• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.140-147
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• 2002

We investigated the temporal variations in the heterotrophic dinoflagellates (hereafter HTD), tintinnid ciliates(TC), and naked ciliates(NC) from August to November 1999 in the coastal waters off the southern Saemankeum areas where a huge red tide dominated by Cochlodinium polykrikoides/Gymnodinium impudicum was first observed in 1998. We took water samples from 2-5 depths of 4 stations in each of the 5 cruises and then measured the species composition and abundances of HTD, TC, and NC The maximum species numbers and densities of HTD, TC, and NC(11, 12, and 10 cells $m\ell$$^{-1}$ , respectively) were observed when the density of diatoms was highest (August 10), while the lowest values (1.0, 0.5, and 2.4 cells $m\ell$$^{-1}$ , respectively) were found when the red tide dominated by C. polykrikoides/G. impudicum took placed (October 18). On August 10 and November 11 when diatoms dominated the abundance of phytoplankton, the correlation coefficients between TC, NC and diatoms were relatively high. However, On September 16 and October 18 when autotrophic+mixotrophic dinoflagellates(ATD+MTD) were abundant, the correlation coefficients between HTD and ATD+MTD were relatively high. The large HTD Noctiluca scintillans was the most dominant heterotrophic protists during the C. polykrikoides/G. impudicum red tide on October 18. N. scintillans has been known to feed on the prey cells when the swimming speeds of C. polykrikikoides/G. impudicum markedly reduced at the decline stage of the red tide. Therefore, N. scintillans could be effective grazers on C. polykrikoides/G. impudicum. The maximum densities of HTD, TC, and NC in the study area were fairly lower than those obtained in the waters off Kohung-Yeosu areas in the summer-fall, 1997. The results of the present study provide the basis of understanding predator-prey relationships between dominant phytoplankton and heterotrophic protists and the roles of the protist grazers in bloom dynamics in the waters off the western Korea.

• Fisheries and Aquatic Sciences
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• v.26 no.12
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• pp.738-751
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• 2023

The Sembilan Archipelago is famous for its great biodiversity, in which the humphead wrasse (Cheilinus undulatus) (locally named Napoleon fish) is the primary commodity (economically important), and currently, the environmental degradation occurs due to anthropogenic activities. This study aimed to examine the eco-environmental parameters and assess their influence on the abundance of humphead wrasse and other coral reef fish compositions in the Sembilan Archipelago. Direct field monitoring was performed using a visual census throughout an approximately one km transect. Coral cover data collection and assessment were also carried out. A coastal water quality index (CWQI) was used to assess the water quality status. Furthermore, statistical-based analyses [hierarchical clustering, Pearson's correlation, principal component analysis (PCA), and canonical correspondence analysis (CCA)] were performed to examine the correlation between eco-environmental parameters. The Napoleon fish was only found at stations 1 and 2, with a density of about 3.8 Ind/ha, aligning with the dominant composition of the family Serranidae (covering more than 15% of the total community) and coinciding with the higher coral mortality and lower reef fish abundance. The coral reef conditions were generally ideal for supporting marine life, with a living coral percentage of about > 50% in all stations. Based on CWQI, the study area is categorized as good and excellent water quality. Of the 60 parameter values examined, the phytoplankton abundance, Napoleon fish, and temperature are highly correlated, with a correlation coefficient value greater than 0.7, and statistically significant (F < 0.05). Although the adaptation of reef fish to water quality parameters varies greatly, the most influential parameters in shaping their composition in the study area are living corals, nitrites, ammonia, larval abundance, and temperature.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.2
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• pp.319-344
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• 2015

A seasonal characteristic of marine environment and fish assemblages in the coastal waters of Jeju Island were determined using samples collected by a trammel net in from 2012 to 2013. Annual mean temperature and salinity were $18.8^{\circ}C$, 33.7psu (2012) and $18.8^{\circ}C$, 33.8psu (2013) which shows stable water mass. nutrient concentrations represent that dissolved inorganic nitrogen (DIN) ranged from 0.030 to 0.217mg/L, dissolved inorganic phosphorus (DIP) from 0.002 to 0.010mg/L, and silicate ($SiO_2$) from 0.096 to 0.292mg/L. Chlorophyll a concentrations of phytoplankton ranged from 0.905 to $1.125{\mu}g/L$ were appeared the highest in summer and the lowest in winter. Suspended Solid(SS) concentrations ranged from 1.200 to 2.100mg/L (mean, 1.634mg/L) were appeared the highest in autumn and the lowest in spring. During the survey period, a total of 83 species (48 families and 12 orders) of fishes were identified, Perciformes and Scorpaeniformes accounted for 63.9% of the total number. The number of species was higher in summer than in winter, showing a peak in summer at 57 species and a low in winter at 47 species. The number of individuals and the biomass peaked in summer at 694 individuals and 151.9kg, and were the lowest in autumn at 466 individuals and 106.5kg. The diversity index, evenness index and richness index were appeared 2.92~3.14, 0.75~0.83 and 7.06~8.56 at each stations. the dominance index were appeared highest in spring and summer, were appeared the lowest in winter and autumn. The Filefish (Stephanolepis cirrhifer), Bluestriped angelfish (Chaetodontoplus septentrionalis), Marbled rockfish (Sebastiscus marmoratus), Rabbit fish (Siganus fuscescens), Blackfin sweeper (Pempheris japonica) were dominant species, which occurred abundantly during the entire survey period. The subtropical fishes were identified total of 41 species (49.4%) and the number of species was higher in summer at 29 (50.9%) species and a low in winter at 20 (42.6%) species. The dominant species of subtropical fishes were appeared Bluestriped angelfish, Blackfin sweeper, Rabbit fish, Scarbreast tuskfish (Choerodon azurio), Ballonfish (Diodon holocanthus), Flagfish (Goniistius zonatus), Blue-spotted boxfish (Ostracion immaculatus) in study sites. The subtropical fishes of species, individual and biomass showed significant correlation with environmental factors (Chlorophyll a, DIN, DIP, $SiO_2$) in almost all sampling sites.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5206-5210
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• 2012

We studied the effect of food concentration on grazing, growth and fecundity of cyclopoid copepod Paracyclopina nana. Marine phytoplankton Tetraselmis suecica was used as a livefood for the copepod. Six stage compositions were used and food concentrations for the experiment were 0.5, 1, 2, 5, 10, 20, 40, 60 and $80{\times}10^4$ cells/mL. Range of food concentrations with 0.2, 0.5, 1, 2, 3 and $4{\times}10^4$ cells/mL were used for nauplii production experiment. Grazing rates of P. nana in all developmental stages on the different concentrations were increased with increasing diet concentration. While the growth of nauplius was not affected by increase of food concentration, food concentration outside of $1{\times}10^4$ to $5{\times}10^4$ cells/mL range negatively affected that of copepodite. Daily nauplii production was increased with increasing food concentration but $3{\times}10^4$ and $4{\times}10^4$ cells/mL treatments were not significantly different with $2{\times}10^4$ cells/mL treatment. As a result, optimum concentration of T. suecica for mass culture of P. nana was considered to be 5,000 cells/mL for nauplius stage, 10,000 cells/mL for copepodite stage and adult male, 20,000 cells/mL for adult female, respectively.

• Korean Journal of Environmental Biology
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• v.28 no.4
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• pp.202-211
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• 2010

The variations of physico-chemical factors and the species compositions of phytoplanktons were investigated to analyze the marine ecosystem at the depths during summer in the coast of Dokdo (stations DOK 1-3). The mean values of conductivity (48.9 mS $cm^{-1}$), salinity (32.9 psu) and total suspended solids (57.9 mg $L^{-1}$) were the highest in DOK 1. The biomass (Chl-a) of phytoplanktons was the highest in the surface of DOK 1 (2.61 ${\mu}gL^{-1}$). By the means of physicochemical factors (salinity, turbidity, Chl-a, TN, TP and Si), the water estimated in the coast of Dokdo was more eutrophicated than that in 2008. The phytoplanktons were a total of 42 species in Dokdo, which were composed of 33 species (78.6%) for Bacillariophyceae and 9 species (21.4%) for Dinophyceae. The standing crops of phytoplanktons were the highest ($18{\times}10^3$ cells $L^{-1}$) in the surface of DOK 2 and in the surface of DOK 3, while they were the lowest ($2{\times}10^3$ cells $L^{-1}$) at depth of 40 m of DOK1 and at depth of 30 m of DOK 3. The dominant species of phytoplanktons were Chaetoceros castracanei ($6{\times}10^3$ cells $L^{-1}$) in the surface, Rhizosolenia alata f. gracillima ($3{\times}10^3$ cells $L^{-1}$) at depth of 20 m and Protocentrum compressum ($4{\times}10^3$ cells $L^{-1}$) at the depth of 30 m of DOK 1. At the surface of DOK 2, the dominant species was Bacillaria paxillifer ($6{\times}10^3$ cells $L^{-1}$), while it was Hemiaulus indicus ($12{\times}10^3$ cells $L^{-1}$) at the surface of DOK 3. The DOK 1, which is affected by upwelling, whirlpool and circulation due to the East Korean Warm Current, was the most eutrophicated water body among three stations. The monitoring of marine ecosystem in the coast of Dokdo should be continued to propose the alternatives for water quality and species conservation and to purify the eutrophicated water body due to artificial pollutants as well as natural effectors by the global warming, the climatic change, etc.

• Ocean and Polar Research
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• v.30 no.3
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• pp.303-312
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• 2008

Despite the impacts of the climate changes on the pelagic ecosystem, few studies have examined the pelagic-benthic coupling in the adjacent East China Sea and Korea Strait. Therefore, the species composition and abundance of the macrobenthic community, as well as the potential food sources of benthic fauna were investigated in the present study using stable isotope analysis (${\delta}^{13}C\;and\;{\delta}^{15}N$) for suspended particulate organic matter (SPOM), sedimentary organic matter (SOM), phytoplankton, and zooplankton. A total of 157 macrobenthic fauna were collected, and the density of the macrobenthic fauna ranged from 4 to 434 ind./0.25 $m^2$, with an average density of 149 ind./0.25 $m^2$. The density of the benthic fauna increased moving from offshore shelf sites to coastal sites adjacent to the Korea Strait. Cluster analysis showed that the macrobenthic communities consisted of three distinct groups: group A in the Korea Strait, group B in the East China Sea, and group C near Ieodo. The dominant species in group A were the amphipods Photis japonica and Ampelisca miharaensis, followed by the polychaete Scolotoma longifolia. Environmental variables, such as the temperature of the seawater and sediment, and oxygen, and chlorophyll a levels, appeared to affect the structure of the community, suggesting the importance of coupling with the pelagic system. The ${\delta}^{13}C$ values of SPOM and zooplankton ranged from -22.97 to -23.5% and -19.92 to -21.86%, respectively, showing a relatively narrow range(<1%) between the two components. The difference between the ${\delta}^{13}C$ values of SOM and pelagic organic matter was also within 1%, suggesting that the SOM originated from the pelagic system, which is an important factor controlling the macrobenthic community.

• Journal of Aquaculture
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• v.13 no.1
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• pp.39-46
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• 2000

Successive management of prawn farm is strongly dependent upon monitoring of pond seawater quality which is generally influenced by an excessive food supplied sediment type and phytoplankton composition in the pond. For good condition of seawater quality it must need exchangning of fresh seawater by tidal current. Two distinct shrimp ponds Galha and Yunho which were different in seawater exchanging system and sediment type were selected to understand how some factors affected to seawater and sediment qualities in the pond. Prawn growth was also determined. Galha pond characterized by sand bottom with water exchanging by turn of the tidal current accumulated 1.8 mgS/g-dry as sulfide in sediment while Yunho pond mud- bottomed with seawater exchanging of pumping system showed 4.7mgS/g-dry when it was highest, Ammonia-N and hydrogen sulfide measured in the seawater were 0.31mg/${\ell}$ and 21.2 ${\mu}$${\ell}$/${\ell}$in Yunho and 0.10mg/${\ell}$and 10.8${\mu}$${\ell}$/${\ell}$in Galha pond respectively. Dissolved oxygen remained below 6.0mg/${\ell}$ in Galha and 5.0mg/${\ell}$in Yunho pond from June through August. Less growth of prawn was found in Yunho pond than in Galha pond. Prawn growth expressed as body length and weight were 138.3mm 22.9g in Yunho pond while they were length 158.2mm and 28.9g in Galha pond respectively when they were harvested in October. These results indicate that higher levels of ammonia-N and hydrogen sulfide and lower dissolved oxygen in bottom seawater of Yunho pond might affect the growth of cultured prawn.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.59-69
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• 2003

As part of study on the microbial food web in the southern Jeju Island of Korea, Planktonic tintinnids and aloricate oligotrichs were investigated from July 1998 to June 2000 to understand seasonal variation and water mass indication with environmental factors. 39 species of tintinnids were identified representing 1 order, 11 families, 20 genera. Tintinnid abundance ranged from 100 to 5,400 cells.1$^{-1}$ (mean 314 cells.1$^{-1}$ ), and oceanic species were mainly dominant in fall and winter season, while neritic species were a little pre- dominant in spring and summer season. 15 species of aloricate oligotrichs were identified representing 1 order, 5 families, 7 genera, and many belonged to genus Strombidium which was most abundant and most frequently occurred in many months. Abundance of aloricate oligotrichs ranged from 140 to 21,000 cells.1$^{-1}$ (mean 2,356 cells.1$^{-1}$ ). Species diversity and standing crops of tintinnids were quite different according to seasons, but few seasonal variations were detected in aloricate oligotrichs. In terms of water mass indication tintinnids represented obvious characteristics which were affected by marine environmental factors, but alor- icate oligotrichs had no such apparent indication as tintinnids. Ciliates were more abundant and more diverse in inshore than in offshore station. Total carbon biomass of ciliates ranged from 0.01 to 136.06 $\mu\textrm{g}$C.1$^{-1}$ (mean 5.01 $\mu\textrm{g}$C.1$^{-1}$ ). The carbon biomass, however, did not coincided with seasonal variations of abun- dance Vertical profiles of mean abundance of both tintinnids and aloricate oligotrichs were similar, and had same trend as those of mean chlorophyll o concentration. It suggests that phytoplankton and ciliates reflected the prey-predator relationship in the study area.

• Journal of Environmental Health Sciences
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• v.45 no.5
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• pp.426-433
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• 2019

Objectives: Zooplankton communities play important roles in aquatic ecosystems as secondary producers that graze on phytoplankton and in turn are preyed upon by planktivorous and juvenile fish. They can shift their distribution, species composition, and abundance in response to environmental changes. Therefore zooplankton communities are important for understanding the energy flow in aquatic ecosystems and can be valuable indicators of environmental conditions. However, zooplankton in streams are still not well-studied, especially in northern Gyeonggi-do Province. This study aims to investigate the zooplankton communities in major streams in northern Gyeonggi-do Province. Methods: Zooplankton is important in the nutrient cycle and energy flow of aquatic ecosystems. Therefore, we surveyed zooplankton and measured temperature, DO, BOD, COD, T-N, T-P, and Chl-a in major streams (Sincheon, Gongneungcheon, Wangsukcheon, and Gapyeongcheon Streams) and stagnant water (Gomoji Reservoir). Results: The water quality in Gapyeongcheon Stream was the highest grade, while that of Gomoji Reservoir was mesoeutrophic and eutrophic during the research period. In the zooplankton community, Nauplius, Rotaria, and Monostyla spp. were dominant in Sincheon, Gongneungcheon, and Wangsukcheon Streams, and the dominance index was also high. In the case of Gapyeongcheon Stream, it was found that water quality and aquatic ecosystem health were good, and the lowest dominance index reflected this. In Gomoji Reservoir, Polyarthra spp., Nauplius, and Bosmina longirostris, which can be easily observed as eutrophication progresses, showed a high dominance rate. Therefore, it is necessary to monitor the progress of eutrophication in further research. Conclusions: We collected data on the zooplankton communities in streams and investigated their characteristics. As a result, specific species were found to be dominant at each survey sites and some of them are known to be observed as eutrophication progresses. Therefore, we should investigate the zooplankton community of streams around us and apply ecological stream management.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.4
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• pp.325-332
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• 2008

To characterize the initiation, propagation and termination of Cochlodinium polykrikoides blooms in the southeast coastal waters of Korea, 2007, we have analyzed the data set of phytoplankton composition, physical and chemical water properties, and meterological data. The development of C. polykrikoides bloom in 2007 can be summarized in three steps. The first stage from middle of July to end of August was characterized by an unusually persistent and strong southerly wind. C. polykrikoides blooms established already by the strong wind in the middle of south coastal waters were advected intermittently into the study area. Accordingly, highly variable cell densities of C. polykrikoides were observed. At the second stage a favorable growing conditions for C. polykrikoides was developed, which was directed by changes in wind direction from south to northeast and thus enhanced transportation of offshore waters into inshore (August 8 to 30). C. polykrikoides bloom occurred through typical mechanism and showed high cell density. The last stage was represented by disappearance of C. polykrikoides. Typoon 'Nari' carrying heavy rain brought an unfavorable habitat to C. polykrikoides. Low saline condition formed in coastal water due to typoon effects continuously drove the dominant species to diatoms and flagellates which were prevailing over C. polykrikoides in this circumstances(from the middle of September). These stepwise processes could be the causative mechanism of the extraordinarily persistent C. polykrikoides bloom observed in southeast coastal water of Korea, 2007.