• Animal cells and systems
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• 제14권2호
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• pp.125-128
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• 2010

This study investigated the effect of different light intensities on first feeding of chub mackerel Scomber japonicus larvae. Fertilized eggs, obtained from LHRHa-induced spawning of captive broodstock, were stocked (60 larvae/l) into twelve 30-1 aquaria under light intensities of 0, 100, 200, 500 and 1000 lx, with three replicate aquaria per treatment. Temperature was maintained at $20^{\circ}C$ and salinity was 35 psu. Larvae were fed the rotifer Brachionus rotundiformis at a density of five rotifers/ml. Feeding incidence was measured as the percentage of larvae with prey in the digestive tract. Feeding intensity was evaluated as the number of prey in the digestive tract of the larvae. Larvae fed in darkness (0 lx) had significantly lower (P < 0.05) feeding incidence ($13{\pm}0.05%$ larvae with prey) and feeding intensity ($1.00{\pm}0.05$ rotifers per larva) than those larvae fed at 100 ($30{\pm}0.07%$, $1.17{\pm}0.09$ rotifers per larva), 200 ($43{\pm}0.08%$, $1.24{\pm}0.11$ rotifers larvae$^{-1}$), 500 ($53{\pm}0.08%$, $1.48{\pm}0.14$ rotifers per larva) and 1000 lx ($60{\pm}0.08%$, $1.38{\pm}0.13$ rotifers per larva). The feeding incidence of S. japonicus larvae increased with light intensity while feeding intensity showed no significant difference (P > 0.05) between light treatments.

• 수산해양교육연구
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• 제28권2호
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• pp.315-322
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• 2016

This study determined the optimum microalgae species and concentration for growth of small rotifer Proales similis, in community cultures by feeding it several different foods. Four single trials (Tetraselmis suecica, TET; Isochrysis galbana, ISO; Nannochloropsis oculata, NAN; freshwater Chlorella vulgaris, CHL) were conducted at 5 psu and $25^{\circ}C$. The maximum density and specific growth rate (SRG) were highest for rotifer fed CHL reaching 1,075 individuals (inds.)/mL and 0.83 respectively. By contrast, other foods of ISO, NAN and TET resulted in poor growth rates and maximum density. In the freshwater C. vulgaris experiments examining a range of 0.05 to $8.8mg/10^4rotifers$, the growth of rotifer tended to decrease with the amount of supplement. The maximum density and SGR of females was highest at 910 inds./mL and 0.55 respectively, at $0.05mg/10^4rotifers$. These results suggest that the best microalgae species for the culture of P. similis is freshwater C. vulgaris and the optimum concentration is $0.05mg/10^4rotifers$.

• 한국해양공학회지
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• 제28권3호
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• pp.236-244
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• 2014

This study considered a seagrass habitat in order to analyze the characteristics of a marine environment of seagrass located in the Seomjin river estuary, through an analysis of the distribution of the water depth, field observation, and three-dimensional numerical experiments using an EFDC model. The seagrass habitat was usually distributed at D.L(-) 0.5~0.0 m, and was hardly seen in the intertidal zone higher than that range. The distribution of the water temperature was within the range of $7.0{\sim}23.2^{\circ}C$, and the seagrass was demonstrated to have a strong tolerance to changes in the water temperature. In addition, the salinity distribution was found to be 27.2~31.0 psu, with suspended solids of 32.1 mg/L, which were higher than the previous research results (Huh et al., 1998), implying that there may be a reduction in the amount of deposits caused by the suspended solids. As for the sedimentary facies, they were comprised of 62.7% sand, 19.1% silt, and 18.2% clay, indicating that the arenaceous was superior and the sedimentary facies were similar to that of Dadae Bay. According to a numerical experiment, the maximum tidal current was 75 cm/s, while the tidal residual current was 10 cm/s, confirming that it sufficiently adapted to strong tidal currents. The erosion and deposition are predicted to be less than 1.0 cm/year. Thus, it is judged that the resuspension of sediments due to tidal currents and the changes in sedimentary facies are insignificant.

• Environmental Analysis Health and Toxicology
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• 제22권3호
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• pp.211-218
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• 2007

Even though some standard developmental bioassay protocols for environmental assessment using sea urchins have already been described, there have not been many attempts to apply and modify these protocols with Korean species. Therefore, there is a strong need to establish standard bioassay protocols using sea urchins commonly found in Korea. Prior to developing a new protocol, it is essential to know the optimal conditions for the bioassay procedures. We investigated the optimal conditions (temperature, salinity, and embryo density) of the sea urchin Strongylocentrotus intermedius. The ideal temperature for developmental bioassay of S. intermedius was determined to be $15^{\circ}C$ and the time required for the embryo to become pluteus larva was 72 hr. The optimal range of salinity for the embryo toxicity using S. intermedius was between 30 to 32 psu, which is similar to the range found in the natural habitats of adult populations. The optimum density of embryos at the beginning of bioassays was 100 embryos/mL. When the assays were carried out at higher densities, the proportion of normally developed larvae decreased significantly.

• 대한원격탐사학회지
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• 제23권3호
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• pp.161-169
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• 2007

A study was conducted in the Hong Kong with the aim of deriving an algorithm for the retrieval of suspended sediment (SS) and sea surface salinity (SSS) concentrations from Aqua/MODIS level 1B reflectance data with 250m and 500m spatial resolutions. 'In-situ' measurements of SS and SSS were also compared with coincident MODIS spectral reflectance measurements over the ocean surface. This is the first study of SSS modeling in Southeast Asia using earth observation satellite images. Three analysis techniques such as multiple regression, linear regression, and principal component analysis (PCA) were performed on the MODIS data and the 'in-situ' measurement datasets of the SS and SSS. Correlation coefficients by each analysis method shows that the best correlation results are multiple regression from the 500m spatial resolution MODIS images, $R^2$= 0.82 for SS and $R^2$ = 0.81 for SSS. The Root Mean Square Error (RMSE) between satellite and 'in-situ' data are 0.92mg/L for SS and 1.63psu for SSS, respectively. These suggest that 500m spatial resolution MODIS data are suitable for water quality modeling in the study area. Furthermore, the application of these models to MODIS images of the Hong Kong and Pearl River Delta (PRO) Region are able to accurately reproduce the spatial distribution map of the high turbidity with realistic SS concentrations.

• 한국환경과학회지
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• 제28권11호
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• pp.1005-1017
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• 2019

Environmental factors and changes in phytoplankton community structure before (August 5, 2017), during (August 18 and 25) and after (August 30 and September 15) freshwater input were analyzed to investigate the effects of freshwater input from Ganwol and Bunam lakes located in the upper part of Cheonsu Bay. Due to the large amount of freshwater input in the Cheonsu Bay, the surface salinity of the bay decreased by more than 8 psu, and the thermocline existing in the bay during August weakened. In addition, hypoxic phenomena occurred temporarily in the bay as the low oxygen water mass from the freshwater lakes flowed into the bay, and chemical oxygen demand, nutrients, and N/P increased with freshwater inflow. The density of phytoplankton during the freshwater inflow increased owing to their input from the freshwater lakes. Diatom species (Eucampia zodiacus) dominated the phytoplankton community in the bay before freshwater input; nanoflagellates, chlorophyta, cyanobacteria, and diatoms (Pseudonitzschia delicatissima, Chateocceros spp.) entered during freshwater input; and after freshwater inflow ended, diatoms (Chateocceros spp.) again became predominant indicating a return to previous conditions. The amount of phytoplankton standing crops increased sharply due to the inflow of freshwater species into the bay on the second day of discharge compared to before freshwater input; pre-discharge conditions were restored at most stations except at some sites close to the Bunam Lake three days after discharge. Therefore, the large amount of freshwater flowing into the bay affects not only the geochemical circulation in the bay but also the phytoplankton community structure. In particular, the high concentration of nutrients in the freshwater lake affect the marine ecosystem of the bay during August.

• 한국수산과학회지
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• 제54권4호
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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.

• 한국어류학회지
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• 제31권1호
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• pp.23-29
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• 2019

이번 연구에서 바리과 어종의 새로운 교잡종을 생산하기 위한 연구의 일환으로 능성어 (Hyporthodus septemfasciatus) ♀${\times}$대왕바리 (Epinephelus lanceolatus) ♂ (CGGG)의 발생 양상, 부화율, 기형 발생률 그리고 부화 소요시간을 조사하고, 교잡종의 모계어종의 순종 (능성어 ♀${\times}$♂, CG)과 비교하였다. CGGG와 CG 수정란은 자외선 살균 해수가 채워진 5-L 용량의 비이커 9개에 3,000~5,000개/비이커의 밀도로 수용되었으며, 발생 기간 중 수온은 $23.5{\sim}24.8^{\circ}C$ 그리고 염분은 32.1~32.8 ppt 였다. CGGG의 수정률과 부화율은 각각 $69.4{\pm}1.5%$와 $59.0{\pm}5.1%$로서 CG에 비해 유의하게 낮았다 (p<0.05). CGGG는 비균등 난할, 배체 체형 기형 그리고 부화자어의 척추 기형이 높게 출현한 것을 제외하고, CG와 동일한 난발생 양상을 보였다. CGGG의 부화까지 소요 시간은 CG에 비해 약 2시간 느렸다(p<0.05). 이상의 결과에서 CGGG는 수정률, 부화율 그리고 기형률 등 발생능력이 CG에 비해 낮았지만 부화자어의 대량생산이 가능할 것으로 판단된다.

• 한국수산과학회지
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• 제56권4호
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• pp.558-568
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• 2023

The spatio-temporal distribution of the sand crab Ovalipes punctatus larvae was investigated in the Korean waters in 2019. Sea surface temperature (SST) was the lowest in February and highest in September. Sea surface salinity (SSS) was the lowest in September and highest in March. Further, sea surface chlorophyll a (SSC) was the highest in September. Larvae were distributed in the South Sea and coastal area of Jeju Island from April to June, and the abundance was the highest in May. The spatio-temporal distribution analysis suggested that larval groups showed a tendency to be dispersed over a wider area as the larvae developed, due to the increase in their swimming ability. The correlation analysis between environmental factors and larval density suggested that larvae appeared in the SST range 11.8-20.9℃ and SSS range 31.5-35.3 psu. The Megalopal stage appeared in a wider range of SST and SSS than other larval stages, possibly due to the increased environmental tolerance before settlement. Results of redundancy analysis (RDA) and Spearman's rank correlation analysis between the larval density by developmental stages and the environmental factors suggested that SST showed a positive correlation and SSC showed a negative correlation in the later stage.

• 한국수산과학회지
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• 제56권2호
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• pp.221-227
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• 2023

The vertical distribution of snow crab Chionoecetes spp. larvae in the East Sea were investigated in April 2021 using the Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS). The water temperature ranged from 0.86 to 17.2℃, and salinity from 34.0 to 34.7 psu. Zoea I and II occurred range from 29 to 1,982 inds.10³ m^-3 at 10 stations, and range from 4 to 11 inds.10³ m^-3 at 3 stations, separately. Therefore, Zoea I occurred in wider area and higher density than Zoea II at all stations. In the vertical distribution of larvae, all zoeal stages were mainly distributed in the 30-40 m strata, and the larvae showed nocturnal vertical migration similar to that of most zooplankton. Zoea I appeared in the range from 13.7 to 15.8℃ and occurred at the highest density of 1982 inds.10³ m^-3 at 14℃. And Zoea II appeared range from 13.4 to 14.5℃ and occurred in the highest density of 11 inds.10³ m^-3 at 13.4℃. In conclusion, the early larval stage (zoea I) occurred at a higher range of sea surface temperature than later larval stage (zoea II).