• Korean Journal of Environmental Biology
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• v.32 no.3
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• pp.168-175
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• 2014

In order to understand the phytoplankton community structure based on their cell size duringlow water temperature periods, we studied 10 stations in the East Sea, Korea on March, 2012. The minimum standing crops of total phytoplankton were $3.4{\times}10^6cells\;L^{-1}$ at the station 5. The maximum values were $7.6{\times}10^6cells\;L^{-1}$ at the station 8, which is two times the amount of the minimum. The carbon mass at the station 4 ($6.3{\times}10^8pg\;L^{-1}$) was more than forty times higher compared with station 5 ($0.08{\times}10^8pg\;L^{-1}$). From these results, we found a significant difference between standing crops and carbon mass which might have caused due to their differences in community structure and cell size. Therefore, we considered the types of plankton biomass to estimate the primary product in the specific location and/or time. The phytoplankton communities were classified in 3 types: microplankton (> $20{\mu}m$), nanoplankton (< $20{\mu}m$) and picoplankton (< $2{\mu}m$). In the case of picoplankton, various morphological types were observed during the study period. These various picoplankton species were further classified as S (spherical), SF (spherical&flagella), O (oval), OF (oval&flagella) or R (rod) type, and we analyzed their community structure based on these categories. The picoplankton was found to be the most dominant type at 8 stations and S type as the most popular. The picoplankton seems to be the significant organism in the marine ecology during low water temperature periods in the coastal waters of East Sea. Therefore, picoplankton \;-with scientific surveys can be considered as the database for their identification. In conclusion, we suggest that cell size of the phytoplankton would be the best criteria to accurately analyze their community structure and to reveal groups having more ecological influence.

• KSBB Journal
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• v.20 no.4
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• pp.266-270
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• 2005

The effect of the weight ratio of carbon source to nitrogen source on the growth and the composition change of fatty acids of Thraustochytrium aureum ATCC 34304 was investigated. The cell concentration of 5 days' culture increased and then decreased according to the increase of C/N, The ratioes for the maximum biomass were unique respectively and distributed between 1 and 4 with the initial sugar concentration in the range of 5 g/L to 25 g/L. The biomass yield, $Y_{x/s}$ decreased along with the increase of C/N, but maintained a constant value 0.35 between 10 and 20. The composition of myristic acid $(C_{14:0})$, one component of the lipid synthesized by T. aureum, was not affected with the change of C/N, but the composition of palmitic acid $(C_{16:0})$ was around $20\%$ below 4 of C/N and decreased to $15\%$ according to C/N about 4. The compositions of oleic acid $(C_{18:1})$ and linoleic acid $(C_{18:2})$ increased from 0 to $20\%\;and\;7\%$ respectively. The composition of $\gamma-linoleic$ acid $(C_{18:3})$, however, reduced from $5\%\;to\;2\%$. EPA $(C_{20:5})$ and DPA $(C_{22:5})$ showed a tendency of reduction in the weight composition according to the increase of C/N, but DHA $(C_{22:6})$ had a trend maintaining an approximately constant value, around $40\%$, irrespective of the change of C/N.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.303-314
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• 2021

To understand how to efficiently observe the biomass and community of phytoplankton, phytoplankton sampling was carried out from June to October 2019 at the Yeongju dam sediment control reservoir(YJ) and Bohyeonsan dam reservoir(BH1 and BH2). The results derived from microscopic observation, such as the conventional phytoplankton qualitative/quantitative analysis, and from the CHEMTAX method based on the pigments, were compared. The relative contribution of phytoplankton, calculated by the microscopy and CHEMTAX methods, showed a significant difference in all four classes: cryptophyta, chlorophyta, cyanobacteria, and diatoms. In addition, the correlation between the two observation methods was poor. This might be caused by methodological differences in microscopy that do not consider the varying cell sizes among phytoplankton species. In this study, by converting the cells into carbon, the slope between both carbon biomasses based on microscopy and CHEMTAX was improved close to the 1 : 1 line, and the y-intercept was closer to 0 for cryptophyta and diatoms. For cyanobacteria, the slope increased, the y-intercept decreased, and the plot approached 1 : 1 although the correlation coefficients were not improved in all classes. The present study suggests that application of CHEMTAX based on pigment analysis could be a possible approach to efficiently determine the relative carbon proportions of individual classes of phytoplankton community composition.

• KSBB Journal
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• v.7 no.4
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• pp.296-301
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• 1992

A Pseudomonas fluorescens was selected from mushrooms and studied in both batch and fed-batch cultures in order to get maximal biomass concentration. P. fluorescens is an aerobic bacterium and antagonistic to Pseudomonas tolaasii which causes blotch disease on the mushroom cap. P fluarescens and P. tolaasii were identified by Gram staining, gelatin liquefaction, oxidase test, etc. and were characterized by pigment production, temperature sensitivity, salt tolerance and rapid pitting test, etc., Celts of P. fluorescens well in medium containing 30g/L of glucose, whereas the growth was inhibited at the glucose levels at higher than 30g/L. The highest values of specific growth rate and productivity were obtained when using 10g/1 of yeast extract. Optimum concentrations of $NH_4Cl$ and ${(NH_4Cl)}_2SO_4$ for culture were found to be 1.0g/L and 0.1g/L respectively. Optimum concentration of $MgSO_4{\cdot}7H_2O$ used as a sulfursource was 1.0g/L. It was also found that the cell concentrations reached the maximum level when grown on the medium containing 1.0g/L of $KH_2PO_4$ and 0.1g/L of $CaCl_2$. Also, the optimum culture conditions were $30^{\circ}C$ and pH 6.0. Cultivation of P. fluarescens at high dissolved oxygen (DO) concentration led to a decrease of bacterial productivity in batch culture. Maximum productivity was achieved at 40% DO concentration.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.294-302
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• 2007

This study was to evaluate microcystin production by Microcystis aeruginosa in response to three different levels of indirect (0, 10, 50% of fish cultured media filtrate; control, FCMF1 and FCMF2) exposures to omnivorous and planktivorous fish (Carassius gibelio langsdorfi and Hypophthalmichthys molitrix, CCMF and HCMF, repectively). The cell biomass, intracellular microcystin (MC) and extracellular MC were measured everyday. The intracellular MC contents of all treatments were significantly increased than the controls (CCMF1, P=0.015; CCMF2, P<0.001; HCMF1, P<0.001; HCMF2, P<0.001). The intracellular MC contents of M. aeruginosa were significantly higher in CCMF2 than in CCMF1 (P=(0.023), Those of M, aeruginosa in HCMF2 were significantly higher than that in HCMF1 (P<0.001). The extracellular MC contents were not significantly different between control and CCMFs but those of M, aeruginosa in HCMF1 and HCMF2 were significantly higher than that in control (HCMF1, P=0.003; HCMF2, P<0.001). This study strongly supports that induced-defensive MC production (intra and extracellular MC) of potentially toxic cyanobacteria in response to kairomone concentration and this results can consider the biomanipulation of eutrophic waters as well as an information concerning strategies for recovering eutrophic waters.

• 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.

• Microbiology and Biotechnology Letters
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• v.41 no.2
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• pp.207-214
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• 2013

A concerted effort to develop alternative forms of energy is underway due to fossil fuel shortages and its deleterious effects. Recently, bioenergy from microalgae has gained prominence and the use of municipal wastewater as a low cost alternative for a nutrient source has significant advantages. In this study, we have employed municipal wastewater directly after primary treatment (primary settling basin) in a small scale raceway pond (SSRP) for microalgal growth. Indigenous microalgae in the wastewater were encouraged to grow in the SSRP under optimal conditions. The mean removal efficiencies of TN, TP, and $NH_3-N$ after 6 days were 77.77%, 63.55%, and 89.02%, respectively. The average lipid content of the microalgae was 19.51% of dry cell weight, and linolenate and linoleate (18:n) were the predominant fatty acids. The 18S rRNA gene analysis and microscopic observations of the indigenous microalgae community revealed the presence of Chlorella vulgaris and Scenedesmus obliquus as the dominant microalgae. These results indicate that untreated municipal wastewater, serving as an excellent nitrogen and phosphate source for microalgal growth, could be treated using microalgae in open raceway ponds. Moreover, microalgal biomass could be further profitable by the extraction of biodiesel.

• The Korean Journal of Malacology
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• v.15 no.2
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• pp.105-113
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• 1999

This study was measured environmental factors of flat oyster habitats and biomass of flat oyster to improve the productivity of flat oyster. Water temperature and salinity of the flat oyster habitat ranged from 5.5 to 27.4$^{\circ}C$ and from 31.2 to 33.4 , respectively. Average concentrations of DO, COD, DIN and PO$\_$4/$\^$3/ -P were 7.11 mg/l, 4.55 $\mu\textrm{g}$-at./l and 0.36 $\mu\textrm{g}$-at./l respectively. Surface sediments at the sampling area were composed of coarse sand, sandy silt and silty sand. Average level of IL, COD and AVS in the surface sediments were 2.6%, 13.70 mg/g dry and 0.33 mg/g dry respectively. In each sampling station, total standing crops of phytoplankton showed peaks twice in February and August. Dominant species of phytoplankton occurred in Haechang Bay throughout the year were Skeletonema costatum, Paralia sulcata, Eucampia zodiacus, Chaetoceros curvicetus, C. affinis, C. debilis, C. decipiens, Asterionella glacialis, Pseudonitzschia longissima, Pseudonitzschia seriata, Ceratium furca and C. fusus. Ten species of the bivalves were collected at the flat oyster habitat. Most of bivalves were the eutrophic species Ostrea denselamellosa, Crassostrea gigas, Ruditapes philippinarum, Scaphraca subcrenata, Scapharca broughtonii, Atrina pectinata, Fulvia mutica, Mytilus edulis, Protothaca jedoensis and Megacardita ferruginosa. The mean density of them was 21 inds./㎡ (479.14 g/㎡), while that of the flat oyster was at 0.25 inds./㎡ (231.25 g/㎡).

• Journal of Plant Biology
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• v.35 no.4
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• pp.323-332
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• 1992

Chlorophyll-a concentrations of phytoplankton and primary productivities in closed marine ecosystem, Inchon Dock, were measured and analyzed monthly from August, 1990 to December, 1991. Chlorophyll-a concentrations ranged from 1.61 to $28.67\;\mu\textrm{g}\;Chi-a/I$, where nanoplankton ($2-20\;\mu\textrm{m}$) fractions contributed in 19.0-82.3% and picoplankton ($0.2-2\;\mu\textrm{m}$) fractions in 4.5-51.4%. Primary productivities measured by $^{14}C$ method ranged from 49.4 to $4359.4\;mg\;C{\cdot}m^{-2}{\cdot}day^{-I}$, where nanoplankton ($20\;\mu\textrm{m}$) contributed in 18.8-94.6%. These results implied that very tiny cell-sized phytoplankton populations were important in point of chlorophyll-a concentration and primary productivity of phytoplankton community. In monthly variations of chlorophyll-a concentration by phytoplankton, the first peak occurred in March and the second in August. Nitrogen requirement by phytoplankton ranged from 0.7 to $60.7\;mg\;at-N{\cdot}m^{-2}{\cdot}day^{-I}$ and the turnover time of inorganic nitrogen showed maximum during winter and minimum in summer. Carbon assimilation number increased in summer and decreased in winter.winter.

• KSBB Journal
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• v.20 no.6
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• pp.453-457
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• 2005

We investigated the effect of sulfate re-addition on hydrogen production under sulfur-deprived condition. When the final concentration of sulfate to cell suspensions($0{\sim}120{\mu}M$) was increased, chlorophyll concentration, culture density, and total amount of $H_2$ produced, increased up to an optimal concentration of $30{\mu}M\;MgSO_4$. Maximum hydrogen volume was 236 mL $H_2/L$ culture at $30{\mu}M\;MgSO_4$. However, the addition of excess sulfate(above $MgSO_4\;60{\mu}M$) delayed the start of hydrogen production and the induction of hydrogenase. Accordingly, the final yield of hydrogen production was reduced. Using these results, we attempted the continuous and sustained hydrogen production by sulfate re-addition($30{\mu}M\;MgSO_4$) using a single C. reinhardtii culture for up to 4 cycles. In total, hydrogen production volume was 625 mL $H_2/L$ culture.