results, I outline variations or changes that can be anticipated in the Ross Sea in the future, and make an appeal to researchers regarding the importance and necessity of continuous observations in the Ross Sea.

• Korean Journal of Microbiology
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• v.53 no.2
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• pp.137-140
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• 2017

Caballeronia sordidicola strain PAMC 26510 was isolated from Psoroma sp., a lichen material, collected from Barton Peninsula of King George Island in Antarctica. The draft genome sequence of PAMC 26510 consisted of 224 contigs and they was 7,872,143 base pairs with 59.7% G+C content. The genome included 7,580 protein coding sequences and 6 ribosomal RNA genes and 46 tRNA genes. The strain PAMC 26510 is also a metabolic generalist as we have observed in previous genomic studies in the arctic strain of Caballeronia sordidicola. The draft genomic sequences of PAMC 26510 had six CRISPR arrays on six contigs, and there were two clusters of CRISPR-associated genes that were linked with respective CRISPR arrays.

• Journal of fish pathology
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• v.18 no.2
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• pp.105-118
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• 2005

Anemia in fish can be easily recognized by examining the gill color and physical properties of sampled blood. The number of erythrocytes is generally within 1-3 ${\times}10^6$. Hematocrit (Ht) reportedly ranges 35-45% in many of reports which is nearly the same as that in mammals. Anemia in fish can also be classified as hemorrhagic, hemolytic and hypoplastic ones. Fish are also expected to have similar pathological effects by anemia as in mammals. From the fact that fish can survive under extremely low hematocrit below 10% and antarctic icefish (Chanenocephalus aceratus) has no erythrocytes, different pathological effects were expected. Anemia is considered to have one of the most important health parameters, based on the pathological aspect. Therefore, by reviewing clinical and histopathological findings of most of fish diseases already known and then adding our results of experimental anemia, diseases and factors related to anemia were summarized and the pathological effects was discussed.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.147-157
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• 2020

Mass change in the Antarctic Ice Sheet(AIS) is the most important indicator of changes in Earth's climate system including global mean sea level rise that are largely affected by ongoing global warming. In this study, AIS mass variations are examined with satellite gravity data and outputs from a regional climate model. The analysis of gravity data shows that along the coastal region the Western AIS has experienced a continuous and significant ice loss while a slight increasing in the Eastern AIS during the study period (2002.08-2016.08). The temporal and spatial variations in ice mass changes are recovered by a regional climate model, but the recovered amplitudes are much smaller than those of observations. This under-estimation is remarkably resolved by modifying a base flow field for the ice discharge. The recovered estimates based on the ice-flow field can explain about 97% of the rate of mass change in observations before 2009. This implies that changes in ice flow dynamics along the coast line plays a pivotal role in regulating long-term budget of ice mass in AIS.

• Ocean and Polar Research
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• v.37 no.2
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• pp.127-140
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• 2015

A continuous series of 60 snow samples was collected at a 2.5-cm interval from a 1.5-m snow pit at a site on the Styx Glacier Plateau in Victoria Land, Antarctica, during the 2011/2012 austral summer season. Various chemical components (${\delta}D$, ${\delta}^{18}O$, $Na^+$, $K^+$, $Mg^{2+}$, $Ca^{2+}$, $Cl^-$, $SO_4{^2-}$, $NO_3{^-}$, $F^-$, $CH_3SO_3{^-}$, $CH_3CO_2{^-}$ and $HCO_2{^-}$) were determined to understand the highly resolved seasonal variations of these species in the coastal atmosphere near the Antarctic Jang Bogo station. Based on vertical profiles of ${\delta}^{18}O$, $NO_3{^-}$and MSA, which showed prominent seasonal changes in concentrations, the snow samples were dated to cover the time period from 2009 austral winter to 2012 austral summer with a mean accumulation rate of $226kgH_2Om^{-2}yr^{-1}$. Our snow profiles show pronounced seasonal variations for all the measured chemical species with a different pattern between different species. The distinctive feature of the occurrence patterns of the seasonal variations is clearly linked to changes in the relative strength of contributions from various natural sources (sea salt spray, volcanoes, crust-derived dust, and marine biogenic activities) during different short-term periods. The results allow us to understand the transport pathways and input mechanisms for each species and provide valuable information that will be useful for investigating long-term (decades to century scale periods) climate and environmental changes that can be deduced from an ice core to be retrieved from the Styx Glacier Plateau in the near future.

• Journal of Life Science
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• v.33 no.12
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• pp.978-986
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• 2023

Inflammation by the innate immune system is a protective mechanism of the organism against infection-mediated environmental factors. It is also responsible for the pathogenesis of various human diseases, including the progression of cancer. Lichens are receiving increasing attention as a source of bioactive molecules with therapeutic potential for a variety of diseases. Additionally, the antioxidant, anti-inflammatory, and anticancer potential of lichen and its secondary metabolites have been widely reported. However, the underlying mechanism is still unknown. In the present study, to investigate molecular mechanisms of anti-inflammation and anti-cancer activity in the Antarctic lichen, Usnea aurantiaco-atra, methanol extract of Usnea aurantiaco-atra (MEUS) was used in vitro assays in RAW 264.7 macrophages cell and HCT116 colon cancer cells. Based on our data, MEUS had the anti-inflammatory activity through the modulation of main inflammatory indicators such as COX-2, IL-6, iNOS, TNF-α and NO production in a concentration-dependent manner. In addition, we observed that MEUS had cytotoxic activity against HCT116 colon cancer cells in a concentration-dependent manner, leading to a significantly reduced proliferation of the cancer cells through apoptotic induction by activating caspase-3. Taken together, this work firstly reported the anti-inflammatory and anti-cancer activities of an Antarctic lichen, Usnea aurantiaco-atra, and MEUS may provide a new insight into the molecular mechanisms underlying a link between inflammation and cancer.

• Genomics & Informatics
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• v.17 no.1
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• pp.5.1-5.9
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• 2019

The chinstrap (Pygoscelis antarcticus) and gentoo (P. papua) penguins are distributed throughout Antarctica and the sub-Antarctic islands. In this study, high-quality de novo assemblies of blood transcriptomes from these penguins were generated using the Illumina MiSeq platform. A total of 22.2 and 21.8 raw reads were obtained from chinstrap and gentoo penguins, respectively. These reads were assembled using the Oases assembly platform and resulted in 26,036 and 21,854 contigs with N50 values of 929 and 933 base pairs, respectively. Functional gene annotations through pathway analyses of the Gene Ontology, EuKaryotic Orthologous Groups, and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were performed for each blood transcriptome, resulting in a similar compositional order between the two transcriptomes. Ortholog comparisons with previously published transcriptomes from the $Ad{\acute{e}}lie$ (P. adeliae) and emperor (Aptenodytes forsteri) penguins revealed that a high proportion of the four penguins' transcriptomes had significant sequence homology. Because blood and tissues of penguins have been used to monitor pollution in Antarctica, immune parameters in blood could be important indicators for understanding the health status of penguins and other Antarctic animals. In the blood transcriptomes, KEGG analyses detected many essential genes involved in the major innate immunity pathways, which are key metabolic pathways for maintaining homeostasis against exogenous infections or toxins. Blood transcriptome studies such as this may be useful for checking the immune and health status of penguins without sacrifice.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.737-747
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• 1999

To estimate biomass and distribution of the Antarctic krill (Euphausia superba), hydroacoustic survey was conducted on board of R/V Yuzhmorgeologiya, which was chartered by Korea Antarctic Research Program (KARP) group from 18 to 21 December 1998, in the northern part of the South Shetland Islands, Antarctic Ocean, The scientific echo sounder (towing body type) used was EK- 500 (SIMRAD, Norway) with echo integrator (BI-500) at 38 kHz frequency and recorded mean backscattering cross-section coefficient (SA) per 1 $mile^2$ of sea surface. Also, Bongo net sampling was carried out to determine the size of krill and CTD (Conductivity, Temperature and Depth) casting to understand physical structure. Water column was divided into 5 layers (22$\~$65 m, 65$\~$115 m, l15$\~$65 m, 165$\~$215 m and 215$\~$315 m) to know vertical distribution of krill biomass. The standard length of krill collected was between 30 mm and 51 mm, and adult krill had single mode (41 mm). Maximum horizontal length of krill patch was about 35 nautical mile and vertical thickness was about 275 m. High density of krill was appeared in frontal area between Circumpolar Deep Water (>$1^{\circ}C$) and very low temperature water mass (< $-0.5^{\circ}C$) that originate from Weddell Sea. According to the results calculated using target strength equation, krill density was totally higher in continental slope and open water areas than in coastal area. In the study area, krill seems to distribute in depth; density was low at first layer ($\={\rho}=17.0\;g/m^2$) and higher at fourth layer ($\={\rho}=40.19\;g/m^2$). The estimated krill biomass at total survey area and water column was about 2.77 million metric ion ($\={\rho}=151.0\;g/m^2$) and coefficient of valiance ( CV, $\%$) was 19.92. The proportions and biomass of krill biomass at each layer were as follows; layer 1 ($11.3\%$, 0.31 million metric ton, CV=16.24), layer 2 ($13.3\%$, 0.37 million metric ton, CV=34.91), layer 3 ($23.7\%$, 0.66 million metric ton, CV=41.5), layer 4 ($26.6\%$, 0.74 million metric ton, CV=27.84) and layer 5 ($25\%$, 0.69 million metric ton, CV= 26.83).