• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.2 s.25
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• pp.75-79
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• 2006

In order to study the characteristics of water quality in coastal water and mechanism of phytoplankton blooms, factors of water quality were investigated in diatom bloom area due to rainfall event and no diatom bloom area Diatom blooms occurred after heavy rain and the dominant species were Skeletonema costatum($1,200{\sim}5,000cells/mL$) and Thalassiosira spp.($750{\sim}1,200cells/mL$). In diatom bloom area, water temperature, pH, and dissolved oxygen were observed at higher level than in no diatom bloom area Although these two areas were only 20 meters apart from each other, sharp difference in coastal water quality between two areas was observed. In diatom bloom area, concentrations of nitrogen, phosphorus, and silicate were observed at lower level than in no diatom blooms area. This seems to be due to inflow of much trace metal such as Fe, Mo, Se and so on than nitrogen, phosphorus, and silicate by rainfall events. However, distinct differences in DIN/DIP and $DIN/SiO_2-Si$ between these two areas were not observed.

• Ocean and Polar Research
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• v.29 no.2
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• pp.101-112
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• 2007

In order to examine the short-term variations of phytoplankton and heterotrophic protozoa community structures with bloom events, water samples were collected every other day at one site in the coastal water off Incheon, Korea, from August 15-September 30, 2001. $Chlorophyll-{\alpha}$ concentrations varied widely from 1.8 to $19.3\;{\mu}g\;l^{-1}$ with the appearances of two major peaks of $Chlorophyll-{\alpha}$ concentration during the study period. Size-fractionated $Chlorophyll-{\alpha}$ concentration showed that net-size fraction ($>20\;{\mu}m$) comprised over 80% of total $Chlorophyll-{\alpha}$ during the first and second bloom periods, nano-size fraction ($3{\sim}20\;{\mu}m$) comprised average 42% during the pre- (before the first bloom) and post-bloom periods (after the second bloom), and pico- size fraction ($<3\;{\mu}m$) comprised over 50% during inter-bloom periods (i.e. between the first and second bloom periods). Dominant phytoplankton community was shifted from autotrophic nanoflagellates to diatom, diatom to picophytoplankton, picophytoplankton to diatom, and then diatom to autotrophic nanoflagellates, during the pre-, the first, the inter, the second, and the post-bloom periods, respectively. During the blooms, Chaetoceros pseudocrinitus and Eucampia zodiacus were dominant diatom species composed with more than 50% of total diatom. Carbon biomass of heterotrophic protozoa ranged from 8.2 to $117.8\;{\mu}gC\;l^{-1}$ and showed the highest biomass soon after the peak of the first and second blooms. The relative contribution of each group of the heterotrophic protozoa showed differences between the bloom period and other periods. Ciliates and HDF were dominant during the first and second bloom periods, with a contribution of more than 80% of the heterotrophic protozoan carbon biomass. Especially, different species of HDF, thecate and athecate HDF, were dominant during the first and the second bloom periods, respectively. Interestingly, Noctiluca scintillans appeared to be one of the key organisms to extinguish the first bloom. Therefore, our study suggests that heterotrophic protozoa could be a key player to control the phytoplankton community structure and biomass during the study period.

• Korean Journal of Ecology and Environment
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• v.37 no.2 s.107
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• pp.236-240
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• 2004

To examine the algicidal effect of co-treatment of biological control agent on centric diatom Stephanodiscus hantzschii in the filtered water, an endemic algicidal bacterium (Pseudomonas putida) and a heterotrich ciliate (Stentor roselli) were iso-lated from Pal'tang reservoir, Korea. Bacterial isolate and ciliate removed 98% and 80% of the diatom for 7 days of cultivation. Co-treatments of these two agents perfectly inhibited the diatom growth, compared to the single treatment of each agent. This synergistic interaction of the bacterium and ciliate could provide an effective tool in the biomanipulation to control the diatom bloom in freshwater lakes and streams.

• Journal of environmental and Sanitary engineering
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• v.19 no.2
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• pp.23-29
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• 2004

An algicidal effect of endemic algicidal bacterium (Pseudomonas putida) and rotifer zooplankton (Brachionus calyciflorus) on diatom Stephanodiscus hantzschii were examined in the filtered water, and were compared with those of bacterium plus ciliate. Bacteria removed as 80% of the diatom within 3.5 days, while ciliate and zooplankton suppressed 57% and 40% of diatom during the same period, respectively. Mixed treatment of bacteria plus ciliate removed as 54% of diatoms, while that of bacteria plus zooplankton decreased as 85%. Although single bacteria and mixed treatment of bacteria plus zooplankton quickly decreased the diatom in the initial of experiment, bacteria plus ciliate perfectly removed the diatom in culture flask within 5.5 days of the study. On the other hand, other single and mixed treatments did not clear the diatom during the same period, and over 10% of them still remain in culture flask. Predator biomass in the presence of algicidal bacteria showed the growth patterns; zooplankton gradually decreased, and ciliate sustained over 0.5 cells/ml. These results indicated that the addition of ciliate to the algicidal bacterium in controlling the diatom Stephanodiscus hantzschii is more effective than that of zooplankton. Therefore, this synergistic interaction relationship between the bacterium and ciliate play an important role in the bio-manipulation using bio-agents to control the diatomal bloom in freshwater lakes and streams.

• ALGAE
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• v.18 no.4
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• pp.361-363
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• 2003

This study was conducted at Seomjin River estuary to identify the causative species of algal bloom and their blooming cycles. Field surveys were conducted at 4 stations in every week from April to December of 1999. Thirty species were observed as the causative species of alga bloom. Skeletonema costatum, Thalassiosira sp., and microflagellate spp. (mixed red tide: Chroomonas sp. and two species of Prasinophycea) made algal blooms during the present study period. In addition, toxic algal species of diatom Pseudo-nitzschia multiseries and dinoflagellate Dinophysis acuminata were observed. The algal blooms were caused by microflagellate spp. in June, Thalassiosira sp. in July and Skeletonema costatum in August. Generally, the algal blooms persisted for about 5 days in this area.

• Korean Journal of Environmental Biology
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• v.28 no.1
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• pp.20-29
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• 2010

Cochlodinium polykrikoides has occurs regularly during the summer in the South Sea of Korea. To investigate photosynthetic pigments concerned with phytoplankton community structure as bloom of Cochlodinium polykrikoides, the experiment was sampled at 20 stations three times between July and September 2002 in the Southern Sea of Korea. The distribution of peridinin, the biomarker of dinoflagellate, was higher at the blooming time than it was before and it disappeared after bloom. The correlative coefficients between Chl. a and peridinin at the blooming time and out of bloom were 0.9253 and 0.1613, respectively. This result indicated that the bloom was caused by dinoflagellate. The correlative coefficients between Chl. a and fucoxanthin were 0.3282 and 0.9759, respectively, and the correlative coefficients showed the succession from dinoflagellate to diatom. This result means that the bloom of Cochlodinium polykrikoides can be detected by Chl. a information from satellite remote sensing. Therefore, if the algorithm to detect peridinin in addition to Chl. a were to be developed, dinoflagellate red tide could be monitored more effectively.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.567-577
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• 2020

The infection of marine diatom Coscinodiscus wailesii by a parasitic protist from the Yongho Bay of Busan, Korea was observed during the diatom bloom events in 2017 through 2018. The morphological and molecular features suggested that the parasitic nanoflagellate Pirsonia diadema was responsible for the infection. During the study period, the parasite prevalence ranged from 0.3% to 3.3%, and infected C. wailesii cells were observed only at surface seawater temperatures ranging between 10.9 and 19.9℃, although the host population appeared at temperatures above 25℃. The parasite and host system was successfully established as cultures. Using the cultures, we determined the morphological features over the infection cycle, parasite generation time, parasite prevalence as a function of inoculum size, and zoospore infectivity and survival time. The diatom C. wailesii was readily infected by the parasite P. diadema, with a parasite prevalence reaching up to 100% and a zoospore to host inoculum ratio above 20:1. The survival and infectivity of the parasite zoospores decreased with age. While the zoospores could survive up to 88 hours, they quickly lost their ability to infect after 48 hours. These results could lead to a better understanding of the biology and ecology of the parasitoid infecting the giant-sized diatoms in coastal waters.

• Journal of the Korean earth science society
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• v.36 no.2
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• pp.190-197
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• 2015

This study investigated the paleoclimatic change using diatoms that were extracted from the high-resolution laminated layers of diatom ooze sediment cores GC08-EB01 in the eastern basin of the Bransfield Strait, Antarctica. The range of diatom valves per gram of dry sediment was from $0.4-4.2{\times}10^8g^{-1}$ in quantitative diatom assemblage analysis. Laminations are classified using visually dominant diatom species and terrigenous content. Biogenic diatom ooze laminae characterised by bloom of Corethron crilophilum, Eucampia antarctica, Fragilariopsis curta, F. kerguelensis, Odontella weissflogii, Proboscia inermis, R. styliformis, Thalassiosira antarctica, and Chaetoceros resting spores. Terrigenous laminae characterised by mixed diatom assemblage. The ratio of (Fragilariopsis curta+F. cylindrus)/Thalassiosira antarctica increase in horizons, suggesting increased sea-ice cover in the study area during the late Holocene (cold events). As a result, five cold events are identified on the basis of frequency of the critical taxa throughout the section.

• 한국해양학회지
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• v.12 no.1
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• pp.13-32
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• 1977

In order to determine the distributional ecology, and to investigate factors influencing these features, the diatom communities in plankton at depths of one, twenty-five, fifty, and seventy five meters in the area were studied and measured over a fifteen month of period. Measurements of environmental factors including temperature and salinity and algal nutrients such as phosphate, silicate, nitrate, and ammonia were also made at the same depths and locations. The results indicate that the size of diatom communities and the species population changes were heavily dependent upon to season and location parameters as well as nutrient concentrations and hydrographic factors. Major factors influencing population distributions varied with principal species responsible for dominant species and species sucession. Two distinct distributional patterns in total diatom crop were observed in the study area. Maximum standing crop observed during spring and/or summer were related to the concentration of nutrients available at the onset of the spring bloom on a large scale. On a small scale, however, the distributions of total diatom standing crops were significantly correlated with both season/location factors and with hydrographic parameters as well. Vertical stratification of diatoms was observed only in the presence of the thermocline in the water column. Within the study area there was some seasonal consistancy in the composition of the species groups. However, some species association in these environments may vary with the change of season.

• 한국해양학회지
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• v.26 no.2
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• pp.144-154
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• 1991

After the completion of the Nakdong River estuary barrage, environmental characteristics and phytoplankton communities in the estuary were investigated from April to December, 1989. dissolved oxygen seems to have decreased in the just lower region of the barrage off Janglim, while ammonia and phosphate concentration increased, probably due to the waste discharge from the Janglim stream and stagnation of water after the barrage construction. Concentrations of nitrate and dissolved silicate were negatively correlated with salinity, suggesting that major source is the Nakdong River discharge. In April, there was a diatom (Asterinella sp.) bloom in the upper region of the barrage, while in July, a diatom (Skeletonema costatum) bloom in the estuary mouth. The green and blue-green algae in species composition seem to have increased after the barrage construction. The relatively high concentration of chlorophyll b in the upper region of the barrage probably result from the high density of freshwater green-algae there. Among the species occurred in the study area, many were indicative of water pollution. It seems that environmental characters and phytoplankton communities are changing after the barrage construction.