• Korean Journal of Soil Science and Fertilizer
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• v.46 no.1
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• pp.40-48
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• 2013

This study evaluated the close crop recycling method by using the extract from defective onions. The mixture of the diluted extract (1/500) and nutrients was applied seven times on the onion leaves without spilling it onto the field. The yield and quality of the onions produced by this method (recycle) were compared to those grown organically (control) and conventionally (normal). The yield from the recycling field was increased significantly by 9% compared to that of the control field, while it was decreased by 11% compared to the normal field (p < 0.05). This lower yield was explained by the differences of the mulching vinyl and the fertilizers between the treatments which effect the onion growth during the winter. The content of quercetin in the onions from the recycling filed was increased significantly by 34% and 44% compared to those of the control and normal field, respectively (p < 0.05). It seemed that minerals and biologically active substances in the defective onion extract were effective in increasing the onion growth. In terms of soil microbial biomass, arbuscular mycorrhizal fungi was increased significantly in the recycle field by 40.1% and 30.6% compared to those of the control and normal fields, respectively (p < 0.05). On the other hand, microbial stress (cy19:0/18:1w7c) was decreased in the recycle field by 21.0% and 14.1% compared to those of the control and normal fields, respectively.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.22 no.3
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• pp.77-87
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• 2017

Picophytoplankton, an important primary producer especially at the oligotrophic region, is known to contribute a significant portion of the total phytoplankton biomass in the East Sea of Korea. During autumn in the southwestern East Sea, frequent upwellings and oligotrophic conditions occur and annual variation of primary productivity is known to be significant. Moreover sea surface temperature (SST) of the East Sea is steeply increasing compared to global average increase, so various changes in marine ecosystem related with increase of SST are reported. Taking such circumstances into consideration, we measured the contribution from picophytoplankton fraction to total phytoplankton composition by size fraction of phytoplankton biomass during the autumn seasons from 2011, 2013 and 2015 and examined the variation of the phytoplankton composition. As a result of size fraction analyses, we found that the variation of contribution from picophytoplankton(<$3{\mu}m$) to total community of phytoplankton was high and the average fractions of picophytoplankton were measured as 38% (2011), 59% (2013), 7% (2015), respectively. The difference between measured SST and annual mean SST (${\Delta}T$) was highest ($+1.6^{\circ}C$) in autumn of 2013 and lowest ($-0.9^{\circ}C$) in autumn of 2015. The close positive correlation between ${\Delta}SST$ and fraction of picophytoplankton was confirmed($R^2$ > 0.9). The increase in SST at the southern East Sea was confirmed as one of the main environmental factors in the increase in the increase of the contribution from picophytoplankton. Monitoring of changes in the community structure of primary producers and the influences of the environmental factors including SST in the East Sea is necessary to understand the interactions of ecosystem of the East Sea and the climate change in the near future.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.627-632
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• 2019

In this study, Laminaria japonica was used as a substrate for a mixed aerobic microbial consortium. Laminaria japonica is well-known as a representative brown algal biomass possessing advantages of cheap cost, and high productivity and carbohydrate content. A biological saccharification system was established by inoculating and enriching the mixed aerobic microbial consortium. Production of the soluble carbohydrate and reducing sugar at different hydraulic retention times (HRT) was observed. The efficiency of saccharification increased according to the decrease of HRT. The maximum saccharification yield in a continuous biological pretreatment process was 17.96 and 4.30 g/L/day for the soluble carbohydrate and reducing sugar, respectively at the HRT of 1 day. In contrast, the staccharification yield decreased drastically at the HRT of 0.5 day. Experimental results indicate that Laminaria japonica is a promising material for the production of useful products, in particular for the saccharification through a biorefinery process. It can thus be concluded that a continuous biological pretreatment process using a mixed cultivation system can be successfully employed for the biorefinery technology.

• Korean Journal of Environmental Agriculture
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• v.29 no.2
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• pp.109-114
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• 2010

Rape residue as green manure is an emerging alternative of chemical fertilizer to improve soil quality and crop productivity. Objective of this research was to evaluate the effectiveness of rape residue as green manure on reduction of chemical fertilizer and suppression of weed occurrence in rice-rape double cropping system. Greenhouse experiment was conducted with four treatments: the combination of rape residue and three different N application rates (0, 30 and 70% of recommended application rate (7.8 kg N $10a^{-1}$)) and 100% chemical fertilizer as a control. No difference in rice clum length was observed for all treatments, while panicle length was highest in a treatment of rape residue+70% chemical fertilizer (Rape+70%CF). In addition, rice grain weight at a Rape+70%CF treatment increased by 19% compared to the control. This treatment also reduced weed density and biomass by 58 and 53%, respectively, compared to the control. Our results suggest that use of rape residues as green manure is an environment friendly and effective way to reduce chemical fertilizer and to enhance crop productivity in rice-rape double cropping system in Korea.

• 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.

• 한국해양학회지
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• v.30 no.5
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• pp.426-435
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• 1995

In order to assess the significance of ciliate grazing on bacterial population in carbon flow of the estuarine pelagic ecosystem of the Mankyung and Dongjin river (MD estuary), abundance and biomass of ciliates and grazing rate on bacteria of small (<40 um) ciliates were measured. Saplings were carried out four times from October 1993 to March 1995 in the estuarine system. Ciliates smaller than 40 um occupied more than 49.5% of total ciliates abundance. Clearance rate of small ciliates ranged from 18.0 to 16.3 nl cell/SUP -1/ h/SUP -1/. As bacterial abundance increased, ciliate's clearance rate decreased, suggesting that bacterial abundance effects on ciliate's grazing rate. Ciliate grazing rate was equal to 0.1 to 12.2% of bacterial productivity, and the ratio of ciliate ingestion over bacterial production increased exponentially with the increase of bacterial abundance (r$^2$=0.62, p$\leq$0.001). It seems that the effect of ciliate grazing on bacteria would be small in coastal waters and large in more eutrophic waters of high bacterial abundance. Carbon supplied by ciliate grazing on bacteria was avg. 3.1% of carbon amount required for the ciliate maximum productivity. Thus, the ecological role of ciliate in microbial loop was probably more important as a final consumer than as a direct consumer of bacteria.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.237-247
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• 1991

To characterize the community structure and spatial distribution of phytoplankton, observations on seawater temperature, salinity, nutrients, primary productivity and abundance and species composition of phytoplankton were made in the polar front region and its neighborhood off the east coast of Korea in summer 1990. Among the 96 taxa identified, Rhizosolenia setigera and Thalassionema nitzschioides were the most dominant species. The assemblage at the surface and 50 m depth was quite different in the northern inshore part of the study area but similar in the southern and offshore part. Principal component analysis by the species abundance showed that the phytoplankton consisted of the communities representing the surface of the northern inshore part with the neritic-warm dinoflagellates, the Northern Korean Cold Water with the cold water diatoms and the southern and offshore part, which seems to represent the Eastern Korean Warm Water, with the warm water diatoms. At the frontal region, diatoms were mixed with warm and cold water species. Primary productivity and phytoplankton standing crops were higher at the front than the neighboring waters. Nutrients were markedly high at the Northern Korean Cold Water. Horizontal advection of the Northern Korean Cold Water accompanied by nutrient supply seems to contribute to the high phytoplankton biomass at the front.

• Journal of Aquaculture
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• v.13 no.1
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• pp.87-99
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• 2000

Field survey on the variational characteristics of water quality and chlorophyll a concentraion were carried out at the 25 stations for four seasons in Kogum-sudo(Straits) southern coast of Korean Peninsula from Feburuary to October in 1993. We made an analysis on biological factor as chlorophyll a concentraion as well as physicio-chemical factors such as water temperature salinity sigma-t transparency dissolved oxygen(DO) chemical oxygen demand(COD) nutrients (ammonia, nitrite, nitrate, phosphate, and silicate) N/P ratio and suspended solid(SS). The waters in the Kogum-sudo were not stratified due to the tidal mixing. And the high productivity in photic layer were supported by high nutrients concentration from bottom waters. The high concen-trations of suspended solid in straits had a bad influence upon marine biology of nature and cultivations. In Kogum-sudo had a sufficient nutrients for primary productivity during a year. Especially phosphate and inorganic nitrogen were high the other side silicate was very low. The source of nutrients supply depend on rather mineralization of organic matters and input of seawater from outside than input of freshwaters from lands. Phytoplankton biomass as measured by chlorphyll a concentratiion was very high all the year round and it was controlled by the combination o f several environmental factors especially of phosphate in summer and dissolved nitrogen in other seasons.

• Journal of Plant Biotechnology
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• v.32 no.2
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• pp.105-109
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• 2005

To enhance salidroside productivity from a cell suspension cultures of Rhodiola sachalinensis, various combinations of auxin (NAA) and cytokinins (BA, Kinetin) concentration and addition of $GA_3$, TDZ, zeatin, spermine and spermidine at a hormone combination to be established were examined. NAA/BA combination is superior to NAA/kinetin combination in biomass and salidroside content. Maximum salidroside production ($64.6{\pm}8.9\;mg/L$ medium) was obtained from $2B_5$ medium with 1 mg/L NAA and 5 mg/L BA. The adding of $GA_3$ ($0.01\;mg/L{\sim}5\;mg/L$) was beneficial for salidroside accumulation and the highest productivity of salidroside, $90.3{\pm}8.34\;mg/L$, was obtained from $2B_5$ medium supplemented with 1 mg/L NAA, 5 mg/L BA and 0.1 mg/L $GA_3$. On TDZ, zeatin, spermine and spermidine, expectant results were not obtained except a little affirmative effect of spermidine ($69{\pm}2.88$ at 1 mg/L).

• Korean Journal of Ecology and Environment
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• v.56 no.2
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• pp.151-160
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• 2023

Cyanobacteria Pseudanabaena strains are known to produce 2-MIB(odorous material) in freshwater systems, thereby causing problems in water use. However, their physiological responses to environmental factors in relation with 2-MIB production is not well explored. This study was conducted to evaluate the effect of temperature on the growth and 2-MIB production of Pseudanabaena redekei. The experimental cyanobacteria strains were separated from the Uiam Reservoir (North Han River) and cultured in the BG-11 medium. Temperature was set to 10, 15, 20, 25, and 30℃ for the experiment, in the reflection of the seasonal water temperature variation in situ. For each temperature treatment, cyanobacterial biomass(Chl-a) and 2-MIB concentration (intra-cellular and extra-cellular fractions) were measured every 2 days for 18 days. Both maximal growth and total 2-MIB production of P. redekei appeared at 30℃. While intra-cellular 2-MIB contents were similar (26~29 ng L^-1) regardless of treated temperatures, extra-cellular 2-MIB concentration was higher only in high temperature conditions (25~30℃), indicating that the extents of 2-MIB biosynthesis and release by P. redekei vary with temperature. The 2-MIB productivity of P. redekei was much higher in low-temperature conditions (10~15℃) than high temperature conditions (25~30℃). This study demonstrated that temperature was a critical factor contributing to 2-MIB biosynthesis and its release in cell growth (r=0.605, p<0.01). These results are important to understand the dynamics of 2-MIB in the field and thereby provide basic information for managing odorous material in drinking water resources.