• Korean Journal of Environment and Ecology
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• v.33 no.5
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• pp.605-619
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• 2019

The objective of this study was to analyze eutrophication characteristics, empirical model analysis, and variation of water quality according to monsoon intensity in Hapcheon Reservoir for 16 years from 2002 to 2017. Long-term annual water quality analysis showed that Hapcheon Reservoir was in a meso-nutrition to eutrophic condition, and the eutrophic state intensified after the summer monsoon. Annual rainfall volume (high vs. low rainfall) and the seasonal intensity in each year were the key factors that regulate the long-term water quality variation provided that there is no significant change of the point- and non-point source in the watershed. Dry years and wet years showed significant differences in the concentrations of TP, TN, BOD, and conductivity, indicating that precipitation had the most direct influence on nutrients and organic matter dynamics. Nutrient indicators (TP, TN), organic pollution indicators (BOD, COD), total suspended solids, and chlorophyll-a (Chl-a), which was an estimator of primary productivity, had significant positive relations (p<0.05) with precipitation. The Chl-a concentration, which is an indicator of green algae, was highly correlated with TP, TN, and BOD, which differed from other lakes that showed the lower Chl-a concentration when nutrients increased excessively. Empirical model analysis of log-transformed TN, TP, and Chl-a indicated that the Chl-a concentration was linearly regulated by phosphorus concentration, but not by nitrogen concentration. Spatial regression analysis of the riverine, transition, and lacustrine zones of $log_{10}TN$, $log_{10}TP$, and $log_{10}CHL$ showed that TN and Chl-a had significant relations (p<0.005) while TN and Chl-a had p > 0.05, indicating that phosphorus had a key role in the algal growth. Moreover, the higher correlation of both $log_{10}TP$ and $log_{10}TN$ to $log_{10}CHL$ in the riverine zone than the lacustrine zone indicated that there was little impact of inorganic suspended solids on the light limitation in the riverine zone.

• Korean Journal of Environmental Biology
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• v.20 no.4
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• pp.339-346
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• 2002

From March 1998 to August 2000, the phonology and morphometrics change of Zostera caespitosa Miki were examined at the Duksan Port in the eastern coast of Korea. Morphometric characteristics (shoot height, leaf length, sheath length, leaf width, and number of leaf per shoot), size and number of reproductive structures (spathe, spadix, and seeds), shoot density, biomass and physiochemical parameters (water temperature and nutrient concentrations) were measured. Significant differences between months (p < 0.05) existed for morphometric characteristics except for sheath length. The sequence of shoot heights clearly showed cyclical annual variation with water temperature. Vegetative shoots of Z. caespitosa were present throughout the year, but reproductive shoots were rarely occurred from mid January to early April in water temperature of $9-12^\circ{C}$. Flowering in the spathe began in mid February, and seed maturing was occurred in early April. Water column nitrate and phosphate concentration showed seasonal variation, but ammonia concentration was variable with season. Relationships between shoot morphometrics and physiochemical parameters were not significantly correlated but water temperature seemed to regulate the re-productive phase and annual life cycle. The mean shoot density and above biomass of the populations were $511.6\pm{25.6}\;shoots\;m^{-2}$ and $413.4\pm{19.8}\;g\;dry\;wt\;m^{-2}$, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.2
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• pp.146-154
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• 2002

To assess the adsorption and removal mechanism of dissolved inorganic nutrients in seawater by scattering yellow loess, a laboratory experiment was conducted for the change of nutrient concentration in seawater during the course of time depending on particle size and scattered concentration of the yellow loess. Twenty four hours after the addition of yellow loess in the size range of 0 $\mu$m to 500 $\mu$m in seawater, the removal rate of dissolved inorganic phosphorus (DIP) was increased with increasing amount of yellow loess. There was little difference among the removal rates depending on the size of yellow loess. On average, $26\%$ of dissolved inorganic silicate was reduced for the same period. No greate difference among the removal rate depending on both size and amount of yellow loess was found. Our results suggested that the removal mechanism of DU seemed to be associated with mostly the chemical bond with iron. More than $99\%$ of initial DU concentration was likely to be removed by this mechanism. In the case of inorganic dissolved silicate, the removal mechanism was likely to be attributed to a cation exchange between the yellow loess and seawater.

• Korean Journal of Ecology and Environment
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• v.37 no.2 s.107
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• pp.193-204
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• 2004

This study was conducted to evaluate both temporal and spatial dynamics of phytoplankton community and environmental parameters in a newly made reclaimed esturine lake (L. Hwaong). Monthly sampling was conducted at 4 sites covering the longest transect of longitudinal gradient of the lake from June to November, 2002. Total 5 classes 8 orders 26 families 83 genus 192 species were identified at all study sites during the study period. Phytoplankton total cell density ranged 24${\sim}$ 1,882 cells $mL^{-1}$ and highly varied both temporally and spatially. Total cell density was significantly related with salinity, pH, BOD, COD, SS, TN and TP concentration. Diatom density also was significantly correlated with salinity, SS, BOD, COD and TN concentration, Although there was spatial difference, a longtudinal gradient appeared in phytoplankton cell density, Chl-a, TN and TP concentration from the mouth of river in June and August. In conclusion, phytoplakton community structure was dominated by diatoms (Bacillariophyceae), and appeared to be largely influenced by salinity, precipitation, and nutrients during the summer and the fall.

• Journal of Marine Life Science
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• v.5 no.2
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• pp.72-80
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• 2020

A sea dike in the Yeongsan River estuary was constructed in 1981 to supply water and reclaim tidal flats for agriculture, separating the estuary into the freshwater and seawater zones. However, the sluice gates are frequently opened and freshwater is discharged in summer when more rainfall is recorded than other seasons, then converting the estuary to brackish water system. In this study, the direct effect of freshwater discharge was investigated by monitoring daily variation in water properties and phytoplankton size structure before and after the freshwater discharge events from 2013 to 2015. Freshwater discharge resulted in a sharp decrease in salinity and dissolved oxygen (DO) at surface water whereas it increased the turbidity of water column. However, salinity did not decrease sharply in 2014 when freshwater was discharged one day before the monitoring and salinity remained low prior to the monitoring. Levels of nutrients especially dissolved inorganic nitrogen (DIN) increased after the discharge and this contributed to potential limitation of nutrients such as P or Si rather than N in the estuary. Freshwater discharge also caused the changes in phytoplankton biomass (chlorophyll a) and size structure although their responses were different between years. The changes may affect growth of grazers and thus structure of marine food web by alternating food availability in the Yeongsan River estuary.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.4
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• pp.337-348
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• 2007

Characteristics in distributions of T, S, nutrients, chlorophyll ${\alpha}$ concentrations and meso-zooplankton abundances and the relations among these parameters were investigated with the data collected in Asan Bay around the rainy season from May 24 till August 25, 2006 at about 10 days interval. Freshwater input during the rainy season clearly affected the distributions of zooplankton and phytoplankton (chlorophyll ${\alpha}$). Freshwater discharge resulted in high nutrients decreased zooplankton abundances. On the contrary, chlorophyll ${\alpha}$ concentrations increased at the end of the rainy season. It seemed that the increase of chlorophyll ${\alpha}$ concentrations was the result of the decreased zooplankton and enriched nutrients caused by freshwater discharges. Seawater temperatures were certainly the reason for the zooplankton succession. However, overall abundance of zooplankton and abundances of some zooplankton such as Noctiluca scintillans, Acartia pacifica, and Sagitta crassa seemed to be influenced by lowered salinity caused by heavy rain rather than seawater temperatures.

• The Korean Journal of Food And Nutrition
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• v.13 no.3
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• pp.242-248
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• 2000

수산물 가공시 흘러나오는 폐수 중에 함유되어 있는 수용성 단백질을 chitosan에 흡착시키기 위하여 albumin과 hemoglobin, albumin-myoglobin 혼합단백질을 이용하여 chitosan과의 흡착 및 chitosan 제조조건에 따른 흡착효과와 chitosan의 수용성 단백질 흡착에 미치는 인자를 살펴본 결과는 다음과 같다. Chitosan위 탈아세틸화 조건을 60, 70, 80%로 달리하여, albumin, hemoglobin, albumin-myoglobin 혼합용액에 적용했을때 chitosan의 탈아세틸화도가 높을수록 chitosan과 단백질 사이의 흡착률은 높게 나타났다. 초음파 처리에 의하여 chitosan의 분자량이 작을수록 chitosan과 단백질 사이의 흡착률은 높게 나타났다. pH변화에 따른 chitosan과 수용성 단백질의 흡착률은 albumin 및 albumin-myoglobin 혼합용액에서는 pH 4.0에서, hemoglobin용액에서는 pH 7.0에서 흡착률이 높게 나타났다 chitosan과 수용성단백질과의 흡착에서 반응시간은 albumin및 albumin-myoglobin 혼합용액에서는 4시간, hemoglobin용액에서는 3시간까지 흡착률이 증가하였고, 그 이후의 시간이 경화하여도 흡착률의 증가는 거의 보이지 않았다. 수용성 단백질 용액에 NaCl 농도를 0.1M에서 1.0M로 증가시켜 첨가했을때 염의 농도가 높을수록 chitosan과 단백질 사이의 흡착이 잘 일어나지 않았다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.3
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• pp.430-436
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• 2000

식품첨가제의 사용없이 저장성과 품질이 우수한 저염의 새우젓을 rokf하기 이한 바업으로 방사선 조사기술을 이용하였다. 식염농도를 각각 10%, 15%, 20%로 조절한 새우젓에 감마선을 조사한 후 15$^{\circ}C$에서 발효시키면서 일반성분, 염함량, 수분활성도, pH, 총균수 및 관능적 품질 변화를 조사하였다. 감마선 조사직후 및 발효기간 중 일반성분과 식염함량 및 수분활성은 감마선 조사에 의해 영향을 받지 않았다. 새우젓의 총균수와 pH는 식염농도와 감마선 조사선량이 높을수록 변화가 적었다. 관능검사 결과, 15%의 식염 첨가와 10 kGy의 감마선 조사 및 20%의 식염첨가와 5 kGy 이상의 감마선 조사를 병용처리한 새우젓을 발효시킨 경우 비조사구에 비해 적절한 미생물의 생육 억제로 저장기간 연장 효과를 보였고, 발효 10주까지도 관능적 품질이 적합하게 유지되었다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.4
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• pp.392-400
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• 1993

The present study was accomplished to understand the occurrence and time serial variations of oxygen-deficient watermass in wonmun Bay from 1989 to 1991. From the results of this work, oxygen-deficient water was periodically observed in bottom layer and in Summer in this region. The stratification of water began to develop in Spring and the strong formation of oxygen-deficient water showed in Summer but it gradually disappeared in Autumn. It seems that the occurring and continuing period of very low dissolved oxygen watermass is intensively controlled by meteorological conditions and vortical stratification of water column. On formation of oxygen-deficient watermass, high nutrient concentrations in the bottom layer appear to be due to release of nutrients from bottom sediment. The dissolved inorganic phosphate versus AOU shows two linear curves according to the level of AOU. In the relationships between phosphate and AOU, the gradient of a linear curve over approximately 5mg-AOU/l was significantly large, presumably indicating dissolution of phosphate from the sediment.

• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.191-199
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• 2003

This study was conducted to investigate a seasonal variation of phytoplankton communities at 6 stations in the Hantan River from November, 2001 to August, 2002. Electric conductivity gradually increased from the upper reaches to the down reaches. DO differed not much from the upper reaches to down reaches, but it decreased at the station where the pollutants inflowed. T-N and T-P concentrations were high at station 4${\sim}$6. Chlorophyll-a concentration gradually increased at the mid and down reaches. It was high in May but decreased in August by the heavy rains. Phytoplankton communities were identified a total 354 taxa composed of 99 genus, 320species, 19 varieties, 3 forma and 12 unidentified species. There were 135 taxa of Chlorophyceae, 134 taxa of Bacillariophyceae, and the other taxa were Euglenophyceae, Cyanophyceae, Xanthophycaea, Chrysophyceae and Dinophyceae. Standing crops ranged from 8,600 to 337,100 cells/mL and it was lower in August than May by the rains. Dominant species included Achnanthes alteragracillima, Achnanthes convergens, Achnanthes minutissima and Cymbella minuta var. silesiaca which were the saproxenous species at the reaches, and were Cyclotella meneghiniana, Chlamydomonas pseudopertyi and Nitzschia which were saprophilous and eutrophic species at the down reaches. The correlation coefficients between phytoplankton standing crops and EC, BOD and T-N, T-P was 0.68, 0.60, 0.60 and 0.70, respectively. All correlation coefficients between Chlorophyceae and EC, BOD and T-P were higher than 0.6. A. convergens were negative correlations with EC and BOD, but N. palea were positive with EC, BOD, T-N and T-P.