• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.95-106
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• 2009

The Shihwa constructed wetland was established for the treatment of severely poluted water from Banwoul, Donghwa and Samhwa streams. This study was focused on investigating the structure of epiphytic diatom communities on reed (Phragmites communis) planting area at Banwoul high wetland (3 stations) and low wetland (3 stations) from March to October 2005. The concentration of T-N of inlet stations from the streams were decreased by flowed through the wetland, but the concentration of T-P were increased at outflow part. Epiphytic diatoms on the reed were a total 109 taxa which were composed of 103 species, 5 varieties, 1 unidentified species. The standing crops were rapidly decreasing tendency from spring to autumn but chlorophyll-a concentration were showed a very irregulated changes. Dominant species were 6 taxa which were Achnanthes minutissima in the early investigation, and were changed to the genus Navicula and the genus Nitzschia in the summer. DAIpo were ranged the values of $20.2{\sim}51$, which were mesosaprobic states at the high wetland and ranged the values of $12.4{\sim}52$, which were polysaprobic to mesosaprobic states at the low wetland. TDI were ranged the values of $28.8{\sim}94.5$, which were oligotrophic to eutrophic state at the high wetland and ranged the values of $33.3{\sim}89.7$ which were mesotrophic to eutrophic states at the low wetland. The healthy assessment (DAIpo and TDI) of water ecosystem were showed clean-bad from spring to autumn. These epiphytic diatom communities were determinated by the biological factor such as the growth of reed and the physical factors such as water temperature, light penetration and SS and so on.

• ALGAE
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• v.33 no.4
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• pp.319-327
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• 2018

Ettlia sp. YC001, a highly settleable and productive microalga, was shown to be effective in removing nutrients and capturing suspended solids from eutrophic pond water. The optimum conditions for the Ettlia sp. YC001 cultivation were investigated using water from a landscape pond. The pond water was supplemented with different N : P ratios by weight, and the biomass production and nutrient removal compared in batch cultures. The maximum removal rate of N and P was with an N : P ratio of 16 : 1. Plus, the turbidity dropped to near zero within 4 days. Meanwhile, chemostat cultivation showed that the biomass productivity and nutrient removal rate increased when increasing the dilution rate, where a dilution rate of $0.9d^{-1}$ showed the highest N and P removal rate at $32.4mg\;L^{-1}\;d^{-1}$ and $1.83mg\;L^{-1}\;d^{-1}$, respectively, and highest biomass and lipid productivity at $0.432g\;L^{-1}\;d^{-1}$ and $67.8mg\;L^{-1}\;d^{-1}$, respectively. The turbidity was also reduced by 98% in the chemostat cultivation. Moreover, auto-flocculation and pH were closely connected to the turbidity removal. As a result, this study identified the optimal N : P ratio for small pond water treatment using an Ettlia sp. YC001, while also establishing the optimal conditions for nutrient removal, turbidity reduction, and biomass production.

• Journal of Korean Society on Water Environment
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• v.35 no.4
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• pp.340-351
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• 2019

In this study, the relationship between trophic state indices was analyzed based on the monthly or weekly water quality data of 81 lakes (mostly man-made) in Korea between 2013-2017. Carlson's $TSI_C$ and Aizaki's $TSI_m$ were calculated using the summer (Jun.-Sep.) average data at the upper water layer. The previous Korean trophic state index ($TSI_{KO}$) and the newly suggested index ($TSI_{KON}$) was calculated using the annual average data at the whole layer and at the upper layer, respectively. While previous trophic state index (TSI) such as Carlson's TSI included logarithmic function, we devised newly Monod-type $TSI_{KON}$(Chl) that is 50 when half-saturation concentration of chlorophyll ${\alpha}$ ($Chl.{\alpha}$) measured by UNESCO-method is $10{\mu}gL^{-1}$. MMF-type $TSI_{KON}$(TP) was derived based on the relationship between TP and $Chl.{\alpha}$. A comprehensive $TSI_{KON}$ was decided as the larger one of the two $TSI_{KON}$ values. The range of previous TSI was usually 40-50 for the mesotrophic state, which seemed narrow to discriminate trophic characteristics of the class. The upper limits of $TSI_{KON}$ for oligotrophic, mesotrophic, and eutrophic state were set to 23, 50 and 75, respectively. Classification by $TSI_C$ and $TSI_m$ showed higher frequency of eutrophic class compared to $TSI_{KO}$ and $TSI_{KON}$. This means that the estimation by TSIs developed in foreign natural lakes can lead to distorted results in the classification of the trophic state of Korean lakes. This is due to the decrease of transparency by non-algal material and the reduction in phosphorus availability to algal growth, particularly in Monsoon period.

• Korean Journal of Ecology and Environment
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• v.56 no.1
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• pp.83-93
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• 2023

This study compares the abundance and community structure of zooplankton organisms from pelagic regions, and considers particularly the trophic levels vs. zooplankton abundances and biomass. Zooplankton samples were collected three times from May to November 2022, at 30 temperate lakes and reservoirs, which belong to four different river basins. The total zooplankton abundance, biomass and species index were showed considerable spatial variation. The spatial pattern of rotifer abundance was similar to that of total zooplankton abundance, while there were not showed similar patterns of zooplankton biomass (㎍ L^-1) in lentic ecosystems. The rotifer strongly dominated the zooplankton assemblage in smaller lentic system than that of larger. A total of 130 species of zooplankton were identified (83 rotifers, 34 cladocerans and 13 copepods). The total average of zooplankton abundance and biomass were 213.7±342.3 Ind. L^-1 (n=129) and 1382.8±1850.4 ㎍ L^-1, respectively. Total and average of zooplankton abundance were usually dominated by the rotifers (>56.9%), while those of zooplankton biomass were dominated by the cladocerans and copepods (>73.6%) in lentic ecosystems. Considering the Trophic State Index (TSI), the factors of zooplankton abundance and biomass were included in between meso- and eutrophic states(27 lakes, 90% of all). The mean abundance and biomass of zooplankton in eutrophic systems were higher than that of meso- and hypertrophic systems. From this result, we suggest that management strategy for the lentic ecosystem water environment has to be focused more on small-sized lakes and reservoirs, in terms of zooplankton assemblages.

• Korean Journal of Ecology and Environment
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• v.40 no.1
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• pp.121-129
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• 2007

This study was conducted to evaluate the causes and effects of cyanobacterial development and succession in a shallow eutrophic reservoir from March 2003 to February 2004. Phytoplankton succession, sedimentation rate, and sediment composition were analyzed. Algal bioassay also was conducted with the consideration of light, water temperature and nutrients. Cyanobacteria dominated throughout the year, except for spring season (March${\sim}$April) in which diatoms and flagellates dominated. Total cell density increased in July and November when P loading through inflows was high. Oscillatoria spp. and Aphanizomenon sp. were dominant in May and June, respectively, but replaced with Microcystis spp. in July. Thereafter, Microcystis spp. sustained until December, and again shifted to Oscillatoria spp. and Aphanizomenon sp. The dominance of Oscillatoria spp. in May was accompanied with high TN/TP ratio and the increase of water temperature and light intensity. While the dominance of Microcystis spp. was related with relatively low TN/TP ratio, ranging from 46 to 13 (average: 27). The sedimentation rate was highest in March (0.6 m $day^{-1}$) when diatoms dominated. During the period of cyanobacterial dominance, relatively high sedimentation rate was observed in May (0.4 m $day^{-1}$) and October (0.36m $day^{-1}$). C/N ratio of the sediment ranged $6{\sim}8$. Inorganic P concentration in the pore water was low when DO concentration was < 2 mg $O_2$ $L^{-1}$ in the hypolimnion, reflecting the P release from the sediment. Cyanobacterial growth rate depended on phosphorus concentration and water temperature, and high P concentration compensated for the low temperature in the growth rate. Our results suggest that the potential of cyanobacterial development and substantiality in eutrophic reservoirs be high throughout the year, as being supplied with enough P, and emphasize the consideration of sediment man. agement for the water quality improvement and algal bloom control.

• Korean Journal of Microbiology
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• v.39 no.2
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• pp.95-101
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• 2003

The total bacterial numbers, Eubacterial community structures and environmental factors which affect bacterial community were estimated monthly using DAPI and fluorescent in situ hybridization monthly, from June to November 2000 to evaluate the correlation between the bacterial community and environmental factors in eutrophic agricultural Masan reservoir in Asan. Average water temperatures varied from 12.3 to $27.5^{\circ}C$, pH 7.5 to 9.0, DO 7. I~12.8 mg/L, COD 6.4~13.0 mg/L, chlorophyll a 30.5~99.0 mg/㎥, SS 7.S~25.7 mg/L, TN 1.748~3.543 mg/L., and TP 0.104~0.581 mg/L, respectively. Total bacterial numbers showed high ranges from 0.4 to 9.6$\times$ $10^{6}$ cells/ml, and these indicated the mesotrophic or eutrophic state. The ratio of Eubacteria to total bacteria was 67.6-88.0%, which was higher than that in other reservoir. The relationships of total bacteria and Eubacteria community were more significant with organic nitrogen (Org-N), and organic phosphorus (Org-P) than with water temperature. Proteobacteria groups showed strongly significant relationships with Org-P and Org-N and significant relationships with water temperature, conductivity, COD, and inorganic nitrogen. C-F group was the most significant with Org-N, and HGC group with water temperature. However, relationships of Chl-a, pH, DO and SS showed no significance with any bacterial community. These results were different from other studies, because of the specific characteristics of Masan reservoir such as old, shallow and eutrophic states. The seasonal variation of bacterial community in Masan reservoir does not seem to depend on phytoplankton dynamics but on storm event and organic materials from watershed and the sediment of reservoir.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.350-363
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• 2009

Inter- and intra-specific differences in removal activities, filtering rates (FR) and production of feces-and pseudo-feces (PF) between a native freshwater bivalve in Korea, Anodonta woodiana Lea and Unio douglasiae Griffith et Pidgeon, were compared using a continuous removal of organic matters (CROM) system. The CROM system comprised five steps; input of polluted water, control of water flow, mussel treatment, analysis of water quality and discharge of clean water. The study was designed to compare the removal activity of organic matters between A. woodiana and U. douglasiae, and the intra-specific differences between density and length in A. woordiana. Results clearly indicate that two kinds of mussels had obvious removal activities of seston in the eutrophic reservoir. First, if both are similar in shell length, there were no significant inter-specific differences in removal activity between A. woordiana and U. douglasiae (P>0.5), but FRs of U. douglasiae was relatively high due to low ash-fee dry weight. Second, if both are same in animal density, the smaller mussels (1$\sim$2 years old) showed a higher filtering rate and production of feces- and pseudo-feces and less release of ammonium than the larger mussels. Third, if both are same in biomass, FRs and PF of mussels were higher in the low-density tank than the high-density tank, While the Concentration of $NH_4$-N and $PO_4$-P released WRS similar to each other (P>0.5). Therefore, these results suggest that CROM system using a young bivalve A. woordiana can be applied to control the nuisance seston in eutrophic lake system, if a relevant species and density were selected. Additional pilot tests to optimize the age and density of domestic bivalves were needed for the generalization of CROM operation.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.55-68
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• 2010

The seasonal variation of microbial community, based on the bacteria, heterotrophic nanoflagellates (HNF), phytoplankton and ciliates, was investigated at three sites in the eutrophic brackish water of Lake Shihwa and its adjacent areas from May 2007 through May 2008. At the upstream-region site St. 1, compared to the other two sites, significantly lower salinities and higher concentrations of nutrients and chlorophyll $\alpha$ (Chl. $\alpha$) were recorded. The annual average abundances of bacteria at St. 1, St. 2 and St. 3 were $6.8{\times}10^6$, $7.4{\times}10^6$ and $4.6{\times}10^6\;cells\;mL^{-1}$, respectively. As for the annual average concentrations of HNF, $19{\times}10^2$, $6.7{\times}10^2$ and $5.9{\times}10^2\;cells\;mL^{-1}$, were recorded in St. 1, St. 2 and St. 3 respectively. The highest ciliate abundance appeared at St. 1 on 29 April, 2008 and in which, 99% were autotrophic ciliate Mesodinium rubrum (Myrionecta rubra). Significant linear correlations between the biomass of bacteria and Chl. $\alpha$ were found, however, no significant relationships between ciliates abudance/biomass and their prey organisms were detected in all three sites, implying relatively low energy transfer efficiencies between them. These results indicated that the trophic relationship between ciliates and their prey organisms in the microbial community might be influenced by indirect route since higher trophic level organisms did not directly correlate to those of lower trophic level, although high primary productions were detected in the eutrophic brackish water of Lake Shihwa and its adjacent areas.

• Economic and Environmental Geology
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• v.9 no.2
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• pp.77-83
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• 1976

Diatoms collected from the upper part of the Eoil Formation of the study area are identified as comprising 5 species/2 genera, whose known ecologic properties imply that the stratigraphic interval concerned was deposited under freshwater, eutrophic, and stagnant lake environment.

• Journal of Ecology and Environment
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• v.36 no.4
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• pp.267-271
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• 2013

To examine the density effect and food concentration in the competitive output of two Bosmina species, the population growths of Bosmina fatalis were investigated by manipulating the density of B. longirostris and the concentration of algae. The B. fatalis density did not increase in conditions with abundant B. longirostris regardless of the food concentrations. The B. fatalis increased only at low densities of B. longirostris with high food concentrations. Based on the current results, a possible mechanism underlying the seasonal shift from B. longirostris to B. fatalis in Japanese eutrophic lakes will be explored below.