Seawater System Research Articles

Effects of dietary phosphorus level and stocking density on tiger puffer Takifugu rubripes: Growth performance, body composition, lipid metabolism, deposition of phosphorus and calcium, serum biochemical parameters, and phosphorus excretion

An 8-week feeding trial was conducted to comprehensively investigate the effects of dietary phosphorus level and stocking density on tiger puffer. A 3 × 3 factorial design was used. The three dietary phosphorus levels were 0.68% (LP), 0.98% (MP), and 1.31% (HP) of dry matter, of which the available phosphorus level was 0.44%, 0.76%, and 1.06%, respectively. The three stocking density grades were 1.53 (LD), 2.30 (MD), and 3.06 (HD) kg m−3. The feeding trial was conducted in an indoor flow-through seawater system. Three replicate tanks were used for each group. The results showed that HP resulted in the highest growth rate. Higher dietary phosphorus levels reduced the whole-body lipid content, serum cholesterol contents, and hepatic mRNA expression of lipid metabolism-related genes such as ACACβ, DGAT1, and PPARα2. High stocking density levels reduced the growth rate and feed intake, but rarely affected other physiological parameters. Significant interactions were observed between effects of dietary phosphorus level and stocking density on phosphorus and calcium metabolism, but not between effects of both variables on the growth performance. Synergetic enhancement of phosphorus excretion by high phosphorus level and high stocking density was observed. These results shed new lights into the phosphorus physiology of marine fish and the interactions between phosphorus nutrition and rearing condition.

Preparation of amidoxime functionalized titanate nanosheets for efficient extraction of uranium from aqueous solution

An efficient adsorbent of amidoxime-decorated titanate nanosheets (TNSs-AO) were prepared and characterized by multiple analytical methods (XRD, TEM, FTIR and TGA). Batch experiments were performed systematically to investigate the influence of the operational parameters such as adsorbent dosage, initinal U(VI) concentration, solution pH, reaction time and temperature on the adsorption performance, as well as evaluate adsorption performance in simulated seawater. Experimental data showed that TNSS-AO presented more excellent U(VI) ions binding affinity than TNSs, and that the optimal pH regime of TNSs-AO was wider than that of TNSs. Langmuir model was more suitable for explaining equilibrium data, and the monolayer adsorption capacity of TNSs and TNSs-AO were 240.38 ​mg/g and 401.61 ​mg/g, respectively. The adsorption process followed the pseudo-second-order rate equation, indicating chemical adsorption was the mian mechanism in the adsorbate-adsorbent interactions. Thermodynamic studies indicated the adsorption process was spontaneous and endothermic. By means of FT-IR and XPS, it was concluded that surface complexation and ion exchange were the main adsorption mechanisms. Moreover, adsorption performance in simulated seawater system suggested the feasibility of TNSs-AO in the presence of multiple interfering ions. Therefore, the as-obtained TNSs-AO could be potentially used as a promising adsorbent for the preconcentration and separation of U(VI) from aqueous solutions.

Spawning of French grunts, Haemulon flavolineatum, in recirculating aquarium systems.

BackgroundBecause the French grunt, Haemulon flavolineatum, is an ecologically important reef fish prized by both recreational anglers and public aquariums, the wild population requires limits on harvests. Yet, the environmental conditions conducive for French grunt spawning in aquarium settings is not well understood. Therefore, the goal of this study was to document the conditions leading to voluntary spawning and the number of eggs produced by French grunts without the use of hormones or artificial insemination.MethodsWe hypothesized and verified that it is possible for French grunts to spontaneously spawn in human care. Forty individuals were collected around the Florida Keys and haphazardly stocked in five recirculating seawater systems each containing two 250-L circular tanks. Over the course of 87 days, eggs were collected daily from each system and environmental parameters were monitored.ResultsTotal daily number of eggs released ranged from 0 to 207,644 eggs. Of the observed environmental parameters, temperature and alkalinity had the greatest impact on number of eggs released. This study demonstrates that it is possible for French grunts to reproduce in captivity with little environmental manipulation, thus an ideal candidate to culture for the zoo/aquarium industry.

Oil spill cleanup by raw flax fiber: Modification effect, sorption isotherm, kinetics and thermodynamics

Modification of raw flax fiber by acetylating process and microwave energy was useful in the application of oil spill cleanup. The change in fibers was characterized by scientific analysis(FTIR, SEM, XRD and contact angle). The results indicate that the modified fibers by the acetylating process have extra hydrophobic properties than both microwave radiation and raw fibers. Oil/Artificial seawater(3.5% salinity by NaCl) system (O/W-S) was used as a liquid phase operation system. Fast oil sorption was reached at 6 min and attained(equilibrium) at 10 min. Acetylated fiber(ACF)has higher oil sorption capacity(24.54 g/g) than both raw(13.75 g/g) and microwave fiber(17.42 g/g) with exothermic effect. The sorption kinetics and isotherms indicate that the oil sorption onto ACF agreement with pseudo second-order kinetic model and Freundlich isotherm model. Also, the economic reusing of fiber was evaluated. The process of acetylation demonstrated the ability to improve the absorptive properties of the fibers, which makes them able to compete with synthetic fibers in the oil spill cleanup and industrial applications, as well as cheap and eco-friendly due to their biodegradation.

A High Precision Method for Calcium Determination in Seawater Using Ion Chromatography

Calcium (Ca2+) is an important major cation in seawater, which is closely related to the oceanic biogeochemistry cycle. Direct and accurate determination of Ca2+ concentration is required for a more comprehensive study of the carbonate system in seawater. Due to the high background concentration of Ca2+ in seawater and small variances of Ca2+ during CaCO3 precipitation and dissolution process, a precision of better than 0.1% (of approximately ±10 µmol/kg) is very much desired for carbonate chemistry related studies. In this study, a simple, non-toxic and labor-saving technique using ion chromatography (IC) has been developed to determine Ca2+ in seawater with an overall precision of better than 0.1%. This proposed method, using IAPSO standard seawater as a reference, can get a result within 15 min and only requires a small sample volume (~1 ml). The concentrations and flow rates of the eluent have been optimized to achieve the best chromatographic separation (20 mmol/L and 1.0 mL/min were selected in this study). Our work suggests that sample dilutions have no discernible effect on Ca2+ determinations. However, the measured Ca2+ concentration shows a linear decrease with the increasing Mg/Ca ratio in samples, which could be corrected by a derived formula to achieve high accuracy within 0.1%. This optimized method has been applied to the analysis of Ca2+ distribution in Southwest Indian Ocean and the laboratory study on the calcite precipitation in seawater.

Photocatalytic Dinitrogen Fixation with Water on Bismuth Oxychloride in Chloride Solutions for Solar-to-Chemical Energy Conversion.

Ammonia is an indispensable chemical. Photocatalytic NH3 production via dinitrogen fixation using water by sunlight illumination under ambient conditions is a promising strategy, although previously reported catalysts show insufficient activity. Herein, we showed that ultraviolet light irradiation of a semiconductor, bismuth oxychloride with surface oxygen vacancies (BiOCl-OVs), in water containing chloride anions (Cl-) under N2 flow efficiently produces NH3. The surface OVs behave as the N2 reduction sites by the photoformed conduction band electrons. The valence band holes are consumed by self-oxidation of interlayer Cl- on the catalyst. The hypochloric acid (HClO) formed absorbs ultraviolet light and undergoes photodecomposition into O2 and Cl-. These consecutive photoreactions produce NH3 with water as the electron donor. The Cl- in solution compensates for the removed interlayer Cl- and inhibits catalyst deactivation. Simulated sunlight illumination of the catalyst in seawater stably generates NH3 with 0.05% solar-to-chemical conversion efficiency, thus exhibiting significant potential of the seawater system for artificial photosynthesis.

Design of Capacitive Wireless Power Transmission System in Seawater

As an emerging power supply method, wireless power transmission has attracted extensive attention from researchers at home and abroad. Since there is no direct contact of the wires, it is expected to solve the problem of power supply life of the underwater robot. First of all, this paper combines the working principle of capacitive wireless power transmission, analyzes the working state of the circuit by using the generalized state space average, and obtains the working frequency of realizing the soft switching state. Secondly, two different coupling mechanisms are designed and Maxwell finite element simulation is carried out to calculate the capacitance value and field strength distribution. Finally, the underwater wireless power transmission system is built. The influence of transmission distance d and different coupling mechanisms on output power is discussed. The following conclusions are obtained: (1) As the transmission distance d increases, the output power decreases and the electromagnetic interference increases. (2) Cylindrical capacitors have higher power density and smaller electromagnetic interference than parallel plate capacitors. The research results provide an important reference for future underwater wireless power transmission systems.

Spectroscopic ellipsometric investigation of optical parameters of oil-water thin multiple systems

To determine the optical parameters of crude oil and seawater systems, we carried out spectral investigations using the ellipsometry method, which is a highly sensitive and accurate optical method for studying the surfaces and interfaces of various media. This method is based on studying the change in the polarization state of reflected light after its interaction with the surface of interfaces of these media. Crude oil and seawater from different regions of Caspian Sea were accessed by spectroscopic ellipsometry over the 200–1700 nm spectral range at room-temperature. Optical constants and dielectric function were obtained for massive samples of each substance, as well as for ultrathin layers of the oil spilled over the sea surface. Dielectric function, when completely determined in the frequency regions corresponding to electronic transitions and excitation of atomic or molecular vibrations in the object, is a unique dielectric fingerprint of this object. Oils with even miserable difference in type and concentration of biomarkers and heterocomponents will have different dielectric functions. The possibility to use dielectric function as a unique optical fingerprint for oil identification is figured out.

Metallurgical investigations on corrosion behavior of simple and heat treated duplex stainless steel 2205 exposed to corrosive media

Duplex stainless steel 2205 has proven to be the most acceptable material for marine and saline applications because of its superior corrosion resistance with good erosion and wear resistance. However, the disadvantage of stainless steel is its sensitivity to local corrosion in a solution containing chloride, which limits their use in seawater systems. The effect of heat treatment on corrosion properties of stainless steels can be studied in marine or chloride environments and investigation of changes in microstructure and corrosive property. This study presents the consequence of heat treatment on the microstructure and corrosion resistance and systematic approach to examine the corrosion behaviour of plain DSS 2205. Precipitation of secondary parts in DSS 2205 led to an extreme reduction in its corrosion resistance and another factor contributing to changes in ferrite and austenite ratios where preferential corrosion occurred in the DSS 2205 ferrite phase. The austenite phase shows better corrosion resistance than the ferrite phase due to maximum Ni content than ferrite. Cr is the most active element in the passive film to develop the resistance of DSS 2205 to localized corrosion. The heat treatment about 1080°C to DSS 2205 improves the corrosion resistance of steel comparatively.

Highly Efficient Capture of Marine Microbial Strains in Seawater Using Bare Fe3O4 Magnetic Beads.

We develop a method to capture marine bacterial strains at high efficiency to replace the conventional two-step collecting method. Lab-made, Fe3O4 magnetic beads were used to firstly verify the feasibility of capture in artificial seawater, using Bacillus velezensis. Almost 100% of the bacteria could be captured and separated within 10min. Then, the salinity of capture medium was proved to have the most marked effect on the capture process. After that, the broad application and high efficiency of capture were verified using four different bacterial strains from the Pacific Ocean. Subsequently, through adjusting the salinity, the capture efficiency for Pseudoalteromonas sp. and Halomonas meridiana was increased from 20 to ~ 80% in a seawater system, which was used to simulate the in-situ capture conditions. Finally, mixed strains in seawater were successfully captured, and their genomic DNAs were isolated and analyzed. Bare Fe3O4 magnetic beads were initially applied to capture marine microorganisms and this method is convenient and highly efficient and thus has great potential to replace the conventional two-step method.

Effects of Irrigation with Desalinated Seawater and Hydroponic System on Tomato Quality

The use of desalinated seawater (DSW) as an alternative to conventional water resources is gradually gaining more interest due to the strong water deficit and increasing pressure on water resources in semi-arid regions. Furthermore, the combination of this alternative irrigation with the hydroponic cultivation system would allow continuous production almost through the whole year and hydroponic-related high crop yield. Nevertheless, the effects of DSW irrigation in hydroponic systems on the product quality need to be firstly studied to avoid product quality losses. In this study, we evaluated the effects on the quality of two tomato cvs. (Ramyle and Racymo) of three different irrigation treatments (T1, DSW; T2, DSW/well water mix; and T3, well water) under hydroponic or traditional cultivation systems. The soluble solid content of samples (highly correlated to dry matter content) grown under hydroponic conditions and T3 irrigation showed the highest values (5.8 °Brix) although such differences (<0.6 °Brix) with T1 might not be sensorially appreciated. Similarly, although T3 samples showed higher acidity than T1 samples, such differences (0.06%) would be not appreciated by the consumer. Tomatoes grown in hydroponic conditions had 1.1–1.2-fold higher firmness than conventional soil conditions showing hydroponic T3 samples had the highest value (21–23 N). Tomato cv. Racymo displayed higher color index (chroma) than cv. Ramyle, registering hydroponic T1 samples the most intense red color correlated with the highest lycopene content of 41.1 mg/kg. T1 irrigation of tomatoes cv. Ramyle did not induce significant changes while differences lower than 10% were observed in the tomato cv. Racymo. The highest total antioxidant capacity, which was highly correlated to the total phenolic content (R2 = 0.80), was found for hydroponic T1 samples with 1637/1243 µmol/kg for the tomato cvs. Ramyle/Racymo. Conclusively, the use of DSW would not compromise the consumer acceptance of tomatoes due to the low (not appreciable) quality differences, with even the total antioxidant capacity of these samples being increased. Furthermore, the mix of DSW with conventional water resources (lower cost) would not compromise the tomato quality.

Dietary taurine stimulates the hepatic biosynthesis of both bile acids and cholesterol in the marine teleost, tiger puffer (Takifugu rubripes).

Taurine (TAU) plays important roles in the metabolism of bile acids, cholesterol and lipids. However, little relevant information has been available in fish where TAU has been identified as a conditionally essential nutrient. The present study aimed to investigate the effects of dietary TAU on the metabolism of bile acids, cholesterol and lipids in tiger puffer, which is both an important aquaculture species and a good research model, having a unique lipid storage pattern. An 8-week feeding trial was conducted in a flow-through seawater system. Three experimental diets differed only in TAU level, that is, 1·7, 8·2 and 14·0 mg/kg. TAU supplementation increased the total bile acid content in liver but decreased the content in serum. TAU supplementation also increased the contents of total cholesterol and HDL-cholesterol in both liver and serum. The hepatic bile acid profile mainly includes taurocholic acid (94·48 %), taurochenodeoxycholic acid (4·17 %) and taurodeoxycholic acid (1·35 %), and the contents of all these conjugated bile acids were increased by dietary TAU. The hepatic lipidomics analysis showed that TAU tended to decrease the abundance of individual phospholipids and increase those of some individual TAG and ceramides. The hepatic mRNA expression study showed that TAU stimulated the biosynthesis of both bile acids and cholesterol, possibly via regulation of farnesoid X receptor and HDL metabolism. TAU also stimulated the hepatic expression of lipogenic genes. In conclusion, dietary TAU stimulated the hepatic biosynthesis of both bile acids and cholesterol and tended to regulate lipid metabolism in multiple ways.

Dietary bile acids regulate the hepatic lipid homeostasis in tiger puffer fed normal or high-lipid diets

Bile acid (BA) plays an important role in lipid metabolism. Tiger puffer has a unique lipid storage pattern; storing lipid predominantly in the liver. The present study aimed to investigate the effects of dietary BA supplementation on hepatic lipid accumulation and metabolism in tiger puffer fed normal or high-lipid diets. An 8-week feeding trial was conducted in an indoor flow-through seawater system. Two diets with suitable (8.5%, diet C) or high lipid level (12.5%, diet HL) were prepared. BA, a porcine bile extract mainly comprised of hyodeoxycholic acid was supplemented into the two diets at the level of 0.02% to formulate diet CBA and diet HLBA, respectively. A fifth diet was prepared by supplementing an excess level of porcine bile extract (0.10%) into diet C (diet CHBA). Each diet was randomly fed to triplicate tanks. Dietary BA supplementation did not significantly affect fish growth performances. Dietary BA tended to decrease the whole-body lipid content, liver lipid content, hepatosomatic index, and viscerasomatic index in both fish fed with normal diets and fish fed with high-lipid diets. Similar results were observed for the contents of triacylglycerol, total cholesterol, and low-density lipoprotein-cholesterol in serum. The quantitative bile acid metabolomics analysis showed that taurocholic acid and taurochenodeoxycholic acid were dominantly abundant in the gallbladder. Dietary BA supplementation increased the concentration of taurohyodeoxycholic acid, glycohyodeoxycholic acid, and glycocholic acid, but affected some other BAs in various patterns. Dietary BA regulated hepatic transcription of lipid metabolism-related genes differentially in fish fed normal diets and fish fed high-lipid diets, decreasing the transcription of lipogenic genes in fish fed normal diets but increasing the transcription of genes related to lipid digestion and lipid/cholesterol transport in fish fed high-lipid diets. In conclusion, dietary BA supplementation tended to reduce the lipid accumulation in juvenile tiger puffer. However, at the transcription level the regulation of lipid metabolism by dietary BA seemed very different between fish fed normal diets and fish fed high-lipid diets. This study contributes to the general knowledge of bile physiology under different nutritional conditions in teleost and is beneficial to lipid management in tiger puffer farming.

CUSUM chart method for continuous monitoring of antifouling treatment of tubular heat exchangers in open-loop cooling seawater systems

A CUSUM chart method is presented as an alternative tool for continuous monitoring of an electromagnetic field-based (EMF) antifouling (AF) treatment of a heat exchanger cooled by seawater. During an initial experimental phase, biofilm growth was allowed in a heat exchanger formed of four tubes until sufficient growth had been established. In two of the tubes, continuous EMF treatment was then applied. The heat transfer resistance and heat duty (heat transfer per unit time) results showed that biofilm adhesion was reduced by the EMF treatment. EMF treatments resulted in a 35% improvement in the heat transfer resistance values. The proposed CUSUM chart method showed that the EMF treatment increased the useful life of the heat exchanger by ∼20 days. Thus, CUSUM charts proved to be an efficient tool for continuous monitoring of an AF treatment using data collected online and can also be used to reduce operation and maintenance costs.

Evaluation of the operation seawater and brackish water desalination system using two-pass nanofiltration

Evaluation of the operation seawater and brackish water desalination system using two-pass nanofiltration

Physicochemical and Microbiological Quality of Shallow Groundwater in Lomé, Togo

The present study aimed to assess the physicochemical and microbiological quality of shallow groundwater tapped by private boreholes for water sale in Togo’s most urbanized coastal areas. Ninety-six (96) groundwater samples were collected at the water sale points for chemical and microbiological analyses using standard methods. The results showed that groundwater is predominantly acidic with fresh and brackish water of Na-Cl type. High concentrations of dissolved inorganic nitrogen (NO3- , NH4+and NO2-) and permanganate indices indicating potential organic matter were found. Among the major ions, Na+ (46.9%), Cl- (51.0%) and NO3- (50.0%) present the highest percentages of unsuitable concentrations compared to WHO guidelines. These findings indicate the control of the natural impact of seawater and lagoon system and anthropogenic pollution from domestic and urban wastes on groundwater’s physicochemical quality. About 65% of groundwater samples did not comply with the drinking water guidelines for microbial indicators, including total mesophilic flora, thermotolerant coliforms, and sulfite-reducing anaerobes. The results showed the failure of sanitation and hygiene conditions around sampling points and fecal contamination from sewage, pit latrines, septic tanks, and refuse and waste disposal. The degradation of physicochemical quality is higher in the old and high-density built-up areas. Simultaneously, microbial contamination represents a high risk of contracting waterborne or hygiene-sanitation-related diseases in the whole study area. This study provides a global view of shallow groundwater’s physicochemical and microbiological quality in the study area. Limitations and suggestions for future research are discussed.

A development of novel Ni–P coating on anodised aluminium alloys for military industries applications in artificial sea water

ABSTRACTThe corrosion behaviour and characterisation properties of a novel Ni–P coating on anodised aluminium alloys were inspected by utilising a salt spray technique and a polarisation system in artificial sea water. The Ni–P layer on anodised coating progression was achieved on aluminium alloys such as Al2014, Al6061 and Al7075, which are utilised in military industries. The outcomes revealed that the coating layer is contingent on the alloy type and coating settings like current density, temperature and time. Also, film thickness and hardness of aluminium alloys have been considered. The corrosion rate was established to be dependent on the alloying element such as copper. The deterioration rates of Al7075 and Al6061 were diminished by about one order of magnitude; however, for Al2014, it was amplified by an equivalent order of magnitude.

Salinity‐Gradient Power Generation with Ionized Wood Membranes

AbstractReverse electrodialysis (RED) is known as an efficient way of converting the salinity gradient between river water and sea water into energy. However, the high cost and complex fabrication of the necessary ion exchange membranes greatly prohibit the development of the RED process. For the first time, an ionized wood membrane is demonstrated for this application, benefiting from the advantages of natural wood, which is abundant, low cost, sustainable, and easy to scale. The wood membrane maintains the aligned nanochannels of the cellulose nanofibers derived from the natural wood. The surface of the nanochannels can be functionalized to positively or negatively charged by in situ modifying the hydroxyl groups on the cellulose chains to quaternary ammonium or carboxyl groups, respectively. These charged aligned nanochannels serve as nanofluidic passages for selective ion transport with opposite polarity through the wood membrane, resulting in efficient charge separation and generating an electrochemical potential difference. The all‐wood RED device with 100 cells using a scalable stacking geometry generates an output voltage as high as 9.8 V at open circuit from a system of synthetic river water and sea water.

Enriched Ulva pertusa as partial replacement of the combined fish and soybean meals in juvenile abalone Haliotis asinina (Linnaeus) diet

The potential of enriched Ulva pertusa meal as feed ingredient in abalone juveniles, Haliotis asinina was evaluated. Four isonitrogenous and isolipidic diets were formulated which contain 27% protein and 5% lipid. Enriched U. pertusa meal replaced 0% (control), 10%, 20%, and 30% of protein from fish and soybean meals in the formulated diets. Thirty randomly selected abalone juveniles with average weight and shell length of 0.45 g ± 0.01 and 12.71 mm ± 0.01, respectively, were placed in each of the twelve 60-L oval fiberglass tanks equipped with a flow-through seawater system. Abalone were given diets at 3–5% body weight daily for 120 days in three replicate samples. Results showed no significant differences (p > 0.05) in percent weight gain, shell length, specific growth rate, feed conversion ratio, and protein efficiency ratio even up to 30% replacement level. Apparent dry matter digestibility of U. pertusa meal in abalone diet was 92%. Crude protein content of the abalone fed diets 1 (10% enriched U. pertusa meal) and 3 (30% enriched U. pertusa meal) was significantly (p < 0.05) higher than those fed on basal diet. Enriched U. pertusa meal can partially replace fish and soybean meals as protein source in formulated diets for abalone, Haliotis asinina juveniles.

The optimal arginine requirement in diets for juvenile humpback grouper, Cromileptes altivelis

An 8-week feeding trial was conducted to evaluate the effects of dietary arginine (Arg) levels on growth performance, gut micromorphology, oxidation resistance and immune responses of humpback grouper, Cromileptes altivelis. Seven isoenergetic (340 kcal per 100 g of dry matter), isoproteic (50% of dry matter) and isolipidic (10% of dry matter) experimental diets were formulated to contain 1.74%, 2.42%, 3.14%, 3.58%, 4.06%, 4.54% and 5.21% dietary Arg levels. Triplicate groups of 12 fish (average initial body weight: 6.55 ± 0.1 g) were fed to apparent satiation by hand twice daily (08:00 h and 16:00 h) in an indoor recirculating seawater system which was consisted of 21 glass tanks (length 60 cm × width 45 cm × height 50 cm) and mechanical and biological water filters. After the feeding trial, all remaining fish were challenged by 2.5 mg Cu(II)·L−1, and survival rates were recorded for 12 h. Results showed that weight gain% (WG%), protein efficiency ratio (PER) as well as protein productive value (PPV) of fish were improved with the increments in dietary Arg from 1.74% to 3.58%, and thereafter, values of these parameters displayed a declining trend as dietary Arg level continued to rise from 3.58% to 5.21%. Fish fed 3.14% and 3.58% dietary Arg had lower FCR and daily feed intake (DFI) than fish fed other dietary Arg levels. Quadratic regression analysis of WG% against dietary Arg levels indicated that optimal dietary Arg level for maximum growth of humpback grouper was 3.39% of dry matter (6.78% of dietary protein). Hepatosomatic index (HSI) was reduced as dietary Arg level increased. Fish fed 3.58% dietary Arg had higher whole-body protein content than fish fed other dietary Arg levels. Expression of hepatic insulin-like growth factor-I (IGF-1), target of rapamycin (TOR), S6 kinase1 (S6K1) and hypothalamus growth hormone receptor (GHR) in fish fed 3.14% and 3.58% dietary Arg was higher than that in fish fed other dietary Arg levels. Gut micromorphology was significantly influenced by dietary Arg levels. After the exposure to 2.5 mg Cu(II)·L−1 water for 12 h, fish fed 3.14% and 3.58% dietary Arg had higher survival ratios and expression of NF-E2-related factor 2 (Nrf2) and heat shock proteins genes 70 (HSP70) in head kiney. In serum, fish fed 3.58% dietary Arg had higher superoxide dismutase (SOD) and catalase (CAT) activities and immunoglobulinM (IgM) concentrations than fish fed other dietary Arg levels. In conclusion, the optimal dietary Arg requirement for maximal growth of humpback grouper was estimated to be 3.39% of dry matter (6.78% of dietary protein), and suitable dietary Arg supplementations improved growth performance, gut micromorphology, oxidation resistance as well as immunity of this species.