• ALGAE
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• v.24 no.2
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• pp.111-120
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• 2009

Choosing an appropriate sample unit is a fundamental decision in the design of ecological studies. While numer-ous methods have been developed to estimate organism abundance, they differ in cost, accuracy and precision.Using both field data and computer simulation modeling, we evaluated the costs and benefits associated with twomethods commonly used to sample benthic organisms in temperatc kelp forests. One of these methods, theTargeted Sampling method, relies on different sample units, each "targeted" for a specific species or group ofspecies while the other method relies on coefficients that represent ranges of bottom cover obtained from visual esti-mates within standardized sample units. Both the field data and the computer simulations suggest that both meth-ods yield remarkably similar estimates of organisnm abundance and among-site variability, although the Coefficientmethod slightly underestimates variability armong sample units when abundances are low. In contrast, the twomethods differ considerably in the effort needed to sample these communities; the Targeted Sampling requiresmore time and twice the persormel to complete. We conclude that the Coeffident Sampling metliod may be bettcrfor environmental monitoring programs where changes in mean abundance are of central conccm and resources arelimiting, but that the Targeted sampling methods may be better for ecological studies where quantitative reIation-ships among species and small-scale variability in abundance are of central concern.

• Journal of the korean society of oceanography
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• v.39 no.4
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• pp.207-211
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• 2004

We used long time series of hydrographic and biological variables to examine the ecosystem consequences of a rare, anomalous event in the south sea of Korea. The highest zooplankton biomass in 36 years of sampling occurred in April 1997. Zooplankton biomass exceeded 2 times than the long-term mean at 35% of the stations. Copepod abundance was low in April and June and also failed to show a seasonal peak in 1997. Mackerel (Scomber japonicus) catches were very low in spring 1997 and 1999, in spite of a positive correlation between zooplankton biomass and mackerel catches at lags of 0, 12 and 24 months. It was discussed that a high zooplankton biomass with low copepod abundance in April 1997 resulted from unusual high temperature and salps abundance. Water temperatures were ca. $2^{\circ}C$ higher than the long-term mean at the surface. Salps and doliolids (thaliaceans), especially the warm-water species Doliolum nationalis, dominated the zooplankton. An unusual incursion of the Tsushima Warm Current may have transported the thaliaceans into the area and/or produced favorable conditions for a bloom. This study suggested that taxonomic composition of zooplankton was important to decide mackerel catches.

• ALGAE
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• v.33 no.4
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• pp.359-366
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• 2018

Mesocosm experiments conducted for ecological purposes have become increasingly popular because they can provide a holistic understanding of the biological complexities associated with natural systems. This paper describes a new outdoor mesocosm designed for $CO_2$ perturbation experiments of benthos. Manipulated the carbonate chemistry in a continuous flow-through system can be parallelized with diurnal changes, while irradiance, temperature, and nutrients can vary according to the local environment. A target hydrogen ion activity (pH) of seawater was sufficiently stabilized and maintained within 4 h after dilution, which was initiated by the ratio of $CO_2$-saturated seawater to ambient seawater. Specifically, pH and $CO_2$ partial pressure ($pCO_2$) levels gradually varied from 8.05-7.28 and $375-2,691{\mu}atm$, respectively, over a range of dilution ratios. This mesocosm can successfully manipulate the pH and $pCO_2$ of seawater, and it demonstrates suitability for ocean acidification experiments on benthic communities.

• Korean Journal of Materials Research
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• v.32 no.4
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• pp.186-192
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• 2022

Collagen is one of the most widely used biological materials in medical design. Collagen extracted from marine organisms can be a good biomaterial for tissue engineering applications due to its suitable properties. In this study, collagen is extracted from fish skin of Ctenopharyngodon Idella; then, the freeze drying method is used to design a porous scaffold. The scaffolds are modified with the chemical crosslinker N-(3-Dimethylaminopropyl)-N'-ethyl carbodiimide hydrochloride (EDC) to improve some of the overall properties. The extracted collagen samples are evaluated by various analyzes including cytotoxicity test, SDS-PAGE, FTIR, DSC, SEM, biodegradability and cell culture. The results of the SDS-PAGE study demonstrate well the protein patterns of the extracted collagen. The results show that cross-linking of collagen scaffold increases denaturation temperature and degradation time. The results of cytotoxicity show that the modified scaffolds have no toxicity. The cell adhesion study also shows that epithelial cells adhere well to the scaffold. Therefore, this method of chemical modification of collagen scaffold can improve the physical and biological properties. Overall, the modified collagen scaffold can be a promising candidate for tissue engineering applications.

• Korean Journal of Environmental Biology
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• v.40 no.4
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• pp.374-386
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• 2022

Phytoplankton communities, with emphasis on picoplankton and nanoplankton, were investigated in Gamak Bay, South Korea, where freshwater input and coastal water intrusion shape ecosystem functions. Shellfish farms and fish farms are located in the inner bay and outer bay, respectively, and tides translocate uneaten food and urine production from aquaculture farms toward the inner bay. Water masses were distinctly different based on a significantly different density between the surface and bottom layer and among three water masses, including the inner bay, outer bay, and Yeosu Harbor. Phytoplankton communities were quantified using flow cytometry and size-fractionated chlorophyll-a (chl-a) was measured. Salinity was a principal variable separating phytoplankton communities between the surface and bottom layer, whereas Si(OH)₄ controlled the communities in the inner bay, and NH₄⁺ and PO₄^3- governed the outer bay communities. While phycocyanin-containing (PC) cyanobacteria dominated in the outer bay, phycoerythrin-containing (PE) cyanobacteria dominance occurred with cryptophyte dominance, indicating that nutrients affected the distribution of pico- and nanoplankton and that cryptophytes potentially relied on a mixotrophic mode by feeding on PE cyanobacteria. Interestingly, picoeukaryotes and eukaryotes larger than 10 ㎛ were mostly responsible for the ecological niche in the western region of the bay. Given that chl-a levels have historically declined, our study highlights the potential importance of increased small phytoplankton in Gamak Bay. Particularly, we urge an examination of the ecological role of small phytoplankton in the food supply of cultivated marine organisms.

• The Journal of the Acoustical Society of Korea
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• v.28 no.3
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• pp.187-197
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• 2009

The bubbles are created by waves, raindrops, water collision, vessels sailing at sea, life activities of various marine organisms in the ocean and other sources. The bubbles affect the intensity and sound speed of acoustic waves in the ocean. We indirectly observed bubbles in order to understand the creation of and the effects of bubbles on sound waves, using an Acoustic Bubble Spectrometer (ABS) and CTD, from 04:00 to 17:00, 19 September, 2007. We also analyzed the correlation of wind speed and the generation of bubbles, the amount of bubbles, and the sound speed variation at 50, 60, and 70 kHz. Finally, We simulated the way how bubbles affect sound transmission based on the analysis results.

• Journal of Species Research
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• v.13 no.1
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• pp.89-99
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• 2024

Larger benthic foraminifera (LBF) are a group of marine organisms that inhabit oligotrophic subtropicaltropical photic zones, commonly possess relatively large shells (i.e., tests) with a complex internal structure and host photosynthetic endosymbionts. In this study, we provide a new report of a LBF species belonging to the genus Sorites Ehrenberg, 1839, with a brief description and images of the test. The sediment samples were collected by SCUBA diving from the east coast of Jeju Island (South Korea). The discoidal test shape and annular series of chamberlets with a single row of apertures surrounded by rim indicate that these specimens belong to the genus Sorites, and this is the first record of the genus in Korea. The arrangement of early chamberlets, septular disposition, and the aperture details suggest that the specimens can be assigned to Sorites orbiculus(Forsskål in Niebuhr, 1775). Only three LBF species, including the present species, have been reported from Korean waters. The present study provides additional information for the evaluation of foraminiferal diversity including LBF in Korea and suggests the necessity of continuous investigations to understand the diversity of Sorites species in Korea.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.2
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• pp.88-101
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• 2013

The International Convention for the Control and Management of Ship's Ballast Water and Sediments was adopted at 2004 and then various BWMS (ballast water management system) have been developed. In this study, WET (whole effluent toxicity) test with algae (diatom) Skeletonema costatum as primary producer, invertebrate (rotifera) Brachionus plicatilis as 1st consumer and fish (olive flounder) Paralichthys olivaceus as predator, chemical analysis and ERA (environmental risk assessment) were conducted to assess the unacceptable effect on marine ecosystem by emitting the discharge water treated with AquaStar$^{TM}$ BWMS using electrolysis as main treatment equipment for removing the marine organisms in the ship's ballast water. The most sensitive test organism on discharge water treated with AquaStar$^{TM}$ BWMS was S. costatum that gave the NOEC value of 25.00%, LOEC value of 50.00% and 72hr-$EC_{50}$ value of 69.97% from WET test result for 20 psu salinity treated discharge water. NOEC and LOEC value of B. plicatilis and P. olivaceus exposed at 20 psu salinity treated discharge water were 50.00% and 100.00%, respectively. In the chemical analysis results, total number of substances produced by AquaStar$^{TM}$ BWMS was 18 which were bromate, 7 volatile halogenated organic compounds, 7 halogenated acetic acids, 3 halogenated acetonitriles and chloropicrin. Eighteen substances did not consider as persistence and bioaccumulative chemicals. Uncertainty of toxic property of 18 substances was high. PECs of 18 substances calculated by MAMPEC model were ranged from $4.58{\times}10^{-4}$ to $4.87{\mu}g\;L^{-1}$, PNECs of them were ranged from $1.6{\times}10^{-2}$ to $3.2{\times}10^2{\mu}g\;L^{-1}$. And, the PEC/PNEC ratio of 18 substances did not exceed 1. Therefore, ERA for produced substances indicate that the discharge water treated with AquaStar$^{TM}$ BWMS does not pose unacceptable effect on marine life. And $EC_{50}$ value of S. costatum on discharge water treated by BWMS using the electrolysis had positive correlation with initial TRO concentration, concentration and kind & level of HAAs.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.78-91
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• 2018

In order to understand the distributions of organic matter and heavy metal concentrations in the surface sediment of Jaran Bay, we measured the grain size, total organic carbon (TOC), total nitrogen (TN), and heavy metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb, and Zn) in surface sediments collected at 15 stations in this bay in November 2014. The sediment consisted of finer sediment such as mud and clay, with 8.6-9.8Ø($9.3{\pm}0.3$Ø) of mean grain size. The concentrations of TOC and TN in the sediment ranged from 1.51-2.39 % ($1.74{\pm}0.22%$) and 0.20-0.33 % ($0.23{\pm}0.03%$), respectively, and did not show spatial difference. The carbon to nitrogen ratio (C/N ratio) ranged from 5-10, indicating that organic matter in the sediment originated from oceanic sources such as animal by-products from fish and shellfish farms. The concentrations of Cr, Fe, and Mn were much higher in the mouth of the bay than in the inner bay, and the concentrations of As, Cd, Cu, Hg, Pb, and Zn showed an opposite distribution pattern. Based on the results of the sediment quality guidelines (SQGs), enrichment factor (EF), geoaccumulation index ($I_{geo}$), pollutant load index (PLI), and ecological risk index (ERI), the surface sediment in Jaran Bay is not polluted or only slightly polluted with Cd, Cr, Cu, Hg, Pb, and Zn, whereas it is moderately to strongly polluted with As. In particular, some regions in the bay were identified as having a considerable risk status, indicating that metal concentration in the sediment could impact benthic organisms. Thus, the systematic management for marine and land sources of organic matter and heavy metals around Jaran Bay is necessary in order to ensure seafood safety and maintain sustainable production on shellfish farms.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.2
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• pp.84-90
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• 2009

We incubated marine columnar sediments at $25^{\circ}C$ for 230 days to simulate the responses of phosphorus in the sediment which was exposed to freshwater. The incubation was composed of three different treatments (FW: freshwater, FWA: freshwater under anoxic condition, and SW: seawater as a Control). Six particulate fractions of phosphorus in sediment were obtained through sequential extraction and, for comparison, phosphate concentrations in porewater and superlying water were also determined. After the incubation, evidently higher concentrations of phosphate were found in FW and FWA compared to SW. Mass extinction of living organisms in marine sediment from freshwater shock and consequent decay of their corps probably contributed such high phosphate spike in the overlying water. Higher concentrations of BD-P(lron-bound P) were found in FW compared to SW. After exposure to the freshwater, we could determine that penetration depth of dissolved oxygen in marine sediment will be deeper. A result of increases of ferrous compounds in freshwater where contained less sulfide has been obtained. Because of these phenomena, BD-P was increased in FW. On the contrary, BD-P was decreased in FWA since poor dissolved oxygen concentration. In FWA, total amount of Leachable P(SUM of LOP) has been remarkably increased through the experiment, which strongly suggested the easy conversion of the leachable P into reactive P. This experiment has shown that most of diverse P species in marine sediment were leachable under freshwater and low oxygen condition. Therefore reclamation of natural tidalfalt and consequent freshwater introduction seems to trigger the conversion of diverse P-species to leachable P in the marine sediments, which will exert high benthic load of phosphate to the overlying water.