• Journal of Environmental Science International
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• v.16 no.10
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• pp.1119-1125
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• 2007

We examined the horizontal distribution of salinity and the concentrations of DIN and DIP after heavy rain-fall events in coastal areas of South Korea from Yeoja Bay to Narodo and from Gwangyang Bay to Geomodo to determine whether fresh water actually flows into areas of Cochlodinium polykrikoides red tides and to observe its effect on the growth of this organism after heavy rainfall. Following heavy rainfall (155 mm) in the Yeosu and Suncheon regions, the average salinity was 21 and 29 psu at Yeoja Bay and in the coastal waters of Narodo, respectively. After 126 mm of rainfall, the values were 19 and 25 psu in the coastal waters of Yeosu and Geomodo, respectively. This may have been caused by an influx of fresh water, after the rainfall event, into the open sea coastal areas around Narodo and Geomodo from the Dong and Seomjin Rivers, which are about 3540 km away. After the rainfall, the concentrations of $NH_4-N,\;NO_2-N$, and $PO_4-P$ were slightly increased; however, the concentration of $NO_3-N$ was greatly increased and diffused throughout the coastal areas of Narodo and Geomodo, which frequently experience C. polykrikoides blooms. The influence of $NH_4-N,\;NO_2-N$, and $PO_4-P$ on the occurrence of C. polykrikoidesred tides in coastal areas around Narodo and Geomodo after heavy rainfall does not appear to be great. Instead, the occurrence C. polykrikoides red tides in the coastal areas of Narodo and Geomodo seems to be facilitated by $NO_3-N$.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.3
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• pp.113-123
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• 2008

We have analyzed a long term data of marine environments, red tide information and meteorology acquired by NFRDI and KMA, in order to understand the characteristics of marine environments in the Narodo coastal waters which is known to be the first outbreak region of Cochlodinium polykrikoides blooms. During the period of from 1992 to 2007, Cochlodinium polykrikoides blooms have first occurred more often in August. However, the outbreak time of the blooms tended to be earlier annually, and in addition, the surface salinity also had a tendency to increase. Consequently, it suggested that there might be a relationship between the transition of the outbreak time of the blooms and salinity. On the other hand, insolation was relatively rich but precipitation was relatively scarce in Gohung Province, compared to Yeosu or Tongyeong, when Cochlodinium polykrikoides blooms first occur in Narodo coastal waters. Average water temperature and salinity in August in Narodo coastal waters were all higher than those in Gamak and Jinhae bays, suggesting that Narodo coastal waters are a region of relatively high water temperature and high salinity. Also, concentrations of nutrients and chlorophyll- a were significantly low than those in Jinhae Bay, which is known to be a eutrophicated region, while the overall water quality seemed to be similar to Gamak Bay. The results of PCA(Principal Component Analysis) proved that insolation and water temperature are the most important factors for the outbreak of Cochlodinium polykrikoides blooms in Narodo coastal waters while concentrations of COD and dissolved oxygen are secondly important. Furthermore, typhoons also appeared to be one of most important factors for the outbreak of Cochlodinium polykrikoides blooms.

• Journal of the korean society of oceanography
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• v.37 no.4
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• pp.212-223
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• 2002

Cochlodinium polykrikoides bloom in 1995 was studied with a focus on an unusual coastal environment in the South Sea of Korea. Data on temperature, salinity, and zooplankton biomass during 1965-1998 and nutrients during 1990-1998 and chlorophyll-a during 1995-1998 were used in this study. These data were obtained from the serial oceanographic observations in Korean waters carried out by the National Fisheries Research and Development Institute. In 1995 the C. polykrikoides bloom began in the coastal area around Narodo Island in August and consequently occurred to the whole coastal area of the South and East Seas of Korea. During June-October 1995, the coastal environment was unusual compared with the long-term means during 1965-1998. In June 1995, sea surface temperature was 1-2$^{\circ}C$ warmer than in other years in all coastal areas, while salinity was high only to the east of Jeju Island. In August 1995, a strong coastal front appeared inshore of a line between Jeju and Tsushima Islands. In particular, a strong coastal front which showed the characteristics of upwelling front occurred in the coastal area around Narodo and Sorido Islands, not only because of a strong intrusion of the Tsushima Warm Current but also because of the upwelling of cold bottom water. Salinity was low in the neighboring waters of western side of Jeju Island. Nutrients and chlorophyll-a were high in the inshore area between Narodo and Sorido Islands in 1995 in contrast with the other years and areas. Zooplankton showed an unusually high abundance in the coastal area in October 1995. We conclude that the Tsushima Warm Current strongly influenced the South Sea of Korea in 1995 and created strong upwelling front bordering cold upwelled water in the coastal area around Narodo and Sorido Islands. It leads us that these physical structures introduce the favorable environment for the development of C. polykrikoides blooms. We suggest that C. polykrikoides has a bio-physical tolerance of high shear and stress and prefers frontal and upwelling relaxed areas as its habitat. We also find that nutrients were not supplied to the coastal area from the offshore where a low salinity water mass with high nutrients appeared around Jeju Island. Because the strong upwelling front protect the reach of offshore low saline water mass. The main source of nutrients was the upwelled water mass in the coastal area of Wando-Narodo-Sorido.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.5
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• pp.414-422
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• 2012

This study evaluated the effect of the inland pollution sources on the bacteriological water quality in Narodo area after rainfall events. Following 16 mm of rainfall, the water discharged from Dohwa Stream and contaminants from Balpo village had a very limited effect on bacteriological water quality in adjacent area and the affected area did not extend to the designated area. In comparion, after 33 mm of rainfall, the density of fecal coliforms at stations located in the mouth of Dohwa stream and the discharg point of contamination sources located in Balpo village were lower than after 16 mm of rainfall. These results were obtained during an extreme high tide near the coast the contaminants discharged from Dohwa stream and Balpo village. Therefore, it is necessary to conduct a detailed survey to examine the dffects of tides on the diffusion characteristics of the contaminants discharged from Dohwa stream and Balpo village in order to manage of Narodo area efficiently.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.1
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• pp.47-58
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• 1994

Field observation and numerical experiments with a two-dimensional depth-integrated model were undertaken in order to investigate some of the effects on the flow structure resulting from the construction of a bridge connecting Kohung Peninsula and the Narodo Islands on the southern coast of Korea. Tidal currents passing through the straits between the Narodo Islands showed that, although the phase lagged one hour behind that passing through the strait between Kohung Peninsula and Naenarodo Island, it still kept strong flows of more than 80cm/sec near the bottom. The seawater temperature and salinity within the study area seemed to be higher southward but uniform vertically. The results of the drogue experiments in the straits between the Narodo Islands showed that the drogues moved northward of Sayangdo in the early part of the flood tide, but southward in the late part of the flood tide and finally stopped a mile from the east coast of Surakdo. On the other hand, the numerical computation showed that the flow structures after construction of the bridge piers were basically in line with those before construction of the bridge piers, except for the slight variations of velocities in the vicinity of the bridge piers. A large scale clockwise circulation has been confirmed in the south area of Namsungri of Kohung Peninsula from the computational results of tide-induced residual currents. Referring to these computational results, the impact category on the flow structures due to the bridge piers construction has been estimated to be within around 2km. The results were in good agreement with the field observations.

• Journal of Life Science
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• v.15 no.2 s.69
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• pp.225-230
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• 2005

The aim of this study was to examine the fluctuation in phytoplankton assemblages with regarding to environmental conditions and nutrients, which were surveyed quarterly over the fours seasons (February, May, July, and October). In turn, an understanding of biological effects should provide insights into a wide range of initiated Cochlodinium blooms in Narodo. Sampling was carried out throughout 2001 on the coasts of Busan (St. 1), Yeosu (St. 2), Narodo (St. 3), Kohung (St. 4), and Kwangdo (St. 5). The maximum surface water temperature was recorded in July, and it ranged from 20 to $22^{\circ}C$. Salinity showed no great variation, which maintained itself in the range of 29-34 psu. The maximum surface salinity was recorded in February, which was about 34 psu. The chlorophyll $\alpha$ concentration of the surface water ranged from 0.01 to $1.3\;{\mu}g\;1^{-1}$. The concentrations of $NH_{4}-N $ were persistently high from February to October; in particular, the peak was observed at St. 1 in February and May (0.15 and $0.19\;{\mu}mol\;1^{-1}$, respectively), while it was detected at St. 2 in July and October (0.22 and $2.2\;{\mu}mol\;1^{-1}$ respectively). Similar trends to those for $NH_4-N $ were observed in the concentrations of $NO_{2}-N$ and $NO_{3}-N$. In contrast to nitrogen, a distinct peak of $NO_{4}-P$ at St. 3, 4, and 5 was observed throughout year $(0.01-0.1\;{\mu}mol\;1^{-1}$ except for October. At St. 1 encounter a peak of cell number of 30,000 and $13{\times}10^3$ cells $1^{-1}$, respectively, in July and October. During the period of this study, the majority of the taxa were diatoms. The dinoflagellates were rather abundant after February, in particular at St. 3, 4, and 5 which attained an abundance of $10\~20\%$without marked fluctuation during the period of this study. At St. 3, the highest average cell width, $178.11\;{\mu}m$, was recorded: the highest cell length, $337.72\;{\mu}m$, was measured in July. Consequently, dinoflagellates bloom in July at Narodo influenced by warm water current are not only associated with a desirable development of cell morphometric characteristics, but also with the health growth of C. polykrikoides. During the period of this study, warm water currents caused an increased water temperature in Narodo, but did not change the amount of nutrients.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.4
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• pp.235-247
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• 2009

In order to elucidate the cause of Cochlodinium polykrikoides blooms in the Korea southern coastal water, we investigated observational data of water temperatures and salinities in summer and winter, obtained from the stoppage of ship by NFRDI (National Fisheries Research and Development Institute) as well as composite images by NOAA from 1995 to 2008. Cochlodinium polykrikoides blooms occurred when water temperature was approximately $25.0{\sim}26.0^{\circ}C$ and salinity was 31.00 psu on average in Narodo neighboring seas. Different thermohaline fronts were observed between the Korea southern coastal water and the open sea water in summer and winter, respectively. That is, in winter four fronts were observed between the Korea southern coastal water with low temperature and low salinity, intermediate water originated from Tsushima Warm Current, Tsushima Warm Current with high temperature and high salinity, and the China coastal water with low temperature and low salinity. In contrast, in summer two fronts were observed between the Korea southern coastal water with low temperature and high salinity, Tsushima Warm Current with high temperature and low salinity, and the China coastal water with high temperature and high salinity. These thermohaline fronts also proved to be formed by two water masses with a different physical property, in terms of T-S diagrams. Consequently, we noticed that C. polykrikoides blooms occurring in Narodo neighboring seas in summer had a close relationship with thermohaline fronts observed between the Korea southern coastal water and Tsushima Warm Current.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.49-62
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• 2001

Hydrographic surveys were carried out seven times during May 31, 1998 and September 24, 1998 in order to study the physical environments of the coastal area between Narodo Is. and Sorido Is. in the southern sea of Korea (the South Sea) where the occurrence of Cochlodinium polykrikoides red tide is frequently observed in summer. Temperature and salinity of the water column from the surface to the depth of 30 m exhibit large seasonal variations. Mean temperature of the water column increased by 6 and mean salinity of the water column decreased by 2.71 psu during the observation period. Both the freshwater supplied from the adjacent land and the precipitation over the study area cannot account for the observed salinity variations. The influx of the low salinity water from the offshore area is considered to be the main cause for the observed salinity changes. Surface salinity in the study area shows different spatial distribution in the period of outbreaking, mid-stage and disappearance of the red tide. Especially, salinity was abruptly lowered at the stage of disappearance of red tide as compared to salinity of the previous observation period. Vertical structure of water properties also became vertically homogeneous at the disappearance stage, while it was highly stratified in the previous observation. Such changes can only be explained by the inflow of low salinity water from the offshore, which is considered as the most possible cause for the disappearance of the red tide in the study area. This study suggests that exchanges of water, and chemical and biological factors between coastal areas and of shore area in the South Sea need to be studied in association with the general circulation of the South Sea in order for the better understanding of the occurrence and disappearance of the red tide in the coastal area of the South Sea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.4
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• pp.378-388
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• 2003

Seasonal variations in abundance and species composition of fish assemblage around Narodo were examined. Fish samples were monthly collected by a beam trawl from December 2000 to November 2001. A total of 62 fish species representing 37 families were collected. Of these, Thryssa kammalensis, T. hamiltoni, Chaeturichthys hexanema, Johnius grypotus, Leiognathus nuchalis, Cynoglossus robustus and Setipinna taty were dominant species comprising $82\%$ of the total number of individuals. Species diversity indices ranged from 1.2 to 2.2 showing the highest values from September to November 2001. The fish assemblage was divided into three different groups by cluster analysis of the fourteen dominant species. The main residence species were J. grypotus, L. nuchalis, C. hexanema, C. robustus, Setipinna tenuifilis, T. kammalensis and Ctenotrypauchen microcephalus. Of the temporal species T. hamiltoni, Liparis tanakai and Erisphex pottii were collected In spring, and Muraenesox cinereus and Trichiurus lepturus were in summer and autumn. Principal component analysis revealed that seasonal variation in the fish assemblage was attributed to the abundance of temporal species due to seasonal variation of environmental factors such as water temperature and ecological pattern (polagic/demersal) of fish species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.5
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• pp.528-533
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• 2013

This study evaluated the impact of antimicrobial resistant bacteria produced by inland pollution sources on coastal areas, and investigates antimicrobial resistance profiles of bacteria isolated from marine filter feeders. A total of 107 shellfish (short-necked clams Ruditapes philippinarum, ark shells Scapharca broughtonii, and oysters Crassostrea gigas) were collected from the southern coast of Korea, from which 204 Escherichia coli strains were isolated. The antimicrobial susceptibility patterns of isolated strains were analyzed for 15 antimicrobial agents used in Korea for clinical or veterinary therapy. Antimicrobial resistance was present in 44.6% of E. coli isolates against at least one antimicrobial agent. The rate of antimicrobial resistance in the Narodo area was higher than isolates from the Gangjinman area and Kamak Bay. E. coli isolates had a higher rate of resistance against: tetracycline (29.9%), streptomycin (25.5%), and trimethoprim (14.2%). Of 204 isolates, 29 (14.2%) were resistant to multiple antimicrobial agents.