• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.1-7
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• 2003

Environmental changes caused by the abrupt climatic change are one of the important issues in the scientific community. In the East Sea, abrupt climatic shift, called Younger Dryas, is identified. The age of the Younger Dryas cold episode occurred at 11.2 ka. Overall, changes in circulation and bottom water conditions occurred during the Younger Dryas cold episode in the study area. Especially, climatic transition from meltwater spike to the Younger Dryas cold episode is characterized by significant shifts of oxygen isotope values, the coiling ratios of Neogloboquadrina pachyderma, and the planktonic foraminifers abundances. The impact of abrupt climate change on the ecosystem is very significant. In the East Sea, the calcium carbonate secreting organism(foraminifers) is replaced by silicon dioxide secreting organisms(diatom, radiolarian) after the abrupt and severe cold climatic event. Based on the Doctrine of Uniformitarianism, at least climate change for the next 100 years would be severely influence on the marine ecosystem.

• Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.339-345
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• 2011

Although culture techniques for the abalone Haliotis discus hannai are well known, mass culture of the benthic microalgae that are essential live food for the abalone larvae is still not practiced. This study was conducted to identify the microalgal species suitable for the growth of early larvae of H. discus hannai. The growth and attachment rates of 31 microalgal species were examined. Acrylic plates were used as the substrate. Among the 31 microalgal species, nine showing high growth and attachment rates were selected and tested for their dietary values via factors including settlement, metamorphosis, and survival rates of abalone larvae. Tetraselmis hazeni and Rhaphoneis sp. induced the highest settlement rate (65-69%) in abalone larvae. The metamorphosis rate was highest (57%) in larvae fed Rhaphoneis sp. and was also significantly higher in larvae fed Oscillatoria splendida (29%) and T. hazeni (22%) than in those fed other species. The highest survival rate of the larvae during the 15 days after metamorphosis was 67% in those fed Rhaphoneis sp., followed by T. hazeni (42%) and O. splendida (35%). In conclusion, Rhaphoneis sp. is the most suitable diatom for use as a live food for the culture of early larvae of H. discus hannai. In addition, T. hazeni and O. splendida are also potential species to be further developed and utilized in larval culture.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.3
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• pp.270-276
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• 2014

Seasonal characteristics of water and sediment qualities and potential effects of the freshwater discharge from a small tide embankment interior in a coastal area in Goheung county were investigated from May to September in 2012. Chemical oxygen demand values (COD) were mostly higher than 2 mg/L in summer ebb tide, which exceed the standard value of water quality criteria II of acceptable level for aquaculture activities. Nitrogen and phosphorus were found as the limiting nutrients for algae growth in summer and fall and in spring, respectively. Nitrogen was the limiting nutrient for diatom growth in the whole studied period. The sudden high values of COD, ammonia, dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) were found in water sample collected from station 5 which located in front of the tide embankment sluice gate during spring ebb tide. The freshwater discharge form the tide embankment interior maybe affected the survey areas during a short time interval. Mean values of eutrophication index of the surveyed coastal region in spring, summer and fall were all bigger than 1. Water quality was mostly considered at level II which acceptable for aquaculture activities. Sediment quality in this study was generally in the range of standard for fisheries environment.

• Korean Journal of Environmental Biology
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• v.32 no.3
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• pp.243-249
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• 2014

In this study, we evaluated the toxic effects of heavy metals (Cd, Cu, Zn) on the population growth rate (r) of the marine diatom, Skeletonema costatum. S. costatum. The population growth rate (r) of the species was determined after 96 hrs. of exposure to Cd (0, 0.63, 1.25, 2.50, 5.00, 10.00 ppm), Cu (0, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50 ppm) and Zn (0, 0.31, 0.63, 1.25, 2.00, 2.50, 5.00 ppm). It was observed that 'r' in the control (absence of Cd, Cu and Zn) were greater than 0.05, however suddenly decreased with increased heavy metal concentrations. Cd, Cu and Zn reduced 'r' in a dose-dependent manner and a significant reduction were occurred at concentration of greater than 1.25, 1.25 and 2.50 ppm, respectively. Based on the toxicity, the heavy metal were ranked as Cu>Zn>Cd, with EC50 values of 1.11, 2.13 and 6.84 ppm, respectively. The lowest-observed-effective-concentration (LOEC) of 'r' in exposed to Cd, Cu and Zn were 1.25, 1.00, 2.00 ppm, respectively. Precisely, a concentration of greater than 1.25 ppm of Cd, 1.00 ppm of Cu and 2.00 ppm of Zn in marine ecosystems induced toxic effect on the 'r' of S. costatum. Based on our results, we suggested that the 'r' of S. costatum might be a useful bio indicator for the toxicity assessment of heavy metals in marine ecosystems.

• Journal of Korean Society on Water Environment
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• v.29 no.2
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• pp.223-231
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• 2013

This study investigated the physio-chemical water quality and the standing crop of the phytoplankton of Dong-stream in Jeollanam-do from May 2010 to Feb 2011. The indicators and the dominant species of phytoplankton were also measured to investigate the water quality of estuary. Nutrients turned out to be eutrophic to hypertrophic in most sites with total nitrogen ranging 1.023~10.743 mg/L and total phosphorous ranging 0.0182~1.6848 mg/L. The site D6 had the highest BOD ranging 0.6~7.5 mg/L. Total of 205 taxa appeared within the research period, Bacillariophyceae being the highest number of taxa. The appeared species were taxa resistant to pollution including Navicula pupula, N. subminuscula, Nitzschia amphibia and N. palea. The downstream is thought to be greatly affected by the ocean water since marine and estuary phytoplankton such as Skeletonema costatum, Coscinodiscus radiatus, Bacteriastrum delicatulum and Eucampia biconcave appeared. Diatom appeared mainly as dominant species including Cymbella minuta, Melosira varians, Gomphonema parvulum, Stephanodiscus hantzschii. As for Stephanodiscus hantzschii, it dominates during fall and winter when the water temperature drops. Diatom showed 50% or higher dominant rate in all seasons at most sites. Most sites turned out to be eutrophic based on the standing crop of cells and chlorophyll a concentration. Total of 15 polluted water indicating taxa including Oscillatoria limosa appeared. From this result, the Dong-stream was considered to be in the eutrophication.

• Journal of Environmental Science International
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• v.23 no.6
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• pp.1003-1012
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• 2014

We examined the combined impacts of future increases of $CO_2$ and temperature on the growth of four marine diatoms (Skeletonema costatum, Chaetoceros debilis, Chaetoceros didymus, Thalassiosira nordenskioeldii). The four strains were incubated under four different conditions: present ($pCO_2$: 400ppm, temperature: $20^{\circ}C$), acidification ($pCO_2$: 1000ppm, temperature: $20^{\circ}C$), global warming ($pCO_2$: 400ppm, temperature: $25^{\circ}C$), and greenhouse ($pCO_2$: 1000ppm, temperature: $25^{\circ}C$) conditions. Under the condition of higher temperatures, growth of S. costatum was suppressed, while C. debilis showed enhanced growth. Both C. didymus and T. nodenskioldii showed similar growth rates under current and elevated temperature. None of the four species appeared affected in their cell growth by elevated $CO_2$ concentrations. Chetoceros spp. showed increase of pH per unit fluorescence under elevated $CO_2$ concentrations, but no difference in pH from that under current conditions was observed for either S. costatum or T. nodenskioeldii, implying that Chetoceros spp. can take up more $CO_2$ per cell than the other two diatoms. Our results of cell growth and pH change per unit fluorescence suggest that both C. debilis and C. didymus are better adapted to future oceanic conditions of rising water temperature and $CO_2$ than are S. costatum and T. nodenskioeldii.

• Journal of Food Hygiene and Safety
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• v.14 no.3
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• pp.270-276
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• 1999

In previous reports, the authors isolated the algicidal marine bacterium, Alteromonas sp. SR-14 and demonstrated its growth inhibition of diatom, Chaetoceros calcitrans (C. calcitrans). In this paper, we studied the effects of cell free culture filtrate of Alteromonas sp. SR-14 on the growth of C. calcitrans, and the characteristics of the algal growth inhibition substance. The culture filtrate of Alteromonas sp. SR-14 grown in peptone broth showed growth inhibition activity against C. calcitrans. The reasonable culture conditions of the bacterium for producing of algal growth inhibition substances were $15~20^{\circ}$ in temperature, 7.0-9.0 in pH and $23~30{\textperthousand}$ in salinity, respectively. The algal growth inhibition activity of culture filtrate was increased from stationary phase in growth curve of Alteromonas sp. SR-14. The molecular weights of algal growth inhibition substances produced by Alteromonas sp. SR-14 were ranged about from 3 KDa to 12 KDa. Among the substances, less than 10 KDa fraction were stable by heating at $100^{\circ}$ for 10 minutes, while more than 10 KDa fraction were heat labile. According to the experimental results, the algal growth inhibition substance produced by the bacterium was not a single compound.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.1
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• pp.79-88
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• 1991

To study the distribution patterns of epiphytic diatom on Porphyra species and ambient water phytoplankton, samples were collected in the Gaeya Island, Kyukpo, and Mokpo of the Yellow Sea from February 1989 to March 1990. Foully species of epiphytic diatoms were observed. Of these, the dominant species of epiphytic diatoms are Limophora dalmatica, L. abbreviata, Melosira nummuloides, Paralia sulcata, Achnanthes javanica var, subconstricta, Grammatophora oceanica, Navicula sp., Synedra sp., Pinnularia sp., Fragilaria striatula, Cocconeis scutellum var. parva. Licmophora dalmatica predominated troughout the study period. Phytoplankton standing stocks were relatively larger than those of other coastal areas in the Yellow Sea, Korea. Distribution patterns of epiphytic diatoms and the ambient water phytoplankton in Gaeya Island were similar to those of Kyukpo, but different from Mokpo.

• Journal of Environmental Science International
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• v.20 no.10
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• pp.1243-1263
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• 2011

This study was carried out to determine marine environments and phytoplankton community in Deukryang Bay during the period of summer in 1987-2010. Water temperature, salinity, pH and dissolved oxygen were shown in much yearly fluctuations. In August, water temperatures in surface and on bottom were the highest, compared with average surface (24.54$^{\circ}C$) and bottom (22.90$^{\circ}C$) water temperature for 18 years in Deukryang Bay. The main reason is assumed to longer duration of sunshine during the period of August. Although the amount of the rainfall in August was the highest, significant impact of marine environment did not show. Most of dissolved inorganic nitrogen and phosphate in Deukryang were lower concentration during summer and N:P ratio also showed below 18 in Redfield. In particular, extreme increasing of N:P ratio in August was occurred by intensive precipitation. Distribution of phytoplankton community was a consistent occurrence for 18 years. The genus of Chaetoceros, Cosinodisucs and Skeletonema were regarded as the represent diatom, whereas the highest occurrence of genus among dinofagellates was Ceratium. It is thought that the relationship between phytoplankton and nutrient has a strong positive signal, although nutrients persist a little concentration and much fluctuations in marine environments were observed. High availability in phytoplankton is contributed to consistently provide the food organism of shellfish. Consequently, recent decreasing production of shellfish and seed are probably associated with higher temperature during the period of summer. However, higher temperature is also occurred ago and after 2000. On the basis of geography, Deukryang Bay had a small mouth and long channel, which is attributed to decreasing genetic diversity. It is assumed that higher temperature and lower genetic diversity have a extreme impact of larvae and shellfish for reproduction in Deukryang. It is necessary to persistently monitor based on water quality and phytoplankton community.

• Proceedings of KOSOMES biannual meeting
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• 2004.11a
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• pp.105-108
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• 2004

Organic acid is made with carbonized organic acid that is produced from charcoal burning process. It is evaluated whether carbonized organic acid is able to removed Enteromorpha in the laboratory and Porphra aquaculture farm test. The optimum condition for Enteromorpha removal are revealed ten times dilution and ten second immersion. The mortality rate of Enteromorpha is $95\%$ and diatom-detaching rate is $100\%$ by the organic acid treatment. On the other hand, the mortality rate of Porphra is lower than $5%\$. It was measured that nitrogen was 0.175 mg/l and phosphorus was 0.0158 mg/l. Therefore, Concentration of nutrients were lower than being necessary to Porphra growth. Growth rate of Porphra was $12\%$ increased by organic acid treatment with carbonized organic acid added nutrient.