• Journal of fish pathology
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• v.18 no.1
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• pp.39-48
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• 2005

Pathogenicity of Vibrio tapetis, the causative bacterium of 'brown ring disease (BRD)' was evaluated in Manila clams (Ruditapes philippinarumi by artificially 0.1 $m\ell$ infection of $1.0\times10^5$cells and $1.0\times10^8$ cells at 20 $^{\circ}C$. A PCR assay based on 16S rRNA to detect the bacteria in clam tissues was established. Accumulative mortality of clams infected with $1.0\times10^7$cells and $1.0\times10^4$ cells per an individual of the bacteria was 67.5% and 7.5%, respectively. However, the deposit of brown pigment in the inner shells by accumulation of chonchiolin was not found. The bacteria were not be able to re-isolate from the infected clams by the conventional agar plate method but were easily detected by PCR assay established in this experiment. In clams artificially infected with 10 species of Vibrio, a 414bp for V. tapetis was detected in PCR assay. The specific band in the clams infected with $1.0\times10^4$cells per an individual of V. tapetis was detected only in gills one day after the infection but never be found in any tissues including gills three days after the infection. In the case of clams infected with $1.0\times10^8$cells per an individual of V. tapetis the specific band was detected in gills and intestine one day after the infection, in all tissues three days after the infection, and then in gills and adductor muscle nine days after the infection. The PCR assay was applied to detect V. tapetis in manila clam, surf clam (Mactra veneriformis), oyster (Crassostrea gigas) and Thomas' rapa whelk (Rapana venosa) taken from Taean and Gochang from April to July 2004. The infection rates were detected to 23.1% and 9.4% in the oyster and surf clam, while manila clam and Thomas' rapa whelk were not found.

• Journal of fish pathology
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• v.31 no.1
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• pp.41-48
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• 2018

The utility of Bacillus spp. organisms for reduction of dissolved hydrogen sulfide ($H_2S$) in white leg shrimp (Litopenaeus vannamei) culture was tested with different combinations of Bacillus spp. microorganisms: combination A (B. subtilis + B. licheniformis); combination B (B. licheniformis + B. amyloliquefaciens); combination C (B. subtilis + B. licheniformis + B. amyloliquefaciens). Of these 3 combinations, C was effective in few hours after addition whereas B needed longer time to be effective. The $H_2S-reducing$ effect of combination C was dependent on the amount of microorganisms added to $H_2S-containing$ test solution. Exposure of white leg shrimp to $H_2S$ at 8 mg/L for 7 days led to survival of 80% and 1 mg/L for 14 days it was 82.5%. The survival rate was 97.5% when combination C was simultaneously added to shrimp tanks during $H_2S$ exposure at 1 mg/L for 14 days. It was demonstrated that combination C microorganisms (B. subtilis + B. licheniformis + B. amyloliquefaciens) can reduce dissolved $H_2S$ concentrations, and this effect can be utilized to protect white leg shrimp from $H_2S$ toxicity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.7 no.1
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• pp.15-27
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• 1974

Since the summer of the year 1972 ulcer disease of common carp, colour carp ana goldfish had suddenly spread widely and caused a serious mortality at fish farms especially around Gim-hae and Yang-san, near Busan. The present study aimed to find out the causative organisms, histopathological changes and the way of treatment, and the results are summarized as follows : Two kinds of pathogenic bacteria, i. e, Chondrococcus columnaris and Aeromonas sp. were isolated from the mucus of the lesion. According to the macroscopic findings, these symptoms began with the hemorrhagic spots under scales which fell out, after the collapse of the dermis, which was followed by lesion to form ulcer, and then the muscle was exposed. The fin was eroded mostly from the distal part, but sometimes from the basal part. Gills showed grey colour, and this part of the tissue collapsed. According to the histopathological findings, the dermis was exposed after the collapsed of the epithelium of the skin, and the necrosis of the musculature occurred, the muscular fibre being destroyed. The epithelial cells of gill tissue proliferated, thus gill filaments were conglutinated and collapsed. Fatty degeneration happened at the liver but the other organs seem to be normal. Treatment with the following mixtures were effective the water temperature of $22\~25^{\circ}C$, but not effective when the temperature was under as low as $13\~15^{\circ}C$. Mixture 1. Aivet (HB-115.HCI) 0.3ppm Malachite green 0.2ppm. Dipterex 0.4ppm Mixture 2. Furanace (P-7138) 0.05ppm Malachite green 0.2ppm Dipterex 0.4ppm When lesion healed, the epithelium, dermis, and the muscular fibre were regenerated.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.5
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• pp.523-530
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• 2020

Based on the results of harmful algal blooms (HABs) monitoring by the National Institute of Fisheries Science and local governments, the effects of changes in the marine environment on HABs are described. Since the beginning of HABs monitoring in 1972, they continued to increase from the 1980s to the 1990s. After the largest number of HAB incidents (109) in 1998; the trend declined until the 2010s. Most HABs in the 1970s were caused by diatoms. In the 1980s, coastal dinoflagellates caused HABs; Cochlodinium polykrikoides blooms have been occurring continuously since 1993. There are three HAB species that cause damage to fisheries in Korea. The high-density bloom of Karenia mikimotoi caused mass mortality in shellfish in Jinhae Bay in 1981. Karenia sp. blooms occurring around Tongyeong in 1992 killed aquaculture fish. Since the occurrence of the largest fisheries damage of KRW 76.6 billion in 1995 caused by C. polykrikoides blooms, they have been occurring continuously. The concentration of nutrients in coastal waters was the highest in the 1980s and has declined since the mid-1990s. This reduction in nutrient concentration is a good explanation for the decreasing number of HABs. Since 2016, a summer high water temperature of 30℃ or more has appeared, and the range and scale of C. polykrikoides blooms have been greatly reduced. In 2016, K. mikimotoi blooms occurred around Wando, Jangheung and Goheung and small scale blooms of C. polykrikoides occurred around Yeosu. There were no C. polykrikoides blooms in 2017; however, Alexandrium affine blooms occurred from Yeosu to Tongyeong. There was a small-scale blooms of C. polykrikoides in 2018 compared to those in the previous years. Our results show that reduction in nutrients and the high water temperature owing to climate change are a good explanation for variation in HABs in Korean coastal waters.

• Journal of Life Science
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• v.15 no.2 s.69
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• pp.225-230
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• 2005

The aim of this study was to examine the fluctuation in phytoplankton assemblages with regarding to environmental conditions and nutrients, which were surveyed quarterly over the fours seasons (February, May, July, and October). In turn, an understanding of biological effects should provide insights into a wide range of initiated Cochlodinium blooms in Narodo. Sampling was carried out throughout 2001 on the coasts of Busan (St. 1), Yeosu (St. 2), Narodo (St. 3), Kohung (St. 4), and Kwangdo (St. 5). The maximum surface water temperature was recorded in July, and it ranged from 20 to $22^{\circ}C$. Salinity showed no great variation, which maintained itself in the range of 29-34 psu. The maximum surface salinity was recorded in February, which was about 34 psu. The chlorophyll $\alpha$ concentration of the surface water ranged from 0.01 to $1.3\;{\mu}g\;1^{-1}$. The concentrations of $NH_{4}-N $ were persistently high from February to October; in particular, the peak was observed at St. 1 in February and May (0.15 and $0.19\;{\mu}mol\;1^{-1}$, respectively), while it was detected at St. 2 in July and October (0.22 and $2.2\;{\mu}mol\;1^{-1}$ respectively). Similar trends to those for $NH_4-N $ were observed in the concentrations of $NO_{2}-N$ and $NO_{3}-N$. In contrast to nitrogen, a distinct peak of $NO_{4}-P$ at St. 3, 4, and 5 was observed throughout year $(0.01-0.1\;{\mu}mol\;1^{-1}$ except for October. At St. 1 encounter a peak of cell number of 30,000 and $13{\times}10^3$ cells $1^{-1}$, respectively, in July and October. During the period of this study, the majority of the taxa were diatoms. The dinoflagellates were rather abundant after February, in particular at St. 3, 4, and 5 which attained an abundance of $10\~20\%$without marked fluctuation during the period of this study. At St. 3, the highest average cell width, $178.11\;{\mu}m$, was recorded: the highest cell length, $337.72\;{\mu}m$, was measured in July. Consequently, dinoflagellates bloom in July at Narodo influenced by warm water current are not only associated with a desirable development of cell morphometric characteristics, but also with the health growth of C. polykrikoides. During the period of this study, warm water currents caused an increased water temperature in Narodo, but did not change the amount of nutrients.

• Journal of the Korean Society of Food Culture
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• v.18 no.1
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• pp.56-68
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• 2003

The objects of this study are to find out (1) real situation of the food supply in prison under Imperial Government of Japan more cleary (historical meaning) and (2) which might help in understanding wrong present food consumption patterns in Korea which causes environmental as well as health problems. It is generally known that the length of the Japanese occupation for Korea is 36 years. However, it is concluded in this study that it was longer (70 years ; from 1875 to 1945 from when Japanese Army attacked and occupied Yungjongdo and Kanghwado island to e time when they were defeated on World War II.) Korea was annexed by Japan in 1910 then the Imperial Government of Japan dismissed the Korea Army, controlled the Office of Justice and the management of prison by force. Since then about 50% of all land was fell into Japanese Government ownership and 80% of Korean farmers became as tenant. After this change, Korea farmers were forced to pay extremely high rent (up to 80% of its harvest). Forced immigration, low price procurement of grain by Japanese government up to more than 30%of their production, was practiced. Accordingly, the food situation of Korean farmers became miserable, which may caused more violations of Imperial Japanese Law. Malnutrition, epidemic diseases, mortality rate of infants soared and average life expectancy shortened to 20-30 years old. This was the period of World Economic Crises and Food Crises in Japan. It was said then that if one Japanese comes to Korea then 200 Koreans will starved to death. Meanwhile, Proconsul Bureau of Chosun requested to the Department of Medicine, the Imperial University of Kyungsung to survey food supply situation of Koreans in prison throughout Korea. Objectives of the survey then was not only to find out scientifically whether it is agreeable in maintaining prisoner's health and also find out the possibility to save food during food crisis. Survey was started from 1923 and ended in 1945, and it focussed on prisoners in the Seodaemoon Prison. This report is the outcome of the first survey. They concluded that the food supplied was nutritionally (had) no problem, in compare with those of workers in the factory, students in the dormitory in Japan and with those of prisoners in Taiwan, France and Germany. Amount of grain supplied were different according to their work lord and was divided into 9 different levels. Total grain was consisted of 50% millet, 30% soybean and 20% indica rice(variety). However, there were no difference in the amount of supply of side dishes between work groups. For the highest working group, 3280g of boiled grain per day was supplied to make stomach full but as a side dishes, salty fermented bean paste, fermented fish and salty soups, etc. was supplied. Deficiency of animal protein were observed, however, high intake of soybean may possibly caused animal protein deficiency problem. On the contrary, the intake of water soluble vitamins were insufficient but the level of calcium and iron intake seems to be sufficient, however, imbalance of intake of nutrition may caused low absorbtion rate which might caused malnutrition. High intake of dietary fiber and low intake of cholesterol may possibly prohibited them from so called modem disease but may caused the defect in disease resistancy againist epidemics and other traditional disease. Over intake of salt(20-30g per day) was observed. Surveyors who attended in this survey, mentioned that the amount of food intake may nutritionally be sufficient enough but the quality of food(and possibly, the taste of food) were like that of animal feed. For the officials who received this report might consider that considering the war situation and food crisis, the supply situation of food in the prison may considered to be good enough(because they are not starving). But as a Korean who studied this report, one feel extremely pity about those situation because (situation of) those period were very harsh under the Imperial Law and keeping the Law by Koreans were almost impossible, therefore, about one third adult violated the Law and were put into jail. And they were treated like animals.