• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.924-942
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• 2021

The expansion of the Changjiang Diluted Water (CDW) plume during summer is known to be a major factor influencing phytoplankton diversity, community structure, and the regional marine environment of the northern East China Sea (ECS). The discharge of the CDW plume was very high in the summer of 2020, and cruise surveys and stationary monitoring were conducted to understand the dynamics of changes in environmental characteristics and the impact on phytoplankton diversity and community structure. A cruise survey was conducted from August 16 to 17, 2020, using R/V Eardo, and a stay survey at the Ieodo Ocean Research Station (IORS) from August 15 to 21, 2020, to analyze phytoplankton diversity and community structure. The southwestern part of the survey area exhibited low salinity and high chlorophyll a fluorescence under the influence of the CDW plume, whereas the southeastern part of the survey area presented high salinity and low chlorophyll a fluorescence under the influence of the Tsushima Warm Current (TWC). The total chlorophyll a concentrations of surface water samples from 12 sampling stations indicated that nano-phytoplankton (20-3 ㎛) and micro-phytoplankton (> 20 ㎛) were the dominant groups during the survey period. Only stations strongly influenced by the TWC presented approximately 50% of the biomass contributed by pico-phytoplankton (< 3 ㎛). The size distribution of phytoplankton in the surface water samples is related to nutrient supplies, and areas where high nutrient (nitrate) supplies were provided by the CDW plume displayed higher biomass contribution by micro-phytoplankton groups. A total of 45 genera of nano- and micro-phytoplankton groups were classified using morphological analysis. Among them, the dominant taxa were the diatoms Guinardia flaccida and Nitzschia spp. and the dinoflagellates Gonyaulax monacantha, Noctiluca scintillans, Gymnodinium spirale, Heterocapsa spp., Prorocentrum micans, and Tripos furca. The sampling stations affected by the TWC and low in nitrate concentrations presented high concentrations of photosynthetic pico-eukaryotes (PPE) and photosynthetic pico-prokaryotes (PPP). Most sampling stations had phosphate-limited conditions. Higher Synechococcus concentrations were enumerated for the sampling stations influenced by low-nutrient water of the TWC using flow cytometry. The NGS analysis revealed 29 clades of Synechococcus among PPP, and 11 clades displayed a dominance rate of 1% or more at least once in one sample. Clade II was the dominant group in the surface water, whereas various clades (Clades I, IV, etc.) were found to be the next dominant groups in the SCM layers. The Prochlorococcus group, belonging to the PPP, observed in the warm water region, presented a high-light-adapted ecotype and did not appear in the northern part of the survey region. PPE analysis resulted in 163 operational taxonomic units (OTUs), indicating very high diversity. Among them, 11 major taxa showed dominant OTUs with more than 5% in at least one sample, while Amphidinium testudo was the dominant taxon in the surface water in the low-salinity region affected by the CDW plume, and the chlorophyta was dominant in the SCM layer. In the warm water region affected by the TWC, various groups of haptophytes were dominant. Observations from the IORS also presented similar results to the cruise survey results for biomass, size distribution, and diversity of phytoplankton. The results revealed the various dynamic responses of phytoplankton influenced by the CDW plume. By comparing the results from the IORS and research cruise studies, the study confirmed that the IORS is an important observational station to monitor the dynamic impact of the CDW plume. In future research, it is necessary to establish an effective use of IORS in preparation for changes in the ECS summer environment and ecosystem due to climate change.

• Journal of Climate Change Research
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• v.1 no.1
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• pp.31-50
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• 2010

The Arctic climate change for the Last Glacial Maximum(LGM) occurred at 21,000 years ago (21ka) was investigated using simulation results of atmosphere-ocean coupled models from the second phase of the Paleoclimate Modelling Intercomparison Program(PMIP2). In the analysis, we used seven models, the NCAR CCSM of USA, ECHAM3-MPIOM of German Max-Planxk Institute, HadCM3M2 of UK Met Office, IPSL-CM4 of France Laplace Institute, CNRM-CM3 of France Meteorological Institute, MIROC3.2 of Japan CCSR at University of Tokyo, and FGOALS of China Institute of Atmospheric Physics. All the seven models reproduces the Arctic climate features found in the present climate at 0ka(pre-industrial time) in a reasonable degree in comparison to observations. During the LGM, the atmospheric $CO_2$ concentration and other greenhouse gases were reduced, the ice sheets were expanded over North America and northern Europe, the sea level was lowered by about 120m, and orbital parameters were slightly different. These boundary conditions were implemented to simulated LGM climate. With the implemented LGM conditions, the biggest temperature reduction by more than $24^{\circ}C$ is found over North America and northern Europe owing to ice albedo feedback and the change in lapse rate by high elevation. Besides, the expansion of ice sheets leads to the marked temperature reduction by more then $10^{\circ}C$ over the Arctic Ocean. The temperature reduction in northern winter is larger than in summer around the Arctic and the annual mean temperature is reduced by about $14^{\circ}C$. Compared to low mid-latitudes, the temperature reduction is much larger in high northern altitudes in the LGM. This results mirror the larger warming around the Artic in recent century. We could draw some information for the future under global warming from the knowledge of the LGM.

• Economic and Environmental Geology
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• v.56 no.1
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• pp.55-63
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• 2023

Variations in geochemical and mineralogical properties of the ferromanganese(Fe-Mn) crust reflect environmental changes. In the present study, geochemical and mineralogical analyses, including micro X-ray fluorescence and X-ray diffraction, were utilized to reconstruct the paleo-ocean environment of western Pacific Magellan seamount cluster. Samples of the Fe-Mn crust were collected using an epibenthic sledge from the open seamount XX (151° 51.12' 7.2" E and 16° 8.16' 9.6" N, 1557 meters below sea level) in the Western Pacific Magellan Seamount. According to the structure and phosphating status, the Fe-Mn crust of the OSM-XX can be divided into the following: phosphatizated (L4-L5), massive non-phosphatizated (L3), and porous non-phosphatizated (L1-L2) portions. All ferromanganese layers contain vernadite, and owing to the presence of carbonate fluorapatite (CFA), the phosphatizated portion (L4-L5) is rich in Ca and P. The massive non-phosphatizated section (L3) contains high Mn, Ni, and Co, whereas the porous non-phosphatizated portion (L1-L2), which comprises detrital quartz and feldspar, is rich in Fe. Variations in properties of the Fe-Mn crust from the OSM-XX reflect changes in the nearby marine environment. The formation of this crust started at approximately 51.87 Ma, and precipitation of the CFA during the global phosphatization event that occurred at approximately 36-32 Ma highlights an elevated sea level and low temperature during the associated period. The high Mn, Ni, and Co concentrations and elevated Mn/Fe ratios of samples from the massive phosphatizated portion indicate that the oxygen minimum zone (OMZ) was enhanced, and reducing conditions prevailed during the crust formation. The high Fe and low Mn/Fe ratios in the porous portion indicate a weak OMZ and dominantly oxidizing conditions. These data reflect environmental changes following the end of the Mi-1 glacial period in the Miocene-Oligocene boundary. Subsequently, Mn/Fe and Co/Mn ratios increased slightly in the outermost part of Fe-Mn crust because of the enhanced bottom current and OMZ associated with the continued cooling from approximately 9 Ma. However, the reduced carbonate dissolution rate in the Pacific Ocean from approximately 6 Ma decreased the growth rate of the Fe-Mn crust.

• Economic and Environmental Geology
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• v.48 no.2
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• pp.147-160
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• 2015

In 2014, on 31 August and 1 September, the emissions of $CH_4$, $CO_2$, and $O_2$ gases were measured six times using the closed chamber method from exposed tidal flat sediments in the same position relative to the low point of the tidal cycle in the Eoeun-ri, Taean-gun, on the Mid-western Coast of Korea. The concentrations of $CH_4$ in the air sample collected in the chamber were measured using gas chromatography with an EG analyzer, model GS-23, within 6 hours of collection, and the other gases were measured in real time using a multi-gas monitor. The gas emission fluxes (source (+), and sink (-)) were calculated from a simple linear regression analysis of the changes in the concentrations over time. In order to see the surrounding parameters (water content, temperature, total organic carbon, average mean size of sediments, and the temperature of the inner chamber) were measured at the study site. On the first day, across three measurements during 5 hours 20 minutes, the observed $CO_2$ flux absorption was -137.00 to $-81.73mg/m^2/hr$, and the $O_2$ absorption, measured simultaneously, was -0.03 to $0.00mg/m^2/hr$. On the second day using an identical number of measurements, the $CO_2$ absorption was -20.43 to $-2.11mg/m^2/hr$, and the $O_2$ absorption -0.18 to $-0.14mg/m^2/hr$. The $CH_4$ absorption before low tide was $-0.02mg/m^2/hr$ (first day, Pearson correlation coefficient using the SPSS statistical analysis is -0.555(n=5, p=0.332, pronounced negative linear relationship)), and $-0.15mg/m^2/hr$ (second day, -0.915(n=5, p=0.030, strong negative linear relationship)) on both measurement days. The emitted flux after low tide on both measurement days reached a minimum of $+0.00mg/m^2/hr$ (+0.713(n=5, p=0.176, linear relationship which can be almost ignored)), and a maximum of $+0.03mg/m^2/hr$ (+0.194(n=5, p=0.754, weak positive linear relationship)) after low tide. However, the absolute values of the $CH_4$ fluxes were analyzed at different times. These results suggest that rate for $CH_4$ fluxes, even the same time and area, were influenced by changes in the tidal cycle characteristics of surface sediments for understanding their correlation with these gas emissions, and surrounding parameters such as physiochemical sediments conditions.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.1
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• pp.1-13
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• 2006

A field survey on the spatio-temporal distribution characteristics and origins of organic matter in surface sediments was carried out monthly at six stations in Gamak Bay, South Korea from April 2000 to March 2002. The range of ignition loss(IL) was $4.6{\sim}11.6%(7.1{\pm}1.6%)$, while chemical oxygen demand(CODs) ranged from $12.25{\sim}99.26mgO_2/g-dry(30.98{\pm}19.09mgO_2/g-dry)$, acid volatile sulfide(AVS) went from no detection(ND)${\sim}10.29mgS/g-dry(1.02{\pm}0.58mgS/g-dry)$, and phaeopigment was $6.84{\sim}116.18{\mu}g/g-dry(23.72{\pm}21.16{\mu}g/g-dry)$. The ranges of particulate organic carbon(POC) and particulate organic nitrogen(PON) were $5.45{\sim}23.24 mgC/g-dty(10.34{\pm}4.40C\;mgC/g-dry)$ and $0.71{\sim}2.99mgN/g-dry(1.37{\pm}0.58mgN/g-dry)$, respectively. Water content was in the range of $43.1{\sim}77.6%(55.8{\pm}5.6%)$, and mud content(silt+clay) was higher than 95% at all stations. The spatial distribution of organic matter in surface sediments was greatly divided between the northwestern, central and eastern areas, southern entrance area from the distribution characteristic of their organic matters. The concentrations of almost all items were greater at the northwestern and southern entrance area than at the other areas in Gamak Bay. In particular, sedimentary pollution was very serious at the northwestern area, because the area had an excessive supply of organic matter due to aquaculture activity and the inflow of sewage from the land. These materials stayed longer because of the topographical characteristics of such as basin and the anoxic conditions in the bottom seawater environment caused by thermocline in the summer. The tendency of temporal change was most prominently in the period of high-water temperatures than low-water ones at the northwestern and southern entrance areas. On the other hand, the central and eastern areas did not show a regular trend for changing the concentrations of each item but mainly showed a higher tendency during the low-water temperatures. This was observed for all but AVS concentrations which were higher during the period of high-water temperature at all stations. Especially, the central and eastern areas showed a large temporal increase of AVS concentration during those periods of high-water temperature where the concentration of CODs was in excess of $20mgO_2/g-dry$. The results show that the organic matters in surface sediments in Gamak Bay actually originated from autochthonous organic matters with eight or less in average C/N ratio including the organic matters generated by the use of ocean, rather than terrigenous organic matters. However, the formation of autochthonous organic matter was mainly derived from detritus than living phytoplankton, indicated the results of the POC/phaeopigment ratio. In addition, the CODs/IL ratio results demonstrate that the detritus was the product of artificial activities such as dregs feeding and fecal pellets of farm organisms caused by aquaculture activities rather than the dynamic of natural ocean activities.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.23 no.4
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• pp.153-178
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• 2018

Most operational uses of wind speed data require measurements at, or estimates generated for, the reference height of 10 m above mean sea level (AMSL). On the Ieodo Ocean Research Station (IORS), wind speed is measured by instruments installed on the lighthouse tower of the roof deck at 42.3 m AMSL. This preliminary study indicates how these data can best be converted into synthetic 10 m wind speed data for operational uses via the Korea Hydrographic and Oceanographic Agency (KHOA) website. We tested three well-known conventional empirical neutral wind profile formulas (a power law (PL); a drag coefficient based logarithmic law (DCLL); and a roughness height based logarithmic law (RHLL)), and compared their results to those generated using a well-known, highly tested and validated logarithmic model (LMS) with a stability function (${\psi}_{\nu}$), to assess the potential use of each method for accurately synthesizing reference level wind speeds. From these experiments, we conclude that the reliable LMS technique and the RHLL technique are both useful for generating reference wind speed data from IORS observations, since these methods produced very similar results: comparisons between the RHLL and the LMS results showed relatively small bias values ($-0.001m\;s^{-1}$) and Root Mean Square Deviations (RMSD, $0.122m\;s^{-1}$). We also compared the synthetic wind speed data generated using each of the four neutral wind profile formulas under examination with Advanced SCATterometer (ASCAT) data. Comparisons revealed that the 'LMS without ${\psi}_{\nu}^{\prime}$ produced the best results, with only $0.191m\;s^{-1}$ of bias and $1.111m\;s^{-1}$ of RMSD. As well as comparing these four different approaches, we also explored potential refinements that could be applied within or through each approach. Firstly, we tested the effect of tidal variations in sea level height on wind speed calculations, through comparison of results generated with and without the adjustment of sea level heights for tidal effects. Tidal adjustment of the sea levels used in reference wind speed calculations resulted in remarkably small bias (<$0.0001m\;s^{-1}$) and RMSD (<$0.012m\;s^{-1}$) values when compared to calculations performed without adjustment, indicating that this tidal effect can be ignored for the purposes of IORS reference wind speed estimates. We also estimated surface roughness heights ($z_0$) based on RHLL and LMS calculations in order to explore the best parameterization of this factor, with results leading to our recommendation of a new $z_0$ parameterization derived from observed wind speed data. Lastly, we suggest the necessity of including a suitable, experimentally derived, surface drag coefficient and $z_0$ formulas within conventional wind profile formulas for situations characterized by strong wind (${\geq}33m\;s^{-1}$) conditions, since without this inclusion the wind adjustment approaches used in this study are only optimal for wind speeds ${\leq}25m\;s^{-1}$.

• Journal of Environmental Impact Assessment
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• v.22 no.2
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• pp.135-145
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• 2013

The recycling of coal bottom ash generated from coal power plants in Korea has been limited due to heterogenous characteristics of the materials. The most common management option for the ash is disposal in landfills (i.e. ash pond) near ocean. The presence of large coarse and fine materials in the ash has prompted the desire to beneficially use it in an application such as fill materials. Prior to reuse application as fill materials, the potential risks to the environment must be assessed with regard to the impacts. In this study, a total of nine test cells with bottom ash samples collected from pretreated bottom ash piles and coal ash pond in a coal-fired power plant were constructed and operated under the field conditions to evaluate the leachability over a period of 210 days. Leachate samples from the test cells were analyzed for a number of chemical parameters (e.g., pH, salinity, electrical conductance, anions, and metals). The concentrations of chemicals detected in the leachate were compared to appropriate standards (drinking water standard) with dilution attenuation factor, if possible, to assess potential leaching risks to the surrounding area. Based on the leachate analysis, most of the samples showed slightly high pH values for the coal ash contained test cells, and contained several ions such as sodium, potassium, calcium, magnesium, chloride, sulfate, and nitrate in relatively large quantities. Three elements (aluminum, boron, and barium) were commonly detected above their respective detection limits in a number of leachate samples, especially in the early leaching period of time. The results of the test cell study indicate that the pollutants in the leachate from the coal ash test cells were not of a major concern in terms of leaching risk to surface water and groundwater under field conditions as fill materials. However, care must be taken in extending these results to actual applications because the results presented in this study are based on the limited field test settings and time frame. Structural characteristics and analysis for coal bottom ash may be warranted to apply the materials to actual field conditions.

• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.193-198
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• 2015

This research was conducted to provide an improvement plan concerning medical treatment on board and medical health care conditions for seafarers. 139 persons from government agencies and seafarer related organizations, who could influence the government's seafarers healthcare policy-making, were asked to fill in the questionnaire prepared for this research about their perceptive views on actual condition of health and disease management for seafarers. The results of the survey on seafarer's health care management conditions(p<0.01), health care manage ability(p<0.01), current radio emergency medical service policy(p<0.01), usefulness of on board medicine chest and medical equipment(p<0.05), and the system of the onboard medical care persons show the difference of perception level among the seafarer related organizations. But generally, the rate of negative responses was high. And this research suggests that there is an urgent need to provide portable health measurement equipment on board, reenforce regular medical examination and establish the seafarer's health promotion center for telemedicine and healthcare management(p<0.01) in order to improve the onboard medical treatment support system for healthcare of seafarers.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.56-67
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• 2018

With the introduction of the maritime safety supervisor system in Korea following the passenger vessel Sewol accident, the safety control system for coastal vessels has been reinforced. A maritime safety supervisor performs marine accident prevention activities by offering periodical or occasional guidance and supervision. When a deficiency is found during guidance or supervision sessions, an order for improvement is issued to rectify the problem by such measures as supplementation or replacement of vessel facilities, improvement of work hours and working conditions for employees, educational and training programs for executives and employees, or the improvement of other affairs relating to maritime safety control. However the present order for navigation suspension by a maritime safety supervisor is limited solely to supplementation or replacement. For this reason, orders for navigation suspension against other facilities is impossible, even if a serious deficiency that could lead to a marine accident such as poor cargo loading conditions or unqualified crew is identified. Therefore, the order for vessel navigation suspension to secure seaworthiness should be expanded to include cargo loading/unloading operations, certificates and documentation, maritime safety management systems, and human elements including emergency drills and working conditions, in addition to the supplementation or replacement of vessel facilities that exists.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.1
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• pp.96-103
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• 2015

The effects of $CO_2$ concentration, nutrient levels, and irradiance on the growth of germlings and juveniles, and on the photosynthesis of adults were examined in a green tide alga, Ulva australis. We used a factorial experimental design with two $CO_2$ concentrations (380 and 750 ppm), two nutrient levels (control and PES medium), and two irradiance levels (50 and $100{\mu}mol$ photons $m^{-2}s^{-1}$). Germlings grew best ($664.15{\pm}61.45{\mu}m$ in length) under conditions of 750 ppm, PES, and $100{\mu}mol$ photons $m^{-2}s^{-1}$ after 10 days in culture. Relative growth rates (RGR) of the juveniles were greatest (4.41% $day^{-1}$) under conditions of 750 ppm, PES, and $50{\mu}mol$ photons $m^{-2}s^{-1}$ after 5 days in culture. Photosynthetic efficiency ($F_v/F_m$) of the adult discs was $0.73{\pm}0.05$ before the experiment and reached a maximum ($0.83{\pm}0.01$) under conditions of 750 ppm, control, and $50{\mu}mol$ photons $m^{-2}s^{-1}$ after 5 days in culture. Growth (germlings and juveniles) and photosynthesis (adult discs) of Ulva australis increased when $CO_2$ levels were 750 ppm. Additionally, the optimal irradiance for growth and photosynthesis differed among stages, wherein germlings grew best at $100{\mu}mol$ photons $m^{-2}s^{-1}$, juveniles grew best at $50{\mu}mol$ photons $m^{-2}s^{-1}$, and adults photosynthesized most at $50{\mu}mol$ photons $m^{-2}s^{-1}$. The performance of Ulva australis at all examined life stages was enhanced under the PES nutrient treatment. In conclusion, the physiological responses of U. australis to varying $CO_2$, nutrient, and irradiance levels differed slightly among life stages. However, growth and photosynthesis always increased with elevated $CO_2$ and nutrient concentrations. These results indicate that U. australis green tide blooms might occur more frequently in coastal areas if $CO_2$ and nutrient concentrations increase.