• Journal of Ecology and Environment
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• v.43 no.1
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• pp.9-13
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• 2019

We investigated the pollinators of Centipede's foot orchid (Cleisostoma scolopendrifolium) at five locations in southern Korea. Only one species of megachilid bee (Megachile yasumatsui) was observed at three of the sites (Mokpo, Haenam, and Wando). We assumed that the megachilid bee worked as a sole pollinator of C. scolopendrifolium based on the visiting behavior of the bees the attached pollinia. Fruits were observed at the three locations that bees visited: 74% fruit set at Mokpo, 59% at Wando, and 31% at Haenam. By contrast, at two of the locations where megachilid bees did not visit the plants (Naju and Jindo), there were no fruits set. The differences in fruit set rates at the three orchid populations where bees were observed appear to be related to bee abundance and flower visitation rate rather than to differences in flower abundance. The pollination interaction between C. scolopendrifolium and megachilid bees appears to involve sexual deception since only male bees were attracted to the flowers. The underlying mechanism involved in this interaction needs investigation.

• Korean Journal of Organic Agriculture
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• v.27 no.4
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• pp.463-477
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• 2019

This study was conducted to compare the community structure and biodiversity of epigeic spiders between pear fields cultivated by integrated pest management (IPM) and organic methods. This is the first study of this kind to be conducted in Korea. Eighty-four spider species from 22 families were identified among the collected 2,489 arthropods, with 754 individuals being sampled from IPM fields and 1,735 individuals from organic fields. Generally, Theridiidae, Linyphiidae, Lycosidae, Agelenidae, Gnaphosidae, and Salticidae were the dominant spider families in the pear orchard regardless of the farming methods, and species richness and abundance were higher in organic fields than in IPM fields. The dominant species were the wolf spiders (Lycosidae) and stone spiders (Gnaphosidae), and their cumulative abundance was 70.7% in IPM fields and 72.7% in organic fields. The community structure between organic and IPM fields was heterogeneous, with a 45% similarity level. Biodiversity, species richness, abundance, and species diversity index were higher in organic fields than in IPM fields, and significantly different between the farming methods. Seasonal fluctuations in biodiversity were similar in both IPM and organic fields. The species richness and species diversity index increased and the abundance decreased in the second half of the cultivation period. This study on the community structure and biodiversity of epigeic spiders, which form one of the most important predator groups, will provide principal ecological and faunistic information required to maintain the biodiversity of useful arthropods in agricultural ecosystems and help implement sustainable agriculture based on the active use of natural enemies.

• ALGAE
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• v.35 no.1
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• pp.45-59
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• 2020

To investigate the spatio-temporal distributions of the mixotrophic dinoflagellate Yihiella yeosuensis in Korean coastal waters and its grazing impact on prey populations, water samples were seasonally collected from 28 stations in the East, West, and South Seas of Korea and Jeju Island from April 2015 to October 2018. The abundances of Y. yeosuensis in the water samples were quantified using quantitative real-time polymerase chain reaction (qPCR). Simultaneously, the physical and chemical properties of water from all sampled stations were determined, and the abundances of the optimal prey species of Y. yeosuensis, the prasinophyte Pyramimonas sp. and the cryptophyte Teleaulax amphioxeia, were quantified using qPCR. Y. yeosuensis has a wide distribution, as is reflected by the detection of Y. yeosuensis cells at 23 sampling stations; however, this distribution has a strong seasonality, which is indicated by its detection at 22 stations in summer but only one station in winter. The abundance of Y. yeosuensis was significantly and positively correlated with those of Pyramimonas sp. and T. amphioxeia, as well as with water temperature. The highest abundance of Y. yeosuensis was 48.5 cells mL^-1 in Buan in July 2017, when the abundances of Pyramimonas sp. and T. amphioxeia were 917.6 and 210.4 cells mL^-1, respectively. The growth rate of Y. yeosuensis on Pyramimonas sp., calculated by interpolating the growth rates at the same abundance, was 0.49 d^-1, which is 37% of the maximum growth rate of Y. yeosuensis on Pyramimonas sp. obtained in the laboratory. Therefore, the field abundance of Pyramimonas sp. obtained in the present study can support a moderate positive growth of Y. yeosuensis. The maximum grazing coefficient for Y. yeosuensis on the co-occurring Pyramimonas sp. was 0.42 d^-1, indicating that 35% of the Pyramimonas sp. population were consumed in 1 d. Therefore, the spatio-temporal distribution of Y. yeosuensis in Korean coastal waters may be affected by those of the optimal prey species and water temperature. Moreover, Y. yeosuensis may potentially have considerable grazing impacts on populations of Pyramimonas sp.

• Archives of Pharmacal Research
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• v.3 no.1
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• pp.57-64
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• 1980

Carbon-13 NMR spectroscopy(abbreviated CMR) is an extremely powerful strategy for the study of natural organic molecules. The information derivable from CMR is often complementary to that obtianed form proton NMR spectroscopy (PMR). Because of low natural abundance of $^{13}C$ nucleus (1.1%) coupled with low inherent sensitivity relative to $^{1}H$ (about 1/64), CMR experiment is approximately 6000 times less sensitive than PMR. Despite of this, now it is possible to measure CMR of small amount of compound by the development of three significant ingenious techniques, i. e. a) computer time-averaging, b) wide-band (or noise modulated) proton decoupling, and c) pulsed Fourier transform (FT) NMR : For general recognition of CMR, its fundamental aspects of CMR are briefly reviewed.

• ALGAE
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• v.36 no.1
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• pp.37-50
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• 2021

Heterotrophic dinoflagellates Gyrodinium spp. are one of the major grazers of phytoplankton in many coastal waters. Gyrodinium dominans, G. jinhaense, and G. moestrupii have similar morphologies but different edible prey species. To explore the variations in the ecological niches of these three species, we investigated their spatial-temporal distributions in Korean waters. Because of the high similarity in morphology among these three Gyrodinium species, we used real-time polymerase chain reactions to quantify their abundance in water samples that were seasonally collected from 28 stations along the Korean Peninsula from April 2015 to October 2018. Cells of G. dominans were found at all sampling stations, G. jinhaense at 26 stations, and G. moestrupii at 22 stations, indicating that all three species were widely distributed in Korea. Furthermore, all three species displayed strong seasonal distributions. The largest numbers of the stations where G. dominans and G. jinhaense cells were present were found during the summer (26 and 23 stations, respectively), but that for G. moestrupii was found in the autumn (15 stations). The abundance of G. dominans was positively correlated with that of G. jinhaense, but not with that of G. moestrupii. The highest abundances of G. dominans (202.5 cells mL-1) and G. jinhaense (20.2 cells mL-1) were much greater than that of G. moestrupii (1.2 cells mL-1). The highest abundances of G. dominans and G. jinhaense were found in July, whereas that of G. moestrupii was found in March. The abundances of G. dominans and G. jinhaense, but not G. moestrupii, were positively correlated with water temperature. Therefore, the spatial-temporal distributions of G. dominans and G. jinhaense were closer than those of G. moestrupii and G. dominans or G. jinhaense. This differs from results based on the relative differences in ribosomal DNA sequences and the types of edible prey reported in the literature. Thus, the variations in spatial-temporal distributions and prey species of these three Gyrodinium species suggest that they may have different ecological niches in Korean coastal waters.

• Proceedings of the Zoological Society Korea Conference
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• 1997.10b
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• pp.137.2-137
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• 1997

No Abstract, See Full Text

• Analytical Science and Technology
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• v.13 no.4
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• pp.539-543
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• 2000

The quantitative aspects of 2D carbon-13 INADEQUATE (Incredible Natural Abundance DoublE QUAntum Transfer Experiment) experiment were studied on the basis of the time needed in various concentrations of samples. In order to evaluate the quantitative time of this experiment, eight compounds were selected (M. W. ca. 150-500). The effect on time needed of various concentrations showed exponential decay function, Y=$8.15X^{-0.64}$.

• ALGAE
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• v.37 no.2
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• pp.149-161
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• 2022

Noctiluca scintillans is a heterotrophic dinoflagellate that causes red-colored oceans during the day (red tides) and glowing oceans at night (bioluminescence). This species feeds on diverse prey, including phytoplankton, heterotrophic protists, and eggs of metazoans. Thus, many scientists have conducted studies on the ecophysiology of this species. It is easy to cultivate N. scintillans at a scale of <1 L, but it is difficult to cultivate them at a scale of >100 L because N. scintillans cells usually stay near the surface, while prey cells stay below the surface in large water tanks. To obtain mass-cultured N. scintillans cells, we developed an automatic system for cultivating N. scintillans on a scale of 100 L. The system consisted of four tanks containing fresh nutrients, the chlorophyte Dunaliella salina as prey, N. scintillans for growth, and N. scintillans for storage, respectively. The light intensities supporting the high growth rates of D. salina and N. scintillans were 300 and 20 µmol photons m^-2 s^-1, respectively. Twenty liters of D. salina culture from the prey culture tank were transferred to the predator culture tank, and subsequently 20 L of nutrients from the nutrient tank were transferred to the prey culture tank every 2 d. When the volume of N. scintillans in the predator culture tank reached 90 L 6 d later, 70 L of the culture were transferred to the predator storage tank. To prevent N. scintillans cells from being separated from D. salina cells in the predator culture tank, the culture was mixed using an air pump, a sparger, and a stirrer. The highest abundance of N. scintillans in the predator culture tank was 45 cells mL^-1, which was more than twice the highest abundance when this dinoflagellate was cultivated manually. This automatic system supplies 100 L of N. scintillans pure culture with a high density every 10 d for diverse experiments on N. scintillans.

• The Korean Journal of Zoology
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• v.39 no.3
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• pp.325-336
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• 1996

Community organization of the drosophilid flies was investigated with respect to the seasonal variation in species abundance and vertical microdistribution on the basis of the trapped collections in the two natural forests on Cheju-do from May to October 1994. The dominant species were Drosophila bizonata, D. curviceps, D. lutescens, D. angu leris, D. tsigana and D. immigrans in the annual collections. The pattern in seasonal changes of the dominant species was similar at the two survey sites. Seasonal fluctuation in the species diversity was more affected by evenness than by species richness (number of species). The seasonal variation of abundance showed an unimodal pattern in all of the dominant species. The seasonal patterns of vertical microdistribution revealed difference in some of the dominant species between the two survey sites. These results suggest that the predominant species in the forest avoid niche overlap by means of seasonal separation of breedings and that the vertical microdistribution is strongly affected by factors associated with season and vertical site in the deep wooded forests.

• Ocean and Polar Research
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• v.27 no.3
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• pp.341-349
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• 2005

Temporal variation of the natural planktonic community in the Southern Sea of Korea was investigated by using low floating enclosed bags (3.2m deep and 2,500 liter) in order to understand the effect of enriched nitrate on the planktonic community in the spring (March-April) of 2002. Prior to beginning the incubation, the bags were placed in two different concentrations of nitrate, which consisted of control (ambient water) and experimental mesocosms (final concentration of $12{\mu}M$). The nitrate concentration in the experimental mesocosms remained significantly higher than those in control mesocosms throughout the study period (ANOYA, p<0.001). Following the addition of nitrate, abundance and chi-a concentration of phytoplankton peaked on Day 1, when diatoms established the peak in the experimental mesocosms. Diatoms consisted mainly of Thalasxiosira decipiens, Pseudo-nitzschia pungem, Leptocylindrus danicu, Thalassionema nitzschioides, Chaetoceros pseudocrinitus and Actinoptychus senariu. However, the peak did not lead to the difference in abundance and composition of phytoplankton between control and experimental mesocosms during the study period. The dinoflagellates began to increase soon after the diatoms decreased in all mesocosms. Copepods, as a dominant group in the rnosozooplankton community, showed no immediate peak in relation to the nitrate addition, but only their own developmental process from the eggs to adult stage during the study period. The bottom-up control from enriched nitrate via phytoplankton to adult copepods was not distinguished in terms of the abundance of the planktonic community. This might stem from the relatively low nitrate availability of phytoplankton at no N-limited seawater and the weak coupling between rapidly sunken diatoms and copepods through the water column.