• Korean Journal of Ecology and Environment
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• v.46 no.4
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• pp.551-560
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• 2013

Environmental factors and epilithic diatom communities in the lower streams near the harbor region of South Korean peninsula were examined during no monsoon period in May 2013. The sampling of water and epilithic diatoms was conducted at both streams, 19 regulated streams (RS) that there are one or several dams constructed in the river system, and 19 un-regulated streams (US) that there are no dams within the river. A cluster analysis based on the number of species and abundance of epilithic diatoms through the stations, divided into three groups such as groups I (mainly US), II (mixed with US and RS) and III (mainly RS), respectively. Group I showed that water quality is good and high diversity of diatom, while Group II and III was water quality is relatively poor, but not differed in biomass of diatom from Group I. In addition, Group II that had high conductivity, nitrogen and phosphorus, was the lowest in diatom diversity among them. Dominant species were Nitzschia palea (17%) and Navicula seminuloides (11%) in Group I, Nitzschia inconspicua (19%) and Navicula perminuta (9%) in Group II, and Nitzschia inconspicua (15%) and Nitzschia palea (14%) in Group III, respectively. These taxa were widely distributed in brackish water, and not closely related with specific water quality, like eutrophic water. However, the groups II and III belonged to RS, had not only little biomass, but bad water quality such as high concentrations of nutrient and chlorophyll-a. Therefore, to determine the effect of dam construction on the lower water ecosystem, the planktonic algae, which can occur algal bloom in the estuary, also was considered to be a parallel investigation.

• Journal of the Mineralogical Society of Korea
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• v.19 no.4 s.50
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• pp.277-289
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• 2006

This study was carried out to find a new material having high removal efficiency for the harmful red tide. C. polykrikoides grow very fast and accumulate into dense and visible patches near the surface of the seawater ('Water bloom'). Some mineral medicines and Hwangto (reddish soil consist of clay minerals and Fe-oxides) were used in this study to remove C. polykrikoides. The pre-determined sprinkling ratio of mineral vs. seawater which contains approximately 5,000 cells/mL of C. polykrikoides was 10 g/L. In order to quantify the removal efficiency, the density of living cells was measured by counting with the Intervals of 0, 10, 30, and 60 minutes after sprinkling. Five Hwangtos feom different localities were examined in this study. It is found that a material with a high concentration of Fe and Al was the most effective to remove C. polykrikoides. After the sprinkling of the Hwangto showing the best removal efficiency in the test, 99% of total algaes were found to be eliminated within 60 minutes. Jeokeokji showed the highest removal efficiency among clay mineral medicines(92% removal efficiency after 60 minutes), and the rests in decreasing order are as follows: Gamto (91%) > Baekseokji (89%) > Hydromica (81%). In addition, Fe-oxide mineral medicine similarly looking as fine-grained earthy Daejaseok showed 100% removal efficiencyafter 30 minutes, and Wooyoeryang, 95% after 60 minutes. It is noted that even little addition (1 g/L) of Daejaseok, 10% of Hwangto concentration into seawater showed the removal efficiency of 100% after 60 minutes. From the results, it could be concluded that the fine-grained earthy Daejaseok was the most effective natural mineral medicine to remove the C. polykrikoides from seawater. Under the microscope the removal mechanism was found to be activated in the following order: adsorption, swelling of chain colony, chain colony crisis and algaecide.

• Ecology and Resilient Infrastructure
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• v.3 no.4
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• pp.221-230
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• 2016

Multi-functional floating wetland island (mFWI) was developed in order to prevent algal bloom and to improve water quality through several unit purification processes. A test bed was applied in the stagnant watershed in an urban area, from the summer to the winter season. For the advanced treatment, an artificial phosphorus adsorption/filtration medium was applied with micro-bubble generation, as well as water plants for nutrient removal. It appeared that the efficiency of chemical oxygen demand (COD) and total phosphorus (T-P) removal was higher in the warmer season (40.9%, 45.7%) than in the winter (15.9%, 20.0%), and the removal performance (suspended solid, chlorophyll a) in each process differs according to seasonal variation; micro-bubble performed better (33.1%, 39.2%) in the summer, and the P adsorption/filtration and water plants performed better (76.5%, 59.5%) in the winter season. From the results, it was understood that the mFWI performance was dependent upon the pollutant loads in different seasons and unit processes, and thus it requires continuous monitoring under various conditions to evaluate the functions. In addition, micro-bubbles helped prevent the formation of anaerobic zones in the lower part of the floating wetland. This resulted in the water circulation to form a new healthy aquatic ecosystem in the surrounding environment, which confirmed the positive influence of mFWI.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.1
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• pp.71-79
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• 1999

As part of an on-going project investigating flux of materials in the Keum River Estuary, we have monitored seasonal variations of nutrients, suspended particulate matter (SPM), chlorophyll, and salinity since 1997. Meteorological data and freshwater discharge from the Keum River Dike were also used, Our goal was to answers for (1) what is the main factor for the seasonal fluctuation of nutrients in the Keum River Estuary? and (2) are there any differences in nutrient distributions before and after the Keum River Dike construction? Nitrate concentrations in the Keum River water were kept constant through the year. Whereas other nutrients varied with evident seasonality: high phosphate and ammonium concentrations during the dry season and enhanced silicate contents during the rainy season. SPM was found similar trend with silicate. During the rainy season, the freshwater discharged from the Keum River Dike seemed to dilute the phosphate and ammonium, but to elevate SPM concentration in the Keum Estuary. In addition, the corresponding variations of SPM contents in the estuarine water affected the seasonal fluctuations of nutrients in the Estuary. The most important source of the nutrients in the estuarine water is the fluvial water. Therefore, the distribution patterns of nutrients in the Estuary are conservative against salinity. Nitrate, nitrite and silicate are conservative through the year. The distribution of phosphate and ammonium on the other hand, display two distinct seasonal patterns: conservative behavior during the dry season and some additive processes during the rainy days. Mass destruction of freshwater phytoplankton in the riverine water is believed to be a major additive source of phosphate in the upper Estuary. Desorption processes of phosphate and ammonium from SPM and organic matter probably contribute extra source of addition. Benthic flux of phosphate and ammonium from the sediment into overlying estuarine water can not be excluded as another source. After the Keum River Dike construction, the concentrations of SPM decreased markedly and their role in controlling of nutrient concentrations in the Estuary has probably diminished. We found low salinity (5~15 psu) within 1 km away from the Dike during the dry season. Therefore we conclude that the only limited area of inner estuary function as a real estuary and the rest part rather be like a bay during the dry season. However, during the rainy season, the entire estuary as the mixing place of freshwater and seawater. Compared to the environmental conditions of the Estuary before the Dike construction, tidal current velocity and turbidity are decreased, but nutrient concentrations and chance of massive algal bloom such as red tide outbreak markedly increased.

• Korean Journal of Environmental Biology
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• v.39 no.2
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• pp.184-194
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• 2021

Since the construction of a dike in 1983, the water quality in the Bunam Lake has continued to deteriorate due to algal bloom caused by agricultural nutrient loading. Therefore, we evaluated the change in water quality and phytoplankton ecological characteristics in Bunam Lake and Cheonsu Bay, Korea. Water temperature, salinity, dissolved oxygen, chemical oxygen demand (COD), chlorophyll, and phytoplankton community were surveyed in April during the dry season and in July during the rainy reason. As a result, during the dry period, phytoplankton proliferated greatly and stagnated in the Bunam Lake while a very high population of cyanobacteria Oscillatoria spp. (8.61×10⁷ cells L^-1) was recorded. Most of the nutrients, except, nitrate and nitrite, were consumed due to the large growth of phytoplankton. However, during the rainy period, concentrations of ammonia, phosphate, silicate, nitrate, and nitrite, were very high towards the upper station due to the inflow of fresh water. Cyanobacteria Oscillatoria and Microcystis spp. were dominant in the Bunam Lake during the rainy period. Even in the Cheonsu Bay, cyanobacteria dominated due to the effect of discharge and diatoms, such as, Chaetoceros spp. and Eucampia zodiacus, which also proliferated significantly due to increased levels of nutrients. Since the eutrophication index was above 1 in Bunam Lake, it was classified as eutrophic water and the Cheonsu Bay was classified as eutrophic water only during the rainy season. In addition, a stagnant seawater-derived hypoxia water mass was observed at a depth of8m in the Bunam Lake adjacent to the tide embankment and the COD concentration reached 206 mg L^-1 in the bottom layer at B3. Based on this result, it is considered that the water quality will continue to deteriorate if organic matters settle due to continuous inflow of nutrients and growth of organisms while the bottom water mass is stagnant.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.346-362
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• 2021

A sediment control dam is an artificial structure built to prolong sedimentation in the main dam by reducing the inflow of suspended solids. These dams can affect changes in dissolved organic matter (DOM) in the water body by changing the river flow regime. The main DOM component for Yeongju Dam sediment control of the Naeseongcheon River was analyzed through 3D excitation-emission matrix (EEM) and parallel factor (PARAFAC) analyses. As a result, four humic-like components (C1~C3, C5), and three proteins, tryptophan-like components (C2, C6~C7) were detected. Among DOM components, humic-like components (autochthonous: C1, allochthonous: C2~C3) were found to be dominant during the sampling period. The total amount of DOM components and the composition ratio of each component did not show a difference for each depth according to the amount of available light (100%, 12%, and 1%). Throughout the study period, the allochthonous organic matter was continuously decomposing and converting into autochthonous organic matter; the DOM indices (fluorescence index, humification index, and freshness index) indicated the dominance of autochthonous organic matter in the river. Considering the relative abundance of cyanobacteria and that the number of bacteria cells and rotifers increased as autochthonous organic matter increased, it was suggested that the algal bloom and consequent activation of the microbial food web was affected by the composition of DOM in the water body. Research on DOM characteristics is important not only for water quality management but also for understanding the cycling of matter through microbial food web activity.

• Korean Journal of Environmental Biology
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• v.41 no.2
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• pp.109-125
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• 2023

This study was conducted to select target fish species as baseline research for accumulation analysis of major hazardous chemicals entering the aquatic ecosystem in Korea and to analyze the impact on fish community. The test bed was selected from a sewage treatment plant, which could directly confirm the impact of the inflow of harmful chemicals, and the Geum River estuary where harmful chemicals introduced into the water system were concentrated. A multivariable metric model was developed to select target candidate fish species for hazardous chemical analysis. Details consisted of seven metrics: (1) commercially useful metric, (2) top-carnivorous species metric, (3) pollution fish indicator metric, (4) tolerance fish metric, (5) common abundant metric, (6) sampling availability (collectability) metric, and (7) widely distributed fish metric. Based on seven metric models for candidate fish species, eight species were selected as target candidates. The co-occurring dominant fish with target candidates was tolerant (50%), indicating that the highest abundance of tolerant species could be used as a water pollution indicator. A multi-metric fish-based model analysis for aquatic ecosystem health evaluation showed that the ecosystem health was diagnosed as "bad conditions". Physicochemical water quality variables also influenced fish feeding and tolerance guild in the testbed. Eight water quality parameters appeared high at the T1 site, indicating a large impact of discharging water from the sewage treatment plant. T2 site showed massive algal bloom, with chlorophyll concentration about 15 times higher compared to the reference site.

• Korean Journal of Ecology and Environment
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• v.56 no.1
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• pp.36-44
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• 2023

Environmental DNA (eDNA) can exist in both intracellular and extracellular forms in natural ecosystems. When targeting harmful cyanobacteria, extracellular eDNA indicates the presence of traces of cyanobacteria, while intracellular eDNA indicates the potential for cyanobacteria to occur. However, identifying the "actual" potential for harmful cyanobacteria to occur is difficult using the existing sediment eDNA analysis method, which uses silica beads and cannot distinguish between these two forms of eDNA. This study analyzes the applicability of a density gradient centrifugation method (Ludox method) that can selectively analyze intracellular eDNA in sediment to overcome the limitations of conventional sediment eDNA analysis. PCR was used to amplify the extracted eDNA based on the two different methods, and the relative amount of gene amplification was compared using electrophoresis and Image J application. While the conventional bead beating method uses sediment as it is to extract eDNA, it is unknown whether the mic gene amplified from eDNA exists in the cyanobacterial cell or only outside of the cell. However, since the Ludox method concentrates the intracellular eDNA of the sediment through filtration and density gradient, only the mic gene present in the cyanobacteria cells could be amplified. Furthermore, the bead beating method can analyze up to 1 g of sediment at a time, whereas the Ludox method can analyze 5 g to 30 g at a time. This gram of sediments makes it possible to search for even a small amount of mic gene that cannot be searched by conventional bead beating method. In this study, the Ludox method secured sufficient intracellular gene concentration and clearly distinguished intracellular and extracellular eDNA, enabling more accurate and detailed potential analysis. By using the Ludox method for environmental RNA expression and next-generation sequencing (NGS) of harmful cyanobacteria in the sediment, it will be possible to analyze the potential more realistically.

• Journal of Wetlands Research
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• v.25 no.4
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• pp.274-283
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• 2023

Buffer zones, an example of nature-based solutions, offer wide range of environmental, social and economic benefits due to their multifunctionality when applied to watershed areas promoting blue-green connectivity. This study evaluated the effects of buffer zone application to the water quality of Yongdam reservoir tributaries. Particularly, the challenges and improvement of the buffer zone design were identified and suggested, respectively. Water and soil samples were collected from a total of six sites in Yongdam reservoir from September 2021 to April 2022. Water quality analyses revealed that among the sites monitored, downstream of Sangjeonmyeon Galhyeonri (SG_W_D2) was found to have the highest concentration for water quality parameters turbidity, total suspended solids (TSS), chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN). This finding was attributed to the algal bloom observed during the sampling conducted in September and October 2021. It was found through the soil analyses that high TN and TP concentrations were also observed in all the agricultural land uses implying that nutrient accumulation in agricultural areas are high. Highest TN concentration was found in the agricultural area of Jeongcheonmyeon Wolpyeongri (JW_S_A) followed by Jucheonmyeon Sinyangri (JS_S_A) while the lowest TN concentration was found in the original soil of Sangjeonmyeon Galhyeonri (SG_S_O). Among the types of buffer zones identified in this study, Type II-A, Type II-B and Type III were found to have blue-green connectivity. However, initially, blue-green connectivity in these buffer zone types were not considered leading to poor design and poor performance. As such, improvement in the design considering blue-green network and renovation must be considered to optimize the performance of these buffer zones. The findings in this study is useful for designing buffer zones in the future.