• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.4
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• pp.348-353
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• 2008

Oxygen isotope has not been used actively in water mass studies because of difficulties on the analysis though it has advantages as a water mass tracer. The most popular method to analysis the oxygen isotope ratio in water samples is equilibration method: isotopic equilibrium of water with $CO_2$ at constant temperature. The precision of oxygen isotope analysis using commercial automatic $H_2O/CO_2$ equilibrator is ${\pm}0.1%o$. This value is not sufficient for studies in open ocean. The object of this study is to improve the analytical precision enough to apply open ocean studies by modification of the instrument. When sample gas is transferred by the pressure difference, the fractionation which is preferential transportation of light isotope can be occurred since the long transportation path between the equilibrator and mass spectrometer. And the The biggest source of error during the analysis is long distance and large volume of the pathway of sample gas between. Therefore, liquid nitrogen trap and high vacuum system are introduced to the system. The precisions of 14 time analysis of same seawater sample are ${\pm}0.081%o$ and ${\pm}0.021%o$ by built-in system and by modified system in this study, respectively.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.1
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• pp.48-55
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• 2009

Seasonal variations of microalgal biomass and community composition in both the sediment and the seawater were investigated by HPLC pigment analysis in an estuarine muddy sandflat of Gwangyang Bay from January to November 2002. Based on the photosynthetic pigments, fucoxanthin, diadinoxanthin, and diatoxanthin were the most dominant pigments all the year round, indicating that diatoms were the predominant algal groups of both the sediment and the seawater in Gwangyang Bay. The other algal pigments except the diatom-marker pigments showed relatively low concentrations. Microphytobenthic chlorophyll ${\alpha}$ concentrations in the upper layer (0.5 cm) of sediments ranged from 3.44 (March at the middle site of the tidal flat) to 169 (July at the upper site) mg $m^{-2}$, with the annual mean concentrations of $68.4{\pm}45.5,\;21.3{\pm}14.3,\;22.9{\pm}15.6mg\;m^{-2}$ at the upper, middle, and lower tidal sites, respectively. Depth-integrated chlorophyll ${\alpha}$ concentrations in the overlying water column ranged from 1.66 (November) to 11.7 (July) mg $m^{-2}$, with an annual mean of $6.96{\pm}3.04mg\;m^{-2}$. Microphytobenthic biomasses were about 3${\sim}$10 times higher than depth-integrated phytoplankton biomass in the overlying water column. The physical characteristics of this shallow estuarine tidal flat, similarity in taxonomic composition of the phytoplankton and microphytobenthos, and similar seasonal patterns in their biomasses suggest that resuspended microphytobenthos are an important component of phytoplankton biomass in Gwangyang Bay. Therefore, considering the importance of microphytobenthos as possible food source for the estuarine benthic and pelagic consumers, a consistent monitoring work on the behavior of microphytobenthos is needed in the tidal flat ecosystems.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.4
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• pp.359-369
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• 2007

Amoebophrya is an obligate endoparasitic eukaryotic dinoflagellate infecting host species and eventually killing them within a short period. Because of its host specificity and significant impacts on population dynamics of host species, it has long been proposed to be a potential biological agent for controlling harmful algal bloom (HAB). For several decades, the difficulties of culturing host - parasite systems have been a great obstacle to further research on the biology of Amoebophrya but recent success of several culture systems reactivates this research field. In this study, as a preliminary work for understanding the impacts of Amoebophrya on the population dynamics of host species, semimonthly occurrence of infected host dinoflagellates by Amoebophrya spp. had been observed in Jinhae Bay for two years and with a host - parasite system cultivated, host specificity of Amoebophrya spp. on several dinoflagellates was tested. Amoebophrya spp. were observed in the cellular organelle and cytoplasm of several species including Akashiwo sanguinea, Ceratium fusus, Dinophysis acuminata, Heterocapsa triquetra, Oblea sp., Prorocentrum minimum, P. triestinum, Scrippsiella spinifera, and S. trochoidea. Among them two host - parasite systems for an athecate dinoflagellate, A. sanguinea, and for a thecate dinoflagellate, H. triquetra, had been able to be successfully established as laboratary cultures. Cross-infection tests for 6 species of dinoflagellates in which Amoebophrya was observed or had been reported to exist confirmed high preference for host species of the parasite. Through the continuous research on Amoebophrya occurring in Korean coastal waters, we need to maintain various host - parasite culture systems, which will be very helpful for understanding its ecological role in marine food webs and for applying the species to biologically control harmful algal blooms.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.29 no.1
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• pp.14-27
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• 2024

Unlike the shelf sand ridges moribund in motion, nearshore sand ridges are highly mobile, sensitive to changes in ocean environments, thereby becoming of particular interest with respect to morphological changes. About 5 km off the Daesan port, the Jangan Sand Ridge has been undergoing severe subsea morphological change over the past two decades. Understanding the nature of sand ridges is critical to elucidate the causes of morphological changes. In this context, this study aims at understanding the characteristics and distribution patterns of surface sediments of the ridge and its vicinity. For this purpose, 227 sediment samples were acquired using a grab-sampler, the grain sizes being analysed by the sieve-pipette method. In addition, comparison of grain sizes in sediments between 1997 and 2021 was made in order to investigate the 25-years change in sediment composition. Surface sediments along the ridge axis are fine to medium sands with 2-3 phi in mean grain size, whereas, in the trough of ridge, the sediments are composed of gravels and muddy sandy gravels with mean sizes of -2 to -6 phi. Sediments in the crest of the ridge are well-sorted with normal distribution, on the other hand, the basal sediments are poorly-sorted and positively skewed. Along the ridge crest, the sediments are negatively skewed. From 1997 to 2021, the ridge sediments became largely coarser about 0.5 phi. Such coarsening trend in mean grain size can be explained either by elimination of fine sediments during high waves in winter or elimination of fines suspended during sand mining activities in the past. Spatial distribution pattern of surface sediments shows that ca. 30 m thick of the sand ridge itself overlies the thin relict gravels. The strong asymmetry of sand ridge, the exposure of ridge base, and reworked gravel lags suggest that Jangan sand ridge is probably sediment-deficit and hence erosive in nature at present.

• Korean Journal of Poultry Science
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• v.51 no.2
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• pp.107-116
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• 2024

The study was conducted to examine age-related development of digestive organs, intestinal microvilli hydrolase, and hepatic antioxidant enzyme in Korean native chicks (KNC) aged from 0-d to 28-d of post-hatching. Body weight did not significantly increase from 0-d to 3-d-old, but after that remarkably increased from 3-d to 28-d-old (P<0.05). The relative weight (g/100 g of BW) of the proventriculus, gizzard, and liver was significantly higher at 3- and 7-d-old chicks than that of the other ages. The relative weight of the intestine, mucosal tissues, and pancreas was markedly developed at the ages of 3-, 14-, and (or) 21-d-old chicks (P<0.05). In the small intestine, the specific activities of maltase and sucrose were significantly higher at 14-d-old compared with the other ages (P<0.05). Leucine aminopeptidase activity showed a constant level from 0- to 28-d-old without significance. The specific activity of alkaline phosphatase was significantly higher at 0-d-old compared with the other ages (P<0.05). In the liver, the specific activities of superoxide dismutase, glutathione peroxidase, and glutathione S-transferase were shown to be lowest at 0-d-old, but they continued to increase as the age increased. The lipid peroxidation was significantly high at the age of 21-d (P<0.05), after that its level decreased at 28-d old. In conclusion, the KNC rapidly developed digestive organs and intestinal microvilli hydrolase activity from 3- to 14-d-old after hatching. Hepatic antioxidant enzyme activity continued to increase as the age increased after hatching, resulting in 28-d-old chicks showing the highest antioxidant enzyme activity in the KNC.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.4
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• pp.292-302
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• 2012

This paper reviews comparison analysis of current and latest application for stock identification methods of Todarodes pacificus, and the pros and cons of each method and consideration of how to compensate for each other. Todarodes pacificus which migrates wide areas in western North Pacific is important fishery resource ecologically and commercially. Todarodes pacificus is also considered as 'biological indicator' of ocean environmental changes. And changes in its short and long term catch and distribution area occur along with environmental changes. For example, while the catch of pollack, a cold water fish, has dramatically decreased until today after the climate regime shift in 1987/1988, the catch of Todarodes pacificus has been dramatically increased. Regarding the decrease in pollack catch, overfishing and climate changes were considered as the main causes, but there has been no definite reason until today. One of the reasons why there is no definite answer is related with no proper analysis about ecological and environmental aspects based on stock identification. Subpopulation is a group sharing the same gene pool through sexual reproduction process within limited boundaries having similar ecological characteristics. Each individual with same stock might be affected by different environment in temporal and spatial during the process of spawning, recruitment and then reproduction. Thereby, accurate stock analysis about the species can play an efficient alternative to comply with effective resource management and rapid changes. Four main stock analysis were applied to Todarodes pacificus: Morphologic Method, Ecological Method, Tagging Method, Genetic Method. Ecological method is studies for analysis of differences in spawning grounds by analysing the individual ecological change, distribution, migration status, parasitic state of parasite, kinds of parasite and parasite infection rate etc. Currently the method has been studying lively can identify the group in the similar environment. However It is difficult to know to identify the same genetic group in each other. Tagging Method is direct method. It can analyse cohort's migration, distribution and location of spawning, but it is very difficult to recapture tagged squids and hard to tag juveniles. Genetic method, which is for useful fishery resource stock analysis has provided the basic information regarding resource management study. Genetic method for stock analysis is determined according to markers' sensitivity and need to select high multiform of genetic markers. For stock identification, isozyme multiform has been used for genetic markers. Recently there is increase in use of makers with high range variability among DNA sequencing like mitochondria, microsatellite. Even the current morphologic method, tagging method and ecological method played important rolls through finding Todarodes pacificus' life cycle, migration route and changes in spawning grounds, it is still difficult to analyze the stock of Todarodes pacificus as those are distributed in difference seas. Lately, by taking advantages of each stock analysis method, more complicated method is being applied. If based on such analysis and genetic method for improvement are played, there will be much advance in management system for the resource fluctuation of Todarodes pacificus.

• Journal of the Speleological Society of Korea
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• no.68
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• pp.23-73
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• 2005

Purpose of study; The purpose of this study is specifically classified as two parts. The one is to attempt the chronological annals of Quaternary topographic surface through the study over the formation process of alluvial surfaces in our country, setting forth the alluvial surfaces lower-parts of Han River area, as the basic deposit, and comparing it to the marginal landform surfaces. The other is to attempt the classification of micro morphology based on the and condition premising the land use as a link for the regional development in the lower-parts of Han river area. Reasons why selected the Lower-parts of Han river area as study objects: 1. The change of river course in this area is very serve both in vertical and horizontal sides. With a situation it is very easy to know about the old geography related to the formation process of topography. 2. The component materials of gravel, sand, silt and clay are deposited in this area. Making it the available data, it is possible to consider about not oかy the formation process of topography but alsoon the development history to some extent. 3. The earthen vessel, a fossil shell fish, bone, cnarcoal and sea-weed are included in the alluvial deposition in this area. These can be also valuable data related to the chronological annals. 4. The bottom set conglometate beds is also included in the alluvial deposits. This can be also valuable data related to the research of geomorphological development. 5. Around of this area the medium landform surface, lower landform surface, pediment and basin, are existed, and these enable the comparison between the erosion surfaces and the alluvial surfaces. Approach : 1. Referring to the change of river beds, I have calculated the vertical and horizontal differences comparing the topographic map published in 1916 with that published in 1966 and through the field work 2. In classifying the landform, I have applied the method of micro morphological classification in accordance with the synthetic index based upon the land conditions, and furthermore used the classification method comparing the topographic map published in 1916 and in that of 1966. 3. I have accorded this classification with the classification by mapping through appliying the method of classification in the development history for the field work making the component materials as the available data. 4. I have used the component materials, which were picked up form the outcrop of 10 places and bored at 5 places, as the available data. 5. I have referred to Hydrological survey data of the ministry of Construction (since 1916) on the overflow of Han-river, and used geologic map of Seoul metropolitan area. Survey Data, and general map published in 1916 by the Japanese Army Survbey Dept., and map published in 1966 by the Construction Research Laboratory and ROK Army Survey Dept., respectively. Conclusion: 1. Classification of Morphology: I have added the historical consideration for development, making the component materials and fossil as the data, to the typical consideration in accordance with the map of summit level, reliefe and slope distribution. In connection with the erosion surface, I have divided into three classification such as high, medium and low-,level landform surfaces which were classified as high and low level landform surfaces in past. furthermore I have divided the low level landform surface two parts, namely upper-parts(200-300m) and bellow-parts(${\pm}100m$). Accordingly, we can recognize the three-parts of erosion surface including the medium level landform surface (500-600m) in this area. (see table 22). In condition with the alluvial surfaces I have classified as two landform surfaces (old and new) which was regarded as one face in past. Meamwhile, under the premise of land use, the synthetic, micro morphological classification based upon the land condition is as per the draw No. 19-1. This is the quite new method of classification which was at first attempted in this country. 2. I have learned that the change of river was most severe at seeing the river meandering rate from Dangjung-ni to Nanjido. As you seee the table and the vertical and horizontal change of river beds is justly proportionable to the river meandering rate. 3. It can be learned at seeing the analysis of component materials of alluvial deposits that the component from each other by areas, however, in the deposits relationship upper stream, and between upper parts and below parts I couldn't always find out the regular ones. 4. Having earthern vessel, shell bone, fossil charcoal and and seaweeds includen in the component materials such as gravel, clay, sand and silt in Dukso and Songpa deposits area. I have become to attempt the compilation of chronicle as yon see in the table 22. 5. In according to hearing of basemen excavation, the bottom set conglomerate beds of Dukso beds of Dukso-beds is 7m and Songpa-beds is 10m. In according to information of dredger it is approx. 20m in the down stream. 6. Making these two beds as the standard beds, I have compared it to other beds. 7 The coarse sand beds which is covering the clay-beds of Dukso-beds and Nanjidobeds is shown the existence of so-called erosion period which formed the gap among the alluvial deposits of stratum. The former has been proved by the sorting, bedding and roundness which was supplied by the main stream and later by the branch stream, respectively. 8. If the clay-beds of Dukeo-bed and Songpa-bed is called as being transgressive overlap, by the Eustatic movement after glacial age, the bottom set conglomerate beds shall be called as being regressive overlap at the holocene. This has the closest relationship with the basin formation movement of Seoul besides the Eustatic movement. 9. The silt-beds which is the main component of deposits of flood plain, is regarded as being deposited at the Holocene in the comb ceramic and plain pottery ages. This has the closest relationship with the change of river course and river beds.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.3
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• pp.154-163
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• 2005

Irregular discharges of freshwater through the water gates of the Keum River Estuarine Weir, Korea, whose construction had been completed in 1998 with its water gates being operated as late as August 1994, drastically modified the estuarine environment. Sharp decrease of salinity along with the altered concentrations of inorganic nutrients are accompanied with the irregular discharges of freshwater into the estuary under the influence of regular semi-diurnal tidal effect. Field sampling was carried out on the time of high tide at 2 fixed stations(St.1 near the Estuarine Weir and St.2 off Kunsan Ferry Station) every other day for 4 months from mid-February 2004 to investigate into the semi-weekly variation of spring phytoplankton community in relation to the freshwater discharges from Keum River Estuarine Weir. CV(coefficient of variation) of salinity measurements was roughly 2 times greater in St.1 than that in St.2, reflecting extreme salinity variation in St.1 Among inorganic nutrients, concentrations of N-nutrients($NO_3^-,\;NO_2^-$ and $NH_4^+$) were clearly higher in St.1, to imply the more drastic changes of the nutrient concentrations in St.1. than St.2 following the freshwater discharges. As a component of phytoplankton community, diatoms were among the top dominants in terms of species richness as well as biomass. Solitary centric diatom, Cyclotella meneghiniana, and chain-forming centric diatom, Skeletonema costatum, dominated over the phytoplankton community in order for S-6 weeks each (Succession Interval I and II), and the latter succeeded to the former from the time of <$10^{\circ}C$ of water temperature. Cyanobacterial species, Aphanizomenon Posaquae and Phormidium sp., which might be transported into the estuary along with the discharged freshwater, occupied high portion of total biomass during Succession Interval III(mid-April to late-May). During this period, freshwater species exclusively dominated over the phytoplankton community except the low concentrations of the co-occurring 2 estuarine diatoms, Cyclotella meneghiniana and Skeletonema costatum. During the 4th Succession Interval when the water temperature was over $18^{\circ}C$, the diatom, Guinardia delicatula, was predominant for a week with the highest dominance of $75\%$ in discrete samples. To summarize, during all the Succession Intervals other than Succession Interval III characterized by the extreme variation of salinity under cooler water temperature than $18^{\circ}C$, the diatoms were the most important dominants for species succession in spring. If the scale and frequency of the freshwater discharge could have been adjusted properly even during the Succession Interval III, the dominant species would quite possibly be replaced by other estuarine diatom species rather than the two freshwater cyanobacteria, Aphanizomenon flosaquae and Phormidium sp.. The scheme of field sampling every other day for the present study was concluded to be the minimal requirement in order to adequately explore the phytoplankton succession in such estuarine environment as in Keum River Estuary: which is stressed by the unpredictable and unavoidable discharges of freshwater under the regular semi-diurnal tide.

• Korean Journal of Heritage: History & Science
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• v.44 no.1
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• pp.72-105
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• 2011

This study explores the value of the Dicentra spectabilis community as a nature reserve in provincial forests at San 1-2, Daea-ri, Dongsang-myeon, Wanju-gun, Jellabuk-do, also known as Gamakgol, while defining the appropriateness of its living environment and eventually providing basic information to protect this area. For these reasons, we investigated 'morphological and biological features of Dicentra spectabilis' and the 'present situation and problems of designing a herbaceous nature reserve in Korea.' Furthermore, we researched and analyzed the solar, soil and vegetation condition here through a field study in order to comprehend its nature reserve value. The result is as follows. According to the analytic result for information on the domestic wild Dicentra spectabilis community, it is evenly spread throughout mountainous areas, and there is one particularly outstanding in size in Wanju Gamakgol. Upon the findings from literature and the field study about its dispersion, Gamakgol has been discovered as an ideal district for Dicentra spectabilis since it meets all the conditions this plant requires to grow vigorously, such as a quasi-high altitude and rich precipitation during its period of active growth duration in May. Dicentra spectabilis grows in rocky soil ranging from 300~375m above sea level, 344.5m on average, towards the north, northwest and dominantly in the northeast. The mean inclination degree is $19.5^{\circ}$. Also, upon findings from analyzing solar conditions, the average light intensity during its growth duration, from Apr. to Aug., is 30,810lux on average and it tends to increase, as it gets closer to the end. This plant requires around 14,000~18,000lux while growing, but once bloomed, fruits develop regardless of the degree of brightness. The soil pH has shown a slight difference between the topsoil, at 5.2~6.1, and subsoil, at 5.2~6.2. Its mean pH is 5.54 for topsoil and 5.58 for subsoil. These results are very typical for Dicentra spectabilis to grow in, and other comparative areas also present similar conditions. Given the facts, the character of the soil in Gamakgol has been evaluated to have high stability. Analysis of its vegetation environment shows a wide variation of taxa numbering from 13 to 52 depending on area. The total number of taxa is 126 and they are a homogenous group while showing a variety of species as well. The Dicentra spectabilis community in the Daea-ri Arboretum is an herbaceous community consisting of dominantly Dicentra spectabilis, Cardamine leucantha, Boehmeria tricuspi and Impatiens textori while having many differential species such as Impatiens textori, Pueraria thunbergiana, Rubus crataegifolius vs Staphylea bumalda, Securinega suffruticosa, and Actinidia polygama. It suggests that it is a typical subcolony divided by topographic features and soil humidity. Considering the above results on a comprehensive level, this area is an excellent habitat for wild Dicentra spectabilis providing beautiful viewing enjoyment. Additionally, it is the largest wild colony of Dicentra spectabilis in Korea whose climate, topography, soil conditions and vegetation environment can secure sustainability as a wild habitat of Dicentra spectabilis. Therefore, We have determined that the Gamakgol community should be re-examined as natural asset owing to its established habitat conditions and sustainability.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.1
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• pp.40-46
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• 2013

The isotope ratios of $^{13}C/^{12}C$ and $^{18}O/^{16}O$ for a sample in a mass spectrometer are measured relative to those of a pure $CO_2$ reference gas (i.e., laboratory working standard). Thus, the calibration of a laboratory working standard gas to the international isotope scales (Pee Dee Belemnite (PDB) for ${\delta}^{13}C$ and Vienna Standard Mean Ocean Water (V-SMOW) for ${\delta}^{18}O$) is essential for comparisons between data sets obtained by other groups on other mass spectrometers. However, one often finds difficulties in getting well-calibrated standard gases, because of their production time and high price. Additional difficulty is that fractionation processes can occur inside the gas cylinder most likely due to pressure drop in long-term use. Therefore, studies on laboratory production of pure $CO_2$ isotope standard gas from stable solid calcium carbonate standard materials, have been performed. For this study, we propose a method to extract pure $CO_2$ gas without isotope fractionation from a solid calcium carbonate material. The method is similar to that suggested by Coplen et al., (1983), but is better optimized particularly to make a large amount of pure $CO_2$ gas from calcium carbonate material. The $CaCO_3$ releases $CO_2$ in reaction with 100% pure phosphoric acid at $25^{\circ}C$ in a custom designed, evacuated reaction vessel. Here we introduce optimal procedure, reaction conditions, and samples/reactants size for calcium carbonate-phosphoric acid reaction and also provide the details for extracting, purifying and collecting $CO_2$ gas out of the reaction vessel. The measurements for ${\delta}^{18}O$ and ${\delta}^{13}C$ of $CO_2$ were performed at Seoul National University using a stable isotope ratio mass spectrometer (VG Isotech, SIRA Series II) operated in dual-inlet mode. The entire analysis precisions for ${\delta}^{18}O$ and ${\delta}^{13}C$ were evaluated based on the standard deviations of multiple measurements on 15 separate samples of purified $CO_2$. The pure $CO_2$ samples were taken from 100-mg aliquots of a solid calcium carbonate (Solenhofen-ori $CaCO_3$) during 8-day experimental period. The multiple measurements yielded the $1{\sigma}$ precisions of ${\pm}0.01$‰ for ${\delta}^{13}C$ and ${\pm}0.05$‰ for ${\delta}^{18}O$, comparable to the internal instrumental precisions of SIRA. Therefore, we conclude the method proposed in this study can serve as a way to produce an accurate secondary and/or laboratory $CO_2$ standard gas. We hope this study helps resolve difficulties in placing a laboratory working standard onto the international isotope scales and does make accurate comparisons with other data sets from other groups.