• The Korean Journal of Malacology
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• v.27 no.1
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• pp.29-33
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• 2011

This study was conducted to investigate the recruitment pattern of sessile organisms on the artificial substrates of PVC in Jangmok Bay, Geoje Island, southern coast of Korea. Five PVC plates were submerged from March to October, 2007 at one month interval, and two plates were retrieved after one month. The dominant recruiters were a green algae, Entermorpha prolifera in March, Mytilus galloprovincialis in April, M. galloprovincialis and Styela plicata in May, S. plicata and Bugula sp. in June. During August, Balanus amphtrite and anthozoans were dominant recruiters, and a serpulid worm, Hydroides ezoensis in October. There was a clear specific recruiting period of sessile faunas depending on their reproduction cycles in a sheltered embayment like Jangmok Bay.

• Ocean and Polar Research
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• v.33 no.3
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• pp.235-253
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• 2011

The annual variation of mesozooplankton community in the Jangmok harbor of Jinhae Bay was studied in relation to environmental variables. Sampling was carried out weekly from January to December 2009. During the study periods, mesozooplankton community consisted of 44 taxa and the annual mean abundance was 8308 inds. $m^{-3}$. The maximum abundance was observed to be 50043 inds. $m^{-3}$ in August and the minimum in April with 1013 inds. $m^{-3}$. Of these, Penilia avirostris, cirripedia larvae, Evadne tergestina, Acartia omorii, Oikopleura s, Paracalanus parvus s. l., Eurytemora pacifica, Podon s, Oithona s, and Acartia steueri were observed as dominant species in Jangmok bay and they also contributed to 79% of total mesozooplankton. According to non-metric multidimensional scaling (nMDS) and cluster analysis based on the mesozooplankton community data from each season, the community was divided into three groups. The first group included appearence species in winter and spring season, which is mainly dominated the copepod such as A. omorii and E. pacifica. The second and third group was composed with observed species in summer and autumn, respectively. Based on the SIMPER (similarity percentages), P. avirostris in summer and cirripedia larvae in autumn were significantly dominated. Our results indicate that although the mesozooplankton abundances in Jangmok harbor fluctuated abruptly, its annual variation was strongly influenced by water temperature.

• Korean Journal of Environmental Biology
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• v.34 no.3
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• pp.141-150
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• 2016

Most previous studies on dinoflagellates in Korean coastal areas were conducted without morphological descriptions and illustrations of the observed dinoflagellates. This indicates that the species and diversity of dinoflagellates may have been respectively misidentified and underestimated in the past, probably due to cell shrinkage, distortion and loss caused by sample fixation. This study provides information on the morphological observations of four dinoflagellate orders (Prorocentrales, Dinophysiales, Gonyaulacales and Gymnodiniales) from Jangmok Harbour in Jinhae Bay, Korea. The unfixed samples were collected weekly from December 2013 to February 2015. A total of 13 genera and 30 species were identified using light and scanning electron microscopy, although some samples were not clarified at the species level. Harmful dinoflagellates, Prorocentrum donghaiense, Tripos furca, Alexandrium affine, A. fundyense, Akashiwo sanguinea and Cochlodinium polykrikoides, were identified based on the morphological observations. The results also reflect the occurrence and identification of dinoflagellates that had not been previously recorded in Jangmok Harbour.

• Ocean and Polar Research
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• v.32 no.1
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• pp.41-52
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• 2010

Daily samples were collected during summer in order to analyse changes in the mesozooplankton community and to identify the major environmental factors that may influence mesozooplankton abundance in Jangmok Bay. A single site in the bay was sampled 47 times from July to September 2003. Mesozooplankton community, hydrographic (watertemperature, salinity, dissolvedoxygen) and biological (chlorophyll-a, ciliates densities, Noctiluca scintillans densities) factors were determined. The mesozooplankton abundance varied remarkably from 954 to $14,816\;inds.\;m^{-3}$. The six taxa of Evadne tergestina, barnacle nauplii and cypris, Paracalanus parvus s.1., Acartia omorii, Penilia avirostris and Sagitta crassa dominated numerically, contributing 86% of total mesozooplankton abundance. Stepwise multiple linear regression analysis was applied to find correlation between environmental factors and fluctuation in the abundance of dominant species and mesozooplankton. A. omorii was significantly correlated with temperature and N. scintillans densities. E. tergestina was correlated with temperature, salinity, and ciliate densities, whereas P. avirostris was correlated with temperature and dissolved oxygen. Among the environmental factors, mesozooplankton abundance correlated most strongly with N. scintillans densities. Accordingly, N. scintillans may be a key player in controlling the fluctuation of mesozooplankton abundance as a strong competitor for same food resources.

• Ocean Science Journal
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• v.40 no.3
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• pp.109-117
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• 2005

Daily changes in phytoplankton abundance and species composition were monitored from July to September 2003 (n=47) to understand which factors control the abundance at a station in Jangmok Bay. During the study, the phytoplankton community was mainly composed of small cell diatoms and dinoflagellates, and the dominant genera were Chaetoceros, Nitzschia, Skeletonema and Thalassionema. Phytoplankton abundance varied significantly from $6.40{\times}10^4$ to $1.22{\times}10^7$ cells/l. The initially high level of phytoplankton abundance was dominated by diatoms, but replacement by dinoflagellates started when the NIP ratio decreased to <5.0. On the basis of the N/P and Si/N ratios, the sampling periofd could be divided into two: an inorganic silicate limitation period (ISLP, $14^{th}$ $July-12^{th}$ of August) and an inorganic nitrogen limitation period (INLP, $13^{th}$ of August - the end of the study). Phosphate might not limit the growth of phytoplankton assemblages in the bay during the study period. This study suggests that phytoplankton abundance and species composition might be affected by the concentrations of inorganic nutrients (N and Si), and provides baseline information for further studies on plankton dynamics in Jangmok Bay.

• Journal of Environmental Science International
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• v.19 no.5
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• pp.607-615
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• 2010

We investigated the temporal variations of heterotrophic dinoflagellates (hereafter HDNF) and photosynthetic dinoflagellates (hereafter PDNF) from 14 June to 4 September 2003 at a single station in Jangmok Bay. We took water samples 47 times from 2 depths (surface and bottom layers) at hide tide. A total of 63 species were encountered and in general the most abundant genera were Prorocentrum and Protoperidinium. The abundance of PDNF and HDNF was in the range of $0.04{\sim}55.8{\times}10^4$ cells/L and in the range of $0.01{\sim}4.35{\times}10^4$ cells/L, respectively. The mean abundance of PDNF was approximately 7 times higher than that of HDNF, and was higher in the surface layer where has enough irradiance for photosynthesis than in the bottom layer. The total dinoflagellate abundance was higher in the NLP (nitrogen limitation period) than in the SLP (silicate limitation period), and the abundance in the hypoxic conditions was similar to that in the normal conditions. The Shannon-Weaver species diversity index were slightly higher in the bottom layer, the SLP and the hypoxic conditions. The PDNF abundance were correlated with temperature, DO, total inorganic nitrogen and phosphate in the whole water column, and the HDNF abundance was significantly correlated with temperature, salinity and DO. This study shows that the dinoflagellate abundance might be affected by abiotic factors such as irradiance, temperature, salinity, DO and the concentrations of inorganic nutrients, and provides baseline information for further studies on plankton dynamics in Jangmok Bay.

• Ocean and Polar Research
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• v.30 no.4
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• pp.419-426
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• 2008

Ciliate plankton samples were collected biweekly from July 2006 to June 2008 in Jangmok Bay of Geoje Island. Species composition and abundances were analyzed by quantitative protargol stain and environmental parameters were also examined. A total of 88 ciliate species occurred during the study period, consisting of 22 tintinnids, 51 oligotrichs, and 15 other species. Higher ciliate abundances appeared from June to October during the warm season ($<20^{\circ}C$) and the maximum ($4.0{\times}10^4\;cells\;L^1$) in August, while the lower abundances were found during the cold season. The minimun ciliate abundance was found in November when water temperature rapidly decreased. The temporal succession of dominant species was very clear and opportunistic. Pelagostrombidium sp., Tontonia simplicidens, Helicostomella subulata, and Myrionecta rubra were co-dominant in summer while Rimostrombidium orientale occurred abundantly in winter. Strombidium tressum and S. compressum, eurythermal species, were observed during all seasons. Based on the species-specific ecology of ciliate plankton, it is suggested that the indicative ciliate species can be applied as a biological tool to detect environmental change in the southern coastal waters of korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.9-15
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• 2016

We investigated >$50-{\mu}m$ marine planktonic organisms (mainly zooplankton) using a bongo net in Masan Bay and Jangmok Bay in order to harvest 75% of natural communities based on Phase-II approval regulations by the United States Coast Guard (USCG). The concentrated volume (in 1 ton) and abundance of zooplankton were $1.8{\times}10^7ind.ton^{-1}$ and $2.3{\times}10^7ind.ton^{-1}$, and their survival rates were 82.6% and 80.1%, respectively. The community structure in Jangmok Bay was similar to that in Masan Bay, and dominant species were adult and immature groups (stage IV) of genus Acartia. Harvested populations were inoculated in a 500-ton test tank. Although the population abundances were $6.0{\times}10^4ind.ton^{-1}$ for both bay samples, the mortality rates were higher in the Masan Bay population (32%) than the Jangmok Bay population (20%). We considered the reason to be that there were 30% more immature individuals of Acartia from Masan Bay than from Jangmok Bay. The younger population may have been greatly stressed by the moving process and netting gear. After applying a Ballast Water Treatment System (BWTS) using a sample form Jangmok Bay, the mortality rates in the treatment groups were found to be 100% after 0 days and 5 days, implying that the BWTS worked well. During the winter season, the zooplankton concentration method alone did not easily satisfy the approval standards of USCG Phase II (> $10{\times}10^4ind.ton^{-1}$ in the 500 ton tank). Increasing the netting frequency and additional fishing boats may be helpful in meeting the USCG Phase II biological criteria.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.483-489
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• 2016

The type approval test for USCG Phase II must be satisfied such that living natural biota occupy more than 75 % of whole biota in a test tank. Thus, we harvested a community of natural organisms using a net at Masan Bay (eutrophic) and Jangmok Bay (mesotrophic) during winter season to meet this guideline. Furthermore, cell viability was measured to determine the mortality rate. Based on the organism concentration volume (1 ton) at Masan and Jangmok Bay, abundance of ${\geq}10$ and $<50{\mu}m$ sized organisms was observed to be $4.7{\times}10^4cells\;mL^{-1}$and $0.8{\times}10^4cells\;mL^{-1}$, and their survival rates were 90.4 % and 88.0 %, respectively. In particular, chain-forming small diatoms such as Skeletonema costatum-like species were abundant at Jangmok Bay, while small flagellate ($<10{\mu}m$) and non chain-forming large dinoflagellates, such as Akashiwo sanguinea and Heterocapsa triquetra, were abundant at Masan Bay. Due to the size-difference of the dominant species, concentration efficiency was higher at Jangmok Bay than at Masan Bay. The mortality rate in samples treated by Ballast Water Treatment System (BWMS) (Day 0) was a little lower for samples from Jangmok Bay than from Masan Bay, with values of 90.4% and 93%, respectively. After 5 days, the mortality rates in control and treatment group were found to be 6.7% and >99%, respectively. Consequently, the phytoplankton concentration method alone did not easily satisfy the type approval standards of USCG Phase II ($>1.0{\times}10^3cells\;mL^{-1}$ in 500-ton tank) during winter season, and alternative options such as mass culture and/or harvesting system using natural phytoplankton communities may be helpful in meeting USCG Phase II biological criteria.

• Ocean and Polar Research
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• v.32 no.2
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• pp.97-111
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• 2010

Phytoplankton production is affected by various physico-chemical factors of environment. However, one of the most critical factors generally accepted as controlling primary production of phytoplankton is nutrients. It has recently been found that the succession of phytoplankton groups and species are closely related to the chemical properties of ambient water including nutrient limitation and their ratios. In Jangmok Bay, silicate and nitrate are primarily supplied by rainfall, while phosphate and ammonia are supplied by wind stress. Typhoons are associated with rainfall and strong wind stress, and when typhoons pass through the South Sea, such events may induce phytoplankton blooms. When nutrients were supplied by heavy rainfalls during the rainy season and by summer typhoons in Jangmok Bay, the dominant taxa among the phytoplankton groups were found to change successively with time. The dominant taxon was changed from diatoms to flagellates immediately after the episodic seasonal events, but returned to diatoms within 3~10 days. Pseudo-nitzschia spp. were dominant mainly in the presence of low phosphate levels during the first of the survey which included the rainy season, while Skeletonema costatum was dominant when phosphate concentrations were high due to the strong wind stress during the latter half of the survey as a result of the typhoon. The competition between S. costatum and Chaetoceros spp. appeared to be regulated by the silicate concentration. S. costatum preferred high silicate and phosphate concentrations; however, Chaetoceros spp. were able to endure low silicate concentrations. These results implied that, in coastal ecosystems, the input patterns of each nutrient supplied by rainfall and/or wind stress appeared to contribute to the summer succession of phytoplankton groups and species.