• Journal of Fisheries and Marine Sciences Education
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• v.23 no.4
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• pp.642-647
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• 2011

In order to analyze the influence of floating marine debris (FMD) in the East China Sea (ECS), a sighting survey was conducted from July 1st to July 14th, 2009 navigating about 966 km using a training vessel "Kaya (1,737 ton)" of Pukyong National University. The sampled zones are divided into 5 transect by observation day during the survey days and again specified with 45 segments per unit hour on the survey routes. The results of distribution of FMD are as follows: 1. The quantities of FMD at the central China Sea(CE) and northern part of Taiwan(NT) were found as total mean of 90.8 ea/hr, 56.7 ea/hr, respectively, and also 36.8 ea/hr, western part of Kyushu district(WJ), 10.7 ea/hr, 8.0 ea/hr, western(OK1) and northern part(OK2) of Okinawa, respectively. 2. Temporal variation of FMD is represented by depicting the sinusoidal curve as shape as tide in CE and OK1. 3. The higher sea surface temperature (SST) is as likely as if Kuroshio current exists strongly, the less quantities are decreased. On the other hand, the coastal zone of ECS and near of Yellow Sea are increased by lower SST.

• Journal of Life Science
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• v.24 no.6
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• pp.626-632
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• 2014

The genetic structure and phylogenetic relationship were investigated in Korean red spotted grouper populations using the nucleotide sequence polymorphisms of the mitochondrial DNA (mtDNA) cytochrome c oxidase subunit I (COI) gene. The COI gene was sequenced showed 99.1-99.8% identity with the EF607565 sequence previously reported. A total of twenty haplotypes were found, and the Korean population showed nineteen haplotypes. Among those, Hap_03 and Hap_08 showed Jeju-do and China-specific COI sequences, respectively. However, Hap_07 had twelve COI sequences from South Korea and records from Hong Kong and Taiwan. Neighbor-joining (NJ) trees constructed from the phylogenetic analyses based on the polymorphisms of the COI haplotypes showed a monophyletic branching pattern within the genus Epinephelus. This indicated that the red spotted grouper populations had evolved from common maternal ancestors. In addition, the Hap_08, which had the COI sequence recorded only from China Sea, was found in the middle of the NJ tree nearby Hap_07 and showed a close relationship with Hap_07. This indicates that Chinese red spotted grouper is also maternally related to other populations in East Asia. Consequently, East Asian red spotted grouper populations are maternally related, as well as sharing the same evolutionary history, and are still affected by the East Asian ocean current (Kuroshio). These findings help to explain the genetic structure and phylogenetic relationship of red spotted grouper and also contribute to research on artificial breeding and industrialization.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.339-342
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• 2003

Sea level variations and sea surface circulations inthe Korean seas were observed by Topex/Poseidon altimeter data from 1993 through 1997. In sea level variations, the West and South Sea showed relatively high variations with comparison to the East Sea. Then, the northern and southern area in the West Sea showed the range of 20-30cm and 18-24cm, and the northern west of Jeju island and the southern west of Tsushima island in the South Sea showed the range of 15-20cm and 10-15cm, respectively. High variations in the West Sea was results to the inflow in sea surface of Yellow Sea Warm Current (YSWC) and bottom topography. Sea level variations in the South Sea was due to two branch currents (Jeju Warm Current and East Korea Warm Current) originated from Kuroshio Current (KC). In sea surface circulations, there existed remarkably three eddies circulations in the East Sea that are mainly connected with North Korea Cold Current (NKCC), East Korea Warm Current (EKWC) and Tushima Warm Current (TWC). Their eddies are caused basically to the influence of currents in sea surface circulations; Cyclone (0.03 cm/sec) in the Wonsan bay on shore with NKCC, and anticyclone (0.06 cm/sec) in the southwestern area of Ulleung island with EKWC, and cyclone (0.01 cm/set) in the northeastern area of Tushima island with TWC, respectively.

• Journal of Ecology and Environment
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• v.35 no.1
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• pp.15-25
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• 2012

Time series of ocean climate indices and catch records were used to identify the alternation patterns of pelagic fish populations in relation to climate regime shifts. During 1910-2008, an orderly alternation of dominant pelagic fish groups was observed in the Tsushima Warm Current (TWC; Yellow Sea-East China Sea-East Sea/Japan Sea) and Kuroshio-Oyashio Current (KOC; Northwestern Pacific) regions. After the collapse of herring fishery in the late 1920s, the sardine (A group) dominated in the 1930s, 3 other species (C group; Pacific saury, jack mackerel, and anchovy) dominated in the 1950s-1960s, chub mackerel (B group) dominated in the 1970s, and then sardine (A group) dominated again during cool regime in the 1980s. As sardine biomass decreased in association with the climate regime shift that occurred in the late 1980s, catches of C group immediately increased after the regime shift and remained at high levels during warm regime in the 1990s. Alternations of dominant fish groups occurred 6 times between 1910 and 2008. The dominant period of the 7 species lasted for 10-20 years. The catch of Pacific sardine in the TWC and KOC regions showed a negative correlation with the catch of the other 5 species (Pacific herring, anchovy, jack mackerel, Pacific saury, and common squid), suggesting that the abundance of the 5 species is strongly affected by the abundance of Pacific sardine in relation to the climate regime shifts. The total catch level of the 7 species in the KOC region was generally higher than that in the TWC region before 1991 but was lower after 1992, suggesting that the fish populations in the Pacific side are shifted to the TWC region by zonal oscillation of the oceanic conditions in relation to the climate regime shift in the late 1980s.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.167-173
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• 2009

Bathymetry survey around the Baengnyeong-do was made by the Korea Hydrographic and Oceanographic Administration (KHOA), using the Simrad EM3000 Multi-Beam EchoSounder (MBES) mounted at the hull of the R/V Badaro 1. Sound velocity were monitored with frequent sound velocity profiler(SVP) casts during the acoustic measurements. The depth distribution and fluctuation of thermocline varied locally owing to the effect of several current flows such as Kuroshio current and Yellow sea coastal waters. These uncertainties cause the falling-off in accuracy of MBES results. In this paper, the bathymetry results will be presented and their accuracy will be discussed along with comparisons to the time and spatial variations in sound velocity profile.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.61-64
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• 2008

Seasonal distribution of the oceanic water intrusion was investigated using satellite SST (sea surface temperature) and chl-a (chlorophyll-a) images taken by the MODIS Aqua sensor. The warm water mass emanating periodically from the meandering Kuroshio Current brings the oceanic water intrusion, known as the 'Kyucho' phenomenon, into Kagoshima bay during the winter. Satellite SST images and buoy robot data show that this warm water intrusion has the characteristics of a semigeostrophic gravity current influenced by the Coriolis effect. However, it is difficult to find the oceanic water intrusion during the summer season considering that it is accompanied by thermal stratification, and SST shows almost the same temperature between the inner side of the bay and the ocean. In this research, the satellite chl-a images taken by MODIS Aqua were employed instead of SST images to reveal the oceanic water intrusion in each season. The enclosed bay has the tendency to undergo eutrophication caused by organic materials from land and differences in chl-a concentration of the bay water and the oceanic water. As a result, distribution of low concentration chl-a with oceanic water intrusion in summer season shows almost the same pattern in winter season. On the other hand, in spring season, both SST and chl-a images are available to differentiate the oceanic water intrusion. Therefore, applying the suitable satellite sensor images for each season is effective in the monitoring of oceanic water intrusion. Moreover, in this area, SST and chl-a distribution reveal not only the oceanic water intrusion into Kagoshima bay but also the intrusion at Fukiage seashore facing East China Sea.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.527-534
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• 2015

The twenty six specimens of leptocephali (15.8-32.6 mm TL) of the family Congridae, collected from southeastern waters offshore of Jeju Island during August 2014, and were identified by means of morphology and genetics. Those specimens were identified as belonging to the family Congridae based on various combinations of morphological characters. An analysis of the partial 12S rRNA sequences (886 base pairs) of mitochondrial DNA showed that our specimens must be Gnathophis nystromi, because their sequences were concordant with those of G. nystromi adult (genetic distance= 0.001), furthermore their total myomeres being consistent with those of G. nystromi adult. Catch rates of G. nystromi leptocephali were higher in the offshore regions than coastal regions of Jeju Island. The smallest leptocephali (< 20 mm TL) were collected offshore from Jeju Island. We hypothesize that one of the spawning grounds of G. nystromi is located offshore in the Jeju Island. In conclusion, the hatched preleptocephali of G. nystromi might have been transported from offshore near Jeju Island to the Korea Strait by the Kuroshio Current and Tsushima Warm Current.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.456-466
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• 2021

The distribution and abundance of euphausiids were investigated in Korean waters in 2016. Euphausiids were sampled with a Bongo net. A CTD (Sea Bird Electronics 9 plus) measured the water temperature and salinity while sampling. Mean water temperature ranged from 4.2-31.0℃. The highest temperatures occur in September and lowest temperatures in February. The mean water salinity ranged from 27.9-34.8 psu, with the highest salinities in March and lowest in September. Euphausiid species in group W consisted of four species. Among the euphausiid species, Euphausia pacifica was the dominant species with peak densities in September. The E. pacifica from group W was distributed in the bottom cold water during summer when a thermocline was formed. Five euphausiid species occurred in group S. E. pacifica and E. nana were the dominant species. In group S, E. nana was located in the warm and saline Tsushima Warm Current, a branch of the influential Kuroshio Current. Five euphausiid species occurred in group E. E. pacifica and T. longipes were the dominant species. In group E, E. pacifica and T. longipes were distributed in the deep and cold waters, these species prefer low water temperatures and perform vertical migration. The distribution of euphausiids in Korean waters were highly influenced by mass water characteristics, such as temperature and salinity.

• Ocean and Polar Research
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• v.35 no.2
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• pp.157-170
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• 2013

We investigated the seasonal succession of phytoplankton assemblages in the eastern part of the South Sea of Korea in relation to surface water masses. The study areas are under the direct influence of the Tsushima Warm Current (TCW) throughout the whole year, with its strength known to be seasonally variable. The region is also influenced by coastal waters (CW) driven from the South Sea of Korea and East China Sea, particularly in summer, as indicated by low salinity in the surface water. Nutrient property of the TCW can reveals whether the origin of the TCW is the nutrient-rich Kuroshio Current or the oligotropic Taiwan Warm Current. Surface chlorophyll-a (Chl-a) concentrations displayed a large seasonal variation for all stations, with high values found in spring and autumn and low values in summer and winter. At station M (offshore) and P (intermediate location between M and R), Chl-a concentrations in October were higher than those in March, when spring bloom normally occurs. This may be related to deeper mixed layer depths in October. Diatoms dominated under conditions of high nutrient supply in which Chaetoceros spp. and Skeletonema costatum-like spp. were abundant. S. costatum-like spp. dominated at stations R (onshore station) and P in December when there was greater nutrient supply, especially of phosphate. Flagellates and dinoflagellates dominated at all three stations after diatoms blooms. Dominant species were Scrippsiella trochoid in April and Ceratium furca in October at station R, and Gyrodinium spp. and Gymnodinium spp. at station M during summer, when the effect of the oligotropic Taiwan Warm Current and the oligotropic coastal water from East China Sea were strong. Redundancy analysis showed clear seasonal successions in the phytoplankton community and environmental conditions, in which both principal components 1 and 2 accounted for 69.6% of total variance. Our results suggested that environmental conditions seemed to be determined by the origin of the TCW and the relative seasonal strength of the water masses of the TCW and CW, which may affect phytoplankton growth and compositions in the study area.

• Korean Journal of Environmental Biology
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• v.37 no.1
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• pp.93-108
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• 2019

To investigate the temporal-spatial distribution of picophytoplankton in relation to different water masses in the northern East China Sea (ECS), picophytoplankton abundance were investigated using flow cytometry with environmental factors in 2016-2017. The results from the analysis of flow cytometer data showed that Synechococcus appeared across all seasons, exhibiting its minimum abundance in winter and maximum abundance in summer. Furthermore, high abundance was detected in the surface mixed layer during spring and summer when vertical stratification occurs; in particular, Synechococcus exhibited maximum abundance in thermocline layer, indicating a close correlation to water temperature and thermocline formation. In addition, the abundance of Synechococcus indicated a decrease in the western seas in 2017 compared to 2016 under the strong influence of the Changjiang Diluted Water (CDW). This was determined by the significant influence of the CDW on the abundance of Synechococcus during summer in the northern waters of the ECS. In contrast, Prochlorococcus did not appear during winter and spring, and its distribution was limited during summer and autumn in the eastern seas under the influence of the Kuroshio current. The largest range of Prochlorococcus distribution was confirmed during autumn without the influence of the CDW. Thus, the distribution pattern of each picophytoplankton genus was found to be changing in accordance to the extension and reduction of sea current in different seasons and periods of time. This is anticipated to be a useful biological marker in understanding the distribution of sea currents and their influence in the northern waters of the ECS.