• Korean Journal of Ecology and Environment
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• v.36 no.4 s.105
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• pp.455-462
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• 2003

This study evaluated the change of water quality and chlorophyll - a at the birth stage of a large reclaimed estuarine lake (Lake Hwaong) of which the dike was finally constructed in March, 2002. Physico -chemical parameters and chlorophyll - a were investigated along a longitudinal transect, including 3 in-lake sites and 1 out-lake site from June to November, 2002. Salinity at all in-lake sites was over 21 psu during the study period, indicating that lake is still in the seawater phase. Salinity was periodically diluted at times when precipitation was high, especially in August. Chemocline was established in July near the dam site, and correspondingly vertical profile of dissolved oxygen was very clear during that Period. Total nitrogen and phosphorus concentrations at all lake sites were in the eutrophic range, and they were especially high at the stream inlet site. Nutrients concentration was not much varied vertically but significantly varied temporally, and correlated significantly with precipitation and chlorophyll-a concentration, indicating that inflowing water from the watershed seemed not to improve lake water by dilution but cause eutrophication of the lake, and thereby stimulate phytoplankton development. Based on the analyses of nutrient ratio (N/P) and trophic state deviation, both phosphorus and nitrogen appeared to limit phytoplankton growth in the lake. Phosphorus limitation appeared to be probable at all in-lake sites with being most severe at the stream inlet site. Nitrogen limitation seemed to occur at both in-lake and out-lake sites. These results indicate that in Lake Hwaong experiencing the very early stage of a reclaiming lake, water quality and phytoplankton development appear to be affect-ed largely by salinity and hydrology and nutrients from the inflowing water. Lake biogeochemistry is still very unstable, and thus further long-term study is necessary to understand the effects of seawater to freshwater conversion on lake biology and water chemistry.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.330-337
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• 2018

The Korean Eutrophication Index($TSI_{ko}$) was estimated using water quality monitoring data of eight main sites in the SoOoak River watershed. The environmental characteristics of rivers were classified and evaluated using the $TSI_{ko}$ for each factor calculated by COD, T-P, and Chl-a. There is a good condition for the algae to grow due to shallow water depth, inflow of non-point source pollution during rainfall, influx of sewage treatment effluent and increase of residence time. It shows trophic state more than mesotrophication year round. Especially, in case of Chuso point, which is the inflow point of Daecheong Lake, the water quality deteriorated due to hydraulic characteristics and showed the eutrophic state. Therefore, it is necessary to establish the measures to improve the water quality through the precise monitoring of SoOak River.

• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.350-357
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• 2000

This paper evaluated the influence of point source and flow events on inorganic nitrogen fractions at 17 sites of Taechung Reservoir during 1993${\sim}$1994. Total nitrogen (TN) averaged 1.53 mg/L during the study and ranged between 0.70 and 2.56 mg/L. Dissolved inorganic nitrogen(DIN) accounted for >90% of TN regardless of season and location, indicating a nitrogen-rich system showing eutrophic${\sim}$hypereutrophic conditions. Some 67${\sim}$94% of DIN was NO$_{3}$-N, whereas mean level of NH$_{4}$-N was less than 5% of DIN. During monsoon 1993, dilution of NO$_{3}$-N was evident in the headwaters as a result of mixing of lake water with rain water, while NH$_{4}$-N increased>100% compared to the premonsoon. Values of NH$_{4}$-N had a positive correlation with rainfall (r=0.85; p<0.001) and negative correlations with theoretical water residence time(r=-0.90; p<0.001) and conductivity(r=-0.78, p<0.001), respectively. These outcomes suggest that NH$_{4}$-N came from external input from the watershed during the monsoon. In both years, mean TN was greater in the mid-lake sites than any other sites. A great amount of TN in the mid-lake was most pronounced in monsoon 1994 because of an accumulated influence of the point sources during low inflow. Overall data suggest that concentrations of TN in this system did not show large differences along the longitudinal gradients and its distributions is likely determined by point-sources rather than inflow regime.

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.332-343
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• 2004

This study was conducted to test a possibility of water quality improvement using a filter-feeding bivalve (Corbicula leana). In mesocosm scale (width ${\times}$ length ${\times}$ depth: 3 m ${\times}$ 3 m ${\times}$ 0.5 m), we investigated the changes of dissolved nutrient and particulate matter including both abiotic and biotic seston. Short term (16 days) mesocosm experiment was conducted in two stages: the first stage for 8 days and consecutive 8 days of the second stage. Both treatment and control mesocosm were switched over by translocating mussels from the treatment mesocosm to the control, at 8th days since the start of the experiment. This design made it possible to compare mussel effect on the water quality change more clearly. The high mortality of mussel was observed in the treatment of the first stage, but it decreased rapidly and stabilized on the 8th day to less than< 4 ind $day^{-1}$. Chl. a concentration in the treatment mesocosm of the first and second stage decreased to 71 and 88% of initial concentration, respectively, and suspended solids decreased to 70 and 77%. At those times, average filtering rate were 0.46 and 0.61 mL AFDW $mg^{-1}$ $hr^{-1}$, respectively. Both $NH_3-N$ and dissolved total phosphorus (DTP) concentrations increased with the mussel mortality. $NH_3-N$ concentration was positively correlated with the mussel mortality, while DTP concentration showed negative correlation with it. After translocating mussel from the treatment to the control, $NH_3-N$ concentration significantly increased compared with that of initial control. Although DTP concentration also increased, there was no significant difference relative to that of initial control. These results suggest that application of this filter-feeding bivalve in a eutrophic reservoir could be a potential tool to improve water quality if mussels could acclimatize successfully in early stage of the introduction.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.411-422
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• 2004

A limnological survey was conducted in a reservoir, Lake Hoengsung located in Kangwondo, Korea, from July 2000 to September 2001 on the monthly basis. Phosphorus loading from the watershed was estimated by measuring total phosphorus concentration in the main tributary. Secchi disc transparency, epilimnetic (0-5 m) turbidity, chlorophyll a (Chl-a), total phosphorus (TP), total nitrogen(TN) and silica concentration were in the range of 0.9-3.5 m, 0.1-8.5 NTU, 0.3-32.4 mgChl $m^{-3}$, 5-46 mgP $m^{-3}$, 0.83-3.55 mgN $L^{-1}$ and 0.5-9.6 mgSi $L^{-1}$, respectively. Green algae and cyanobacteria dominated phytoplankton community in warm seasons, from July through October, 2000. In July a green alga (Scenedesmus sp.) was dominant with a maximum cell density of 10,480 cells mL. Cyanobacteria (Microcystics sp.) dominated in August and September with cell density of 3,492 and 295 cells mL ,respectively. Species diversity of phytoplankton was highest (2.22) in July. The trophic state of the reservoir can be classified as eutrophic on the basis of TP, Chl-a, and Secchi disc transparency. Because TP concentration was high in flood period, most of phosphorus loading was concentrated in rainy season. TP loading was calculated by multiplying TP and flow rate. The dam managing company measured inflow rate of the reservoir daily, while TP was measured by weekly surveys. TP of unmeasured days was estimated from the empirical relationship of TP and the flow rate of the main tributary; $TP=5.59Q^{0.45}\;(R^2=0.47)$. Annual TP loading was calculated to be 4.45 tP $yr^{-1}$, and the areal P loading was 0.77 gP $m^{-2}\;yr^{-1}$ which is similar to the critical P loading for eutrophication by Vollenweider's phosphorus model, 0.72 gP $m^{-2}\;yr^{-1}$.