• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.5
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• pp.446-457
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• 1993

Monthly distribution of marine bacteria and phytoplankton in Suyeong Bay were investigated with laboratory experiment of dominant algal species and bacterial flora. During the periods of study, the highest density of phytoplankton and bacteria occurred in May with the number of $3.3{\times}10^6cells/l$ and $1.93{\times}10^8cells/ml$, respectively. 10 genera of bacteria and 22 genera of phytoplankton were isolated and identified. In May when phytoplankton bloom occurred, dominant species of bacteria were Acinetobacter calcoaceticus($29.1\%$) and Bacillus subtilis($22.9\%$), and dominant species of phytoplankton were Chaetoceros spp.($62.8\%$) and Skeletonema spp. ($19.4\%$). Pseudomonas spp., which was the most abundant bacterial species during the study periods, were rapidly decreased in May. In laboratory studies of culturing bacteria and phytoplankton isloated in May, the growth of Pseudomonas vesicularis seems to be influenced by the concentrations of excretion matter of Chaetoceros spp. To examine the result colsely, the problem of pure isolation for phytoplankton must be solved and more experimental process have to be conducted.

• Korean Journal of Environmental Biology
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• v.30 no.1
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• pp.39-46
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• 2012

The distributions of phytoplankton community are investigated from 29 reservoirs in Yeongsan and Seomjin River Basins, Korea. As a microalgal flora, a total of 424 species of phytoplankton were identified. They were 157 Chlorophyceae, 161 Bacillariophyceae, 39 Cyanophyceae, and 67 other algal taxa. The phytoplankton diversity were low in stream type reservoirs such as Kumho, Youngsan and Youngam Reservoirs. The population density of phytoplankton ranged from 29 cells $mL^{-1}$ to 53,161 cells $mL^{-1}$. The dominant phytoplankton species more than 20% of total standing crops were $Asterionella$ $formosa$, $Aulacoseira$ $ambigua$, $Aulacoseira$ $distans$, $Aulacoseira$ $granulata$, $Cyclotella$ sp., $Synedra$ $acus$, $Coelastrum$ $reticulatum$, $Pandorina$ $morum$, $Scenedesmus$ $arcuatus$, $Aphanothece$ $clathrata$, $Microcystis$ $aeruginosa$, $Phormidium$ sp. The concentration of chlorophyll $a$ ranged from 0.41 mg $m^{-3}$~220.72 mg $m^{-3}$, and showed highest concentration in Gaecho-je. The concentrations of TN and TP have no clear relationships with chlorophyll $a$ concentrations.

• Korean Journal of Ecology and Environment
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• v.43 no.3
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• pp.418-427
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• 2010

In the four swamps of Jjokjibeol, Mokpo, Upo and Sajipo in the Upo wetland, the nitrogen nutrients, phosphorus nutrients and chl-$\alpha$ had been observed during the period from April 2005 to December 2009 on monthly basis. Based on the results, the fluctuations of trophic state in the Upo wetland were estimated. Measurements of the nitrogen nutrients such as $NO_3$-N, $NH_3$-N and T-N showed to be generally decreased in comparison with those in the precent studies. Yet the T-N was still considerably higher than the general concentration level of eutrophication and algal blooming. $PO_4$-P and T-P showed to have reduced considerably in comparison to precedent studies. However, T-P also turned out to be dissolved over the nutrient standard. Nitrogen nutrients and phosphorus nutrients were the lowest in Jjokjibeol in the Upo wetland. The chl-$\alpha$ concentrations were the highest at summer periods in Jjokjibeol and Mokpo. However, the highest at non-summer periods in Upo and Sajipo. Among the four swamps, Upo had the highest density on average of chl-$\alpha$, and Mokpo the lowest. Through TRIX (Trophic Index) analysis evaluating trophic state of the Upo wetland, all four swamps were estimated of poor water quality (eutrophication).

• Ecology and Resilient Infrastructure
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• v.4 no.3
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• pp.130-141
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• 2017

We evaluated the field application feasibility that biologically derived substances (Naphthoquinone derivate: NQ 2-0) can be used for the eco-friendly mitigation of natural harmful cyanobacterial blooms in freshwater. We conducted a 30 ton scale mesocosm experiment to investigate the effects of NQ 2-0 on biotic and abiotic factors in water collected from Gi-heung reservoir. In the mesocosm experiments, the abundance of Microcystis sp. was continuously increased in the control. However, the Microcystis sp. cell density was sharply decreased on the $10^{th}$ day. In the treatment, NQ 2-0 showed the strong and selective algicidal activity toward the target cyanobacteria (Microcystis sp.). Accordingly, the algicidal activity of NQ 2-0 compound increased gradually until $10^{th}$, $15^{th}$ days and algal biomass was decreased to 99.4 and 100 %, respectively. NQ 2-0 compound was not only selective algicidal activity but also the growth of other phytoplankton and increased the Shannon-Wiener diversity index of phytoplankton. In the mesocosm experiments, the dynamics of biotic (bacteria, heterotrophic nanoflagellate, ciliates, zooplankton) and abiotic (water temperature, dissolved oxygen, pH, conductivity, nutrients) factors remained unaffected. These results suggest that NQ 2-0 could be a selective and ecologically safe algicide to mitigate harmful cyanobacterial blooms. In addition, it is believed that NQ 2-0 will play a major role in forming a healthy aquatic ecosystem by facilitating habitat and food supply of aquatic organisms.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.3
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• pp.262-270
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• 2012

Seaweeds provide habitats in which marine animals can spawn and develop, and serve as a food supply for algaegrazing species such as sea urchins and abalone. Recently, seaweed species have disappeared from coastal ecosystems, leaving barren ground, defined as habitats that have lost their algae forests and where coralline algae containing calcium carbonate components have become encrusted on rocks. The biological causes of barren ground include grazing by herbivores and excessive seaweed harvest. The environmental harm caused by the spread of barren ground includes accelerated eutrophication following the reduction in seaweed, which plays an important role in oceanic purification. In the present study, we identified the relationships between various seaweed species and the occurrence of barren ground. Subtidal benthic macroalgal flora and community structure were observed seasonally on barren ground along vertical transects of rocky shores of Bihwa, Samchuck, and the east coast of Korea from February to November 2006. Fifty-eight seaweed species were identified, including 7 green, 15 brown, and 36 red algae species. There were between 6 and 28 species among seasons. Over the whole study period, average seaweed biomass (g wet wt $m^{-2}$) was 241.90 g, with a seasonal range of 25.26 to 760.34 g. Seaweed biomass declined with increasing seawater depth and ranged between 91.26 and 422.08 g. The vertical distribution of algae was characterized by Undaria pinnatifida and Sargassum honeri at 5 m, S. honeri and U. pinnatifida at 10 m, and U. pinnatifida and Agarum clathratum at 15 m depth. Seasonal patterns in community indices were not found. Community indices showed different patterns along vertical shoreline gradients; the dominance index increased but the richness, evenness, and diversity indices decreased with seawater depth. Sea urchin density was 8 to 24 individ. $m^{-2}$ in Bihwa. These urchin populations had significantly aggregated spatial patterns and recurrent destructive grazing appeared to be occurring.

• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.267-276
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• 2001

The downstream reach of the Han River adjoining Seoul in Korea was the upper boundary of an estuary where tidal effect on the flow rate could be exerted. According to the comprehensive river regulation project, the river was channelize dand impounded by two overflow dams, which provided favorable condition for algal growth in this sewage polluted eutrophic reach. In this study primary productivity of phytoplankton was measured in the down reach and the autochthonous and allochthonous organic carbon loadings were estimated. Primary production of phytoplankton measured by C-14 uptake and P-I model method ranged from 140 to $4,890\;mgC\;m^{-2}\;d^{-1}$ (median value $1,865\;mgC\;m^{-2}\;d^{-1}$) showing the level of eutrophic lakes. Phytoplankton density that varied according to water flow rate was highest in spring. Allochthonous organic carbon loading was dominated by sewage input through tributaries in most of days except flood flow period. The average proportion of autochthonous carbon generation by phytoplankton was 40.9%, which is very high proportion for a lotic habitat.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.475-481
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• 2005

In an effort to identify a new environment-friendly algicide, we examined the ability of extracts from the leaves and stems of nine Korean oak tree species to inhibit growth of the bloom-forming cyanobacterium, Microcystis aeruginosa. At a concentration of 100 mg $L^{-1}$, five of the oak tree extracts (QAT-L, QAT-5, QAS- L, QGI-5, and QSA- L) decreased the cell density of M. aeruginosa by over 90% for 7 days. At a concentration of 20 mg $L^{-1}$, the same five extracts inhibited the growth of M. aeruginosa by approximately 50%. The minimum concentration of oak tree extracts required for effective inhibition of M. aeruginosa (20 mg $L^{-1}$) is comparable to that of the known algicide, tannic acid (17 mg $L^{-1}$), which is thought to be one of the main active ingredients in the oak tree extract. These findings suggest that oak extracts may be useful as an environment-friendly algicide to control the bloomforming cyanobacterium, M. aeruginosa, in eutrophic waters.

• The Korean Journal of Malacology
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• v.19 no.2
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• pp.143-152
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• 2003

Water temperature during the culturing period was 10.4-25.5$^{\circ}C$ and there was a little difference between rearing sites. Salinity (25.00-31.17 psu) and DO (over 6.13 mg/l) showed reasonable condition for the growth of bay scallop. Concentrations of chlorophyll-a were ranged 1.69-7.40 $^{\mu}$g/l, and they fluctuated monthly in the every sampling site. During the growing period from June to October, dominant phytoplankton species were Ceratium sp. in Nammeon and Hoejin, Chaetoceros sp. in Dolsan. Density of phytoplankton was high in July, August and October, but it was low in September and November. When young bay scallops were cultured for 185 days in Nammyeon, Hoejin and Dolsan, shell heights were grown for 0.19 mm/day, 0.18 mm/day and 0.16 mm/day, respectively, and total weights were increased 0.16 g/day, 0.16 g/day and 0.13 g/day, respectively. Daily growth rates of shell height were 0.606%, 0.581% and 0.549%, and daily growth rates of total weight were 1.972%, 1.857% and 1.746%, respectively. Maximum predicted values of shell height calculated by von Bertalanffy growth model were 52.62 mm, 51.74 mm and 48.91 mm, respectively. Survival rate was the highest in Nammyeon (87.0%), but the rates in Hoejin and Dolsan sharply decreased after November.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.943-952
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• 2013

Algae blooms have soared recently in the lakes across the nation due to eutrophication. Blue-green algae cause unpleasant scene, produce taste and odor problem, and hinder processes in drinking water treatment. Algae toxicity monitoring has been strengthened, because the damages of wild lives and livestocks by algal toxins have been reported. Investigation on the characteristics of cyanobacterial occurrence and concentration distribution of Cyanotoxins in Hoeya reservoir have been conducted. Physical and chemical influences of water environment on cyanobacterial occurrences have also been studied. Movements of four species of Microcystin and five species of Anatoxin-a among Cyanotoxins were observed by LC-MS/MS analysis. Microcystis spp. among the cyanobacteria have mainly dominated in the Hoeya reservoir during the investigating period. The density of cyanobacteria were positively correlated with temperature and pH of water. Highest concentrations of Microcystin-LR and Microcystin-RR were $0.424{\mu}g/L$ and $0.117{\mu}g/L$ at the sampling points. Total concentration of Cyanotoxins in water coming into the water treatment plant was $0.182{\mu}g/L$, and they were not detected in treated water.