• ALGAE
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• v.19 no.3
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• pp.235-245
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• 2004

A study on seasonal characteristics of phytoplankton dynamics and environmental factors was carried out at four stations including Mara-do and U-do located in the western and eastern coast of Jeju Island in southern Korea from April 2003 to March 2004. Out of 101 phytoplankton species identified, 84 belong to Bacillariophyceae, 9 Dinophyceae, 6 phytoflagellates and 2 coccolithophorids, and the highest value of species diversity was observed in April. Phytoplankton was more abundant at the western coast than at the eastern coast from March to September and its highest abundance was 49.24 ${\times}$ 10$^3$ cells L$^{-1}$ at Mara-do in July. The pennate diatoms were more abundant at the western coast than at the eastern coast with the highest abundance of 38.75 ${\times}$ 10$^3$ cells L$^{-1}$ at Mara-do in July, and during this period Nitzschia longissima contributed 68.5% of the total phytoplankton abundance. Naviculaceae was more abundant at Gosan (western coast) in November when Stauroneis membranacea represented 80.1% of the abundance. Leptocylindrus dances contributed 49.4% of the abundance at U-do in November. Dinophyceae was more abundant at U-do in August. Water temperature and pH fluctuated from 11.7${^{\circ}C}$ to 27.1${^{\circ}C}$ and from 7.31 to 8.70, respectively. Water temperature of Mara-do was about 1-2${^{\circ}C}$ higher than the other stations. Salinity varied from 30.4 to 35.0 psu with the minimum in rainy season and the maximum at the end of winter. The concentration of NH$_4$-N, NO$_3$-N, NO$_2$-N, PO$_4$-P and SiO$_2$-Si ranged 0.07-6.79, 1.0-62.0, 1.0-8.0, 1.0-7.0 and 7.0-191.0 $\mu$g-at L$^{-1}$, respectively. Chlorophyll a concentrations varied from 0.10 to 1.17 $\mu$g L$^{-1}$. NH$_4$-N concentrations were high at U-do from May to December, and at Mara-do from January to February. The high concentrations of NO$_3$-N were found at Mara-do from June to September and at U-do from January to May. The effects of various physicochemical parameters on the seasonal distribution and succession of phytoplankton population suggest that there is a classical pattern of phytoplankton dynamics in Jeju coastal waters.

• The Korean Journal of Malacology
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• v.7 no.1
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• pp.49-57
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• 1991

A study on the distribution and community structure of the benthic macroinvertebrates on the intertidal zones of Gapa and Mara islets were carried out from March to June 1991. The macroinvertebrates collected and identified were composed of 7 phyla, 14 classes, 29 orders, 68 families and 132 speies in Gapa islet and of 7 phyla, 12 classes, 23 orders, 49 familis and 90 species in Maara islet. The first and second dominant species and the community dominance indices of the upper tidal zones of Gapa and Mara islets were Nodilittorina exigua, Pollicipes mitella and 79.01, 69.77 respectively. However, the dominant species of the middle and lower intertidal zones of the two islets were not identities and different among the tidal zones.

• Journal of Veterinary Clinics
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• v.31 no.3
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• pp.206-211
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• 2014

Anaplasmosis is a rickettsial zoonosis mediated by blood-sucking arthropods, such as ticks, flies, and mosquitos. Migratory birds are common hosts of ticks that are mediators of anaplasmosis, in particular, the tick infection rate in thrushes (family Turdidae) has been known to be high. The main purpose of this study is to survey the occurrence and prevalence of Anaplasma spp. from the migratory thrushes in Jeju island. We collected blood samples from 6 thrushes rescued at the Jeju Wildlife Rescue Center and from 34 wild-caught thrushes on Mara island which is a satellite island of Jeju. As a result, the nested PCR confirmed that seven out of 40 individuals (17.5%) were infected by Anaplasma spp. and all of them were identified as A. phagocytophilum based on sequences obtained from partial 16S rRNA. All the infected birds were on their northward migration in spring, our results suggest that the Turdidae family, which is a common and abundant migrant group passing through Jeju island, may act a role as active reservoir and disperser of A. phagocytophilum causing potential influx of the zoonotic pathogens from its wintering grounds in lower latitude to the mainland Korea as well as Jeju.

• Korean Journal of Environment and Ecology
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• v.34 no.1
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• pp.9-17
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• 2020

Domestic cats (Felis catus) introduced to insular environments can be invasive predators that often threaten endemic species and cause biodiversity loss or local extinction on the island. This study was conducted from March to July 2018 to understand the population size, home range, and spatial use of cats introduced to Mara Islet (N 33° 07', E 126° 16') in Jeju Special Governing Province, the Republic of Korea. Observation records based on their natural marks revealed that there were 20 adult cats on Mara Islet. A capture-recapture method also estimated 20 adult individuals (95% confidence interval: 20-24 individuals). According to our telemetry study on ten adults deployed with GPS-based telemetry units, the home range size was 12.05±6.99 ha (95% KDE: kernel density estimation), and the core habitat size was 1.60±0.77 ha (50% KDE). There were no significant differences in the home range and core habitat sizes by sex. The home range of domestic cats overlapped with the human residential area, where they might secure easy foods. Five of ten tracked cats were active at potential breeding colonies for the Crested Murrlet (Synthliboramphus wumizusume), and six approached potential breeding areas of the Styan's Grasshopper Warbler (Locustella pleskei), suggesting the predation risk of the two endangered species by cats. This study provides novel information on the population size and home range of introduced cats on Mara Islet which is an important stopover site of migratory birds as well as a breeding habitat of the two endangered avian species. Reducing the potential negative impacts of the introduced cats on migratory birds and the endangered species on Mara Islet requires monitoring of the predation rate of birds by cats, the population trends of cats and endangered breeding birds as well as the effective cat population control and management.

• Ocean Science Journal
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• v.41 no.3
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• pp.175-179
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• 2006

The Ieodo Ocean Research Station(IORS) is an integrated meteorological and oceanographic observation base which was constructed on the Ieodo underwater rock located at a distance of about 150 km to the south-west of the Mara-do, the southernmost island in Korea. The underwater ambient noise level observed at the IORS was similar to the results of the shallow water surrounding the Korean Peninsula (Choi et al. 2003) and was higher than that of deep ocean (Wenz 1962). The wind dependence of ambient noise was dominant at frequencies of a few kHz. The surface current dependence of ambient noise showed good correlation with the ambient noise in the frequency of 10 kHz. Especially, the shrimp sound was estimated through investigations of waveform and spectrum and its main acoustic energy was about 40 dB larger than ambient noise level at 5 kHz.

• Clinical and Experimental Reproductive Medicine
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• v.49 no.3
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• pp.215-218
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• 2022

Herein, we report an exceptionally rare case of a 25-year-old woman with cloacal exstrophy/omphalocele-exstrophy-imperforate anus-spinal defects (OEIS) syndrome achieving a viable pregnancy despite many gastrointestinal and genitourinary malformations and multiple respective corrective operations. The patient was born with two vaginas, two uteruses, four ovaries, an imperforate anus, a large omphalocele including bowel and bladder exstrophy, and diaphysis of the pubic rami. This patient is the only documented OEIS patient not to have tethered spinal cord as an anomaly, perhaps contributing to her successful pregnancy. After experiencing preeclampsia with severe features at 35 weeks, the baby was born via cesarean section.

• Economic and Environmental Geology
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• v.43 no.1
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• pp.53-66
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• 2010

We report petrologic characteristics including $^{40}Ar-^{39}Ar$ absolute ages of the subsurface lavas recovered from borehole cores in two islets, Marado and Gapado, off the southwestern coast of Jeju in southernmost Korea and discuss on the volcanism in the region. The lavas in Gapado are apparently divided into one unit with bright colored, aphanitic texture and sheet jointed, and another unit with dark colored and massive. The outcrops often show differentially weathered pattern due to textural difference. While, the lavas in Marado have vesicular and glomerporphyric texture, even though each lava flow unit in Marado has slight unique texture with variation of vesicularity and phenocrysts. The chemical composition of rock core samples from Gapa borehole and Mara borehole shows that the lavas from Gapado and Marado are classified into basaltic trachyandesite($SiO_2$ 52.6-53.6 wt%, $Na_2O+K_2O$ 7.3-7.5 wt%) and tholeiitic andesite($SiO_2$ 51.7-52.8 wt%, $Na_2O+K_2O$ 3.6-4.1 wt%), respectively. The measured $^{40}Ar-^{39}Ar$ plateau ages range from $824{\pm}32\;Ka$(MSL -69 m) to $758{\pm}\;Ka$(MSL 19 m) for core samples of Gapa borehole and $259{\pm}168\;Ka$(MSL -26 m) for a core sample of Mara borehole, respectively. The absolute age of Gapado basaltic trachyandesite is well correlated with that of Sanbangsan trachyte(Won et al., 1986). Meanwhile, the age of a sample in Marado has $259{\pm}168\;Ka$(MSL -26 m) with poor plateau age formation and high error range. We report the data in caution but the rock composition and absolute age of Marado tholeiitic andesite are relatively correlated with those of lava units from Duksu and Sangmo-2 boreholes, indicating the volcanism during 260-150 Ka. On the basis of interpretation of occurrences of exposed and subsurface volcanic rocks of the study area, stratigraphic relationship with adjacent borehole cores and the bathymetry chart of surrounding area, it indicates that the lavas in Gapado were formed around 800 Ka during relatively early stage of volcanic activity in Jeju Island. Meanwhile, Marado may have originated around 260-150 Ka during relatively young stage of volcanism in Jeju Island. It is inferred that the volcanisms have originated in land and these islets were individual ancient volcanoes. The apparent topography has been re-shaped by tidal erosion due to transgression.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.141-155
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• 1999

Korea Ocean Research & Development Institute(KORDI) conducted an offshore geotechnical investigation for the Eardo Ocean Research Station with the help of the Fugro International Limited at a site location approximately 152 km away from Mara Island, Korea. The primary purpose of the geotechnical investigation was to obtain information on soil and foundation conditions, and to develop foundation design data for a fixed offshore observation platform. This paper discussed the details of the geotechnical investigation and the foundation design recommendations for the Ocean Research Station. Clear recommendations were proposed for the foundation type of driven pile considering the existing soil conditions.

• Korean Journal of Environment and Ecology
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• v.22 no.6
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• pp.648-657
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• 2008

This research was conducted to investigate the breeding density and seasonal food items of the magpies in Jeju Island and the near-manned islets. The examination of nest distribution to determine breeding density was performed during breeding season from February 2006 to April 2008, and that of food items from May 2006 to February 2008. A total of 2,113 nests were found across Jeju Island, the average density was $1.33\;nest/km^2$, and the magpies were distributed up to 600 meters above the sea level. The nest density was the highest in the central areas of Jeju Island, with 688 nests at $3.61\;nest/km^2$, while that in the eastern areas was the lowest, with 214 nests at $0.66\;nest/km^2$. In terms of the number of nests depending on the height above the sea level, 1,172 nests, which was equivalent to the density of $1.85\;nest/km^2$, was observed below 100m and highest among the intervals of height, but 16 nests found at 500-600m were the lowest, corresponding to $0.20\;nest/km^2$. The number of nests found in the manned islets near Jeju Island was eight in Biyang-do with the density of $15.38\;nest/km^2$, nine in U-do with $1.49\;nest/km^2$, and one in Gapa-do with $1.15\;nest/km^2$, whereas none of nests were observed in Mara-do. The contents of stomach consisted of 17 types of prey sources including countless bones, eggshells, plants, and seed, most of which were the individuals of the order Coleoptera. In spring and summer, the foraging frequency for invertebrate animals such as insects was high, but less than 30% in winter. In contrast, the magpies preyed upon plants and seeds at the frequency of 10% and 30%, respectively, in spring, while the foraging frequencies for both of them were 100% in winter and higher than any of other seasons. Eggshells and bones of birds were also detected infrequently. If the density of the magpies, which may play role as the upper predator within the ecosystem, increases, it would be expected to affect directly the reduction of the number of the species and population of endemic animals such as small birds and reptiles, etc. Therefore, it is considered that long-term monitoring for the density of the magpies and precaution is prerequisite to minimize adverse effects on ecosystem.

• Parasites, Hosts and Diseases
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• v.52 no.3
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• pp.281-285
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• 2014

Ticks were collected from 35 animals from 5 provinces and 3 metropolitan cities during 2012. Ticks also were collected by tick drag from 4 sites in Gyeonggi-do (2) and Jeollabuk-do (2) Provinces. A total of 612 ticks belonging to 6 species and 3 genera were collected from mammals and a bird (n=573) and by tick drag (n=39). Haemaphyalis longicornis (n=434) was the most commonly collected tick, followed by H. flava (158), Ixodes nipponensis (11), Amblyomma testudinarium (7), H. japonica (1), and H. formosensis (1). H. longicornis and H. flava were collected from all animal hosts examined. For animal hosts (n>1), the highest Tick Index (TI) was observed for domestic dogs (29.6), followed by Siberian roe deer (17.4), water deer (14.4), and raccoon dogs (1.3). A total of 402 H. longicornis (adults 86, 21.4%; nymphs 160, 39.8%; larvae 156, 38.9%) were collected from wild and domestic animals. A total of 158 H. flava (n=158) were collected from wild and domestic animals and 1 ring-necked pheasant, with a higher proportion of adults (103, 65.2%), while nymphs and larvae only accounted for 12.7% (20) and 22.2% (35), respectively. Only 7 A. testudinarium were collected from the wild boar (6 adults) and Eurasian badger (1 nymph), while only 5 I. nipponensis were collected from the water deer (4 adults) and a raccoon dog (1 adult). One adult female H. formosensis was first collected from vegetation by tick drag from Mara Island, Seogwipo-si, Jeju-do Province.