• ALGAE
• /
• v.32 no.2
• /
• pp.139-153
• /
• 2017

The ability of a red tide species to take up nutrients is a critical factor affecting its red tide dynamics and species competition. Nutrient uptake by red tide species has been conventionally measured by incubating nutrient-depleted cells for a short period at 1 or 2 light intensities. This method may be applicable to certain conditions under which cells remain in oligotrophic water for a long time and high nutrients are suddenly introduced. Thus, a new method should be developed that can be applicable to the conditions under which cells are maintained in eutrophicated waters in healthy conditions and experience light and dark cycles and different light intensities during vertical migration. In this study, a new repletion method reflecting these conditions was developed. The nitrate uptake rates of the red tide dinoflagellate Prorocentrum micans originally maintained in nitrate repletion and depletion conditions as a function of nitrate concentration were measured. With increasing light intensity from 10 to $100{\mu}E\;m^{-2}s^{-1}$, the maximum nitrate uptake rate ($V_{max}$) of P. micans increased from 3.6 to $10.8 pM\;cell^{-1}d^{-1}$ and the half saturation constant ($K_{s-NO3}$) increased from 4.1 to $6.9{\mu}M$. At $20{\mu}E\;m^{-2}s^{-1}$, the $V_{max}$ and $K_{s-NO3}$ of P. micans originally maintained in a nitrate repletion condition were similar to those maintained in a nitrate depletion condition. Thus, differences in cells under nutrient repletion and depletion conditions may not affect $K_{s-NO3}$ and $V_{max}$. Moreover, different light intensities may cause differences in the nitrate uptake of migratory phototrophic dinoflagellates.

• ALGAE
• /
• v.18 no.4
• /
• pp.281-288
• /
• 2003

To study the environmental features causing a bloom of the novel dinoflagellate Heterocapsa circularisquama (Dinophyceae), hydrographic and chemical aspects were measured in the Uranouchi Bay, Kochi Prefecture, Japan, from January to December, 1997. The cell density of H. circularisquama increased rapidly in early October, and dropped sharply in mid-October. Growth rate of H, circularisquama during bloom period appeared 1.50 division day$^{-1}$ under high water temperature (25$^{\circ}C$) and salinity (32 psu) conditions. Althought the result from hydrographic aspect indicated good condition for their growth, dissolved inorganic phosphorus (DIP) concentration in surface layer before bloom formation was less than 0.70uM, which is lower than their half saturation constant(Ks). Dissolved inorganic nitrogen(DIN): DIP ratio was > 30, indicating potential P-limitation. However, before bloom formation period of H. circularisquama, DIP concentrations were high in bottom layer (> 4.0 uM). Some studies reported that H. circularisquama had the ability to migrate vertically and to utilize dissolved organic phosphorus (DOP). Thus, DIP in bottom layer might have been utilized by H. circularisquama for their growth.DOP might have weakly affected their growth because of low reactive DOP concentrations owing to low DOP concentration (ca. 0.39 uM). Thus, if nutrient condition of bottom layer in Uranuchi Bay is not improved, the outbreaks of H. circularisquama red tides may became an annual feature.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.53 no.4
• /
• pp.386-395
• /
• 2017

For scientific research, a number of acoustic surveys using commercial echosounders equipped in fishing vessels were conducted throughout the world; however, few studies were performed in South Korea. Hence, this research is an preliminary study for presenting the application of a sounder from a fishing vessel. The fishing operations using a pair trawler (7 Cheonghae) was conducted in the Northwest-Western sea of Jeju Island from 20 to 23 April, 2016. Substantial impulse noises and attenuated signals were eliminated by the latest algorithms. Acoustic signals were grouped into the fish aggregations and long layer-like signals. The fish aggregations appeared between 30 and 60 m, and long layer-like signals showed the diurnal vertical migration. Energetic, morphological and positional properties of the fish aggregations and layer-like signals were described. The fish aggregations appeared mainly between sunrise and sunset; however layer-like signals tended to be presented regardless of time in consideration of the time series analysis. On the basis of the consignment sales, Scomberomorus niphonius, the target species of F/V 7 Cheonghae, was the highest catch with 4,280 kg (74.6%) and might have appeared in fish aggregations and layer forms.

• Journal of Korean Orthopaedic Sports Medicine
• /
• v.1 no.2
• /
• pp.124-130
• /
• 2002

Purpose: The results of meniscal repair of peripheral tear of meniscus with meniscal arrow was analysed. Materials and Methods: Peripheral tears of posterior 1/2 of menisci of 25 cases including 18medial, 6 lateral and 1 both menisci were repaired with meniscal arrows. One to six meniscal arrows were used for each meniscus according to the length of tears. Concurrent tears of ACL were noted in14 cases. The follow-up period was 3.4 years in average. The findings of physical examination and MRI which were taken once or twice in 1$\~$5 years after operation were evaluated. Results: Healing of the tear was achieved in all cases. However, a vertical longitudinal tear of body occurred in two medial menisci along the line of insertion of arrows. An arrow migrated subcuta-neously in two cases, respectively. Conclusions: The meniscal arrow was effective in the treatment of the peripheral tear of menicus. However, there was a chance of occurrence of longitudinal tear of the meniscus in case of insertion of arrows in a row. Migration of the arrow may occur.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.36 no.6
• /
• pp.749-756
• /
• 2003

Hydroacoustic and open-closing zooplankton net survey were conducted to understand the characteristics of the sound scattering layer (SSL) and to estimate the density of an euphausiid (Euphausia pacifica) in the SSL, in the northwestern part of the East China Sea. The survey was carried out during July 6-9 2002 at 8 sampling stations for zooplankton. The virtual echogram technique was used to identify E. pacifica from all acoustic scatters. Mean volume backscattering strength difference $(MVBS_{120kHz-38kHz})$ and target strength equation for E. pacifica were derived from the Distorted-wave Born Approximation (DWBA) model. Although vertical migration of the SSL is similar to the general pattern, dispersion at night shows some differences. Estimated mean density using acoustic data ranged from $20.4-221.4\;mg/m^3$ over the whole depth, and $87.1-553.5\;mg/m^3$ in the SSL. The density using the zooplankton net ranged from $0.2-362.4\;mg/m^3$ and was not related to net deploying method. The results from the acoustic and net survey suggest that E. pacifica might be an important zooplankton community in the northwestern part of the East China Sea.

• The Journal of the Acoustical Society of Korea
• /
• v.38 no.6
• /
• pp.678-686
• /
• 2019

Underwater communication performance is degraded by the influence of Inter-Symbol Interference (ISI) due to multipath. Passive time reversal processing is the most effective technique for mitigating multipath, and the diversity combining method can be used to improve its performance. This paper analyzed communication performance using the beam diversity combining method, which combines signals obtained through the beam steering to various angles. Directions of arrival were estimated through the beam-time migration, which, in turn, was estimated from probe signals received by a vertical line array. The performance was analyzed based on the number and type of combinations among the estimated angles. In this paper, the data obtained from the Biomimetic Long range Acoustic Communications 2018 (BLAC18) experiment, which was conducted in the East sea, ~50 km east of Pohang, in October 2018, were used for the analysis. The output Signal to Noise Ratio (SNR) was used as communication indicators.

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

• Journal of Radiation Protection and Research
• /
• v.47 no.1
• /
• pp.30-38
• /
• 2022

Background: Residential areas have some factors on the external exposure of residents, who usually spend a long time in these areas. Although various survey has been carried out by the government or the research institutions after the Fukushima Daiichi Nuclear Power Plant accident, the mechanism of radiocesium inventory in the terrestrial zone has not been cleared. To better evaluate the radiation environment, this study investigated the temporal changes in air dose rate and ¹³⁷Cs inventories (Bq/m²) in residential areas and agricultural fields. Materials and Methods: Air dose rate and ¹³⁷Cs inventories were investigated in residential areas located in an evacuation zone at 5-8 km from the Fukushima Daiichi Nuclear Power Plant. From December 2014 to September 2018, the air dose rate distribution was investigated through a walking survey (backpack survey), which was conducted by operators carrying a γ-ray detector on their backs. Additionally, from December 2014 to January 2021, the ¹³⁷Cs inventories on paved and permeable grounds were also measured using a portable γ-ray detector. Results and Discussion: In the areas where decontamination was not performed, the air dose rate decreased faster in residential areas than in agricultural fields. Moreover, the ¹³⁷Cs inventory on paved surfaces decreased with time owing to the horizontal wash-off, while the ¹³⁷Cs inventory on permeable surfaces decreased dramatically owing to the decontamination activities. Conclusion: These findings suggest that the horizontal wash-off of ¹³⁷Cs on paved surfaces facilitated the air dose rate decrease in residential areas to a greater extent compared with agricultural fields, in which the air dose rate decreased because of the vertical migration of ¹³⁷Cs. Results of this study can explain the faster environmental restoration in a residential environment reported by previous studies.

• Geomechanics and Engineering
• /
• v.29 no.1
• /
• pp.91-97
• /
• 2022

The cohesive non-swelling soil (CNS) cushion technology has been widely applied in the subgrade and slope improvement at expansive soil regions. However, the mechanism of the inhibition effect of the CNS layer on expansive soil (ES) has not been fully understood. We performed four outdoor model tests to further understand the inhibition effect, including different kinds of upper layer and thickness, under the unidirectional seepage condition. The swelling deformation, soil pressure, and electrical resistivity were constantly monitored during the saturation process. It is found that when a CNS layer covered the ES layer, the swelling deformation and electrical resistivity of the ES layer decreased significantly, especially the upper part. The inhibition effect of the CNS layer increases with the increase of CNS thickness. The distribution of vertical and lateral soil pressure also changed with the covering of a CNS layer. The electrical resistivity can be an effective index to describe the swelling deformation of ES layer and analyze the inhibition effect of the CNS layer. Overall, the CNS deadweight and the ion migration are the major factors that inhibit the swelling deformation of expansive soil.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.5
• /
• pp.500-506
• /
• 2008

Enhanced phytoremediation with EDTA or PSM(Phosphate solubilizing microorganism) was studied using green foxtail (Setaria viridis) in columns packed with 1,200 mgPb/kg contaminated soil to investigate the effects of EDTA or PSM on the plant uptake and vertical migration of Pb. EDTA, equimolar amount of total Pb in the column soil, was administered in two methods: the one was treated with 1/6 aliquots of the equimolar EDTA every week for 6 weeks and the other was treated with single dose of the equimolar EDTA before 14 days of harvest. The results showed that higher concentrations of Pb accumulated in the biomass of green fowtail after the chemical or biological treatment. The plant-root Pb concentration in PSM treatment(M), EDTA aliquot treatment(ES), and single dose treatment(E) was 2.6, 3.0, and 3.3 times higher, respectively, than that in the plant-root of control(164.7 mg/kg). The plant-stem Pb concentration in the M, ES and E treatment was 27, 37, and 40 times higher than that in the stem of control(8.1 mg/kg). The translocation factor, the ratio of shoot/root Pb concentration, was 0.6 in the two EDTA treatment, 0.5 in the M treatment, and 0.05 in the control, respectively. The largest amount of Pb was phyto-extracted in the E treatment whereas vertical migration of EDTA was significant in the ES treatment. This result showed that a single large dose of EDTA before harvest serves better for enhanced phytoremediation of Pb. Although, treatment with PSM showed less Pb phytoextraction by the plant but enhanced both the growth of plants in the column and microbial dehydrogenase activity in the soils. Therefore, enhanced phytoextraction of Pb with PSM treatment can be an alternative option for EDTA treatment, which is toxic to plants and soil ecosystem.