• ALGAE
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• v.20 no.3
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• pp.207-216
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• 2005

Myrionecta rubra, a mixotrophic ciliate, is a cosmopolitan red tide species which is commonly found in neritic and estuarine waters. M. rubra had long been listed as an “nculturable protist”until 2 different laboratory strains were finally established in 2 research groups at the beginning of this century, enabling us to perform initiative investigation into various aspect of the live M. rubra strains (Gustafson et al. 2000; Yih et al. 2004b; Johnson and Stoecker 2005). Field sampling was carried out on high tide at 2 fixed stations around Kunsan Inner Harbor (St.1 near the Estuarine Weir and St.2 off Kunsan Ferry Station) every other day for 4 months from mid-February 2004 to understand detailed figure of the recurrent spring blooms of M. rubra following the onset of the water gates operation of the Keum River Estuarine Weir on August 1994. With its maximum abundance of 272 cells mL$^{-1}$ in St.1, fluctuation pattern of the M. rubra population at the 2 stations was strikingly similar. Notable growth of M. rubra population started on late April, to cause M. rubra red tides during one month from mid-May in which “xceptionally low salinity days”without its red tide were intermittently inserted. High abundance of M. rubra over 50 cells mL$^{-1}$ was recorded at samples with their water temperature and salinity higher than 15${^{\circ}C}$ and 4.0 psu, respectively. During pre-bloom period when salinity fluctuation is moderate and the water temperature is cooler than 15°C, Skeletonema costatum, a chain-forming centric diatom, was most dominant. Cyanobacterial species such as Aphanizomenon flos-aquae and Phormidium sp. replaced other dominant phytoplankters on the days with “xceptionally low salinity”even during the main blooming period of M. rubra. To summarize, M. rubra could form spring blooms in Keum River Estuary when the level of salinity fluctuation was more severe than that for the dominant diatom Skeletonema costatum and milder than that for the predominance by freshwater cyanobacteria. Therefore, optimal control of the scale and frequency of freshwater discharges might lead us to partially modify the fluctuation pattern of M. rubra populations as well as the period of spring blooms by M. rubra in Keum River Estuary. Sampling time interval of 2 days for the present study or daily sampling was concluded to be minimally required for the detailed exploration into the spring blooms by M. rubra populations in estuaries with weirs like Keum River Estuary.

• Journal of Soil and Groundwater Environment
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• v.16 no.3
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• pp.17-27
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• 2011

Recently, a physically based model of water-table fluctuation due to precipitation is developed based on aquifer water balance model. In the model, it was assumed that the water infiltration into ground surface is advection dominant and immediately reaches to water-table. The assumption may be suited for the sites where the water-table is shallow and/or the permeability of the unsaturated zone is high. However, there are more cases where the model is not directly applicable due to thick and low permeable unsaturated zone. For the low permeability unsaturated zone, the pattern of water flux passing through unsaturated zone is diffusive as well as advective. In this study, to improve the previously developed water-table fluctuation model, we combined the delayed drainage model, which has long been used in well hydraulics, to the water-table fluctuation model. To test the validity of the development, we apply the developed model to 5 different domestic sites. The model parameters are calibrated based on the groundwater hydrograph and the precipitation time series, and the correlation analyses among the parameters are pursued. The overall analyses on the delineated model parameters indicate that the delayed drainage parameters or delay index used in the developed model are able to reveal drainage information in the unsaturated zones.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.4
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• pp.339-344
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• 2009

The joint cruises of six times between Korea and China were carried out for a better understanding of the environmental and oceanographical characteristics of the Yellow Sea for 6 years from 1998 to 2003. Zooplankton samples were collected one time per year at 24 stations on 3 lines of the Yellow Sea. The aim of this study is to understand the seasonal fluctuation of zooplankton community in the Yellow Sea. There is no trend on the spatio-temporal distribution of zooplankton. Copepoda, the major taxon of the Yellow Sea, was high in distribution in the eastern part and Chaetognatha in the western part of the Yellow Sea. In this results, the dominant copepods were Calanus sinicus, Paracalanus parvus s.l., Oithona atlantica, and Corycaeus affinis during the study periods. The density fluctuation of these dominant species may be an important factor in determining the fisheries resource of the Yellow Sea.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.6
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• pp.111-121
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• 2016

This study was carried out to assess the riparian vegetation health in the fluctuation area and vicinity of reservoirs. The results of this study could be a basic data to improve the ecological function and establish green-network of waterside ecosystem. The study site is Daecheong lake reservoirs which the representative landscape of Geum river and with great number of visitors near metropolitan city. The 6 survey plots of 2 survey area were selected, survey area 1 had 4 survey plots and survey area 2 had 2 survey plots, and to compare the study results 4 control plots were selected in Gyeongcheon reservoir. The main dominant specie of survey sites was Salix koreensis in tree and subtree layer, were Salix koreensis and Salix glandulosa. in shrub layer. 2 survey plots of Samjeongdong and Kyeongcheon reservoir were assessed as 'Good', 2 survey plots of chudong were assessed as 'Fair' in vegetation health assessment. In the fluctuation area from flood water level to low water level, 58 populations of Salix koreensis were found in survey sites and Salix koreensis, Salix glandulosa and Acer tataricum subsp. ginale were found in control sites. The most adequate species at the condition affected by inundation impacts would be Salix koreensis and Salix glandulosa was more healthy at the area less affected by inundation. This study was carried out the vegetation health assessment on Daecheong reservoir which has been advanced natural succession for more than 30 years after the construction. Further, it should carry continuously out the research on the planting model of the waterside ecosystem for ecological restoration.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.1
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• pp.39-47
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• 2008

The fluctuation in the abundance and species composition of fish was investigated using a fyke net with entrances on both sides in the coastal waters of Geumo-do, Yeosu, Chollanam-do, Korea, from May 2003 to April 2004. A total of 2,379 fishes (392.13 kg) were sampled and classified into 11 orders, 34 families, and 53 species. The dominant orders were Perciformes, Scorpaeniformes, and Pleuronectiformes, which accounted for 67.9% of the collected fishes. The dominant species was Acanthopagrus schlegelii (235 individuals, 19.00 kg), followed by Konosirus punctatus (182 individuals, 9.53 kg), and Apogon lineatus (161 individuals, 1.69 kg). The number of individuals and biomass were higher in spring and summer than in winter, and the monthly variation may be related to the water temperature. The diversity index was highest in September (H'=2.9) and lowest in December (H'=1.8). The evenness index was highest in August (J=0.9) and lowest in December (J=0.7). The dominance index was highest in December (D=0.7) and lowest in August (D=0.2). The economically important species in this area are Acanthopagrus schlegelii, Konosirus punctatus, Lateolabrax maculatus, Argyrosomus argentatus, Trichiurus lepturus, Lateolabrax japonicus, and Sebastes schlegelii.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.3
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• pp.133-149
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• 1975

1. A quantitative ecological investigation of the intertidal sand beach at Yong-ho Bay, located about 6km NE of Busan Harbour was carried out from February, 1974 to February, 1975. Composition of the fauna, diversity, faunal affinity and distributions in time and space were studied. Some ecological factors influencing to the community also discussed. 2. The beach can be classified as a fine-sand beach which is dominated by Armandia lanceolata and Nephtys sp. (A). Thirty two species of animals representing 29 genera were found. In number, two polychaetes, A. lanceolata and Nephtys sp. (A) were dominant, while one polychaete, Neanthes japonica and one bivalvia, Laternula limicela were dominant in weight. 3. Distribution of the fauna was devided into three areas of different faunal compositions with sediment types particularly by mud fraction content, and it well agreed with faunal affinity and diversity index value. 4. Seasonal fluctuation of the three dominant species, A. lanceolata, Nephtys sp. (A) and N. japonica was studied. Except Nephtys sp. (A), the fluctuation were closely related to the brooding time. 5. There was no relationship between faunal distribution and organic matter content. Submergence time affected the distribution of some species but the influence to the whole-community was little.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.44 no.2
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• pp.112-119
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• 2008

The fundamental data on the catch fluctuation in the rectangular set net according to the tide age were developed based on the catches recorded from the year 1986 to 2004 in the coastal waters of Hamdeok, Jeju. Total catch by the rectangular set net had a deep connection with the tide age. In particular, during increasing tide, total catch were reduced gradually from the neap tide to the high tide. As it turned out, the slope of total catch declined by degree and showed a correlation coefficient of determination of 0.76. On the contrary, in the case of decreasing tide, there was little sign of rise in total catch. In particular, large catch seemed to occur at the next tide to the neap tide. In the relation between the catch and the tide age, the level of the correlation coefficient chosen at $p{\leq}0.05$ decreased in the order rabbitfish(-0.84) and horse mackerel(-0.71), while the significance of other dominant species were not selected.

• Journal of The Geomorphological Association of Korea
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• v.24 no.1
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• pp.39-50
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• 2017

This study was conducted to analyze the variation of hydro-geomorphological environment along Baekgok wetland, which experiencing periodical inundation, in that water-level fluctuation of reservoir caused by irrigation. Since the field data is unavailable, modeling techniques, involving models such as HSPF and TELEMAC-2D, have been applied to simulate hydrological cycle in watershed and hydrodynamics in channel scale. The result of simulation indicates that the water-level of reservoir determines both the water surface extension and water depth in the wetland. Furthermore, it also shows that water-level functions as a spatial limit factor for a fluvial environment and woody vegetation such as willow. The fact of which the scale of water-level fluctuation being larger than an average topographical relief along the wetland can explain the result. While the water-level kept high, the wetland is submerged and waterbody becomes lentic. In contrast, while the water-level is lowered, fluvial phenomena of which being dependent on flow rate and channel shape become active. Hence, the valid fluvial process is likely to take place only for 4 months annually just near the channel, and it advances to a conclusion expecting a deposition to be dominant among the wetland except for such area. It is anticipated that such understanding can contribute to establishing plans to preserve the geomorphological and ecological value of the Baekgok wetland.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.351-356
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• 2002

Groundwater recharge rate was estimated by applying the groundwater level fluctuation method utilizing Theis (1937) approach with specific yield estimation technique of Shevenell (1996) and the temperature method using observed data from National Groundwater Observation Stations. Results based on analysis of water level observation data of 10 alluvium wells reveal that the recharge rates for 5 wells of Kum river area range 3.7~25.0% and those for 5 wells of Nakdong river area range 3.6~21.7%. Results obtained from the temperature method based on water temperature data indicated that the upward flow resulted from evapotranspiration is dominant for 4 wells of the Kum river area and 5 wells of the Nakdong river area. The other wells showed the downward flow which is related to groundwater recharge in these areas.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.2
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• pp.59-68
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• 1995

In this study, the effects of the power transmission units on the rotational accuracy are investigated experimentally in a hydrostatic spindle. The effects of warm up time, unbalancing and the position of measuring sensor are pre-examined for the determination of measuring conditions. The misalignment of the power transmission units and the vibration excited by the fluctuation of belt are considered as the dominant parameters of error motion. The variation and scatter of run out at the range of 0 to 3,000rpm in rotational speed are appropriated for the camparison of availabilities of the transmission units to precision spin- dles.