Closed Aquaculture Systems Research Articles

Assessment of the Carbon Footprint of Large Yellow Croaker Farming on the Aquaculture Vessel in Deep Sea in China

The present study conducted a Life Cycle Assessment (LCA) to evaluate the carbon emissions associated with large yellow croaker farming on Aquaculture Vessel “Conson No. 1”. The functional unit considered was 1 kg of fresh large yellow croakers delivered to a wholesaler. The life cycle of large yellow croaker farming on the aquaculture vessel was divided into five processes: feed production (FP), ship construction (SC), fingerling breeding (FB), adult fish farming (AF), and fish distribution (FD). Results showed that the carbon footprint (CF, kgCO2e/kg LW) for the complete life cycle amounted to 6.2170 kgCO2e/kg LW, while the CF per unit economic value of “Conson No. 1” large yellow croaker was estimated at 31 gCO2e/CNY. Among all processes, AF and FP had the highest CF contribution rates at 69.30% and 24.86%, respectively. Notably, energy consumption by aquaculture equipment on board emerged as the primary contributor across all sources of CF comparative analysis demonstrated that the CF of marine fish farming on the aquaculture vessel was lower than that of closed aquaculture systems’ average level and it was a viable option for implementing low-carbon aquaculture in the deep sea. In order to reduce energy consumption and promote a low-carbon economy in aquaculture vessels, several suggestions were proposed, including adjusting energy structure, enhancing energy efficiency, improving feed ratio, and optimizing feeding methods.

Growth performance and survivability of the Asian seabass Lates calcarifer (Bloch, 1790) reared under hyper-saline, hypo-saline and freshwater environments in a closed aquaculture system.

Salinity is one of the most critical environmental parameters regarding fish physiology, modifying food intake and growth performance in many fish species. The present study has investigated the effects of different salinity levels on growth performance, feeding and survival of Asian seabass Lates calcarifer juveniles. Asian seabass juveniles were reared at 0 (T1), 5 (T2), 22 (T3), 36 (T4), and 42 (T5) ppt salinity. Approximately eight hundred thirty fish individuals with an average weight of 1.24±0.52 g were randomly distributed (166 fish/Tank) in 5 concrete tanks (each tank 30×6×4 ft, volume 19,122 L) for forty days. Juveniles were initially fed 42% crude protein-containing diets at a rate of 6% of their body weight per day. The results showed that salinity level had a significant effect on the weight gain (WG), average daily weight gain (ADWG), specific growth rate (SGR), feed conversion ratio (FCR), survival rate (SR), total biomass and health indices (p<0.05). The highest WG (39.11±1.49 g), ADWG (1.00±0.12 g), SGR (8.74±0.03% d-1) and lowest FCR (0.96±0.20) were observed with T3 treatment, which was significantly higher compared to other treatment groups (p<0.05). Among the health indices, the highest hepatosomatic index and viscerosomatic index were found with T3 treatment, significantly higher than the other groups (p<0.05). No significant differences were found among the treatments in terms of survival rate (p>0.05), but the maximum survival rate (98.89±0.0%) was observed in the T3 and T2 treatments. The maximum level of crude proteins (19.99±1.4%) was found in the whole-body biochemical composition of Asian seabass juveniles in the T3 treatment group. The second-order polynomial regression showed that 20 ppt salinity is optimum for the best growth of Asian seabass. Thus, the present study recommends 20 to 36 ppt salinity for the commercial farming of Asian seabass under a closed aquaculture system.

Physico-Chemical Dynamics of Vanname Shrimp (Litopenaeus vannamei) Cultivation Pond Water Quality with A Recirculation System

In 2021 Indonesia was experiencing an increase in shrimp exports. Litopenaeus vannamei shrimp is one of the shrimp with a good increase in exports and a type of shrimp with high resistance to environmental disturbances. Indonesia has land potential of about 2,964,331.24 hectares which can be used to increase shrimp production. The cultivation technique that can maximize this potential is a superintensive technique that uses closed aquaculture system. Recirculating Aquaculture system (RAS) is a closed aquaculture system that is suitable for shrimp farming because the water treatment is separated so that there is no significant change in environmental conditions. In this study, the RAS system was equipped with the use of an ultrafiltration membrane as a tool for the inflow water treatment. This study observe the physico-chemical water dynamics that occur during one cultivation cycle. It was observed that the DO of the pond decreased as the shrimp grew, the salinity increased during the cultivation process if there was no water replacement, the brightness decreased every day until it reached a specified point. Temperatures tended to be low due to weather factors, ammonia levels tended to decrease but nitrite and nitrate levels tended to increase due to the slower transformation rate of nitrite and nitrate. The operating system for this process was carried out by adding CaO and sugar. The addition of CaO ranges from 100-600 g/day. The effective addition of sugar if there was a spike in ammonia levels was 1.25 kg/day.

Biofloc Application Using Aquaponics and Vertical Aquaculture Technology in Aquaculture: Review

Some aspects of traditional aquaculture have negative impacts on the aquatic environment, leading to pollution and disease outbreaks in farmed organisms. Biofloc technology (BFT) is a closed aquaculture system that utilizes specific microbial communities to remove ammonia emitted from aquaculture organisms or adds carbon to the aquaculture system to improve water quality. BFT has benefits, such as increasing production and improving water quality, and reducing disease spread and pollution, without the need for water exchange. However, there are disadvantages, such as rapid changes in water quality due to accumulation of dissolved nutrients and total suspended soils (TSS) and the requirement for expensive aeration equipment to maintain dissolved oxygen. BFT can be enhanced in value and efficiency by combining it with other aquaculture technologies, such as aquaponics and vertical aquaculture to overcome the disadvantages. The integration of biofloc with technologies from the fourth industrial revolution holds potential for further development, while aquaponics and vertical farming can eliminate geographical limitations and accelerate the urbanization of aquaculture. The integration of aquaponics and vertical aquaculture with BFT has potential for development, accelerating the urbanization of aquaculture and removing geographic limitations.

Management of inorganic nitrogen compounds in a closed aquaculture system during imitation for nursery of Litopenaeus vannamei under brackish condition

It was aimed to estimate the efficiency of management of inorganic nitrogen compounds under a closed system condition, via addition of carbon source. For this purpose, an imitation experiment for nursery of Litopeanaeus vannamei postlarvae under a brackish condition was conducted, in two closed systems with a salinity of about 18‰: systems with (CS) and without (control) addition of carbon source (molasses) at a carbon to nitrogen ratio (C:N) of 20:1. The levels of total ammonia nitrogen (TAN, 1.39±0.14 mg L−1), nitrite (0.023±0.003 mg L−1) and nitrate (0.49±0.06 mg L−1) in CS system were significantly lower than those in the control system (6.92±0.60, 0.809±0.050 and 2.39±0.47 mg L−1, P < 0.05). The results indicated that carbon source addition to the closed system imitating nursery of L. vannamei postlarvae under a brackish condition well managed the level of inorganic nitrogen compounds during experiment, making it possible to environment-friendly culture L. vannamei at inland areas under a closed condition.

The hybrid Pelteobagrus fulvidraco (♀) × Leiocassis longirostris (♂) exhibits improved trait on hypoxia-tolerance

Hypoxia has become a significant issue both in open aquatic environment and closed aquaculture system. Development of hypoxia-tolerant breeds is one of the practical strategies in further fish farming. In present study, the hybrid Pelteobagrus fulvidraco (PF) × Leiocassis longirostris (LL) was generated by artificial insemination. Both PF ♀ × LL ♂ and LL ♀ × PF ♂ could produce F1 offspring, assigned as hybrid PL and hybrid LP, respectively. The hybrid PL exhibited higher hatching rate, expectant morphological traits, and an improved trait on hypoxia-tolerance compared to hybrid LP. However, the growth trait was not strengthened at early development stage until 90 dpf compared to hybrid LP and LL. To further examine the hypoxia-tolerant machinery of the hybrid PL strain, we systematically investigated the tissues morphology, hypoxia inducible factor (HIF)-related genes expression, and oxidative stress enzymes activity of gill, liver, and intestine under acute hypoxia and reoxygenation. The histological results showed that the interlamellar cell mass was expanded in the gill, obvious vacuolation and swell of hepatocytes was found in the liver, and expanded submucosa was observed in the intestine, suggesting the tissues remodeling was evidenced in hybrid PL responding to hypoxia. A rapid HIF-related genes response (Hif-1α, Hif-2α, Vhl, Fih-1, Phd3, and Vegf-a) and activation of anti-oxidant enzymes activity (T-SOD, CAT, and GPx) among three tissues were patently illustrated. Our results indicated that the complex combination of morphological, molecular, and biochemical adjustments might contribute jointly to the hypoxia-tolerance of hybrid PL. This study provided an alternative and possible method for hypoxia-tolerant fish strain generation using hybridization breeding in aquaculture.

Application of proteomics and metabolomics to assess ammonia stress response and tolerance mechanisms of juvenile ornate rock lobster Panulirus ornatus.

Ammonia is a common pollutant in the aquatic ecosystem and closed aquaculture systems. It may pose a threat to the lobster growth, reproduction and survival. However, there is lack of research of the mechanisms on the toxic effects ammonia at molecular levels. In this work, proteomics and metabolomics were integrated to analyze the proteome and metabolome responses in the ornate spiny lobster Panulirus ornatus treated with ammonia (20 mg L-1) for 48 h. A total of 199 proteins and 176 metabolites were significantly altered in P. ornatus following ammonia treatment. The responsive proteins and metabolites were predominantly involved in immune response, phase I and phase II biotransformation, carbohydrate metabolism, amino acid metabolism, and lipid metabolism. Furthermore, an increase in urea levels was observed, and amino acid metabolism was induced, indicating that the urea cycle was utilized to biotransform ammonia so as to reduce endogenous ammonia content. Ammonia exposure also affected the antioxidant system and induced cellular apoptosis. Overall, our results provide comprehensive insights into the molecular mechanisms underlying the response of P. ornatus to ammonia stress. We believe that the data reported herein should contribute to the development of novel, efficient methods for P. ornatus aquaculture.

Применение продуктов гидролиза шпротных отходов при кормлении европейского сига Coregonus lavaretus в аквакультуре

European whitefish are widely used for artificial reproduction in aquaculture. Relevant is the search for alternative solutions for protein supplements in the composition of animal feed for its cultivation. A promising source of valu-able protein is fish waste from canning industries. In the Kaliningrad region, 80% of Russian canned food "Sprats in oil" is produced. The daily amount of sprat waste is 2-10 tons. The use of protein products of hydrolysis of smoked sprat heads instead of a part of fishmeal in compound feeds for whitefish juveniles was studied in this work. Hy-drolysis was carried out by a high-temperature method in an aqueous medium to obtain two types of protein sup-plements. In the first experiments, a 5% low molecular weight peptide supplement with a protein content of 82.7% was introduced into the model feed instead of the corresponding amount of fishmeal. In the second series of exper-iments, a 10% protein-mineral supplement was introduced with a protein content of 54.5% and mineral substances of 24.0%. The experiments were carried out in a closed aquaculture system based on AtlantNIRO. After 56 days of feeding, the fish breeding, morphobiological and organosomatic parameters of the fish were comparatively studied. . The promising potential of additives as feed components has been established. The introduction of a 5% peptide additive led to an increase in the fry survival rate. The use of a 10% protein-mineral supplement resulted in higher growth rates and lower feed ratios. In both experiments, there was no negative effect on the growth and morpho-physiology of the studied fish. For more reliable results, further study of alternative amounts of inclusion of these additives in the feed is required.

Transcriptomic profiles of Florida pompano (Trachinotus carolinus) gill following infection by the ectoparasite Amyloodiniumocellatum

The dinoflagellate Amyloodinium ocellatum is an important pathogenic parasite infecting cultured marine and brackish water fishes worldwide. This includes cultured Florida pompano (Trachinotus carolinus), which is one of the most desirable marine food fish with high economic value in the USA. A. ocellatum infects fish gills and causes tissue damage, increased respiratory rate, reduced appetite, and mortality, especially in closed aquaculture systems. This study mimicked the natural infection of A. ocellatum in cultured pompano and conducted a transcriptomic comparison of gene expression in the gills of control and A. ocellatum infected fish to explore the molecular mechanisms of infection. RNA-seq data revealed 604 differentially expressed genes in the infected fish gills. The immunoglobulin genes (including IgM/T) augmentation and IL1 inflammation suppression were detected after infection. Genes involved in reactive oxygen species mediating parasite killing were also highly induced. However, excessive oxidants have been linked to oxidative tissue damage and apoptosis. Correspondingly, widespread down-regulation of collagen genes and growth factor deprivation indicated impaired tissue repair, and meanwhile the key executor of apoptosis, caspase-3 was highly expressed (25.02-fold) in infected fish. The infection also influenced the respiratory gas sensing and transport genes and established hypoxic conditions in the gill tissue. Additionally, food intake and lipid metabolism were also affected. Our work provides the transcriptome sequencing of Florida pompano and provides key insights into the acute pathogenesis of A. ocellatum. This information can be utilized for designing optimal disease surveillance strategies, future selection for host resistance, and development of novel therapeutic measures.

Supplementation of ex situ produced bioflocs improves immune response against AHPND in Pacific whiteleg shrimp (Litopenaeus vannamei) postlarvae.

The emergence of Vibrio diseases, including acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio spp., had resulted in heavy losses in global shrimp production. Biofloc technology is a closed aquaculture system developed as one of the sustainable solutions to increase system resilience in the shrimp industry. In this study, biofloc was formed externally (ex situ biofloc) with probiotics Bacillus sp. strain BME and Bacillus sp. strain BCE, diatom microalgae Chaetoceros calcitrans, and a consortium of nitrifying bacteria, in the ratio of 1:1:6:6 as a starter. The study showed that the ex situ biofloc supplementation in Pacific whiteleg shrimp (L. vannamei) postlarvae culture can increase the shrimp culture performance (shrimp survival and growth), reduce Vibrio counts in the water and shrimp body, and provide stimulation of the shrimp immune response through humoral immune responses, such as pattern recognition protein (C-type lectin) and melanization process (proPO). Overall, the results indicate that the supplementation of ex situ biofloc provided protection to shrimp under Vibrio infection, regardless of the timing of addition (before, simultaneously, or after addition of Vibrio sp. strain VPA). This suggests that the ex situ biofloc can be effective as a preventive and a supportive treatment against potential AHPND infection in L. vannamei postlarvae culture. Taken together, the ability of the ex situ biofloc to modulate immune-related gene expression and resistance of L. vannamei against potentially AHPND-causing Vibrio sp. strain makes it an effective aquaculture technology for infectious disease control in shrimp production with high-density and minimal water exchange culture. KEY POINTS: • Supplementation of ex situ produced biofloc in shrimp postlarvae culture. • Ex situ biofloc reduces Vibrio counts in the water and shrimp body. • Ex situ biofloc stimulates shrimp humoral immune responses and survival.

Integrated physiological, transcriptome and metabolome analyses of the hepatopancreas of the female swimming crab Portunus trituberculatus under ammonia exposure

Ammonia is a common environmental pollutant in aquatic ecosystem and is also a significant concern in closed aquaculture systems. The threat of ammonia has been increasing with rising anthropogenic activities including intensified aquaculture. In this study, we aimed to investigate ammonia toxicity and metabolism mechanisms in the hepatopancreas, a major organ for Vitellogenin (Vtg) synthesis and defending against ammonia stress, of female swimming crab Portunus trituberculatus which is an important fishery and aquaculture species, by integrating physiological, transcriptome and metabolome analyses. The results revealed that ammonia exposure (10 mg/L, an environmentally relevant concentration) resulted in a remarkable reduction in vtg expression and depression of multiple signaling pathways for reproductive regulators including methyl farnesoate, ecdysone and neuroparsin, demonstrating for the first time that ammonia impairs swimming crab female reproduction. In addition, a number of important genes and metabolites in glycolysis, the Krebs cycle, fatty acid β-oxidation and synthesis were significantly downregulated, indicating that changes in ammonia levels lead to a general depression of energy metabolism in hepatopancreas. After ammonia exposure, an increased level of urea and a reduction of amino acid catabolism were observed in hepatopancreas, suggesting that urea cycle was utilized to biotransform ammonia, and amino acid catabolism was decreased to reduce endogenous ammonia generation. Furthermore, antioxidant systems were altered following ammonia exposure, which was accompanied by proteins and lipid oxidations, as well as cellular apoptosis. These results indicate that ammonia leads to metabolic suppression, oxidative stress and apoptosis in P. trituberculatus hepatopancreas. The findings improve the understanding for the mechanisms of ammonia toxicity and metabolism in P. trituberculatus, and provide valuable information for assessing potential ecological risk of environmental ammonia and improving aquaculture management.

Growth performance, haematological assessment and chemical composition of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) fed different levels of Aloe vera extract as feed additives in a closed aquaculture system.

A 105-day experimental trial was conducted to assess different levels of dietary Aleo vera extract supplementation on water quality parameters, proximate composition, growth performance and haematological parameters of fry Oreochromis niloticus. Four different percentages of dietary leaf extract powder of Aleo vera (ALE) with a basal feed, designated as, i.e., T0 (Control group; without ALE), T1 (1% ALE), T2 (2% ALE), and T3 (3% ALE). Fish fry was reared in concrete tanks (7.0 m, 1.6 m, 1.0: L, W, H; water volume 11.2 m3/tank), with an average initial weight 4.04 ± 0.03 g/ fry, and each treatment was triplicated. Fry was randomly distributed at a stocking rate of 450 individuals/ tanks. The water quality parameters revealed that temperature, pH, salinity, dissolved oxygen (DO) and nitrates were found in a promising range as given by FAO/WHO limits. However, the record values obtained for Electric Conductivity (EC), Total dissolved solids (TDS), and alkalinities were not found in all tanks' suitable range according to FAO/WHO limits. The results revealed a significant impact of different percentages of dietary ALE supplementation on fry's body composition and haematological parameters. Moreover, the final body weight, final body length, average daily weight gain (g), net weight gain (g) and specific growth rate (%) were significantly higher (p < 0.05) in T1 and T2 compared with T0 and T3 treatments. The poorest feed conversion ratio was recorded in the T2 group compared with other treatments. Thus, the current study provides information about the nutritional quality of Nile tilapia culturing in Pakistan.

Growth performances and nutrient compositions of pabda Ompokbimaculatus (Bloch, 1797) grown in recirculating and closed aquaculture systems

This study evaluated the growth performances and nutrient compositions of pabda Ompok bimaculatus (Bloch, 1797) in a recirculating aquaculture system (RAS) and a closed aquaculture system (CAS). The average daily weight gain (ADG) and specific growth rate (SGR) of pabda in RAS (ADG: 0.18 g/d; SGR: 3.40 %/d) was 3.61- and 1.41-folds higher than that of the CAS (ADG: 0.05 g/d; SGR: 2.40 %/d). Fish had significantly higher level of PUFA (Poly-unsaturated fatty acid) in CAS (41%) than in RAS (33%). The ratio between omega-3 and omega-6 fatty acids in RAS and CAS were 0.73 and 0.69, respectively. This study’s results have demonstrated that the culture of pabda in RAS is more suitable than CAS in terms of growth.&#x0D; J. Asiat. Soc. Bangladesh, Sci. 47(1): 1-12, June 2021

Absolute quantification of priority bacteria in aquaculture using digital PCR

Modern aquaculture systems are designed for intensive rearing of fish or other species. Both land-based and offshore systems typically contain high loads of biomass and the water quality in these systems is of paramount importance for fish health and production. Microorganisms play a crucial role in removal of organic matter and nitrogen-recycling, production of toxic hydrogen sulfide (H2S), and can affect fish health directly if pathogenic for fish or exerting probiotic properties. Methods currently used in aquaculture for monitoring certain bacteria species numbers still have typically low precision, specificity, sensitivity and are time-consuming. Here, we demonstrate the use of Digital PCR as a powerful tool for absolute quantification of sulfate-reducing bacteria (SRB) and major pathogens in salmon aquaculture, Moritella viscosa, Yersinia ruckeri and Flavobacterium psychrophilum. In addition, an assay for quantification of Listeria monocytogenes, which is a human pathogen bacterium and relevant target associated with salmonid cultivation in recirculating systems and salmon processing, has been assessed. Sudden mass mortality incidents caused by H2S produced by SRB have become of major concern in closed aquaculture systems. An ultra-sensitive assay for quantification of SRB has been established using Desulfovibrio desulfuricans as reference strain. The use of TaqMan® probe technology allowed for the development of multi-plex assays capable of simultaneous quantification of these aquaculture priority bacteria. In single-plex assays, limit of detection was found to be at around 20 fg DNA for M. viscosa, Y. ruckeri and F. psychrophilum, and as low as 2 fg DNA for L. monocytogenes and D. desulfuricans.

Assessment of growth characteristics, the survival rate and body composition of Asian sea bass Lates calcarifer (Bloch, 1790) under different feeding rates in closed aquaculture system.

One of the essential factors to be addressed in the development of aquaculture is the feeding regime. This study was investigated to assess the effects of feeding rate on growth performance, feed utilization, chemical body composition survival rate, cannibalism and morphological indices of Asian Seabass, Lates calcarifer. Intended for the trial, one hundred forty sea bass individuals with an average weight 5.47 ± 0.11 g were randomly distributed in 4 concrete tanks (914 cm × 183 cm 122 cm) each; length × width × depth) and volume 18,399 L, for total 68 days. The fishes were fed with a pelleted diet containing 46% crude protein for different feeding groups designated as (T1, T2, T3 and T4). The feed was supplied with a rate of (T1) 3%, (T2) 4%, (T3) 6%, and (T4) 9% of fish biomass per day and feeding frequency were maintained three times per day to all the groups. At the end of the trial water physicochemical parameters was in acceptable range for Asian sea bass growth. The average daily weight gain (g), weight gain (g) and specific growth rate (%) was significantly higher (p < 0.05) in T3 and T4 as compared to T1 and T2 group. The poorest feed conversion ratio was recorded in T1 group with 3% biomass per day. The cannibalism rate was significantly (p < 0.05) higher in T1 (3%) compared to T3 and T4 treatment. The morphological indices, condition factors (CF), viscerosomatic index and hepatosomatic index (HSI) was significantly higher in T4 group as compared to other treatments. The protein, moisture and ash contents of the whole biomass of the Asian sea bass were not significantly influenced by feeding rate. The fat levels in the fish bodies increased significantly (p < 0.05) with increasing feeding ratio. The phenomenal regression indicates that 6.5% feeding rate per day is optimum for best growth performance, survival and minimum cannibalism rate for Asian sea bass in captivity. The outcome of the finding will help in promotion for not only the coastal aquaculture in Pakistan abut also elsewhere.

Aeration strategy in the intensive culture of tambaqui, Colossoma macropomum, in the tropics

As the demand for fish increases and limitations are placed on water use, intensification in closed aquaculture systems could help to increase its sustainable production. The Amazon region stands out for its stable warm climate with fast-growing and resilient fish. This study evaluated the efficacy of two aeration regimes on intensive rearing of tambaqui, Colossoma macropomum, in six 46.4-m3 concrete-wall earthen bottom ponds, with no water exchange. Two aeration regimes were tested: (1) emergency aeration (EA), in which the aeration system was activated with dissolved oxygen (DO) levels below 3 mg L−1; (2) supplemental aeration (SA), with 8 h of aeration every night, and also during days with low solar radiation. Water quality, fish performance and health (haematological and parasitological indicators), aeration use and cost were assessed. Juveniles (44.39 ± 9.72 g, mean weight ± SD) were stocked in six concrete-wall ponds with earthen bottoms at 32,300 ha −1 and fed commercial feed (36–32% crude protein) for 17 weeks (122 days). Mean values of the water quality parameters showed no difference between treatments, but occurrences of hypoxia were significantly higher in SA (31 hypoxias with DO <2 mg L−1 and 11 extreme hypoxias with DO <0.5 mg L−1) than in EA (5 and 0.6 occurrences, respectively). Significantly more erythrocytes were observed in the fish in SA than in EA, which indicates a response to a low DO concentration. The parasitological analyses revealed 100% prevalence of Monogenoidea (Dactylogyridae) in animal gills, with higher abundance in the SA fish. All treatments showed high fish survival rate (99.6 ± 0.8% for EA; 99.3 ± 1.2% for SA) and low FCR (1.22 ± 0.1 for EA; 1.32 ± 0.1 for SA), but weight gain, specific growth rate and yield were higher (p < .05) and water use and energy cost was lower (p < .05) for EA. In conclusion, the aeration strategy influenced hypoxia frequency and aeration cost, resulting in superior fish performance and health conditions and lower energy cost in EA, which suggests this strategy to be more beneficial for tambaqui production than SA.

Metabolite profiling of whiteleg shrimp Litopenaeus vannamei from super-intensive culture in closed aquaculture systems: a recirculating aquaculture system and a hybrid zero water discharge-recirculating aquaculture system.

The production of the whiteleg shrimp Litopenaeus vannamei now accounts for approximately 75% of the total shrimp production in Indonesia. The techniques used to produce whiteleg shrimp in Indonesia are still dominated by conventional rearing strategies using open-pond systems, which often contribute to unpredictable culture performance and weak sustainability. Alternative production strategies of closed aquaculture systems, including the recirculating aquaculture system (RAS) and hybrid zero water discharge-recirculating aquaculture system (hybrid system), have been developed and implemented for higher productivity, stability and sustainability of whiteleg shrimp grow-out production in Indonesia. Despite the positive aspects of the application of closed aquaculture systems in shrimp aquaculture, the differences in the characteristics of shrimp grown in closed RAS and hybrid systems compared to open-pond systems remain unclear. This study aims to investigate the differences in the metabolite profiles of shrimp grown in intensive closed aquaculture systems, including an RAS and hybrid system, compared to those of shrimp grown in a semi-intensive, open, earthen pond system by means of non-targeted GC-MS metabolite profiling. Shrimp cultured in the closed systems (RAS and hybrid system) and an open system (pond) were harvested and subjected to GC-MS non-targeted metabolomics analysis. A total of 112 metabolites were annotated from shrimp samples and subjected to principal component analysis (PCA). The metabolites annotated from GC-MS mainly included organic compounds, proteinogenic and non-proteinogenic amino acids, sugars, nucleosides and fatty acids. The results of principal component analysis showed several metabolites with high variable importance in projection (VIP) scores, including shikimic acid, β-alanine, uric acid, hypoxanthine, inosine, homocysteine, methionine, phenylalanine, tryptophan and lysine, as the main metabolites differentiating the shrimp grown in the three production systems. Our findings showed that shrimp cultured in different aquaculture systems exhibited distinct metabolite profiles, and the metabolites showing high VIP scores, including shikimic acid, β-alanine, uric acid, hypoxanthine, inosine, homocysteine, methionine, phenylalanine, tryptophan and lysine, may serve as candidate markers to indicate the differences in shrimp from different production systems.

Effluent treatment in an aquaponics-based closed aquaculture system with single-stage nitrification–denitrification using a down-flow hanging sponge reactor

A laboratory-scale demonstration of the aquaculture effluent treatment was conducted in a system that combined a down-flow hanging sponge (DHS) reactor and a hydroponic cultivation bed (HCB). Cyprinus carpio was used as a model aquaculture fish and Cupsicum frutescens was used as a model hydroponic plant. The aquarium water was circulated through the HCB and DHS using a submerged pump. The experiment was divided into six phases in which the sodium acetate solution was supplied using different feeding patterns. The sodium acetate solution acted as a carbon source and not only eliminated nitrogen through denitrification but also increased the alkalinity through biological degradation of the acetate. Denitrification was observed to eliminate 7.7% of the total nitrogen at the inlet out of which 53.5% was converted by C. frutescens to form a fruit. The microbial community in the sludge that was retained in the DHS contained both nitrifying and denitrifying bacteria. Nitrososhaera was the dominant ammonia-oxidizing bacterium, whereas Nitrospira was the dominant nitrite-oxidizing bacterium. Further, Opitutus acted as the dominant denitrifying bacterium. No major bacterial pathogen was detected in the DHS–HCB system. The study confirmed that the DHS system provided single-stage nitrification–denitrification and that the overall DHS–HCB system provided a low-cost and high-performance aquaculture effluent treatment system that is capable of being used for safe food production.

Microbiome Dynamics in a Large Artificial Seawater Aquarium.

ABSTRACTArtificial habitats for animals have high commercial and societal value. Microbial communities (microbiomes) in such habitats may play ecological roles similar to those in nature. However, this hypothesis remains largely untested. Georgia Aquarium's Ocean Voyager (OV) exhibit is a closed-system aquatic habitat that mimics the oligotrophic open ocean and houses thousands of large marine animals, including fish, sea turtles, and whale sharks. We present a 14-month time series characterizing the OV water column microbiome. The composition and stability of the microbiome differed from those of natural marine environments with similar chemical features. The composition shifted dramatically over the span of 2 weeks and was characterized by bloom events featuring members of two heterotrophic bacterial lineages with cosmopolitan distributions in the oceans. The relative abundances of these lineages were inversely correlated, suggesting an overlap in ecological niches. Transcript mapping to metagenome-assembled genomes (MAGs) of these taxa identified unique characteristics, including the presence and activity of genes for the synthesis and degradation of cyanophycin, an amino acid polymer linked to environmental stress and found frequently in cyanobacteria but rarely in heterotrophic bacteria. The dominant MAGs also contained and transcribed plasmid-associated sequences, suggesting a role for conjugation in adaptation to the OV environment. These findings indicate a highly dynamic microbiome despite the stability of the physical and chemical parameters of the water column. Characterizing how such fluctuations affect microbial function may inform our understanding of animal health in closed aquaculture systems.IMPORTANCE Public aquariums play important societal roles, for example, by promoting science education and helping conserve biodiversity. The health of aquarium animals depends on interactions with the surrounding microbiome. However, the extent to which aquariums recreate a stable and natural microbial ecosystem is uncertain. This study describes the taxonomic composition of the water column microbiome over 14 months in a large indoor aquatic habitat, the Ocean Voyager exhibit at the Georgia Aquarium. Despite stable water column conditions, the exhibit experienced blooms in which the abundance of a single bacterial strain increased to over 65% of the community. Genome analysis indicated that the OV's dominant strains share unique adaptations, notably genes for storage polymers associated with environmental stress. These results, interpreted alongside data from natural ocean systems and another artificial seawater aquarium, suggest a highly dynamic aquarium microbiome and raise questions of how microbiome stability may affect the ecological health of the habitat.

Conceptual and methodological advances for holobiont research.

Conceptual and methodological advances for holobiont research.