• Journal of Korean Society of Environmental Engineers
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• v.39 no.5
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• pp.288-302
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• 2017

Accurate measurement of benthic nutrient fluxes (BNF) is a prerequisite for evaluating the effect of sediments on nutrient cycle in the surface water. The intact sediment cores were collected in July 2015 at the midstream of Nakdong River. We identified pre-incubation time (6, 12, 24 hr), dissolved oxygen concentration (90, 70, 50% saturation), diffusive boundary layer thickness (0, 0.6-0.8, 1.2-1.4 mm), and incubation temperature (10, 17, 20, $25^{\circ}C$) as the most important control factors, and measured the BNF fluctuation with the variation of these factors using the laboratory sediment core incubation method. Since the chemical composition, redox condition, hydrodynamic regimes and microbial activities at the sediment-water interface were changed as a result of the alteration of control factors, sediment core incubation should be conducted under as close to the natural conditions of study site as possible, in order to produce the results similar to actual values. Relative percentage differences between two replicates were below 20% in most control factors, which showed satisfactory precision for strict compliance with the experimental conditions and procedures. In the further studies, we will compare the results of core incubation with those of in situ measurements to confirm the accuracy of the sediment core incubation method.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2002.10a
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• pp.139-139
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• 2002

금강 하구 연안에서 2001년 4월부터 10월까지 월 2회씩 관측 및 분석한 자료를 가지고, 금강 하구 연안역의 해황과 관련하여 영양염, 부유물질 및 chl-a의 분포 특성을 살펴보았다. 담수 유출이 없을 때에는 금강 하구 연안에서 조석 주기에 따른 수층의 성층과 혼합이 교대로 반복되지만, 담수의 유출이 있을 경우에는 조석 강도에 관계 없이 금강 하구에서 저염수가 표층에 잔존하며 성층을 유지하고 있었다. (중략)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.218-219
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• 2000

바다목장화는 자연급이형 재배어업시스템이며, 해류제어 막구조물(Fig. 1)은 (1)어패류의 서식환경 조성 및 제공, (2)기초생산의 증대를 통한 고차 소비자의 위집과 생산 증대 및 (3)어류의 사료가 되는 저서생물의 증식 효과라는 직접적인 효과와 (4) 와류, 상승류에 수반된 유동변화, 음향발생 등에 의한 부차적인 집어효과를 가질 뿐 아니라 (5) 저층 영양염의 분산 소모를 통한 계절적 영양염의 집중부상에 의한 계절적 부영양화의 감소효과를 가지는 기능시설로서 중요한 증식시설이다(김과 류, 1997). (중략)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.487-488
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• 2001

저서동물은 생태계 내에서 여러 가지 중요한 역할을 수행하고 있다. 저서생물은 유용저서어류나 유용 무척추동물의 먹이로서 매우 중요한 부분을 차지하고 있다. (Dean, 1973: McIntyre, 1978; McIntyre and Eleftherion,1968) 따라서 저서동물은 먹이생물로서 저서어류의 성장효율과 생산에 큰 영향을 미치는 요인이 될 수가 있다(Mills,1975). 또한 저서동물은 부식질 먹이 연쇄를 통하여 퇴적물내의 영양염을 변화 시킬 뿐만 아니라 최적물 내에서 수괴로의 영양염 재순환의 중요한 매개자 역할을 한다. (중략)

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.34-42
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• 2016

In order to prepare for the type approval test for the United States Coast Guard (USCG) Phase-II of Ballast Water Treatment System (BWTS), a phytoplankton mass culture was conducted in a mesocosm enclosure. We evaluated the response of the phytoplankton community after nutrient addition (+N, +P, and +NP) and investigated the development of the species with increasing culture time. After nutrient dosing, the phytoplankton population significantly (p < 0.05) increased from day 1 to day 3, depending on the nutrient treatments In particular, the specific growth rate of the phytoplankton community in the case of +NP treatment and + N treatment were estimated to be $2.47d^{-1}$ and $1.98d^{-1}$, respectively. The phytoplankton population density in the case of + NP treatment was approximately 50 times higher than that of the control group, suggesting that these treatments could be useful for mass culturing phytoplankton (> 75% of natural community) for the approval regulation of USCG Phase-II. In the phytoplankton community of the mesocosm, Pseudo-nitzchia spp. dominated in the logarithmic growth phase. The cell density decreased significantly (p < 0.05) with increasing time, coinciding with the nutrient limitation. At that time, the dominance of Pseudo-nitzchia spp. shifted to that of Cylindrotheca closterium. Therefore, the optimum nutrient concentration ($N:30{\mu}M$, $P:3{\mu}M$) and reasonable harvesting time (after 3 days in summer) found in this study for the mass culturing of phytoplankton may be helpful to meet the USCG Phase-II biological criteria to be used in BWTS.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.854-862
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• 2016

In summer 2010, we measured the concentration of dissolved oxygen (DO) and nutrients in the water collected at the bottom of Cheonsu Bay, off the west coast of Korea. We also measured nutrient fluxes across the sediment-water interface by deploying a fully-automated benthic lander, which collected time-series water samples inside a benthic chamber. We confirmed on-going hypoxia in the northern parts of the bay where polluted lake water was discharged. DO content in the water at the bottom was 2 mg/l, compared to 5 mg/l at the mouth of the bay in the south. Nutrient concentrations showed a trend that was opposite to that of DO. The variation of N/P ratios implies phosphate desorption and a release of nutrients caused by hypoxia. The organic carbon oxidation rate and oxygen consumption rate in the northern parts of the bay were about twice as fast as those at the mouth of the bay. Benthic fluxes of nutrients in the northern part of the bay were 4 to 6 times higher than those at the mouth. Our results imply that it is important to understand the role of hypoxia events to make an accurate estimation of material fluxes across the sediment-water interface.

• Korean Journal of Environmental Biology
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• v.32 no.1
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• pp.35-48
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• 2014

In order to estimate the effect of additional nutrients on phytoplankton growth and horizontal phytoplankton community distribution during the autumn season in 2010 and 2011, we investigated the abiotic and biotic factors of surface and bottom waters at 20 stations of inner and offshore areas in Gwangyang Bay, Korea. Also, nutrient additional experiments were conducted to assess additional nutrient effects on phytoplankton assemblage using the surface water. In both years, the total nutrients were high at the enclosed inner bay and the mouth of Seomjin River, whereas it was low at the St.15~20 where in influenced by the surface warm water current from offshore of the bay. On the other hand, nano- and pico-sized Chl. a were gradually increased towards the outer bay and their trends were significant in 2011 than in 2010. The cryptophyta species occupied more than 85% of total phytoplankton assembleges in 2010, whereas their abundance in 2011 remainds to be 1/10 levels of 2010. Following the cryptophata species, the diatom Chaetoceros spp. and Skeletonema-like spp. were found to be dominant species. Further the biosaasy experimental results shows that the phytoplankton biomass in the +N and +NP treatments was higher compared to control and +P treatments and its trend was significant at St.8 and St.20 where nutrient concentration were low. Based on the bioassay and field survey, providing the high nutrients may have stimulated to phytoplankton growth such as S. costatum-like spp.. In particular, opportunistic micro-algae such as Cryptomonas spp. were able to achieve the high biomass under the relatively mid nutrient condition from bottom after break down of seasonal stratification in the Gwangyang Bay.

• Proceedings of the Zoological Society Korea Conference
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• 1997.10b
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• pp.152.2-152
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• 1997

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.1
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• pp.22-29
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• 1999

Biological and chemical characteristics and trophodynamics in the frontal zone were investigated in the southern waters of Korea, Temperature, nutrients (dissolved inorganic nitrogen, $PO_4^{3-}-P$, and $SiO_2^{-}-Si$) chlorophyll a and zooplankton were collected and analyzed along the two transects, the frontal zone and the non-frontal zone, in April, 1994. Nutrients were higher in the non-frontal zone than in the frontal zone. But chlorophyll a concentration was high in the frontal zone, particularly at the 20 m depth of the main frontal station (St. TII-2), where was located at the junction between the stratified layer and the non-stratified layer with the lowest nutrients. Zooplankton was more abundant in the frontal zone than in the non-frontal zone, particularly at the innermost station of the frontal zone. Copepods showed high composition rate more than $90\%$ at all stations except the main frontal station (St. TII-2). At the main frontal station (St. TII-2), euphausiids and siphonophores were dominated. Chlorophyll a revealed a significant relationships with $SiO_2^{-}-Si$ in both transects and copepods in the non-frontal zone. Copepods also showed very close relationship with siphonophores in the frontal zone. This suggests that the abundance of copepods could be controlled as bottom-up in the non-frontal zone and as top-down in the frontal zone.

• 한국해양학회지
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• v.23 no.4
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• pp.194-206
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• 1989

Seasonal variations of nutrients (ammonium, nitrite, nitrate, phosphate and silicate), primary productivity and ammonium regeneration rate of macrozooplankton were investigate to understand the relationship between nitrogen recycling and nitrogen requirement by phytoplankton from Feburuary 1986 to November 1987 in the Kyunggi Bay, shallow estuarine water of Yellow Sea. In general, nutrients increased during the winter and depleted during the spring and the early summer except temporally sharp increase after flood in September. Ammonium was prevalently generally found in high concentration throughout the study area and it occasionally raised N/P ratio in the range of 30 to 70 as in the freshwater environment. Daily net primary productivity ranged from 30.3 to 3580.0 mgC/$m^2$/d with an average of 883.9 mgC/$m^2$/d. Annual primary productivity was determined to be 320.0 gC/$m^2$/yr. Carbon assimilation number ranged from 2.9 to 19.4 mgC/mg chl-a/h which increased in the summer and decreased in the winter. Nitrogen requirement by phytoplankton ranged from 0.4 to 45.0 mg at-N/$m^2$/d and turnover time of inorganic nitrogen ranged from 2.4 in the late summer to 122.7 days in the winter. Nitrogen regeneration rate of mixed macrozooplankton determined by bottle incubation method ranged from 0.02 to 1.34 mg at-N $m^2$/d and it could contribute from 2.8 to 38.7% with an annual average of 14.9% of total nitrogen requirement by phytoplankton in this shallow estuarine environment.