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This research demonstrates how using Padina pavonica extract to create zinc oxide nanoparticles (ZnO-NPs) can be toxic to aquatic organisms. Blue Parrotfish ( Scarus coeruleus ) were used to evaluate the effects of ZnO-NPs over a 15-day period at different concentration levels (0–80 mg/L). The mortality rate was closely related to the concentrations tested; therefore, at 80 mg/L, every single fish died from exposure. The indication of oxidative stress through the decrease of glutathione (GSH) levels, and a nonlinear relationship of the reactive oxygen species (ROS) suggests cellular adaptation occurred during this time. As expected, there was also an overall decrease in activity of hepatic enzymes (ALT, AST, ALP) due to damage done to the liver; this was supported further through the tissue analysis by histopathology assessment. Additionally, the ionic homeostasis is disrupted by increased tissue levels of sodium (Na + ), potassium (K + ), and calcium (Ca² + ). At sublethal levels, ZnO-NPs also inhibited bacterial growth ( Streptococcus and Vibrio ), demonstrating both toxic and antibacterial properties These findings highlight the ecological risks associated with nanoparticle-driven marine pollution and emphasize the need to establish environmentally safe exposure limits to protect coastal and marine ecosystems.

Rapid population growth and urbanization has put a lot of stress on existing water bodies in most developing countries such as the Marriott Lake of Egypt. Three constructed wetland configurations including Typha angustifolia planted with enhanced atmospheric aeration by using perforated pipes networks (CWA), planted without perforated pipe network (CWR), and a control non-planted and without perforated pipes wetland (Control) were used in the study. Changes in physicochemical properties and microbial community over four seasons and hydraulic loading rate (HLR) (50, 100, 200, 300, and 400 L day −1  m −1 ) were monitored using influent from Marriott Lake in Egypt. Overall, the removal performance followed the sequence CWA>CWR>control . Turbidity removal of 98.4%; biochemical oxygen demand (BOD 5 ) removal of 83.3%; chemical oxygen demand (COD) removal of 95.8%; NH 3 -N removal of 99.9%; total nitrogen (TN) removal of 94.7%; NO 3 − -N and NO 2 − -N increased; total P (TP) removal of 99.7%, Vibrio sp. of 100%, Escherichia coli 100%; total bacterial count of 92.3%; and anaerobic bacteria reduction of 97.5% were achieved by using CWA. Seasonal variation and variation in HLRs had significant effect on performance. The modified planted CWA system enhances the removal of pollutants and could present a novel route for reducing the cost associated with integrating artificial aeration into wetlands.

Antimicrobial nanoparticle therapy was proposed as an alternative strategy to reduce the use of antibiotics in larval-rearing systems. Antibacterial potential of the prepared squilla chitosan–silver nanoparticles and its protective effect on Dicentrarchus labrax (sea bass) larvae in the early stages were studied against Vibrio angularium. Different concentrations of squilla chitosan (Csq) and squilla chitosan–silver nanoparticles (Csq–AgNps) (1, 2, 5, 10, and 20 %) were, in vitro, tested against V.anguillarum and expressed as a role of Log 10 mean. Sea bass larvae were treated using: 10 % Csq and 5 % Csq–AgNps as effective inhibitory concentrations against the pathogen either encapsulated during the feeding regime or added directly to the model system via the water from the onset of 4 weeks. The long-term administration of Csq–AgNps through enriched food for both non-infected and infected systems had survival % of 74.5 ± 1.5 and 72.5 ± 2.5, respectively. Larval clinical observations using Csq–AgNps were studied compared with the two controls. The current study found that 5 % encapsulated Csq–AgNps was enough to suppress infection and considered as an alternative to antibiotics in controlling virulent fish pathogens.

Larvae nutrition is considered to be the ‘bottle neck’ for marine finfish culture. Nowadays, marine larviculture can be significantly enhanced by producing new protocols of live feed using modern microbial trends. Primary goals of successful farmed larvae mainly rely on excellent survival and growth, since marine fish larvae record unpredicted high mortality rate and poor performance on designed diets during weaning stage. Adding live or inactive food to the rearing systems is also a widespread technique that has a significant impact on larval survival and performance. The bulk of mass-cultured marine fish larvae still need live feeding species, particularly at the beginning of larval nutrition such as: Artemia (brine shrimp), rotifers Brachionus spp., and microalgae. Bacteria are also added with live food and microalgae in the larval tanks for the rearing water system. Therefore, this review shed light on the developments of water rearing systems and improvements in marine fish larvae diets by discussing different types of live feeds and formulation of weaning microdiets. Since larval development is the most crucial stage of marine aquaculture production during which the greatest death rates can exceed 70%. Hence, the ontogenic development and digestive physiology of fish model larvae are also highlighted. Beneficial effects of prebiotics and probiotics on improving feed utilization and water quality, promoting larval growth and enhancing disease resistance were also discussed. Moreover, additional case studies about live food enrichment and reared fish larvae were presented to elucidate their effective role in improving water quality and larval growth performance. Despite recent substantial advancements in marine larviculture, many questions about fish larvae nutrition remain unanswered and numerous research avenues remain unexplored. Suggestions, recommendations and future considerations were mentioned to improve diets during larval rearing and pinpoint the research gaps that need to be addressed in manual hatchery operations.

This study was undertaken to assess the effects of dietary sodium propionate (SP) supplementation on the growth, haemato-immunological parameters, gut microbiota, and intestinal histology of European seabass (Dicentrarchus labrax) fry. In total, four diets were evaluated during a 90-day growth trial: a control (CTRL) diet without SP supplementation and three diets including 0.1%, 0.2%, or 0.3% SP, which were called SP1, SP2, and SP3, respectively. Diets were assigned to seabass (initial body weight: 0.45 ± 0.23 g), and the results revealed a 34%, 19%, and 15.6% increase in weight gain in SP3-, SP2-, and SP1-fed fish, respectively, concomitant with a lower feed conversion ratio in these fish than in fish not receiving the supplement (CTRL), which exhibited the lowest performance among all fish groups. Administration of 0.3% or 0.2% SP elevated the carcass protein content, major blood constituents, and immune function indicators compared to the CTRL. In addition, dietary inclusion of SP positively modified the bacterial community composition in the distal intestine (DI) of fish, causing an approximately 95% and 87% reduction in total microbial count in SP3- and SP2-fed fish, respectively, compared to CTRL fish. Vibrio spp. were non-existent (zero or negligible) in fish fed the SP2 and SP3 diets, and the number of faecal coliform bacteria gradually decreased to zero in SP3-fed fish. Additionally, an improvement in fish intestinal features, particularly in the DI, was evident from measurements of histological sections from the proximal, mid, and distal intestine. The greater villus area (height and width) and goblet cell count in fish fed the SP3 or SP2 diet than in fish not receiving the supplement suggested stimulation of digestive secretions with enhanced mucus production. In conclusion, enrichment of the diet with either 0.3% or 0.2% SP is capable of improving seabass fry growth performance, general health status, immune response efficiency, and intestinal function.

In more than two-thirds of the diabetic foot ulcer (DFUs) cases, lower limb amputation of foot ulceration is caused by the infection. The role of transition a metal complex as a therapeutic compound is becoming increasingly important. In vitro, four groups of antibiotics and one sulfa drug were tested against diabetic foot resistant bacteria. Using three concentrations of two different prepared metal complexes: copper (Cu) and silver (Ag) — isoniazid (Iso) and nicotinamide (Nicot) were tested against diabetic foot isolates. Results revealed that β-lactam drugs (cephradine and piperacillin) showed the minimum averages of MIC 265 μg/ml against Gram-positive and Gram-negative isolates. Silver isoniazid (Iso-Ag-1) metal complex was selected depending on the maximum averages of MIC against both types of clinical isolates. The combination between β-lactams and Iso-Ag-1 showed maximum FICI averages of 0.24 for Gram-positive and 0.28 for Gram-negative. In addition, a combination between Iso-Ag-1 with squilla chitosan nanoparticles (CSSq-nAg) showed averages of synergistic index by 0.23 against Staphylococcus aureus and 0.13, 0.30, and 0.27 against E. coli , K. pneumoniae , and Ps. aeruginosa , respectively. Final formula of Iso-Ag-1+CSSq-nAg + β-lactams (cephradine and piperacillin) showed a synergistic effect at FICI = 0.044 and 0.047, against G+ve and –ve, respectively. These two combinations showed a slight toxicity against the water flea Daphnia magna by 3.49 and 3.6 ppm, respectively. Results suggest the use of Iso-Ag-1-CSSq-nAg as enhancing agent in combination with β-lactams as a blind therapy in pharmaceutical preparations.

Screening of fungal isolates collected from different locations of Alexandria coast, Egypt, was carried out to obtain new biologically active metabolites against some virulent fish pathogens (Edwardsiella tarda, Aeromonas hydrophila, Vibrio ordalli and Vibrio angularuim). Among 26 fungal isolates, Aspergillus terreus var. africanus was identified as the most potent isolate. Production of the bioactive material was optimized using response surface methodology including fermentation media, incubation period, temperature, pH, and thermo-stability. Spectral properties of the gas chromatography/mass spectrum of the ethyl acetate crude extract were determined. Partially purified components of the crude extract were chromatographically separated and bioassayed. Out of ten separated compounds, five were with considerable antibacterial agent. The bio-toxicity of crude showed a slight toxicity against the brine shrimp Artemia salina (LC50 = 1,500 μg/l). Antibacterial activity of the crude was compared with some known standard antibiotics and found to be superior over many where its MIC against some pathogen reached 1 μg/ml.

The effect of replacing fish meal (FM) in juvenile European seabass (Dicentrarchus labrax) diets with fish wastes (FW) and fermented FW (FFW) by marine fungus Beauveria bassiana was investigated. Seven diets were prepared: control (CTRL) and six diets containing either FW or FFW to substitute FM at 15, 30 and 45% (FW15/FFW15, FW30/FFW30 and FW45/FFW45 each in turn). Fish (initial weight Ca. 30 g) were reared for 90 days in 21 PVC tanks (3 m3) and fed to apparent visual satiation. The recorded values for growth, feed utilization efficiency, survival rate and amino acids composition of fish fed either FW or FFW diets, at all tested levels, are not significantly different relative to those values of control group. Carcass protein content was not influenced by diet, but lipid content of FW45 and FFW45-fed fish showed a significant elevation relative to that of other fish groups. Blood parameters indicate an improvement in general health status and both liver and kidney function of FW-fed fish up to 30% FM replacement level, relative to those of CTRL and FFW-fish. Fish fed the FW-diets showed higher fungal and acid fermentative bacterial counts and lower count of Vibrio spp. and coliform, suggesting better gut health as compared to FFW-fed fish. These results indicate that 30% of dietary FM can be replaced with FW meal without adverse effects on fish growth performance, feed utilization, general health status or intestinal microbiome and fermentation with B. bassiana has some negative influence on gut integrity at 45% FM substitution level.