• Ocean and Polar Research
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• v.26 no.2
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• pp.175-185
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• 2004

To delineate Late Pleistocene paleoceanographic change of the West Pacific, we analyzed the oxygen and carbon isotopic ratios of two planktonic foraminifera species (G. sacculifer and N. dutertrei) from a piston core (KODOS-313) taken from the West equatorial Pacific, and they are compared with the published results of the East Pacific (ODP site 847 and RC 11-210), in terms of relative amounts and mass accumulation rates of $CaCO_3$ and eolian component, back to marine isotopic stage (MIS) 6. Differences in oxygen and carbon isotope values between two foraminifear species ($0.75%_{\circ}$ in ${\delta}^{18}O$, $0.05%_{\circ}$ in ${\delta}^{13}C$) are less than those of the East Pacific ($1.30%_{\circ}$ in ${\delta}^{18}O$, $0.14%_{\circ}$ in ${\delta}^{13}C$), which indicates smaller vertical contrasts in both temperature and nutrient between mixing-zone and thermocline in the West Pacific. Strong deviation in${\delta}^{18}O$ of G. sacculifer from SPECMAP suggests the carbonate fraction of KODOS-313 was subjected to partial dissolution by bottom water under lysocline. Lower accumulation rates of $CaCO_3$ and eolian component during glacial times are likely due to low sedimentation rate (ave. 0.75 cm/1000 yr) combined with carbonate dissolution in KODOS-313 site. However, the high $CaCO_3$ contents during the glacial periods clearly follow the general pattern of equatorial Pacific ocean.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.5
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• pp.459-473
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• 2014

The recent mass appearances of jellyfish in Korea have caused economic and social damage, as they plague swimmers and fishermen. However, jellyfish have high economic and nutritional value, and contain low levels of calories and hydrolysates. Thus, jellyfish are a natural, healthy food that can improve high blood pressure, bronchitis, and a multitude of other diseases. Here, we present research on the ecology, classification, bloom, damage caused, food component characterization, and tissues of jellyfish, with the aim of facilitating further study. Research on use of jellyfish as salted products, and for collagen and qniumucin would also be valuable. A jellyfish body is classified into three parts: the body, termed the umbrella; the oral arm; and the tentacle. Jellyfish are planktonic marine members of a group of invertebrate animals comprising the classes Schypozoa (phylum Cnidaria) and Cuboza. In Korea in 2012, jellyfish damage resulted in decreases of annual catch and commercial value estimated at 177 and 141 billion won, respectively. Because concentrations of heavy metals are below the safety limits for seafood, dried jellyfish appear to be safe raw materials for food. The proximate compositions of Nemopilema nomurai and Aurelia aurita were 97.1% and 96.5% moisture, 0.9% and 1.2% crude proteins, undetected and 0.1% crude lipids, and 1.7% and 1.8% ash, respectively. According to their total contents of essential, total, and non-essential amino acids, jellyfish gonads were deemed good-quality protein. Because the major functional components of jellyfish are collagen and qniumucin, jellyfish can be used salted, or these components of healthy diets can be extracted from them. For more effective use of jellyfish, unit costs should be decreased and safety guaranteed. Additionally, dehydrators attached to conveyor belts should be developed. Since jellyfish can be used throughout the year, they should be listed in the Korean Food Standards Codex as a food source.

• Proceedings of the KSRS Conference
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• v.1
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• pp.471-474
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• 2006

Several planktonic dinoflagellates, including Cochlodinium polykrikoides (p), are known to produce red tides responsible for massive fish kills and serious economic loss in turbid Northwest Pacific (Korean and neighboring) coastal waters during summer and fall seasons. In order to mitigate the impacts of these red tides, it is therefore very essential to detect, monitor and forecast their development and movement using currently available remote sensing technology because traditional ship-based field sampling and analysis are very limited in both space and temporal frequency. Satellite ocean color sensors, such as Sea-viewing Wide Field-of-view Sensor (SeaWiFS), are ideal instruments for detecting and monitoring these blooms because they provide relatively high frequency synoptic information over large areas. Thus, the present study attempts to evaluate the red tide index methods (previously developed by Ahn and Shanmugam et al., 2006) to identify potential areas of red tides from SeaWiFS imagery in Korean and neighboring waters. Findings revealed that the standard spectral ratio algorithms (OC4 and LCA) applied to SeaWiFS imagery yielded large errors in Chl retrievals for coastal areas, besides providing false information about the encountered red tides in the focused waters. On the contrary, the RI coupled with the standard spectral ratios yielded comprehensive information about various ranges of algal blooms, while RCA Chl showing a good agreement with in-situ data led to enhanced understanding of the spatial and temporal variability of the recent red tide occurrences in high scattering and absorbing waters off the Korean and Chinese coasts. The results suggest that the red tide index methods for the early detection of red tides blooms can provide state managers with accurate identification of the extent and location of blooms as a management tool.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.5
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• pp.667-676
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• 1995

Settlement, recruitment, growth and production of Mactra venerifomis were investigated at Kunsan tidal flat located in the west coast of Korea from lune 1993 to May 1994. High density of planktonic larvae of M. veneriformis was observed between the mid and early July in 1993. The size of the newly settled larvae ranged from 250 to 350um in shell length with mean density of 601$inds.\cdot m^{-3}$. Recruitment of M. veneriformis larvae was occurred mainly in the mid June to mid July 1993. The larvae have no substratum preference during the larval settlement phase. Mortality of larval was affected by environment (substratum, exposure time, density of adult clams). After settlement they grew until November, and stopped growing in winter from December. The estimated turnover rate of M. veneriformis larvae was estimated as high as 4.91 and 4.94. Annual production of the 0-age group was estimated to be 2,900g $m^{-2}\;\cdot\;yr^{-l}$, which was relatively high compared with those of other age groups.

• Journal of the Korean earth science society
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• v.26 no.7
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• pp.714-724
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• 2005

The East Sea, a semi-enclosed marginal sea with shallow straits in the northwest Pacific, is marked by the nearly geographic isolation and the low sea surface salinity during the last glacial maximum (LGM). The East Sea might have the only connection to the open ocean through the Korea Strait with a sill depth of 130 m, allowing the paleo-Tsushima Water to enter the sea during the LGM. The low paleosalinity associated with abnormally light $\delta^{18}O$ values of planktonic foraminifera is interpreted to have resulted from river discharge and precipitation. Nevertheless, two LGM features in the East Sea are disputable. This study attempts to estimate volume transport of the paleo-Tsushima Water via the Korea Strait and further examines its effect on the low sea surface salinity (SSS) during the lowest sea level of the LGM. The East Sea was not completely isolated, but partially linked to the northern East China Sea through the Korea Strait during the LGM. The volume transport of the paleo-Tsushima Water during the LGM is calculated approximately$(0.5\~2.1)\times10^{12}m^3/yr$ on the basis of the selected seismic reflection profiles along with bathymetry and current data. The annual influx of the paleo-Tsushima Water is low, compared to the 100 m-thick surface water volume $(about\;79.75\times10^{12}m^3)$ in the East Sea. The paleo-Tsushima Water influx might have changed the surface water properties within a geologically short time, potentially decreasing sea surface salinity. However, the effect of volume transport on the low sea surface salinity essentially depends on freshwater amounts within the paleo-Tsushima Water and excessive evaporation during the glacial lowstands of sea level. Even though the paleo-Tsushima Water is assumed to have been entirely freshwater at that time period, it would annually reduce only about 1‰ of salinity in the surface water of the East Sea. Thus, the paleo-Tsushima Water influx itself might not be large enough to significantly reduce the paleosalinity of about 100 m-thick surface layer during the LGM. This further suggests contribution of additional river discharges from nearby fluvial systems (e.g. the Amur River) to freshen the surface water.

• ALGAE
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• v.30 no.4
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• pp.281-290
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• 2015

We explored phagotrophy of the phototrophic ciliate Mesodinium rubrum on the cyanobacterium Synechococcus. The ingestion and clearance rates of M. rubrum on Synechococcus as a function of prey concentration were measured. In addition, we calculated grazing coefficients by combining the field data on abundance of M. rubrum and co-occurring Synechococcus spp. with laboratory data on ingestion rates. The ingestion rate of M. rubrum on Synechococcus sp. linearly increased with increasing prey concentrations up to approximately 1.9 × 10⁶ cells mL^-1, to exhibit sigmoidal saturation at higher concentrations. The maximum ingestion and clearance rates of M. rubrum on Synechococcus were 2.1 cells predator^-1 h^-1 and 4.2 nL predator^-1 h^-1, respectively. The calculated grazing coefficients attributable to M. rubrum on cooccurring Synechococcus spp. reached 0.04 day^-1. M. rubrum could thus sometimes be an effective protistan grazer of Synechococcus in marine planktonic food webs. M. rubrum might also be able to form recurrent and massive blooms in diverse marine environments supported by the unique and complex mixotrophic arrays including phagotrphy on hetrotrophic bacteria and Synechococcus as well as digestion, kleptoplastidy and karyoklepty after the ingestion of cryptophyte prey.

• Korean Journal of Ecology and Environment
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• v.41 no.3
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• pp.311-319
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• 2008

To understand the relative immigration activities (RIA) of hibernal diatom community in Lake Ilgam (at the station with and without macrophyte) and River Han (at the station with different current and nutrient), a natural and artificial bed substrate was deposited from 15 to 29 January 2008. For the study period, both waters comprised huge biomass of diatom, over 75% of total abundance. Nutrients in water column, ash-free dry matter (AFDM) and chlorophyll-a (Chl-a) concentration in substrates were decreased with increasing of current in rivers, while in lakes the macrophyte largely affected the diatom community and water quality. Algal RIA in rivers was high at stations with high concentration of nutrient, AFDM and Chl-a, and in high nutrients and no macrophytes in lakes, respectively. The species showing a higher RIA was Nitzschia amphibia in rivers and Aulacoseira italica in lakes, while the dominant species were Navicula sp. in rivers and Syndera acus in lakes, suggesting no relationship between water algal biomass and its RIA. These results suggest that the RIA of stream diatom community depends exclusively on the current, while the planktonic diatom in lake was of the macrophyte.

• 한국해양학회지
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• v.30 no.5
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• pp.382-389
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• 1995

This study intended to investigate the sedimentation rates of core sediments of the western part of the East Sea using Accelerator Mass Spectrometer (AMS) C-age on the planktonic foraminifera or acid-ex-tracted residue, base-soluble and base-extracted residue fractions. On the basis of the depth-age correlations, the sedimentation rates during the late Holocene period of Cores HP-10, HP-3, 94-9 and 92-3 were 30 cm/kyr, 10 cm/kyr, 11 cm/kyr and 112 cm/kyr, respectively. The sedimentation rates of the westem part of the East Sea, however, seems to be ranged from 11 cm/kyr to 30 cm/kyr, because the rates of the only two cores (Cores HP-10 and 94-9) which were dated at more than three depths are considered to be more reliable. The rates in each core sediment showed good linear relationship with the sample depth, suggesting that the sea-level rise had been finished nearly during the early Holocene period and the general depositional environments had been lasted rather constant during the late Holocene period.

• Journal of the korean society of oceanography
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• v.37 no.1
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• pp.27-34
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• 2002

We measured the alkenone concentration of bulk sediments from a piston core collected from the Ulleung Basin in the East Sea in order to reconstruct past sea surface temperatures (SST). Sediment ages are well constrained by AMS $^{14}C$ dates of the planktonic foraminifera Globigerina bulloides. Coretop alkenone SST calibration with modern surface temperatures and sediment trap dat (Hong et al., 1996) indicate that the SST estimated from alkenones most likely represent the temperatures of late fall. Downcore variations in the alkenone saturation index indicate that between 19 and 15 kyr BP the surface waters were about $3^{\circ}C$ warmer than today. Between 15 and 11 kyr BP, the temperatures were about $3^{\circ}C$ lower than today. A rapid SST increase of about $3^{\circ}C$ occurred at approximately 10 kyr BP. After considering the factors which might influence the SST reconstruction from the $U^{k'}_{37}$ values, we conclude that the alkenone temperature estimates are reliable. The reason for glacial warming in the East Sea is not clear, although there is a possibility that it could be caused by shift in the season of maximum alkenone production from summer during the last glaciation to late fall during the Holocene. Cooling between 15 and 11 kyr BP may be due to inflow of cold water into the East Sea such as via the Oyashio Current or ice-melt water. Warming at the early Holocene could be due to inflow of the Tsushima Current into the East Sea through the Korea Strait.

• Korean Journal of Ichthyology
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• v.28 no.2
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• pp.79-86
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• 2016

Stomach contents of Amblychaeturichthys hexanema and A. sciistius (Perciformes: Gobiidae) from southeastern waters off Korea were analyzed to determine dietary habits and the presence of any inter- and intra-specific partitioning of food resources. These two species were bottom-feeding carnivores that consumed mainly benthic crustaceans, and other demersal invertebrates and planktonic organisms were also important in their diets. Non-metric multidimensional scaling (nMDS) ordination and multivariate analyses based on gravimetric contributions of the different prey taxa to stomach contents revealed significant inter-specific dietary differences; i.e. partitioning of food resources between the two species. Size-related changes, however, were not significant for their diets. Differences in the types and range of prey ingested by the two species could often be related to differences in the feeding behaviors. Our results of stomach contents analyses provide clear evidence of niche segregation between co-occurring A. hexanema and A. sciistius in southeastern Korean waters, which would reduce the likelihood of inter-specific competition for food resources.