• Horticultural Science & Technology
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• v.31 no.1
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• pp.38-49
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• 2013

Prohexadione-calcium (Pro-Ca), ethephon and transient water stress were evaluated in a factorial design, as potential inhibitors of early-season shoot growth of high density orchard management of apple (Malus domestica Borkh.) trees. In the experiment, water stress was imposed to one-half of the 7-year-old 'Golden Delicious'/M.9 apple trees in each of 5 blocks, by stopping irrigation for 3 weeks between 35 and 56 days after full bloom (AFB). Within each whole unit, the following Pro-Ca and ethephon treatments were randomly allocated at $2{\times}2$ factorial: a) 0 or 250 $mg{\cdot}L^{-1}$ a.i. Pro-Ca applied at 28 days AFB and b) 0 or 300 $mg{\cdot}L^{-1}$ a.i. ethephon applied twice (35 and 71 days AFB). All trees were hand thinned to king flowers prior to treatments. Vegetative shoot growth was markedly reduced by Pro-Ca, with its effect being obvious within 14 days after application, while ethephon and water stress treatments were less effective. Pro-Ca had no effect on fruit set and yield but slightly increased fruit size. Ethephon substantially reduced the fruit size and yield but had no effect on fruit set. Water stress reduced fruit set, fruit size and yield. With regard to fruit quality, Pro-Ca did not influence fruit shape, flesh firmness and soluble solids contents (SSC) but slightly reduced titratable acidity. Ethephon had no effect on fruit shape but increased firmness, SSC and acidity, while water stress did not influence these fruit quality attributes. Dry weight of dormant spur buds was reduced by both Pro-Ca and water stress, while increased by ethephon. The larger dormant buds led to the larger spur flowers at the tight cluster stage the following spring. Return flowering was promoted only by ethephon, especially on previous season's shoots. There were no significant interactions between Pro-Ca and ethephon or water stress on most variables observed in this study.

• Ocean and Polar Research
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• v.29 no.2
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• pp.135-153
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• 2007

Temporal (seasonal) and spatial distributions and variations of various physico-chemical factors (salinity, temperature, pH, DO, COD, SPM, POC, silicate, DIP, DIN) in surface and bottom waters were studied in the coastal environment with typical macro-tidal range and monsoonal weather condition, Gyeonggi Bay, west coast of Korea. Spacial distribution patterns of these factors were generally similar to each other, and appeared to be inversely related to the distribution pattern of salinity, suggesting that water quality of the study area was primarily controlled by the physical mixing process of Han-River freshwater with nearby coastal seawater. During flooding season, silicate- and nitrogen-rich Han River water directly flowed into offshore as far as $20\sim30\;km$ from the river mouth, probably causing serious environmental problems such as eutrophication and unusual and/or noxious algal bloom, etc. Except the surface water during summer flooding season, high concentrations of nutrients appeared generally in dry season, whereas low values in spring, possibly because of the occurrence of spring phytoplankton bloom. On the other hand, nutrient flux through the estuary seems to be primarily depending on river discharge, sewage discharge and agricultural activities, especially during the rainy season. Also, nutrients in this coastal waters are considered to be supplied from the sediments of tidal-flats, which developed extensively around the Han-River mouth, especially during fall and winter of dry and low discharge seasons, possibly due to the stirring of tidal flat sediments with highly enriched pore-water nutrients by storm. And also, COD and DIN concentrations in the study area consistently increased during the last 20 years, probably because of agricultural activities and increasing discharge of industrial and domestic wastes.

• Korean Journal of Plant Resources
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• v.31 no.1
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• pp.71-76
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• 2018

This study was conducted to investigate the effect of shoot twist on fruitfulness and fruit quality of 'Campbell Early' grapevine. Proper pruning and training are essential to produce a good yield of high-quality fruit and to maintain the balance between vegetative growth and fruiting. The most common problem in spur-pruned 'Campbell Early' cultivar is that vigorous buds has low fruitfulness and thereby the shoot become more vigorous the following spring because of lower crop load. Therefore, shoot twists in very vigorous 'Campbell Early' canes (above 10.0 mm) were performed on the third nodes and the $7^{th}$ nodes of each shoot at 7 days before bloom and full bloom, respectively. Sprouting date, blooming date were not significantly different among the treatments while, harvesting date was delayed approximately 3 days. However, number of berries per cluster, cluster weight and fruitfulness were significantly higher in the shoot twist treatment on the third nodes than the control that was topping alone. Combination treatments of shoot twist and topping had an additive effect on increasing cluster weight resulting in higher increase of yield by 12.1 ㎏ per vine. These results indicated that the shoot twist on very vigorous canes of 'Campbell Early' grapevine for well fruitfulness seemed to be very effective.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.78-86
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• 1997

To clarify the phytoplankton blooms in Lake Shihwa after the construction of a dyke, a study on the environmental factors, the distribution of chlorophyll-a, phytoplankton standing stocks, dominant species and primary productivity was carried out in Lake Shihwa and adjacent coastal areas from October, 1995 to August, 1996. Lake Shihwa is brackish water with mixing of freshwater from tributaries and the remaining salt water at the bottom. The dense phytoplankton bloom of average value of 168.6 ${\mu}gChl-a\;l^{-1}$ have occurred throughout the year in Lake Shihwa which is eutrophicated by the large input of nutrients from inflowing 5 tributaries and Shihwa Industrial Complex. The major organisms of algal bloom in Lake Shihwa were diatoms, Cyclotella atomus, Nitzschia sp. and Chaetoceros sp. in autumn and winter, and dinoflagellate Prorocentrum minimum and Chrysophyceae in spring and summer. The autumn and winter diatom blooms were limited by the depletion of silicate in the lake. Diatom blooms have occurred in the coastal areas adjacent to Shihwa lake from winter to summer due to the inflow of nutrient rich-water from Lake Shihwa. The primary productivities in the Lake Shihwa ranged from 2,653 mgC $m^{-2}\;day^{-1}$ to 9,505 mgC $m^{-2}\;day^{-1}$ with an average of 3,972 mgC $m^{-2}\;day^{-1}$. However, most of the high primary production was limited to the shallow euphotic zone due to the inhibition of light penetration. The primary productivities during autumn and winter were limited by the depletion of silicate. Lack of photosynthesis and the decomposition of falling organic matter under the middle of water column accelerated the depletion of dissolved oxygen in the bottom layer.

• Journal of Korean Society on Water Environment
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• v.31 no.2
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• pp.110-119
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• 2015

The construction of the eight large weirs in the Nakdong River, the second largest river in Korea, caused big changes in the physical environment of the water system. Algal communities and their correlations with environmental factors, mainly nutrients were studied at five weir areas in the Nakdong River from 2010 to 2013. Water quality, hydrodynamics and algal composition were investigated. Results showed that flow velocities were reduced compared with that before weir construction near the areas where are located in the mid and upstreams of the Nakdong River. A seasonal algal community succession was observed and it was mainly correlated with temperature and phosphorus. Diatoms were dominated from winter to spring months and massive diatomic blooms of Stephanodiscus sp. occurred early in March during survey period. Cyanobacterial blooms of Microcystis sp. occurred from July to September 2013 and was preceded by the lower total phosphorus concentration of $0.05mg\;L^{-1}$. The correlations between total phosphorus concentrations and algal abundances were not significant during the survey periods. However, significant correlation with cyanobacteria was found in the period of weir construction after only at the GG survey site and blooms periods of 7 times in the survey sites, and its correlation coefficients were 0.53 (p<0.001) and 0.42 (p<0.01) respectively. When algal bloom was observed, partially low nutrient concentration was observed in the Nakdong River. In conclusion, partially low nutrient concentration which may result from algal bloom was observed, and we presume it caused the reduction of algal abundunces.

• Journal of Korean Society on Water Environment
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• v.29 no.2
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• pp.155-164
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• 2013

To confirm the relationship between climate change and Stephanodiscus in Mulgeum station of Nakdong River, Korea, this study was conducted. The temperature in crease by climate change was observed in the study site, where the temperature was gradually increased in most seasons, except for summer season. The mass proliferation of Stephanodiscus constantly appeared in every year, especially between November and March, and when Stephanodiscus abundance was above 90% in phytoplankton biomass. Among this period, phytoplankton biomass was high related with water temperature ($r^2$=0.249, P<0.01) than nutrient factors such as nitrogen and phosphorus in the study site. Finally, temperature by climate change can be regarded as the affecting factor for chl. a variation, because temperature was strongly related with water temperature ($r^2$=0.748, P<0.01). From 1997 to 2010, the annual maximum phytoplankton biomass was recorded in the range of temperature from $4.8^{\circ}C$ to $8.4^{\circ}C$, and the range was regarded as the temperature condition for the optimal growth of Stephanodiscus in the study site. On the optimal growth temperature, the trend of monthly average temperature corresponded to the trend of chl. a variation from November to March. In future, the increase of temperature by climate change can prolong Stephanodiscus blooming period in winter and spring seasons.

• Ocean and Polar Research
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• v.35 no.2
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• pp.147-155
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• 2013

The purpose of this study is to investigate seasonal difference in linear trends in satellite-derived chlorophyll-a concentration (Chl-a) and their related environmental changes in the South Sea of Korea (SSK) and East China Sea (ECS) for recent 15 years (Jan. 1998~Dec. 2012) by analyzing climatological data of Chl-a, Rrs(555), sea surface wind (SSW) and nutrient. A linear trend analysis of Chl-a data reveals that, during recent 15 years, the spring bloom was enhanced in most of the ECS, while summer and fall blooms were weakened. The increased spring (Mar. - May) Chl-a was associated with strengthened winter (Dec. - Feb.) wind that probably provided more nutrient into the upper ocean from the deep. The causes of decreased summer (Jun. - Aug.) Chl-a in the northern ECS were uncertain, but seemed to be related with the nutrient limitation. Recently (after 2006), low-salinity Changjiang diluted water in the south of Jeju and the SSK had lower phosphate that caused increase in N/P ratio with Chl-a decrease. The decreased fall (Sep. - Nov.) Chl-a was associated with weakened wind that tends to entrain less nutrient into the upper ocean from the deep. This study suggests that phytoplankton in the ECS differently changes in response to environmental changes depending on season and region.

• Proceedings of KOSOMES biannual meeting
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• 2003.11a
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• pp.191-193
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• 2003

Temporal and spatial variability of phytoplankton pigment concentrations around the Korea Peninsula was described, using the monthly mean composite images of the SeaWiFS (Sea-Viewing Wide Field-of-View Sensor). The high pigment concentrations appear in the spring and fall in the East Sea The spring bloom in the southern regions (in April) occurs one month in advance in comparison with tint in the northern regions (in May). In summer season, the pigment concentrations are low all over the region in the East Sea And the high pigment concentrations exist yearly around warm stream along the coast of the East Sea, and in the coast of the West Sea and South Sea In particular, the high pigment concentrations linking near the mouth q the Yangze River to coast of South Sea in Korea appear during August to December.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.95-100
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• 1998

The purpose of this study is to describe the change of the spring bloom and oceanographic condition. The variation of pigment concentration derived from the satellite ocean color data has been analyzed. According to the movement of blooming area, blooming was very concerned with a rising trend of sea surface temperature and a supply of nutrients. A nutrient rich water carried by the Oyashio encounters with the warm Core ring, where mixings and blooms are observed. We examined the correlation by using the satellite observations of the temperature and chlorophyll-a for the spring seasons (May, June, July) of 1998 the off Sanriku area (38-43N, 141- l50E). Using the SeaWiFS data, we process the data into the level-3, which contains the geophysical value of chlorophyll-a. And chlorophyll-a data is mapped for the water between 110E and 160E, and 15N and 52N with a 0.08 * 0.05 degree grid for each image. And Sea Surface Temperature (SST) data is produced using the AVHRR onboard the NOAA. The SST is derived by the MCSST. Then, the data is mapped for the water as much as chi-a data. And these gridded image was made by detection of each water masses, which are Kuroshio Extension, the warm-core ring and the Oyashlo Intrusion, etc., using those satellite images to determine short term change. Off Sanriku is a place where warm-water pool and the Oyashio at-e mixed. When warm streamer has intruded in cold water, the volume of phytoplankton increases at the tip of warm streamer. Warm water streamer was trigger of occurring blooming. And also, SeaWiFS images provided as much information for the studies of chlorophyll-a concentrations in the surface.

• Korean Journal of Environmental Biology
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• v.31 no.4
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• pp.429-439
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• 2013

This study was conducted to identify the relationship between environmental factors and algal bloom, and provide information for efficient management based on the results of monitoring the environmental parameters and algal diversity in the Jundai reservoir from March 2011 to October 2013. Little change in the weather conditions was observed during the study period except for a slight decrease in rainfall. Concentration of TN and TP in the reservoir exceeded water quality standards for agriculture and significant correlation between algal growth and environmental factors was observed. Phytoplankton in Jundai reservoir included 6 classes, 40 genus, 62 species, and the phytoplankton abundance was in the range of $1.3{\times}10^4{\sim}2.8{\times}10^6$ cells $mL^{-1}$. The annual average of phytoplankton abundance and Chl-a gradually decreased as TN and TP concentrations decreased. Overall Anabaena sp., Oscillatoria sp., and Microcystis sp. were the dominant species in Jundai reservoir. As the water temperature increased, the dominant species were Anabaena sp., Microcystis sp. and Oscillatoria sp., in that order. Anabaena sp. was dominant from spring to early summer with increase in water temperature and pollutant concentrations, and high correlation with environmental factors was observed. Microcystis sp. was dominant depending on changes in the nutrient levels. In the case of Oscillatoria sp., there was no significant correlation between phytoplankton biomess and Chl-a. However, efficient management of water environment and practical control of algal bloom in small scale reservoir polluted by livestock and farm irrigation should be achieved by identification of the relationship between algal growth and environmental factors.