• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.3
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• pp.215-225
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• 2004

Biomass and community composition of microphytobenthos in the Saemankeum tidal flat were studied by HPLC analysis of the photosynthetic pigments from November 2001 to November 2002. The environmental factors of sediment were also investigated to examine the relationship between microphytobenthos biomass and sedimentary environments. The detected photosynthetic pigments of microphytobenthos were chlorophyll a, b, c, fucoxanthin, 19'-hexanoyloxyfucoxanthin, violaxanthin, diadinoxanthin, alloxanthin, diatoxanthin, zeaxanthin+lutein, peridinin and beta-carotene. Pheophytin a, the degradation product of chlorophyll a, was also detected. The results of pigmen analysis suggest the presence of diatom (fucoxanthin), euglenophytes (chlorophyll b), chlorophytes (chlorophyll b + lutein), cyanobacteria (zeaxanthin), cryptophytes (alloxanthin), chrysophytes (fucoxanthin + violaxanthin), prymnesiophytes (19'-hexanoyloxyfucoxanthin) and dinoflagellates (peridinin). Chlorophyll a concentration in the top 0.5 cm of sediment was in the range of $0.24\;mg{\cdot}m\^{-2}\;-32.11\;mg{\cdot}m\^{-2}$ in the study area. The increase of chlorophyll a concentration in the spring indicates the occurrence of a microphytobenthic bloom. In the summer, there was a sharp decrease of the chlorophyll a concentration which was probably due to high grazing activity by macrobenthos. The annual mean chlorophyll a concentration in the study area was low compared to that in most of other tidal flat areas probably due to active resuspension of microphytobenthos and high grazing activity by macrobenthos. There was no clear relationship between microphytobenthos biomass and sedimentary environments because of a large variety of physical, chemical and biological factors, Pigment analysis indicated that while diatoms were dominated in the microphytobenthic community of the Geojon tidal flat, euglenophytes and/or chlorophytes coexisted with diatoms in the Mangyung River tidal flat.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.4
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• pp.221-225
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• 2002

The first laboratory culture of host-parasite system of Prorocentrum minimum- Amoebophrya sp. was established by single cell isolation method. Here, we report the life cycle stages of the parasitic dinoflagellate. Amoebophrya sp. of the red tide dinoflagellate P. minimum as observed by light and epifluorescence microscopy. Infections developed inside the nucleus of P. minimum. The trophont developed to occupy almost all the intracellular space of the host at its late stage. The fully developed trophont finally ruptured through the host cell. “Vermiform stage”, the free-swimming extracellular lift cycle stage is followed by another stage for the sudden release of many individual dinospores. Our laboratory strain of the host-parasite system for P. minimum, a causative species fur the huge red tides in spring and summer in Korean coastal waters, could be a useful living material for the in situ biological control of harmful algal blooms.

• Ocean and Polar Research
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• v.43 no.1
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• pp.31-43
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• 2021

To understand the temporal variation of prokaryotic communities in a temperate coastal area, prokaryotic abundance, activity, and community composition were investigated every week for over a year at a coastal monitoring station of Yeong-do, Busan. The prokaryotic abundances fluctuated about 10 times, ranging from 2.0 to 20.1 × 10⁵ cells mL^-1 and tended to be high in spring when phytoplankton bloom occurred. The prokaryotic thymidine incorporation rates (TTI) varied in a low range between 0.2 and 11.5 pmol L^-1 h^-1 in winter. However, in summer, TTI were increased up to a range of 8.3 to 17.4 pmol L^-1 h^-1, showing an increasing pattern in summer. During the study period, Alphaproteobacteria was the most dominant class for most of the year, followed by Flavobacteria. While the seasonal variation of prokaryotic composition was not apparent at the class level, many prokaryotic species showed a distinct temporal or seasonal variation for the year. In the coastal site, prokaryotic biomass and activity did not show significant correlations with temperature and chlorophyll-a, which are well known to regulate prokaryotic growth in marine environments, suggesting that the study area may be affected by diverse sources of organic matter for their growth.

• Journal of environmental and Sanitary engineering
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• v.11 no.1
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• pp.27-37
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• 1996

The taxa of phytoplankton in the Dongbok reservoir consisted of 6 classes, 9 orders, 4 4 suborders, 21 families, 42 genus, 86 species, 4 varieties and 1 formula; totally 91 t taxa appeared. It contained 3 major groups that is Chlorophyceae 51 taxa(56.0 % the most high rate), Bacillariophyceae 23taxa(25.2%), Cyanophyceae 10taxa(10.9%). The most abundant with 47 taxa was in December, the least with 11 taxa was in March during research every month. The component ratio of biomass each main groups, Bacillariophyceae(51 %, the most h high rate), Cyanophyceae(38.9%), Chlorophyceae(9.8%). The most abundant class at the biomass component ratio were Cyanophyceae which contained 82.6-98.0 % of it in May and September, Chlorophyceae 79.0% in August, and Bacillariophyceae increased continuously, specially in winter and autumn. The seasonal dominant groups were Microcystis aemginosa belong to Cyanophyceae in spring and autumn, some species of Chlorophyceae in summer and Melosira granulata belong to Bacillariophyceae in winter and late autumn. Dominant index ranged from 0.33 to 0.95. The season of the lowest index was autumn and the highest was spring. Species diversity indices ranged from 1.09 to 3.99. The water environmental factors of the Dongbok reservoir were that the values of water temperature ranged between $2.4~28.9^{\circ}C$, pH 7.2~8.3, conductivity 77.0~105.5us/cm, and transparency 1.2~2.8m, also the concentration of dissolved oxygen(DO) ranged of 6.9-14.6mg/L, total nitrogen(T-N) 0.38-1.84mg/L, total phosphorus (T-P) 0.011~0.028mg/L, and chlorophyll-a $7.0~29.9mg/m^3$. In this research the proper temperature of water for algae growth, $15~20^{\circ}C$, was maintained in April. May, November and December 1 The number of species that induced water color were 14 species, that caused taste-and-odor problems were 3 species and that caused filter clogging were 5 species. A Among them, the bloom of Anahaena macrospora that caused odor problem occurred l in May and of Microcystis aeruRinosa and M. lνensenberRii that caused filter clogging in May and September.

• Ocean and Polar Research
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• v.35 no.2
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• pp.157-170
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• 2013

We investigated the seasonal succession of phytoplankton assemblages in the eastern part of the South Sea of Korea in relation to surface water masses. The study areas are under the direct influence of the Tsushima Warm Current (TCW) throughout the whole year, with its strength known to be seasonally variable. The region is also influenced by coastal waters (CW) driven from the South Sea of Korea and East China Sea, particularly in summer, as indicated by low salinity in the surface water. Nutrient property of the TCW can reveals whether the origin of the TCW is the nutrient-rich Kuroshio Current or the oligotropic Taiwan Warm Current. Surface chlorophyll-a (Chl-a) concentrations displayed a large seasonal variation for all stations, with high values found in spring and autumn and low values in summer and winter. At station M (offshore) and P (intermediate location between M and R), Chl-a concentrations in October were higher than those in March, when spring bloom normally occurs. This may be related to deeper mixed layer depths in October. Diatoms dominated under conditions of high nutrient supply in which Chaetoceros spp. and Skeletonema costatum-like spp. were abundant. S. costatum-like spp. dominated at stations R (onshore station) and P in December when there was greater nutrient supply, especially of phosphate. Flagellates and dinoflagellates dominated at all three stations after diatoms blooms. Dominant species were Scrippsiella trochoid in April and Ceratium furca in October at station R, and Gyrodinium spp. and Gymnodinium spp. at station M during summer, when the effect of the oligotropic Taiwan Warm Current and the oligotropic coastal water from East China Sea were strong. Redundancy analysis showed clear seasonal successions in the phytoplankton community and environmental conditions, in which both principal components 1 and 2 accounted for 69.6% of total variance. Our results suggested that environmental conditions seemed to be determined by the origin of the TCW and the relative seasonal strength of the water masses of the TCW and CW, which may affect phytoplankton growth and compositions in the study area.

• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.139-149
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• 2003

This study was conducted to determine limiting nutrients and the physiological characteristics of phytoplankton in response of nutrients in Lake Paldang from March 2002 to October 2002. A field research was conducted along with laboratory batch culture experiment to find the limiting nutrients and the growth kinetics. According the results of Chl. a TP relationship, TN/TP ratio, and nutrient addition bioassay, phosphorus appeared to be a major limiting nutrient in Lake Paldang and thus the lake productivity was greatly influenced by it. P limitation for the phytoplankton of Lake Paldang varied with season, and the possibility of limitation by nitrogen and silica also occurred. The degree of P limitation was greatest during spring when the concentration of dissolved phosphorus is relatively much lower than summer and autumn. The maximum growth rate (${\mu}_{max}$) and half saturation concentration ($K_u$) of Lake Paldang phytoplankton ranged from 0.8${\sim}$1.1$day^1$ and from 0.1${\sim}$O.8${\mu}M$, respectively. $K_u$ was highest during May ($0.8{\mu}M$) and the lowest during September ($0.1{\mu}M$). Such result may be induced by the phytoplankton cell quota that showed the lowest concentration ($0.13{\mu}gP/{\mu}gChl.$ a) during May. The growth kinetics showed that phytoplankton growth in Lake Paldang was faster during summer and autumn than spring, suggesting that the Potential of algal bloom is high after the summer monsoon season.

• Korean Journal of Microbiology
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• v.49 no.1
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• pp.30-37
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• 2013

This study was carried out to assess the spatial and tidal effects on the water quality in the lower reaches of Taewha River, Ulsan, Korea and to understand the environmental factors affecting winter algal bloom in the river. From May, 2010 to January, 2011, water samples were collected at five locations (New Samho Bridge, Old Samho Bridge, Mungjung Stream, Taewha Bridge, and Mungchon Bridge) along the river at high and low tides of spring tide. We measured environmental parameters including salinity, dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), chlorophyll a (Chl a) and various nutrient concentrations. Salinity increased towards the downstream direction. Average values of Chl a concentrations ranged $10-26mg/m^3$ at high tide and $11-53mg/m^3$ at low tide depending on sampling locations. It was noteworthy that there were strong increases in Chl a concentrations during the November 21 to December 22 sampling period especially at the Taewha Bridge. At the location, Chl a concentrations were measured as $138-296mg/m^3$ for the period; Rhodomonas lacustris of class Cryptophyceae was the dominant algal species. Chl a concentrations at the Taewha Bridge were positively correlated with such parameters as salinity, BOD, DO, COD, pH, and T-N, and negatively correlated with temperature and $NO_3{^-}$-N. On the other hand, at the Mungchon Bridge the highest concentration of Chl a was $55mg/m^3$ on August 25, and Chl a concentrations were positively correlated with $NH_3$-N, T-N, $PO_4{^{3-}}$-P, T-P, and heterotrophic plate counts. The results suggested that water quality in the lower Taewha River fluctuated a lot with the sampling locations and the patterns of algal blooms were different between Taewha Bridge and Mungchon Bridge sampling locations.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.4
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• pp.305-314
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• 2007

We studied spatial and temporal distributions of the phytoplankton and their relationships to physico-chemical environmental factors in the western Jinhae Bay, Korea from November 2003 to August 2004. In most cases, physico-chemical environmental factors showed homogeneous distribution. The phytoplankton communities were composed of mainly diatoms and dinoflagellates, and their standing crops ranged from $16{\times}10^3\;cells\;l^{-1}\;to\;5,845{\times}10^3\;cells\;l^{-1}$ (with a mean value of $555{\times}10^3\;cells\;l^{-1}$). The bloom of phytoplankton was observed in Gohyun Port in the summer. Seasonal variation of phytoplankton standing crops was higher in winter and summer than in spring and autumn. The dominant species were Skeletonema costatum, Akashiwo sanguinea, Pseudo-nitzschia pungens, Dactyliosolen sp., Leptocylindrus danicus, cryptomonads and etc. Especially, S. costatum was predominant in the summer and A. sanguinea (spring and autumn), Pseudo-nitzschia sp. (summer), Guinardia striata (spring), unidentified flagellates (summer) and cryptomonads (spring) appeared to be an opportunistic species. Concentrations of Chl a ranged from $0.6{\mu}g{\cdot}l^{-1}\;to\;16.7{\mu}g{\cdot}l^{-1}$ (with a mean value of $3.4{\mu}g{\cdot}l^{-1}$). The results of the canonical correspondence analysis implies the study area was grouped into the 2 water masses (inner and outer waters of Gohyun Port) and inner waters had higher abundance and Chl a concentration than outer waters. Also, phytoplankton sanding crops were related with temperature, DO and nutrients ($SiO^2$, TN, TP and etc.) in inner waters. Inner water-mass of Gohyun Port expanded between Gacho Is. and Chilchon Is. during the winter.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.2
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• pp.61-71
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• 2009

Most deciduous trees in temperate zone are dormant during the winter to overcome cold and dry environment. Dormancy of deciduous fruit trees is usually separated into a period of rest by physiological conditions and a period of quiescence by unfavorable environmental conditions. Inconsistent and fewer budburst in pear orchards has been reported recently in South Korea and Japan and the insufficient chilling due to warmer winters is suspected to play a role. An accurate prediction of the flowering time under the climate change scenarios may be critical to the planning of adaptation strategy for the pear industry in the future. However, existing methods for the prediction of budburst depend on the spring temperature, neglecting potential effects of warmer winters on the rest release and subsequent budburst. We adapted a dormancy clock model which uses daily temperature data to calculate the thermal time for simulating winter phenology of deciduous trees and tested the feasibility of this model in predicting budburst and flowering of Niitaka pear, one of the favorite cultivars in Korea. In order to derive the model parameter values suitable for Niitaka, the mean time for the rest release was estimated by observing budburst of field collected twigs in a controlled environment. The thermal time (in chill-days) was calculated and accumulated by a predefined temperature range from fall harvest until the chilling requirement (maximum accumulated chill-days in a negative number) is met. The chilling requirement is then offset by anti-chill days (in positive numbers) until the accumulated chill-days become null, which is assumed to be the budburst date. Calculations were repeated with arbitrary threshold temperatures from $4^{\circ}C$ to $10^{\circ}C$ (at an interval of 0.1), and a set of threshold temperature and chilling requirement was selected when the estimated budburst date coincides with the field observation. A heating requirement (in accumulation of anti-chill days since budburst) for flowering was also determined from an experiment based on historical observations. The dormancy clock model optimized with the selected parameter values was used to predict flowering of Niitaka pear grown in Suwon for the recent 9 years. The predicted dates for full bloom were within the range of the observed dates with 1.9 days of root mean square error.

• Journal of The Korean Society of Grassland and Forage Science
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• v.19 no.3
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• pp.251-258
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• 1999

A field experiment was carried out to determine the effects of chemical /mechanical treatments at mowing on the field drying rate and hay quality of rye (Secale cereale L.). The chemical drying agent/mower conditioner ($K_2CO_3$ 2%, conditioning, $K_2CO_3$ 2% + conditioning and control) were treated at different harvest stage (late boot, heading and bloom stage) for hastening hay-making in the spring of 1996. After field dry, square bales were made by hay baler, and the dry matter(DM) loss, visual estimation and nutritive value of rye hay were evaluated after storing two months. The field drying rate of rye was higher with delayed stage of harvest, and mechanical and chemical + mechanical treatment, but the effectiveness of chemical alone was very low. With mower conditioning, the duration of field dry was shortened by 1.5 to 2 days compared with control. The DM loss of rye hay was reduced by late harvest and mechanical, and chemical + mechanical combined treatment, but the efficiency by chemical alone was very low. The visual score (Ieafiness, green color, odor and softness) of hay after storing was high in mechanical and chemical + mechanical, but the score by chemical alone was very low. The nutritive value (ADF, NDF, digestibility, and relative feed value) of hay was also high with treatment of mechanical and chemical + mechanical, but the quality by chemical alone was similar compared with control. The quality of hay was very low when harvested at bloom stage. In conclusion, mower conditioning can enhance the field drying rate of rye, but the drying effectiveness of chemical drying agent was very low. The effect of chemical/mechanical combined treatment was very similar when compared with mechanical alone. Harvest at early heading to heading stage was recommended for high quality rye hay.