• Korean Journal of Microbiology
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• v.31 no.1
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• pp.85-92
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• 1993

To investigate the eutrophication process and pollution characteristics in Paldang Lake, Korea, water and sediment samples were analysed during July 1986~June 1987. The transparency, chlorophyll-a concentration, dissolved oxygen concentration and biochemical oxygen demand in Paldang Lake ranged 0.5~3 m, 3-17 ${\mu}gI^{-1}$, 7.2~12.3 ppm and 0.5~2.3 ppm, respectively. Heterotrophic bacterial number fluctuated seasonally between $3.0{\times}10^{3}/ml and 5.0{\times}10^{5}/ml$ in the water column and between $2{\times}10^{6} and 1{\times}10^{8}$ in the I g dry sediment. Water turbulence and water quality of up-stream seem to play important roles for determining the water quality in Paldang Lake particularly where the hydraulic retention time is so short as about 5 days. The present water quality in Paldang Lake according to the criteria of lake water quality was shown to be between mesotrophic and eutrophic state by secchi depth(O.5 ~ 3 m) and chlorophyll-a concentration (3~17 ${\mu}gI^{-1}$). The distribution of coliform bacteria showed that the pollution was mainly due to the human activities in this area and it is needed to establish countmeasurements for the problems.

• Korean Journal of Ecology and Environment
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• v.35 no.3 s.99
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• pp.181-186
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• 2002

To evaluate the eutrophication status of the Asan Reservoir in Korea, physicochemical parameters were analyzed for samples of 19 sampling stations collected in the period from March to November in 1997. Water temperature was in the range of $8.3{\sim}35.3{\circ}^C$, with thermocline appearing in summer. Dissolved oxygen also showed similar verticle variation to temperature. Secchi depth was very shallow with a range of 0.1~1m. Suspended solids ranged from 11.3 mg/1 to 2143.3 mg/1, and seemed to be affected by the amount of rainfall and the standing stocks of phytoplankton. Nutrient concentrations were higher in tributaries, and decreased with downflow. Nutrients were low in the summer and early autumn when algal blooms occur, and high in the early spring and winter. The Trophic State Index showed that the Asan Reservoir is in a hypertrophic condition．

• Korean Journal of Remote Sensing
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• v.32 no.3
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• pp.221-234
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• 2016

In Korea, most industrial parks and major cities are located in coastal areas, which results in serious environmental problems in both coastal land and ocean. In order to effectively manage such problems especially in coastal ocean, water quality should be monitored. As there are many factors that influence water quality, the Korean Government proposed an integrated Water Quality Index (WQI) based on in situmeasurements of ocean parameters(bottom dissolved oxygen, chlorophyll-a concentration, secchi disk depth, dissolved inorganic nitrogen, and dissolved inorganic phosphorus) by ocean division identified based on their ecological characteristics. Field-measured WQI, however, does not provide spatial continuity over vast areas. Satellite remote sensing can be an alternative for identifying WQI for surface water. In this study, two schemes were examined to estimate coastal WQI around Korea peninsula using in situ measurements data and Geostationary Ocean Color Imager (GOCI) satellite imagery from 2011 to 2013 based on machine learning approaches. Scheme 1 calculates WQI using estimated water quality-related factors using GOCI reflectance data, and scheme 2 estimates WQI using GOCI band reflectance data and basic products(chlorophyll-a, suspended sediment, colored dissolved organic matter). Three machine learning approaches including Random Forest (RF), Support Vector Regression (SVR), and a modified regression tree(Cubist) were used. Results show that estimation of secchi disk depth produced the highest accuracy among the ocean parameters, and RF performed best regardless of water quality-related factors. However, the accuracy of WQI from scheme 1 was lower than that from scheme 2 due to the estimation errors inherent from water quality-related factors and the uncertainty of bottom dissolved oxygen. In overall, scheme 2 appears more appropriate for estimating WQI for surface water in coastal areas and chlorophyll-a concentration was identified the most contributing factor to the estimation of WQI.

• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.21-31
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• 2006

The objectives of this study were to analyze trends of temporal water quality and trophic state in Andong and Imha reservoirs using chemical dataset during 1993 ${\sim}$ 2004, obtained from the Ministry of Environment, Korea. According to long-term limnological analyses, Suspended solids (SS) in Imha Reservoir were 2 ${\sim}$ 8 fold2 greater, than those in SS of Andong Reservoir, and the high solids increased total phosphorus (TP) and biological oxygen demand ($BOD_5$) and decreased the transparency, measured as Secchi depth (SD). Chlorophyll-a (CHL-a) increased little or decreased slightly in the both reservoirs during the high solids, resulting in reduced yields of CHL-a : TP ratios. The deviation analysis of Trophic State Index (TSI) in Imha Reservoir showed that about 70% of TSI (CHL-a)-TSI (SD) and TSI (CHL-a)-TSI(TP) values were less than zero and the lowest values were-60, indicating that influence of inorganic solids (or non-volatile solids) on phytoplankton growth was evident in Imha Reservoir and the impact was greater than that of Andong Reservoir. Inorganic solids in Imha Reservoir resulted in light limitation on phytoplankton growth and thus contributed variations in the relations among three parameters of trophic state index. Especially, seasonal data analysis of nutrients in both reservoirs showed that during the postmonsoon, mean TP concentration was Imha Reservoir greater in than that in Andong Reservoir. The higher TP concentrantion was mainly attributed to increases of inorganic solids from soil erosions and nonpoint source inputs within the watershed. The high inorganic turbidity in Imha Reservoir should be reduced for the conservation of water quality for, especially a tap water supply.

• Korean Journal of Ecology and Environment
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• v.33 no.3 s.91
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• pp.187-196
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• 2000

This paper describes a simple method that uses differences among Carlson's (1977) trophic state index (TSI) values based on total phosphorus (TP), chlorophyll a (CHL) and Secchi depth (SD) to draw inferences regarding the factors that are limiting to phytoplankton growth and the composition of lake seston. Examples are provided regarding seasonal and spatial patterns in a large subtropical lake (Lake Okeechobee, Florida, USA) and inter- and intra-lake variations from a multilake data set developed from published studies. Once an investigator has collected routine water quality data and established TSI values based on TP, CHL, and SD, a number of inferences can be made. Additional information can be provided where it also is possible to calculate a TSI based on total nitrogen (TN). Where TSI (CHL)<>TSI (SD), light attenuating particles are large (large filaments or colonies of algae), and the phytoplankton may be limited by zooplankton grazing. Other limiting conditions are inferred by different relationships between the TSI values. Results of this study indicate that the analysis is quite robust, and that it generally gives good agreement with conclusions based on more direct methods (e.g., nutrientaddition bioassays, zooplankton size data, zooplankton removal experiments). The TSI approach, when validated periodically with these more costly and time-intensive methods, provides an effective, low cost method for tracking long-term changes in pelagic structure and function with potential value in monitoring lake ecology and responses to management.

• Korean Journal of Environmental Biology
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• v.26 no.4
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• pp.392-401
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• 2008

The vertical changes (upper layer: 0$\sim$0.5 m, middle layer: 4$\sim$5 m and lower layer: 8$\sim$10 m) of the limnological variables, zooplankton dynamics and community filtration rate on the phytoplankton were evaluated monthly intervals from November 2004 to June 2007 at the artificiallake (Okjeong Lake). During the study, the annual mean of water temperatures were 15.2$\pm$7.8$^{\circ}C$ (upper layer), 14.5$\pm$7.4$^{\circ}C$ (middle layer) and 13.0$\pm$6.2$^{\circ}C$ (lower layer), respectively (n=30). The vertical variations of most limnological parameters (DO, pH, conductivity and turbidity) were fairly similar, except for chl.-${\alpha}$ concentration. Annual mean of chl.-${\alpha}$ concentration was highest at the upper layer (21.4 ${\mu}g$ L$^{-1}$), while annual means of concentrations were low at the middle layer and lower layer (4.3 ${\mu}g$ L$^{-1}$ and 3.5 ${\mu}g$ L$^{-1}$, respectively). Annual mean of Secchi depth was 261 cm (n=30). A total 45 species of zooplankton were identified (28 rotifers, 12 cladocerans and 5 copepods) during the study. The mean abundance of rotifers was highest (124$\pm$232 ind. L$^{-1}$, n =90) and that of cladocerans and copepods were relatively low (22$\pm$56 ind. L$^{-1}$ and 13$\pm$30 ind. L$^{-1}$) in the whole layer. Total zooplankton abundance increased from late spring to summer, and then declined and remained low throughout the winter. The annual mean of total zooplankton filtration rate for phytoplankton at the lower layer was much higher than that of both layers (upper layer: 44.4$\pm$107.8, middle layer: 95.1$\pm$436.4 and lower layer: 158.2$\pm$436.4 mL L$^{-1}$ day$^{-1}$). Among the major zooplankton community, relative community filtration rate (RCFR, %) of copepods for phytoplankton (50.2$\sim$54.8%) was much higher than that of cladocerans (27.7$\sim$36.3%) and rotifers (8$\sim$17.6%). The seasonal variation of RCFRs of major zooplankton community was observed. The RCFRs of rotifers were high in winter (44.6%, n=9), while the RCFRs of cladocerans were high in summer (58.0%, n=7). In spring and fall, the RCFRs of copepods were high in the whole layer (spring: 67.4%, n=9; fall: 74.4%, n=5).

• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.30-44
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• 2001

In this study limnological characteristics of Lake Juam was surveyed from June 1993 to May 1994 in order to provides important information regarding water resources. Secchi disc transparency, epilimnetic chlorophyll a (chi-a), total nitrogen (TN), total phosphorus (TP) concentration and primary productivity were in the range of $2.0{\sim}4.5\;m$, $0.9{\sim}13.6\;mgChl/m^3$, 0.78$\{sim}$2.32 mgN/l, $11{\sim}56\;mgP/m^3$, $270{\sim}2.160\;mgCm^{-2}\;day^{-1}$, respectively. On the basis of TP, Chl-a and Secchi disc depth, the trophic state of Lake Juam can be classied as mesotrophic lake. The phosphorus inputs from non-point sources are concentrated in heavy rain episodes during the monsoon season. As a result, phosphorus concentration are higher in summer than in winter. TP loading from the watershed were estimated to be $0.9\;gPm^{-2}yr^{-1}$, which correspond to a boundary of the critical loading ($1.0\;gPm^{-2}yr^{-1}$) for eutrophication. From the results of the algal assay, both phosphous and nitrogen act as limiting nutrients in algal growth. The seasonal succession of phytoplankton community structure in Lake Juam was similar to that observed in other temperate lakes. Diatoms (Asterionella formosa and Aulacoseira granulate var. angustissima)fujacofeira BraHuJafa uar. aHgusHrsiaia) weredominant in spring and winter, cyanobacteria) were dominant in warm season. The organic carbon, nitrogen and phosphorus content of lake sediment were $9.5{\sim}14.0\;mgC/g$, $1.01{\sim}1.82\;mgN/g$ and $0.51{\sim}0.65\;mgP/g$, respectively. The allochthonous organic carbon loading from the watershed and autochthonous organic carbon loading by primary production of phytoplankton were determined to be 1,122 tC/yr and 6,718 tC/yr, respectively. To prevent eutrophication of Lake Juam, nutrient management of watershed should be focus on reduction of fertilizer application, proper treatment of manure, and conservation of topsoil as well as point source.

• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.1-11
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• 2004

The limnological characteristics of a coastal lagoon were studied in Lake Hyangho, one of a series of brackish lagoons along the eastern coast of Korea. Phytoplankton community structure, physical factors, and chemical factors were surveyed from May 1998 through November 2002 on a two-month interval basis. Temperature, salinity, Secchi disc transparency, TN, TP, organic matter content of sediment, chlorophyll a concentration, dominant phytoplankton species, and phytoplankton cell density were measured. Salinity gradient was formed between the overlying freshwater stream water and the permeated seawater at the bottom. The chemocline was persistent at the depth of 2 ${\sim}$ 5 m that caused discontinuities of salinity, DO, and temperature profiles. The inversion of vertical temperature profiles with higher temperature in deeper layer was observed in early winter. Secchi disc transparency was very low with the range of 0.1 to 1.1m. TP, TN, and Chl. a concentration in the epilimnion was 0.011 ${\sim}$ 0.238 mgP $L^{-l}$, 0.423 ${\sim}$ 2.443 mgN $L^{-l}$, and 0.7 ${\sim}$ 145.2 mg $m^{-3}$, respectively. Sediment was composed of silt and coarse silt. COD, TP, and TN content of dry sediment were 19.7 ${\sim}$ 73.3 mg$O_2\;g^{-1}$, 0.61 ${\sim}$ 1.32 mgP $g^{-l}$ and 0.64 ${\sim}$ 0.88 mgN $g^{-l}$, respectively. Dominant phytoplankton species were chlorophytes (Ankistrodesmus falcatus) and cyanobacteria (Oscillatoria sp. and Merismopedia tennuissima). The total cell density was in the range of 560 ${\sim}$ 35,255 cells $mL^{-l}$.

• Journal of Korea Water Resources Association
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• v.33 no.5
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• pp.551-559
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• 2000

In order to diagnose the water environment and assess the water quality restoration, long term trend of water environment has been surveyed at 3-R stations from 1994 to 1999 in Lake Shihwa. Annual mean values of $COD_{Mn}$, Chlorophyll a, total nitrogen, total phosphorus and Secchi depth are ranged in 5.2-15.1 mg/L, 7.3-14R.1 jlg/L, 1.50-4.84 mgN/L, 0.055-0.281 mgP/L and 0.5 -1.4 m, respectively, during the study periods. Carson's trophic state indeies were varied from mesotrophy in 1994 and 1995, hyper-eutrophy in 1996 and 1997, to meso eutrophy in 199R and 1999. After dike construction, water quality were rapidly deteriorated by allochthonous and autochthonous loading of high nutrients and organic carbon. Eutrophication phenomena were characterized by massive phytoplankton blooms and high concentration of COD. However, after onset of restoration program, lake water quality was rapidly restored to the level of just after sea-dike construction. The diversion of waste water inflowing from the Panwol and the Sihwa industrial districts which was started from March, 1997 has contributed to improve water quality in the surface layer. And the tidal mixing (sea water inflowing) through the continuous gate operation was the most effective measure to the whole lake restoration.ration.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.3
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• pp.323-329
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• 1998

The data of Secchi disc observation collected during $1966\~1990$ were analyzed to investigate the seasonal variation of transparency in the southeastern Yellow Sea. The bimonthly distribution of mean transparency showed that the isolines of transparency were roughly parallel to the isobaths. The transparency was low (3 m in february and 8 m in August) if the shallow water less than 20 m depth in comparition to the higher values (10 m in february and 17 m in August) in the deeper water. The lowest transparency was found in winter. The transparency increased in spring and the highest transparency occurred in summer. The water becomes turbid in autumn. Suspended solid concentrations in winter are ranged from 28 to 130 $mg/{\ell}$, and from 8 to 60 $mg/{\ell}$ in summer. The seasonal variation of transparency seems to be mainly affected by resuspension of solid from the bottom. The amounts of suspended solid are large in winter due to the vertical convection by cooling effect and tubulence by the strong wind, and small in summer due to the strong stratification and weak wind.