• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.27 no.2
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• pp.103-125
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• 2022

This study aims to identify the community characteristics of meiofauna inhabiting the Yellow Sea continental shelf. To this end an annual survey was conducted considering the seasons from 2018 to 2020 at 13 stations with a depth of 18~90 m of the Yellow Sea located at latitudes 35, 36 and 37 degrees north latitude. The survey was conducted in three seasons of spring, summer, and autumn at 5 stations in October 2018, 9 stations in April 2019, and 6 stations in August 2020 was used to collect 3 repetitions at each station. The habitat density of meiobenthos in the surveyed area was in the range of 45~1029 inds./10 cm², which was similar to the previous studies conducted in the Yellow Sea. The density of meiobenthos according to the seasons was 800±69 inds./10 cm² in autumn, the highest, and the lowest at 260±48 inds./10 cm² in summer. A total of 19 taxa appeared in meiobenthos, and the average value showed the number of nine taxa. Among the appearing taxa, the most dominant taxon was nematodes, accounting for 80.8% of the total density, followed by benthic copepods (8.8%) and benthic foraminifers (4.7%). As for the size distribution of medium benthic animals, the density of organisms corresponding to the size of 63~125 ㎛ was the highest, and 1~0.5 mm was the lowest. As for the vertical distribution in the sediments of medium benthic animals, the habitat density gradually decreased as the depth increased in the sediment surface layer. As a result of analysis of the N/C ratio, MPI, and ITD index using medium-sized benthic animals to identify the benthic environment, there were differences by season, but no values indicating pollution overall.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.335-340
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• 2010

The paper describes the objectives of Yellow Sea Large Marine Ecosystem (YSLME) project, focusing on procedural and practical aspects. YSLME is a highly productive sea yet possibly one of the most impacted large marine ecosystems, in terms of anthropogenic stressors, due the enormous coastal population. The aim of the YSLME project is the reduction of ecosystem stress through identification of the environmental problems in the Transboundary Diagnostic Analysis (TDA) that are then addressed in the Strategic Action Programme (SAP). One of the major problems found to be affecting biological diversity is habitat modification through wetland reclamation, conversion and degradation. Since the early 1900's more than 40% of intertidal wetlands have been reclaimed in Korea, and 60% of Chinese coastal wetlands have been converted or reclaimed. Damaging fishing practices, pollution and coastal eutrophication have further degraded the coastal environment reducing the biological diversity. To combat this loss, the YSLME project has mounted a public awareness campaign to raise environmental consciousness targeted at all different levels of society, from politicians at parliamentary workshops, local government officer training events, scientific conferences and involvement of scientists in the project research and reporting, to university and high school students in our visiting internship programmes and environmental camps. We have also built networks through the Yellow Sea Partnership and by liaising and working with other environmental organizations and NGOs. NGO's are recognised as important partners in the environmental conservation as they already have extensive local networks that can be lacking in international organisations. Effective links have been built with many of these NGOs through the small grants programme. Working with WWF's YSESP project and other academic and research institutions we have conducted our own biodiversity assessments that have contributed to the science-based development of the SAP for the YSLME. Our regional targets for biodiversity outlined in the SAP include: Improvements in the densities, distributions and genetic diversity of current populations of all living organisms including endangered and endemic species; Maintenance of habitats according to standards and regulations of 2007; and a reduction in the risk of introduced species. Endorsement of the SAP and its successful implementation, during the proposed second phase of the YSLEM project, will ensure that biological diversity is here to benefit future generations.

• 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.

• 한국해양학회지
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• v.30 no.5
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• pp.480-492
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• 1995

Petrographic investigation has been carried out to determine the composition of the beach sediments and the affecting factors which have controlled their compositional variations from Hyupjae, Aeweol, Iho, Samyang, Hamdeok, Sehwa, Pyoseon, Jungmun, and Hwasun areas along the coast of the Cheju Island. Average mean sizes of the beach sediments are Hyupjae 2.2ø, Aeweol 0.8ø, Iho 1.4ø, Samyang 2.4ø, Hamdeok 1.6ø, Sehwa 1.5ø, Pyoseon 2.1ø, Jungmun 0.4ø, and Hwasun 0.9ø, thus, aries from 0.4 to 2.4ø. The beach sediments from Pyoseon and Hwasun areas are poorly sorted, those from Aeweol and Jungmun areas are moderately sorted and those from the rest of the areas are moderately well sorted. While-colored beach sediments in Hyupjae, Aeweol, Hamdeok, Sehwa, and Pyoseon areas are mostly composed of calcareous shells (more than 85%) such as mollusk, red algae, benthic foraminiferas, etc., whereas volcanic rock fragment is the dominant component of the black-colored beach sediments in Iho, Samyang, and Hwasun areas. Especially, the relatively white-colored beach sediment in Jungmun area, which is on e of the carbonate-dominant areas, shows a higher content of rock fragments than the other carbonate-dominant areas. The beach sediments in Pyoseon area show a high content of carbonate intercalates. Considering the contributions by organisms according to grain size, grains with the size range of 1∼2ø are mostly composed of calcareous red algae fragments, and grains with the size range of 2∼3ø consist of mollusk fragments. It is also notable that bryozoan fragments comprise about 48% of the sediment in Samyang area with the size range of 0∼1ø. The composition of the beach sediments in Cheju Island appears o be controlled by the riverine supply rate of volcanic rock fragments, the lithology of the rocks distributed ear the beaches, the direction of alongshore currents, and the direction of storms, etc.. It is suggested that the beach sediments in Iho and Samyang areas show black color because of the higher supply rate of the volcanic rock fragments from the nearby rivers, whereas those in the rest of the areas show white color due to the relatively lower content of volcanic rock fragments and higher content of carbonate components transported from shallow marine environment. In Hwasun area, the content of volcanic rock fragments is high, and they are directly from the tuffaceous rocks distributed nearby. Also, the volcanic rock fragments in Jungmun area are transported not only from the rivers nearby but also from the nearby tuffs by storm activities. The beach sediment in Pyoseon area contains a high content of carbonate intercalates, which formed in the nearby shallow marine environment through marine cementation. This indicates that active marine cementation occurs in shallow marine environment near Pyoseon area.

• Journal of Marine Life Science
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• v.8 no.2
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• pp.104-114
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• 2023

As plastic usage increases globally, the amount of plastic waste entering the marine environment is steadily rising. Microplastics, in particular, can be ingested by marine organisms and accumulated in their digestive tracts, causing harmful effects on their growth and reproduction. Cytochrome P450 (CYP) enzymes are known to metabolize various environmental pollutants as detoxification enzymes, but their role in crustaceans is not well understood. In this study, sequences of nine CYP genes (CYP370A4, CYP370C5 from clan 2; CYP350A1, CYP350C5, CYP361A1 from clan 3; CYP4AN-like, CYP4AP2, CYP4AP3, CYP4C33-like1 from clan 4) were analyzed using conserved domains in the brackish water flea Diaphanosoma celebensis. Additionally, after exposure to three different sizes of polystyrene beads (0.05-, 0.5-, 6-㎛ PS beads; 0.1, 1, and 10 mg/L) for 48 hours, the expression of these nine CYP genes were investigated using real-time reverse transcription polymerase chain reaction (RT-PCR). The results showed that all CYP genes possessed conserved motifs, indicating that D. celebensis CYP has evolutionarily conserved functions. Among these CYP genes, the expression of CYP370C5, CYP360A1, and CYP4C122 showed a significant increase after exposure to 0.05-㎛ PS beads, suggesting their involvement in PS metabolism. This research will contribute to understanding the molecular mode of actions of microplastics on marine invertebrates.

• Journal of Environmental Science International
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• v.24 no.5
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• pp.623-631
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• 2015

Microarray technology provides a unique tool for the determination of gene expression at the level of messenger RNA (mRNA). This study, the mRNA expression profiles provide insight into the mechanism of action of cadmium in Fleshy shrimp (Fenneropenaeus chinensis). The ability of genomic technologies was contributed decisively to development of new molecular biomarkers and to the determination of new possible gene targets. Also, it can be approach for monitoring of trace metal using oligo-chip microarray-based in potential model marine user level organisms. 15K oligo-chip for F. chinensis that include mostly unique sets of genes from cDNA sequences was developed. A total of 13,971 spots (1,181 mRNAs up- regulated and 996 down regulated) were identified to be significantly expressed on microarray by hierarchical clustering of genes after exposure to cadmium for different conditions (Cd24-5000 and Cd48-1000). Most of the changes of mRNA expression were observed at the long time and low concentration exposure of Cd48-1000. But, gene ontology analysis (GO annotation) were no significant different between experiments groups. It was observed that mRNA expression of main genes involved in metabolism, cell component, molecular binding and catalytic function. It was suggested that cadmium inhibited metabolism and growth of F. chinensis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.1
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• pp.56-62
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• 2009

Feeding regimens was investigated for the growth and survival rate of juvenile Maroon clownfish (Premnas biaculeatus) in order to establish a seed production technique for this fish. Three types of feeding regimens were used, and growth and survival were highest under the following regimen: rotifer from day 0, Artemia from day 4, copepod from day 9 and artificial food from day 15, respectively (P<0.05). The average body lengths of the larvae were $6.76{\pm}0.55\;mm$, $7.63{\pm}0.50\;mm$ and $7.33{\pm}0.43\;mm$ in the Nannochloropsis oculata, Isochrysis galbana and control treatments conducted with 3 larvae/L, respectively (P<0.05). There were significant differences in larval growth between the treatments and controls conducted with 6 larvae/L and 9 larvae/L, respectively (P<0.05) but there was no significant difference between the N. oculata and I. galbana treatments (P>0.05). There were no significant differences in larval growth between the treatments at densities of 3-9 larvae/L (P>0.05). At highest density level, the larvae reared in I. galbana had the highest survival rate whereas survival was lowest in the control.

• Journal of the korean society of oceanography
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• v.32 no.1
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• pp.28-37
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• 1997

Two marine bivalve shells were collected from the eastern and western coastal regions of Korea, respectively. Stable oxygen and carbon isotope profiles are constructed using the incremental sampling along the axis of maximum growth to provide the continuous ${\delta}^{18}$O and ${\delta}^{13}$C records, which register the physical, biological and chemical properties of seawater where the organisms live. Cycles in the ${\delta}^{18}$O profiles are interpreted as annual along with the identification of annual growth bands; the maximum ${\delta}^{18}$O values correspond with the coldest temperature of seawater whereas the minimum ${\delta}^{18}$O values with the warmest temperature. The primary control on the amplitude of the ${\delta}^{18}$O profiles is seasonal variation of seawater temperature. The offset of the baseline between ${\delta}^{18}$O values of the two specimens is attributed to differences in both temperature and seawater ${\delta}^{18}$O values between two localities. The ${\delta}^{13}$C profiles show the similar seasonality of carbon cycling associated with phytoplankton productivity. The offset in the ${\delta}^{13}$C profiles between two specimens may be, as in the case of oxygen isotope profile, attributed to the different ${\delta}^{13}$C value of the seawater DIC (dissolved inorganic carbon) between the western coast and the eastern coast. Relationships between the shell isotopic composition and the coastal water properties of shell growth are readily interpreted from the ${\delta}^{18}$O-${\delta}^{13}$C pair diagram of the shell isotope data, similar to the use of salinity-${\delta}^{18}$O diagram for identifying water masses. The preliminary stable isotope results of this study suggest that mollusk shell isotope geochemistry may be useful to monitor the properties of water masses in the coastal and inner shelf setting around Korea and improve the interpretation of paleoceanography, provided the fossil mollusks are well preserved.

• Ocean Science Journal
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• v.42 no.1
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• pp.31-39
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• 2007

Distributional characteristics of dinoflagellate cysts in surface sediments were investigated in relation to environmental factors in the eastern part of Geoje Island, Korea. Samples were collected from 10 stations in February of 2004 and water temperature and salinity were measured in February, May, September and November of 2004. Total 30 taxa of dinoflagellate cysts were identified representing 19 genera, 28 species and 2 unidentified species. Among these dinoflagellate cysts, Brigantedinium spp. of which relative proportion in th e total dinoflagellate cysts was 23.5%, was the most abundant at all stations except St. 1, and was followed by Spiniferites bulloideus (8.6%), Lingulodinium machaerophorum (8.2%) and Diplopsalis lenticula (6.7%). In addition, ellipsoidal cysts of the genus Alexandrium (Alexandrium catenella - tamarense type) and Gymnodinium catenatum, known to be causative organisms for PSP, occurred with high concentrations. Scrippsiella trochoidea was also found; however, its cyst concentration was low. Generally, species composition in the study area was similar to these reported from Jinhae Bay and Busan Harbor and several dinoflagellate cysts reflected the eutrophic condition. Cyst distribution in th e eastern part of Geoje Island seems to be influenced by the Tsushima Warm Current flowing from the southwest. The mean water temperature was $12.0^{\circ}C$ in February, $14.7^{\circ}C$ in May, $20.9^{\circ}C$ in September and $17.2^{\circ}C$ in November, which was most favorable for Alexandrium spp. growth. The abundances of dinoflagellate cysts rang e d from 528 to 2,834 cysts/g dry sediment. Higher concentrations were recognized in sediments of west area of the Jisimdo than at other stations. The cyst composition of this area was closely related to these of Jinhae Bay and Busan Harbor from which currents flow into this area. Higher cyst concentration in the west area of Jisimdo might be due to formation of the gyre.

• Korean Journal of Microbiology
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• v.41 no.3
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• pp.157-163
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• 2005

The acetate kinase gene from the copepod Paracyclopina nana was cloned. The open reading frame (ORF) was 1,200 bp, and poly(A) signal sequence was located in the end of the ORF. After the molecular phylogenetic analysis of P nana acetate kinase gene, it was revealed that it formed the same branch with that of Aspergillus. Also P. nana acetate kinase showed the difference with those of other prokaryotic microorganisms but showed the same clade with those of fungi. We also confirmed that the recombinant protein of P. nana acetate kinase made approximately 50 kDa after expression of recombinant gene construct in E. coli. This may be useful to compare this protein to those of other organisms in biochemical characteristics.