• Fisheries and Aquatic Sciences
• /
• v.26 no.11
• /
• pp.649-659
• /
• 2023

The present study compared the structure of mixilliped of Fenneropenaeus chinensis between the larval and adult stage and investigated the effect of the structural difference on the immunity of F. chinensis. A fourteen day and a one-month long culture trial were conducted each with postlarvae and adults of F. chinensis in the biofloc, mixed water (50% biofloc:50% clear seawater) and seawater control. Immune-related genes mRNA expressions of postlarvae was analysed by quantitative reverse transcription polymerase chain reaction (qRT-PCR). And the analysis of adult stage immunity was carried out using phenoloxidase (PO) enzyme activation in haemocyte. In the postlarvae, the final body weights were 51.43 and 58.47 mg for the biofloc water and the control seawater, respectively. On the other hand, the final body weights of the adults were significantly different between biofloc water and seawater. The survival rate showed the opposite trend to the growth rate. Immune related genes mRNA expression levels in the postlarvae in the biofloc water were significantly lower than those in the seawater. While, the adult stage showed significantly higher PO enzyme activations in the biofloc water than in the seawater with the PO enzyme activation increasing proportionally to the biofloc concentration. This result is considerably explained by the observations of setal morphological structures of the third maxilliped: postlarvae have short serrulated setae that compose the small 'net' structure while adults had long and dense plumose setae. It is understood that the morphological difference of the maxilliped structure resulted in the different feeding abilities in the postlarvae and the adult F. chinensis to use bioflocs as food source.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.38 no.6
• /
• pp.347-352
• /
• 2005

These experiments investigated the conditioning pattern and the nitrification efficiency of a fluidized sand biofilter (FSB) for seawater application. The FSB fed artificial nutrient was fully conditioned within 22 weeks. The maximum nitrification efficiency of the FSB was achieved at a superficial water velocity (SWV) of 1.0 cm/sec. After fixing the superficial water velocity at 1.0 cm/sec, the nitrification rates of the FSB were assessed at 3 total ammonia nitrogen (TAN) loading rates (250, 500, 1,000 g TAN/$m^3$/day) and 3 water temperatures (12, 16, $20^{\circ}C$). The TAN concentration in the simulated culture tank ranged from 2.87 to 9.72 mg/L at TAN loading rate of 1,000 g TAN/$m^3$/day, while that ranged from 0.45 to 1.26 mg/L at TAN loading rate of 500 g TAN/$m^3$/day. The ranges of TAN concentration in the former were too high for aquatic organisms and those in the latter were acceptable. Therefore, the safe TAN loading rate for the FSB in seawater conditions was decided as 500 g TA/$m^3$/day. From these results, daily TAN removal rates (g TAN/$m^3$/day) of FSB under conditions of inlet TAN concentration (C, mg/L) and water temperature (T, $^{\circ}C$) were calculated by the following non-linear multi-regression equation: TAN removal rate: f(z)=-1,311.295+655.714LnT+225.775LnC ($r^2=0.962$).

• Membrane and Water Treatment
• /
• v.15 no.1
• /
• pp.21-29
• /
• 2024

1H,1H,2H,2H-perfluorodecytriethoxysilane (C₁₆H₁₉F₁₇O₃Si) be successfully applied to the hydrophobic modification of Al₂O₃ tubular ceramic membrane. Taking the concentration of modification solution, modification time, and modification temperature as factors, orthogonal experiments were designed to study the hydrophobicity of the composite membranes. The experiments showed that the modification time had the greatest impact on the experimental results, followed by the modification temperature, and the modification solution concentration had the smallest impact. Concentration of the modified solution 0.012 mol·L^-1, modification temperature 30 ℃ and modification time 24 h were considered optimal hydrophobic modification conditions. And the pure water flux reached 274.80 kg·m^-2·h^-1 at 0.1MPa before hydrophobic modification, whereas the modified membrane completely blocked liquid water permeation at pressures less than 0.1MPa. Air gap membrane distillation experiments were conducted for NaCl (2wt%) solution, and the maximum flux reached 4.20 kg·m^-2·h^-1, while the retention rate remained above 99.8%. Given the scarcity of freshwater resources in coastal areas, the article proposed a system for seawater desalination using air conditioning waste heat, and conducted preliminary research on its freshwater production performance using Aspen Plus. Finally, the proposed system achieved a freshwater production capacity of 0.61 kg·m^-2·h^-1.

• Korean Journal of Environmental Biology
• /
• v.35 no.3
• /
• pp.373-379
• /
• 2017

Juvenile Paralichthys olivaceus (mean length $19.8{\pm}2.6cm$, mean weight $97.8{\pm}15.8g$) were exposed for 96 hours to different nitrate concentrations of 0, 62.5, 125, 250, 500, 1,000, and $1,500mg\;L^{-1}$ in biofloc and 0, 62.5, 125, 250, 500, and $1,000mg\;L^{-1}$ in seawater. Median lethal concentration values ($LC_{50}$, the concentration at which 50% of mortality occurred after 96 hours of exposure) of nitrate to P. olivaceus in biofloc and seawater were 1,226 and $597mg\;NO_3L^{-1}$ (P<0.05), respectively, revealing a higher toxicity of nitrate to P. olivaceus in seawater than in biofloc. In hematological parameters, hematocrit level in P. olivaceus exposed to nitrate was significantly increased only at a concentration of $1,000mg\;L^{-1}$ in biofloc and at concentrations higher than $250mg\;L^{-1}$ in seawater, but no significant changes in hemoglobin were found in biofloc and seawater. In plasma parameters, aspartate aminotransferase (AST) and alanine aminotransminase (ALT) were significantly increased by nitrate exposure in biofloc and seawater, but no significant changes in alkaline phosphatase (ALP) were found in biofloc and seawater. Results of this study indicate that nitrate exposure to P. olivaceus have a lethal toxic effect and alter hematological and plasma constituents of flatfish P. olivaceus. Given relatively lower toxicity of nitrate in biofloc than in seawater, the use of biofloc in aquaculture may reduce potential toxic effect caused by nitrate in feces and feed residue.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.20 no.1
• /
• pp.16-28
• /
• 2015

In order to elucidate the spatiotemporal variations of marine environmental parameters, we collected seawater samples in the south-western region of the East Sea in May, August, and November 2012 and February 2013. The concentrations of dissolved inorganic nutrients (dissolved inorganic nitrogen, phosphorus, and silicate) in surface seawater during the summer season were lower than those during autumn and winter seasons, which the mixed layer is deeper. The low nutrient concentration in spring and summer seasons seems by consumption of dissolved inorganic nutrients by phytoplankon photosynthesis (high chlorophyll a concentration) and the limited supply of dissolved inorganic nutrients from subsurface layer having high nutrients. The low nutrient concentration during spring season seems to be related to the limited supply of dissolved inorganic nutrients from land and subsurface layer because the concentration of chlorophyll a was low. The DIN:DIP ratio was a wide range of average $15.6{\pm}13.6$ in the surface seawater compared to that of average $14.8{\pm}4.2$ in the bottom seawater during sampling periods. The dissolved inorganic nitrogen might act as a limiting factor of the growth of phytoplankton because the DIN:DIP ratio (on average $8.35{\pm}4.67$) was low during the spring season.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.46 no.6
• /
• pp.862-867
• /
• 2013

Since the industrial revolution, seawater has increased in temperature and acidity due to the increase in anthropogenic carbon dioxide in the atmosphere. To understand the effect of elevated $CO_2$ on the early life stages of fish, we reared fertilized eggs of black sea bream Acanthopagrus schlegelii under three $CO_2$ concentrations (400, 850 and 1550 ppm) for 3 weeks. The standard length and wet weight of black sea bream larvae declined with enhanced $CO_2$ concentration in the rearing water (P<0.05). However, chemical analysis using ICP-OES on internal tissues of black sea bream larvae indicated that the whole-body calcium concentration increased with $CO_2$ concentration in the rearing water. These conflicting results suggest that future experiments should examine the acid-base balance to investigate the formation of bone and otolith during larval growth.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.37 no.6
• /
• pp.498-504
• /
• 2004

Removal of waste generated by Paralichthys olivaceus in the seawater aquarium using a foam separator was investigated. Protein concentration without a foam separator continuously increased until 3 days after stocking and reached at 25 mg/L after 5 days stocking, but protein concentration became lower than the initial protein concentration (2.5 mg/L) with a foam separator. The trends of other fish wastes such as ammonia, total suspended solids (TSS) and chemical oxygen demand (COD) were similar to protein. Dissolved oxygen (DO) in the aquarium decreased below 6.0 mg/L without a foam separator, but with a foam separator the average DO in the aquarium was 7.3 mg/L. Foam separation with the increase of superficial air velocity (SAV) was more effective than that with the fixed SAV. This study showed that wastewater. treatment of seawater aquarium using a foam separator is effective method for a fish waste removal and oxygen supply.

• Economic and Environmental Geology
• /
• v.36 no.5
• /
• pp.339-347
• /
• 2003

Using 171 groundwater chemistry data, seawater intrusion in the Ulsan area was studied. The area near the downstream area of the Taehwa River shows the higher Cl concentrations(11,300 mg/L in maximum), whereas the Cl concentrations are generally low in the eastern coastal area maybe due to the geology of the area. When Cl concentrations are very low, groundwater shows Br:Cl weight ratios significantly deviating from the Br:Cl ratio of seawater($34.7{\times}10^{-4}$). However, Br:Cl ratios are very close to the value of seawater when Cl concentrations are higher than 100 mg/L. Eleven groundwater samples having very high Cl concentrations(>500 mg/L) show that ionic ratios for Ca, Mg, $SO_4$, $HCO_3$ and $SiO_2$ are considerably different from those of seawater. This indicates that the origin of the high Cl groundwaters occurring along the Taehwa River are likely to be the residual salines from the salterns previously located on the alluviums rather than the seawaters intruded recently. These waters seem to be accumulated in the sediments before the drastic expansion of the city. Considering the characteristics of the urban groundwater system where the inflow exceeds the outflow, it is anticipated that the high Cl concentration in the groundwater show a decreasing trend in the future.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.17 no.4
• /
• pp.333-337
• /
• 2014

The purpose of this study is to develop a process technology to produce high hardness concentrated seawater removing chloride ions but containing useful minerals such as magnesium and calcium in the seawater desalination process. In order to make high hardness concentrated seawater, evaporation system is mostly used recently. Because evaporation system requires a large amount of energy consumption, in this study, it was aimed to produce high hardness concentrated seawater using membrane filtration requiring less energy. Nano filtration membranes were used for the experiments, and different types of high hardness concentrated seawater was produced depending on the membranes' specification, the number of times being concentrated, and pressure. As a result, at between 15bar and 20 bar in pressure, in between the second and the third times of concentration, the experiment result showed the best economic efficiency. By the experiment, production of high hardness concentrated seawater seemed to have a good economic feasibility.

• Journal of Soil and Groundwater Environment
• /
• v.8 no.1
• /
• pp.75-80
• /
• 2003

Understanding the seawater infiltration into tidal flat sediments is very important, because it is significantly correlated with the supply of dissolved oxygen, nutrients and organic matter to benthic organisms for survival. However oil blocks interstitial spaces of sediments, reduces seawater infiltration and results in the decrease in oxygen, nutrients and other food supply to benthic communities. The penetration depth of the stranded oil into the sediments is one of the most significant information to know the effect of spilled oil on biological communities and to set up a cleaning method. So we initiated this study to quantify the penetration behavior of spilled oil and to evaluate the influence of the penetrated oil on seawater infiltration in tidal flat environment and its ecological implications. The penetration depth of the crude oil into the tidal flat sediments was two times deeper than that of the fuel oil C, and the depth was significantly affected by stranded oil volume. However, the penetration depth of stranded oil was abruptly dropped at first falling tide but not significantly fluctuated after that. Moreover, hydrocarbon concentration showed the highest within the upper 2 cm. Seawater infiltration was decreased in proportion to the stranded oil volume. The seawater infiltration was more affected by the penetrated fuel oil C about 1.7 times than the crude oil, because the interstitial spaces of the top of sediments were more cleared by the fuel oil C. Therefore, quick cleaning actions for penetrated oil will be necessary for recovery of seawater infiltration because the seawater contains oxygen and nutrients necessary for the survival of benthic organisms in tidal flat.