Production of biodiesel together with wastewater treatment and CO₂ sequestration is a promising technology. The growing levels of carbon dioxide in the atmosphere increase the amount of dissolved CO₂ in natural watercourses, triggering the increase in concentrations of bicarbonate and hydrogen ions while dropping those of carbonate and hydroxyl ions. The active carbon cycling in coastal areas, which can result in periodic and daily fluctuations in pH and CO₂ concentrations that may surpass those anticipated for the extensive marine ecosystems, is regarded as one of the consequences of climate change. Studies were conducted to examine the effects of various pH levels on algal growth and lipid production in order to better understand how the growth of algae may be influenced in such conditions. In the present study, the influence of three different pH levels (6, 8, and 10) was studied to evaluate microalgae’s carbohydrate utilisation and lipid accumulation during the operation’s starvation phase (SP). Microalgae, in the study, were cultivated in two modes, namely mixotrophic [growth phase (GP)] and autotrophic [pH-induced (SP)] conditions. Enhancement in biomass formation, and intracellular carbohydrate accumulation were recorded during the GP operation, while noticeable lipid productivities (Total/neutral, 26.93/10.3%) were observed during SP operation at pH 8. Pigment analysis showed variations in both the procedures where higher Chl a concentration was noticed in GP, and higher Chl b was detected during SP. Nile red fluorescent staining strongly supports the existence of intracellular lipid bodies (LB). GC analysis of fatty acid methyl esters (FAME) showed the existence of a substantial amount of saturated fatty acids (SFA) compared with unsaturated fatty acids (USFA). Efficient wastewater treatment with nutrient assimilation was reported during the GP operation, demonstrating the phyco-remediation.

A technique called biofloc technology (BFT) is an environmentally friendly method for aquaculture in which a successful growing cycle depends on the maintenance and monitoring of water quality parameters. Studies have revealed that improving water quality in BFT and maintaining the safety range of the parameters can help to increase the growth performance of cultured species. Following a systematic review of the literature, a meta-analysis was performed to explore how some important water parameters such as pH, dissolved oxygen (DO), nitrite (NO₂N), nitrate (NO₃N), ammonia (NH₃N), total ammonia nitrogen (TAN), total suspended solids (TSS), and alkalinity were influenced by different BFT systems. The PRISMA screening process was followed, and 33 studies were eligible for the meta-analysis. The meta-analyses showed that NO₂N and TSS were significantly affected by BFT, while pH, DO, NO₃N, NH₃N, TAN, and alkalinity were not significantly influenced by this system. The analyses revealed that NO₂N had a significant negative effect size due to BFT, whereas TSS showed a significant positive effect size. The study also revealed some publication bias in which few experiments of some studies showed extremely positive and negative effect sizes due to BFT application in the system. Overall, the findings suggest clear evidence of the profound influence of BFT on the water quality parameters in different aquaculture systems, suggesting the future development of BFT for sustainable and environmentally friendly aquaculture production.

Despite the widespread practice of using probiotics in aquaculture for their potential benefits, the consistency of their impact on disease resistance in fish is still being scrutinized. This study aimed to address this gap by investigating the influence of the probiotic Pediococcus acidilactici (PCA) on hematological indices, body composition, serum metabolites, water quality, growth metrics, the transcriptomic profile of genes related to immune function, and the ability of red tilapia (Oreochromis niloticus × O. mossambicus) to resist challenge with the bacterial pathogen Aeromonas hydrophila. A total of 180 tilapia fingerlings (average weight 17.10 ± 0.46 g) were distributed into four groups and fed a basal diet supplemented with 0 (PCA0), 1 (PCA1), 2 (PCA2), and 3 (PCA3) g of PCA per kg of diet for 63 days. Water quality analysis indicated a significant decrease in both salinity and dissolved oxygen concentrations in all PCA-supplemented groups compared to a PCA-free diet (P < 0.05). Fish fed diets having 2 or 3 PCA had superior FBW, SGR, and ADG, while these levels significantly improved the FCR compared to the untreated diet (P < 0.001). In fish supplemented with PCA, body composition analysis showed a statistically significant increase in protein and ash content, accompanied by a statistically significant decrease in lipid content (P < 0.05). Furthermore, dietary PCA significantly enhanced phagocytic index, and serum IgG and IgM levels in a dose-dependent response. Notable improvements in hematological variables and blood protein fractions were observed in the PCA2 and PCA3 groups compared to other groups (P < 0.05). Dietary PCA administration sustained liver enzymes and kidney functions (P < 0.05). Dietary supplementation with PCA resulted in a significant upregulation (P < 0.05) of growth-related genes (GH, IGF-1, and IGF1-R) and immunity-associated genes (CXC chemokine, IL8, and IL1β) in a dose-dependent manner. Furthermore, dietary PCA improved the histological structure of the liver and enhanced intestinal integrity in Tilapia. Following pathogen challenge, the survival rate was significantly higher in all PCA-supplemented groups compared to the control group, with the highest survival observed in the PCA3 group. In summary, this research highlights the significant benefits of dietary Pediococcus acidilactici supplementation at 2 and 3 g/kg for improving growth, blood physiology, immunity, and disease resistance in red tilapia. These findings underscore the potential of Pediococcus acidilactici as a practical and effective strategy for enhancing productivity and sustainability in red tilapia aquaculture.

In euryhaline teleost black porgy, Acanthopagrus schlegelii, the glucocorticoid receptor (gr), growth hormone receptor (ghr), prolactin (prl)-receptor (prlr), and sodium–potassium ATPase alpha subunit (α-nka) play essential physiological roles in the osmoregulatory organs, including the gill, kidney, and intestine, during osmotic stress. The present study aimed to investigate the impact of pituitary hormones and hormone receptors in the osmoregulatory organs during the transfer from freshwater (FW) to 4 ppt and seawater (SW) and vice versa in black porgy. Quantitative real-time PCR (Q-PCR) was carried out to analyze the transcript levels during salinity and osmoregulatory stress. Increased salinity resulted in decreased transcripts of prl in the pituitary, α-nka and prlr in the gill, and α-nka and prlr in the kidney. Increased salinity caused the increased transcripts of gr in the gill and α-nka in the intestine. Decreased salinity resulted in increased pituitary prl, and increases in α-nka and prlr in the gill, and α-nka, prlr, and ghr in the kidney. Taken together, the present results highlight the involvement of prl, prlr, gh, and ghr in the osmoregulation and osmotic stress in the osmoregulatory organs (gill, intestine, and kidney). Pituitary prl, and gill and intestine prlr are consistently downregulated during the increased salinity stress and vice versa. It is suggested that prl plays a more significant role in osmoregulation than gh in the euryhaline black porgy. Furthermore, the present results highlighted that the gill gr transcript’s role was solely to balance the homeostasis in the black porgy during salinity stress.

Identifying natural growth-promoting agents and implementing environmentally sustainable methodologies are paramount strategies for enhancing the performance and welfare of aquatic fish farms. Phyllanthus emblica (PE) possesses a broad spectrum of bioactive properties, including antioxidant, antiviral, antimicrobial, and immunomodulatory effects. Hence, this study aimed to investigate the beneficial effects of PE dietary supplementation on the growth, immunity, redox homeostasis, organ histology, gene transcripts, and disease resistance of Red Tilapia against Fusarium oxysporum. A total of 240 fish (25.0 ± 3.0 g) were randomly distributed among 12 ponds, with 20 fish per pond. The fish were fed a basal diet supplemented with 0 (PE0), 5 (PE5), 10 (PE10), or 20 g of PE powder per kg of diet for 70 days. Following the trial, a challenge test was carried out. The PE5 group achieved significantly greater body weight, weight gain, specific growth rate (SGR) and digestive enzymes (lipase and amylases) than the PE20 group (p < 0.05). However, the PE5 group recorded the best feed conversion ratio compared to the other groups (p < 0.05). All PE-supplemented groups exhibited lower muscle lipid content and higher ash content (p < 0.05). PE-fortified groups displayed substantially lower levels of liver enzymes (AST, ALT, and ALP), creatinine, glucose, and lipid profile (cholesterol, triglycerides) compared to the PE0 group (p < 0.05). PE-fortified diets significantly enhanced the fish’s antioxidant enzyme activities (SOD, CAT, and GPx), immunological parameters (p < 0.05) for phagocytic activity, phagocytic index, and WBCs) and preserved the intestinal and hepatic tissues. The supplementation of 5 g PE/kg in Red Tilapia significantly enhanced the gene expression of growth genes (GH and IGF-1). In contrast, the group supplemented with 20 g PE/kg showed superior results for immune-related genes (including CC chemokines and interleukin-8) and antioxidant enzymes (SOD and GPx) (p < 0.05). Overall, the inclusion of 5 g/kg PE optimized growth performance in Red Tilapia, while the inclusion of 20 g/kg resulted in superior immune and antioxidant capabilities. These results highlight PE’s dual potential to enhance growth and boost health, confirming its promise as a natural feed additive for sustainable Tilapia aquaculture.