• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.4
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• pp.310-321
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• 2016

This study describes the spatial distribution of dinoflagellate cyst assemblages from the fishing ports along Jeju Island. Surface sediment samples from 22 stations revealed the occurrence of 29 species involving the Groups Protoperidinioid (44.8%), Gonyaulacoid (31.0%), Calciodineloid (10.3%), Gymnodinioid (6.9%), Diplosalid (3.5%) and Tuberculodinioid (3.5%). The cyst abundance recorded here is very low ($13{\sim}220cysts\;g-dry^{-1}$) as compared to Korean coastal regions. The abundance of heterothophic cysts increased in several fishing pots with fine sediments and anthropogenic tidal pools. And cyst abundance was well correlated with the grain-size composition of surface sediments. The dinoflagellate cyst assemblages in Jeju fishing ports were characterized by the dominant species, cyst of Gymnodinium sp., cyst of Pyrodinium bahamense and cyst of Scrippsiella trochoidea in 2012, Protoperidinium sp. (Brigantedinium sp.), cyst of Scrippsiella sp./trochoidea and cyst of Gymnodinium sp. in 2014, and Protoperidinium sp. (Echinidinium sp. and Brigantedinium sp.) in 2016. The advent of the toxic dinoflagellate, Pyrodinium bahamense were recorded for the first time in Jeju coastal waters. As a results, we are determined should be to monitoring and management measures for new toxic dinoflegallates from tropical or subtropical reigions and anthropogenic tidal pools by industrial activities.

• Korean Journal of Environmental Biology
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• v.24 no.1 s.61
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• pp.81-88
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• 2006

The cell abundance and marker pigment distribution patterns of picophytoplankton in the Chuuk Lagoon, tropical South Pacific, were analyzed flow cytometry and HPLC. Also, respective contribution of Synechococcus, Prochlorococcus and picoeukaryotes on estimated carbon biomass was evaluated. Synechococcus and Prochlorococcus showed contrasting distributional patterns in the waters of Chuuk Lagoon. Relatively high concentration of Synechococcus was observed near Weno Island but the concentration decreased toward the Northeast Passage. However, Prochlorococcus showed an opposite distributional pattern. Picoeukaryotes did not show any significant variable difference. The range of divinyl chlorophyll a (Chl. $\alpha$) concentration, marker pigment of Prochlorococcus, was $1.2\sim180.3\;ng\;L^{-1}$ and higher concentrations were observed at the stations near the Northeast Passage than stations near Weno Island. This pigment pattern was similar to cell abundance pattern indicating that chi. a2 may be a useful biomass indicator. On the other hand, the range of zeaxanthin concentrations was $61.4\sim135.8\;ng\;L^{-1}$ showing comparatively less significant variation indicating zeaxanthin influence derived from Prochlorococcus. Estimated carbon biomass of Synechococcus contributed 68% of total picophytoplankton biomass. Prochlorococcus and picoeukaryotes respectively contributed 17.1% and 14.9% of total picophytoplankton biomass.

• Parasites, Hosts and Diseases
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• v.34 no.1
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• pp.35-48
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• 1996

Non-biting midges fchironomidae, Dipteral are one of the largest insect families, which are distributed worldwidely and are found in nearly all types of inland waters. They are known to be aggressive inhalant allergens which cause allergenic diseases. In this study, the crude antigens of Chironomus SavipLumn adults which are most widely distributed in Korea were extracted. and their allergens were analysed with the sera from experimentally sensitized mice. The mice were immunized with $1{\;}\mu\textrm{g}{\;}or{\;}10{\;}\mu\textrm{g}$ of the crude antigens, respectively, and the specific serum IgE levels were measured by both ELISA and passive cutaneous anaphylaxis (PCA) techniques. The highest levels of both total IgE and chironomid-specific IgE were found in the mouse sera obtained after 9 weeks of the first infection with $1{\;}\mu\textrm{g}$ crude antigen. The crude antigen was separated into 16-18 protein bands on gel by SDS-PAGE. The crude extract was assessed by SDS-PAGE/immunoblot analysis. One IgE-binding band (65 kDa) was detected by developing with colorimetric substrate, and 4 IgE-binding bands (65, 52, 35 and 25 kDa) by developing with CSPD chemiluminescent substrate. The SDS-PAGE gel of the crude extract of chironomid adults was equally cut into 30 pieces and each of them was eluted to isolate proteins by molecular weight, and the allergenicity of each eluate was assessed by applying P-K test on rats. Proteins of 65, 35 and 15 KDa showed the highest P-K titer (${\times}512$) which was 16 times higher than that of the crude extract (${\times32}$). The P-K titer of 52 kDa protein was also 4 times higher ($128{\times}$) than that of the crude extract, whereas the 25 kDa protein poorly responded, which seemed not antigenic. In conclusion, the present result in mice demonstrated that adults of Chironomus fcuiplumus, a predominent species in Korea, cause allergenic diseases and the main allergens are 65, 52, 35 and 15 kDa proteins, of which 65 kDa protein seems to be a main allergen.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6388-6398
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• 2014

To understand size fractioned chlorophyll a and material cycle characteristics in Jeju marine ranching area (JMRA), 4 times of survey were conducted from April to November 2008. Picoplankton on the surface in JMRA was on average, $0.30{\mu}g/L$(annual mean(M):17.3%) in the $0.03{\sim}0.84{\mu}g/L$ range, accounting for 17.3%. Nannoplankton and picoplankton was on average, $1.35{\mu}g/L$(M:78.0%) in the $0.22{\sim}3.93{\mu}g/L$ range, and $1.73{\mu}g/L$(M:4.7%) in the nd ~ 0.24 range, respectively. The 10m layer was similar to the surface. The measured values changed according to the measurement times but the nanoplankton composition ratio was higher throughout the year. In addition, the size fractioned chlorophyll a distribution in JMRA was similar to that of tropical sea area affected by the Monsoon rather than South Korean offshore coast geographically adjacent to the East China Sea and Japan coastal waters affected by the Kuroshio/Tsushima warm currents. That is, the material cycle of JMRA consists of a microbial food web rather than traditional food chain at a lower trophic levels. Primary production is deemed to have a higher possibility of being adjusted by top-down dynamics, such as micro-zooplankton grazing pressure rather than nutrients supply.

• Korean Journal of Environmental Biology
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• v.37 no.1
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• pp.19-30
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• 2019

To investigate the characteristics of seasonal environment and phytoplankton community structure in the coastal area of Dokdo, a survey of Dokdo around waters was conducted during the four seasons. Phytoplankton of 4 phylum 72 species in four seasons were collected in Dokdo around water. The seasonal mean abundance of phytoplankton were $3.32{\times}10^4cells\;L^{-1}$ in winter, $1.04{\times}10^4cells\;L^{-1}$ in spring, $0.28{\times}10^4cells\;L^{-1}$ in summer, and $4.86{\times}10^4cells\;L^{-1}$ in autumn in Dokdo around water. During winter, the diatoms Chaetoceros spp. had dominated. During spring, when the nutrients in the euphotic layer were depleted, the nano-flagellates and Cryptomonas appeared at surface layer. In summer, the abundance of phytoplankton was relatively low, which lead to occurrence of diatoms such as genus of Chaetoceros, Rhizosolenia, and Skeletonema. In autumn, Pseudo-nitzschia spp. was the most dominant species and tropical species such as Amphisolenia sp. and Ornithocercus magnificus were observed, implying that they may have introduced within warm water current such as Kurosiwo Current. Therefore, although natural phytoplankton communities in the vicinity water of Dokdo are mainly influenced by Tsushima Warm Current branched Kurosiwo Current, their population dynamics was affected on the spatio-temporal change of physicochemical factors by short-term wind events, namely "island effect". Long-term survey research is needed to facilitate food-web response in marine ecosystem associated with phytoplankton biomass and physicochemical factors including the warm water current in oligotrophic offshore water of Dokdo, which may have significant role for sustainable use of Dokdo.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.20 no.4
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• pp.192-198
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• 2015

Picophytoplankton, a group of tiny microorganisms of less than $3{\mu}m$, play an important role as a major primary producer in tropical open ocean as well as temperate coastal waters. Until now, more than 20 and 10 clades of Synechococcus and Prochlorococcus, respectively, have been identified in various marine environments, and its biogeographical distribution have been well studied as well as ecological niches of its major clades. To understand a distribution of diverse picocyanobacterial clades and environmental factors regulating their distribution, picocyanobacterial abundance and genetic diversity was investigated in adjacent waters of Dokdo showing diverse physical properties not only by seasonal variation but also by diverse physical processes. Synechococcus abundances were low in winter and then exponentially increased as water temperature increased up to $20^{\circ}C$. Above $20^{\circ}C$, the abundances tended to be saturated. On the contrary, Prochlorococcus was undetected or occupied a minor fraction of picocyanobacteria in most seasons. In summer, however, Prochlorococcus belonging to HLII ecotype occupied a significant fraction (up to 7%) of picocyanobacteria. In spring and early summer, the steep increase of Synechococcus abundances were resulted from growth of cold water-adapted Synechococcus belonging to clades I and IV. In summer, diverse Synechococcus clades including warm and pelagic water-favoring clade II tended to replace clades I and IV with maintaining high abundance. The water-column stability as well as temperature were found to be important factors regulating the Synechococcus abundances. Moreover, inflow and mixing of distinct water masses with different origins exerted significant influence on the composition of Synechococcus in the study area. Thus, physical processes as well as natural seasonal variation of environmental factors should be considered to better understand ecology of planktonic organisms around Dokdo.

• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.47-60
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• 2020

To assess the characteristics of phytoplankton community structures related to environmental factors, seasonal surveys were conducted in the vicinity of Dokdo. In 2019, phytoplankton of four phyla and 69 species were observed. During winter, unidentified nanoflagellates dominated, with an average of 3.19×10⁴ cells L^-1. In spring, unidentified nanoflagellates occupied about 50% of the composition and a variety of dinoflagellates appeared. The summer phytoplankton population showed very low abundance. In autumn, various species of Chaetoceros appeared, along with diatoms, such as Bacteriastrum spp., Guinardia striata, and Pseudo-nitzschia spp. In addition, tropical species Amphisolenia sp. and Ornithocercus sp. were observed in both 2018 and 2019. The diversity was high in the summer of 2018 and the winter of 2019 and the characteristics of each index varied. Cluster analysis was divided into four groups according to species and population characteristics regardless of the season. The stratification of spring was particularly weak. In the autumn of 2018, the water mass was stabilized in the same way as in the summer, which is considered a suitable condition for phytoplankton growth. However, in 2019, the water masses were mixed, resulting in a low population. In a phytoplankton comparison, the dominant group showed seasonal differences, except for summer when the population was low, and the difference was most pronounced in autumn. Therefore, the waters surrounding Dokdo have different environmental and ecological characteristics from the East Sea, but the seasonal characteristics of each year are considered to be different depending on the topography, various currents, the island effect, and other factors.

• Journal of the Korean earth science society
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• v.27 no.4
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• pp.464-474
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• 2006

The paleoceanography since 14 ka was reconstructed based on the planktic foraminiferal assemblages of core sediments from the outer shelf of the Korea Strait. Planktic foraminifera in the core sediments can be divided into four assemblages: A, B, C, and D. Assemblage A consists mainly of Globigerinoides ruber group and Globigerinoides conglobatus with low abundance (less than 10%), indicating the tropical-subtropical water mass. Assemblage B is composed of Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, the indicator of Kuroshio Current, and shows the aspect of the inflow of the Tsushima Current into the Korea Strait. Assemblage C yields polar-subpolar species, mainly Neogloboquadrina incompta and N. pachyderma. It decreases upward of the core. Assemblage D contains coastal water species such as Globigerina bulloides and G. quinqueloba. It is abundant in the lower to middle region of the core. From the analysis of distributions of each assemblage and the result of age datings in the core, it is suggested that the Korea Strait played a role of channelling the East China Sea and the East Sea after the LGM (ca. 14 ka). During this time, the coastal water, affected by fresh waters originated from the river systems of China and/ or the Korean Peninsula, flourished around the Korea Strait and theses coastal water might entered to the East Sea. Around 8.5 ka, the effect of the Tsushima Current started to strengthen in this region, and the present current system seems to be formed at about $7{\sim}6ka$.

• Journal of Aquaculture
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• v.6 no.4
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• pp.235-253
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• 1993

The freshwater crab, Eriocheir japonicus inhabits from sub-tropical to temperate zone in Asia. This species belongs to a large size group among freshwater crabs. Common size of this crab is 5-6cm in carapace length and occasionally 7cm in carapace length. This species of crab used to inhabit in estuaries, rivers and inland waters in Korea. However, natural population recently has been rapidly decreased because of pollution and lost their habitats by suburban development. Therefore, development of proper methods of seedling production to increase natural stock became necessity. As parts of achieving this goal, duration from mating to spawning, egg incubation period, and egg development of this species were studied. The influence of temperatures and salinities on the egg incubation and hatching was also investigated. It took 2-8 hours from mating to egg spawning and the spawning lasted 3-9 hours from the first spawning. Egg numbers per female (6cm in carapace length) were 380,000­410,000. Optimum temperature for egg incubation was $17\~23^{\circ}C$ and optimum salinity, $14.0\~31.5\%o$. Incubation period of the eggs at $14^{\circ}C,\;17^{\circ}C,\;20^{\circ}C,\;26^{\circ}C,\;and\;28^{\circ}C$ was 42, 28, 21, 15, and 14 days. respectively. Relation between temperature (X) and incubation days (Y) was LogY = Log 2764.267 - 1.608 LogX. A female can spawn 4-6 times per year by manipulation of environmental conditions. Under the conditions of $18^{\circ}C\;and\;24.5\%o$, it took 6 days up to embryo formation, 18 days up to compound eye formation, 22 days up to abdominal movement, and 25 days up to hatch out as zoea larvae.