• Ocean and Polar Research
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• v.27 no.1
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• pp.15-24
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• 2005

In order to investigate the structures and dynamics of phytoplankton communities, each physicochemical environmental factor, species composition, standing crop, and dominant species were examined in the marine ranching ground of Tongyeong coastal waters from April to October, 2000. During the studies, mean water temperature and salinity were $18.8^{\circ}C$ and 33.1 psu, respectively. DO, SS and transparency varied from 5.43 to 11.39 mg/l, 14.6 to 32.4mg/l and 3.5 to 9.0m, respectively. Light intensities varied from 0.02 to $966{\mu}E/m^2/s$, which decreased with depth. $NH_4-N,\;NO_3-N,\;NO_2-N,\;PO_4-P,\;and\;SiO_2-Si$ were fluctuated from 0.059 to 0.332 mg/l, 0.040 to 0.800 mg/l, 0.001 to 0.468 mg/l, 2.3 to $143.0{\mu}g/l$, and 0.007 to 0.600 mg/l, respectively. chlorophyll a concentrations were fluctuated from 0.7 to $8.9{\mu}g/l$. Among 130 taxa of phytoplankton communities observed. diatoms occupied more than 81.54% of the total species, and the others were dinoflagellates and silicoflagellates. Phytoplankton standing crops ranged from $4.6{\times}10^4\;to\;2.6{\times}10^6cells/l$. In October, the standing crops were at bloom level showing more than $10^6cells/lat$ all stations. Dominant species changed by month and station. Leptocylindrus danicus occupied 59.84% in April and 22.03% in June. Pseudo-nitzschia pungens in August and Chaetoceros socialis and Skeletonema costatum in October were predominant species. In order to investigate factors influencing the total phytoplankton standing crops the correlations between the standing crops of diatoms, dinoflagellates, all phytoplanktons occurred and environmental factors were calculated using a multiple regression analysis. The coefficient of determination $(R^2)$ for total standing crops was 0.63 which explained 63% of variance and that of $R^2$ for diatom was 0.82. In statistical analysis, the results showed that the environmental factors influencing the size of the communities were predominantly water temperature, salinity and silicate.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.1
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• pp.25-33
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• 1998

Temporal and spatial variations of nutrient elements (ammonia, nitrate, nitrite, phosphate and silicate) in surface seawater off the west coast of Korea were investigated during three periods of field survey aboard R/V Eardo of KORDI (May 1995 and June 1996) and a patrol vessel of the National Maritime Police (November 1995). In general, the concentrations of nutrient elements were lowest in June and highest in November except for ammonia that showed the lowest concentration in May and the highest in November. The results tell us that the development of thermocline and tidal front restricts riverine and benthic supply of nutrient elements to surface waters in June in the offshore regions of the study area which become nutrient-depleted due to phytoplankton bloom in spring. In late fall (November) the level of nutrient concentrations of the surface waters of the study area become high due to vigorous vertical mixing within the water column, which supplies nutrient-enriched bottom water to the surface waters.

• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.114-126
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• 2020

Bloom-forming toxic cyanobacteria Microcystis spp. are common in the summer season in temperate freshwater ecosystems. Often, it leads to the degradation of water quality and affects the quality of drinking water. In a previous study, NQ (naphthoquinone) compounds were shown to be effective, selective, and ecologically safe algicides for Microcystis spp. blooms. To analyze the superiority of developed NQ derivatives, we conducted a microcosm experiment using clay, which is frequently used in South Korea. Similar to previous studies, the NQ 40 and NQ 2-0 compounds showed high algicidal activities of 99.9% and 99.6%, respectively, on Microcystis spp. at low concentrations (≥1 μM) and enhanced phytoplankton species diversity. However, when treated with clay, a temporary algicidal effect was seen at the beginning of the experiment that gradually increased at the end. In addition, treatment with the NQ compounds did not affect either the abiotic or biological factors, and similar trends were observed with the control. These results showed that the NQ 2-0 compound was more effective, with no ecosystem disturbance, and more economical than the currently used clay. These results suggest that NQ 2-0 compound could be a selective, economically and ecologically safe algicide to mitigate harmful cyanobacterial blooms in the field.

• Korean Journal of Ecology and Environment
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• v.33 no.2 s.90
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• pp.145-151
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• 2000

A porous silicate material named as CellCaSi was tested for the removal of microalgae in the water sample from a eutrophic pond. The effects of the CellCaSi on water qualities were investigated on the basis of both the particle size (under 1, 2,and 4 mm) and the added amount (0, 1, 5, and 10 g/l) of the CellCaSi. The removal efficiency of chlorophyll-a was highest at 79% by the addition of 10 g/l of the CellCaSi (under 1 mm) at day 3 after treatment. That is, the removal efficiency of chlorophyll-a by the CellCaSi increased with smaller particle size and more added amount. The dominant species, Chlorella ellipsoidea, was not changed by the addition of the CellCaSi, but the species number and standing crop of the algae diminished. Total nitrogen concentration was not changed much by the addition of the CellCaSi, whereas total phosphorus concentration was reduced. pH and turbidity were not changed by the addition of the CellCaSi, whereas conductivity showed a high correlation with the amount of added CellCaSi ($Y\;=\;29.2 {\cdot}X+306$, $r^2\;=0.984$). Therefore, it seems to be necessary to limit the amount of the CellCaSi under 6.6 g/1 in consideration of a registered maximum conductivity of $500\;{\mu}mhos/cm$ for raw and potable waters.

• Korean Journal of Agricultural Science
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• v.7 no.1
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• pp.33-37
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• 1980

To clarify the influence of ethylene on flowering and senescence of carnation flowers and the treatment of the floral preservative solution for reducing their ethylene production, bud-cut carnations (Dianthus caryophyllus L. cv. Coral) were sprayed with/without 500 ppm ethephon [(2-chloroethyl) phosphonic acid] and then held in distilled water or preservative solution (5% sucrose+50 ppm $AgNO_3$+300 ppm 8-hydroxyquinoline). 1. Ethylene inhibited to bloom carnation flowers because of causing sleepiness. 2. Carnation flowers were led to senescence after a lot of ethylene was produced by them. Therefore, ethylene seems to act as a trigger of senescence in carnation flowers. 3. The features of senescence in carnation flowers were different in accordance with the amount of ethylene produced by the flowers. 4. Exposure to ethylene decreased fresh weight, flower diameter, and water uptake of carnations. 5. The floral preservative extended vase life markedly by inhibiting ethylene production of cut flowers. The flowers exposed to lots of ethylene, however, were not restored even though they were held in the preservative solution.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.3
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• pp.164-170
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• 2005

To investigate the aquatic environmental factors and processes controlling primary production in the Seomjin River estuary, chlorophyll a, nutrients, pH, SS, DO, temperature, salinity and primary productivity were measured in February, April, August and October, 2001. Primary productivity values ranged between 50.7 and 14,120.3 mg C $m^{-3} day^{-1}$ during the sampling period. In contrast to other estuaries, light condition did not seem to be the important limiting factor far primary production due to high water-column transparency during most of the time. The autumn bloom occurred in regions where salinity values ranged between 10 and 20 psu. This phenomenon appeared to develop every year and deserves further investigation. The behavior of nutrients, which is one of the major factors controlling the primary productivity, appeared to be governed by salinity regimes. The main source of nitrogenous nutrients seemed to be the freshwater runoff from the Seomjin River. However, that of phosphorus seemed to be from the industrial wastewater in Gwangyang area. The primary pro-duction of phytoplankton in the study area varied with space and time, showing a close correlation with water column transparency, and exhibited higher values compared to those of adjacent coastal regions in Gwangyang Bay.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.417-423
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• 2018

It analyzed the efficiency of the runoff reduction of artificial reservoir by analyzing the influent and effluent of reservoir located downstream of the livestock area. Production of non point pollutants in livestock feeding areas, which is located at steep slope land, was mainly due to first flushes. Suspended Solid concentration of influent increased due to amount of rainfall, and T-P also increased over four times and 30 % of total nitrogen increased on average compared to those of dry season. While the concentration of nitrate nitrogen showed little variation, ammonia nitrogen increased over two times. The storage style nonpoint reduction facility showed the highest removal efficiency of 53 % for total phosphorus in dry weather, when the removal efficiency was 37 % for suspended solids, 10% for organic compounds, and 5 % for total nitrogen. Since algal bloom grows due to eutrophication in summer, the minus removal efficiencies of nitrogen concentration through the reservoir occurred with high frequency. Removal efficiency decreased during rainfall, showing 60 % for supended solids, and 22 % for total phosphorus. While having over nine times of capacity than the standard of non-point removal facility from Ministry of Environment, it was impounded with water during rainy season, showing not enough nonpoint removal efficiency, which indicates that maintenance is also an important factor to the nonpoint removal efficiency.

• Korean Journal of Ecology and Environment
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• v.54 no.1
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• pp.39-48
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• 2021

In order to control algal bloom, which causes environmental problems such as eutrophication in freshwater ecological environments, many attempts have recently been made using biological approaches. Among them is filtration using bivalve. Algae control with filter-feeding bivalves is emerging as an eco-friendly method. In this study, bivalves collected at Baekje weir in Geum River in Korea from Jun to Sep 2020 were tested to find out the possibility of algae control using filter-feeding bivalves through laboratory experiments. The Unio douglasiae, Anodonta woodiana, and Anodonta arcaeformis collected from Baekje weir were put into a water tank (2 L) containing Clorella vulgaris, and as a result, the average filtration rate was 95.9% per animal after 24 hrs. Calculating this with the Chl-a concentration converted to a calibration curve, it was found that the average of 154.84 ㎍ L^-1 of Chl-a was reduced. Based on this calculation, the possibility that one bivalve can eliminate Chl-a in one month is 0.0005%. It is expected that the effect is 20.14% when there are 40,000 animals. These results indirectly showed how effective bivalve's ability to control Chl-a in their habitat is. Although this study was limited to calculating the algae control ability of aquatic ecosystem based on the filtration rate of bivalve and the corresponding Chl-a reduction rate, it is thought that it will be used as basic data for integrated research from various factors and viewpoints (phytoplankton, aquatic plants, benthic organisms, and sediments) through additional research.

• ALGAE
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• v.36 no.1
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• pp.37-50
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• 2021

Heterotrophic dinoflagellates Gyrodinium spp. are one of the major grazers of phytoplankton in many coastal waters. Gyrodinium dominans, G. jinhaense, and G. moestrupii have similar morphologies but different edible prey species. To explore the variations in the ecological niches of these three species, we investigated their spatial-temporal distributions in Korean waters. Because of the high similarity in morphology among these three Gyrodinium species, we used real-time polymerase chain reactions to quantify their abundance in water samples that were seasonally collected from 28 stations along the Korean Peninsula from April 2015 to October 2018. Cells of G. dominans were found at all sampling stations, G. jinhaense at 26 stations, and G. moestrupii at 22 stations, indicating that all three species were widely distributed in Korea. Furthermore, all three species displayed strong seasonal distributions. The largest numbers of the stations where G. dominans and G. jinhaense cells were present were found during the summer (26 and 23 stations, respectively), but that for G. moestrupii was found in the autumn (15 stations). The abundance of G. dominans was positively correlated with that of G. jinhaense, but not with that of G. moestrupii. The highest abundances of G. dominans (202.5 cells mL-1) and G. jinhaense (20.2 cells mL-1) were much greater than that of G. moestrupii (1.2 cells mL-1). The highest abundances of G. dominans and G. jinhaense were found in July, whereas that of G. moestrupii was found in March. The abundances of G. dominans and G. jinhaense, but not G. moestrupii, were positively correlated with water temperature. Therefore, the spatial-temporal distributions of G. dominans and G. jinhaense were closer than those of G. moestrupii and G. dominans or G. jinhaense. This differs from results based on the relative differences in ribosomal DNA sequences and the types of edible prey reported in the literature. Thus, the variations in spatial-temporal distributions and prey species of these three Gyrodinium species suggest that they may have different ecological niches in Korean coastal waters.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.402-402
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• 2020

대청호는 1998년 조류경보제 도입 이후 1999년과 2014년을 제외하고 매년 조류 경보가 발령되었으며 2001년 조류 경보 '대발생'이 발령된 후 2017년 가장 높은 조류 발생 수치를 기록하였다. 상시 조류 발생 지역인 대청호 내 녹조를 제어하기 위해 비점오염원 발생원을 기준으로 우선관리지역을 선정하고, 각 지역의 특성을 반영한 관리대책을 제안하였다. 우선관리지역 선정을 위해 대청호 유역 내 오염총량 소유역을 기준으로 각 소유역의 농업 비점오염원의 발생부하량을 산정하고 유출을 고려한 가중치를 추가하였다. 본 연구에서는 농업 비점오염원을 크게 토지계 비점오염원과 축산계 비점오염원으로 분류하였으며, 토지계 농업비점오염원은 논, 밭, 과수원 지역으로 정의하였다. 발생부하량의 산정은 오염총량관리 기술지침(2019, 국립환경과학원)을 기준으로 하였으며, 토지계 발생부하량 산정을 위한 토지계 정보원으로 환경부에서 제작 및 배포하는 세분류 토지피복도를 축산계 발생부하량 산정을 위한 축산 두수는 2017년 기준 전국오염원조사 내 축산두수를 이용하였다. 토지계 비점오염원의 하천까지 유출을 반영하기 위해 각 소유역별 평균 경사도를 가중치로 이용하였으며, 축산계 비점오염원은 오염물질이 발생한 후 하천까지의 평균 유출 정도를 확인하여 가중치로 반영하였다. 실제 하천에 미치는 영향이 높은 지역에 대한 우선적인 관리를 위해 하천수 수질측정망에서 측정한 수질 데이터와의 비교를 통하여 최종 우선관리지역을 보청A03, 보청A05, 금본F14, 금본F22 소유역으로 선정하였다. 각 소유역에 대한 수질 관리목표를 확인하였으며, 지역의 특성을 분석하여 토지계 및 축산계 비점오염원에 대한 적절한 관리대책을 제안하였다. 본 연구에서 사용한 수질 측정망 데이터가 각 소유역보다 적게 분포하여 소유역에서 발생한 비점오염물질이 하천에 미치는 영향을 직접 파악하는데 한계가 있었다. 또한, 축산계의 경우 발생한 비점오염물질이 모두 하천으로 유입되지 않으며, 축산계 비점오염원의 배출경로를 파악하는데 어려움이 있다는 한계를 가진다. 본 연구의 한계를 바탕으로 농림축산식품부 및 축협 등에서 구축하는 사육두수의 데이터를 이용하는 방법론 등의 추가적인 연구가 필요할 것으로 보인다.