Multi-trophic Aquaculture System Research Articles

Effect of in vitro simulated gastrointestinal digestion on the antioxidant activity of the red seaweed Porphyra dioica

Porphyra sp. is one of the most cultivated and commercially valuable species, recognized for its high protein content (up to 47% dry weight) and complete amino acids profile. Based on these characteristics, P. dioica produced in an integrated multitrophic aquaculture system was selected for this study. The aim was to evaluate the effect of in vitro simulated gastrointestinal digestion (SGID) on the antioxidant activity of the hydrolysates generated from dried blades and from the protein isolate (PI) extracted from them. The alkali extraction and isoelectric precipitation (pH 4.5) of P. dioica protein prior SGID allowed isolating/enriching protein, while direct SGID of blades allowed assessing the potential influence of other constituents of the sample on the bioactive properties. Overall, SGID promoted the release of smaller bioactive peptides and their in vitro antioxidant activity, which was assessed by different methods (DPPH and ABTS+ scavenging capacity, ORAC and FRAP), was improved compared to the intact samples. Blades submitted to direct SGID presented significantly higher ORAC values compared to PI (2010 ± 136 vs 542 ± 21 µmol TE/g FDS, respectively). For the remaining assays, PI presented more potent antioxidant activity, especially FRAP (131 ± 2 vs 16 ± 1 µmol TE/g FDS) and ABTS+ (1244 ± 157 vs 230 ± 15 µmol TE/g FDS). The results indicated that gastrointestinal digestion improved the antioxidant activity of P. dioica-derived hydrolysates, as they presented effective activity against different oxidative mechanisms, thus suggesting health-protecting effects.

The budget of carbon in the farming of the Amazon river prawn and tambaqui fish in earthen pond monoculture and integrated multitrophic systems

The present study analyzed the inputs, outputs, and accumulation of carbon in ecological compartments of earthen ponds for the grow-out of Amazon river prawn (Macrobrachium amazonicum) and tambaqui fish (Colossoma macropomum) reared in monoculture and integrated multi-trophic aquaculture (IMTA) systems, using recycled hypereutrophic water. A completely randomized experiment was designed with four treatments and three replications: PM- monoculture with 30 prawn m−2, FM- monoculture with 3 fish m−2, IMTA- fish-prawn polyculture with 30 prawn m−2 and 3 fish m−2 reared free-swimming, POLY-CAGE- fish-prawn IMTA with 30 prawn m−2 reared free-swimming and 40 fish m−3 in net-cages. Animals, rain, water, feed, soil, gases, total suspended solids, settleable solids, and accumulated sludge were collected throughout the experiment to determine their total organic and total inorganic carbon contents and to calculate the carbon budget. Results showed that much of the carbon accumulated as solid organic material (∼55 – 84%) and animal biomass (∼4 – 18%). The remaining carbon was discharged to receiving water bodies in the outlet water during harvesting (∼6 – 8%) or emitted as carbon dioxide (CO2) and methane (CH4) (∼1 – 5%). Feed management appeared to influence the major biological processes in the aquatic carbon cycle, such as photosynthesis and aerobic decomposition. All systems showed absorption of atmospheric CO2 (∼529 – 782 kg C-CO2 ha−1) that was higher than the emissions (∼35 – 93 kg C-CO2 ha−1) and CH4 (∼14 – 123 kg C-CH4 ha−1). Furthermore, all of the culture processes in the present study removed ∼1,000 to 2,000 kg Total Carbon ha−1 from the inlet water, and thus, these systems can provide important ecosystem services. The high accumulation of carbon in the settleable solids (∼69% of outputs) and the adequate water quality maintained in the IMTA demonstrate the resilience of this grow-out system to high allochthonous inputs of organic matter as feed. An increased prawn density or the addition of a mud-feeder species to the culture may enhance the incorporation of carbon from settleable solids into harvested biomass, improving the efficiency of the systems.

Construction of lyapunov function using gradient method to stability analysis of the nitrogen-phosphate-phytoplankton-sediment interaction model

The significant growth in catch fisheries and aquaculture production has enhanced the world’s capacity to consume diverse and nutritious food; however, this fast-growing industry has resulted in the environmental disturbance, especially caused by fish farming. The nutrient was generated from fish excretion and unfed pellet in the form of dissolved organic matter, especially as nitrogen and phosphate particulates. Therefore, applying mathematical models is crucial to understand and minimize the impact on the water ecosystem, thus maximizing productivity. This paper aims to research to analyze the global and stability of the equilibrium point the dynamical system that water and sediment in aquaculture Integrated Multi-Trophic Aquaculture (IMTA) system. Analysis stability global has been proved by constructing the Lyapunov function. The gradient method is used to construct the Lyapunov function in the most general form. The method is based on the assumption of a variable gradient function by determining V and ∇V. In the Lyapunov method construction, if the function V(x) would be definite positive, whereas derivative V(x) would be a definite negative. Models of nitrogen, phosphate, phytoplankton, and sediment system exhibited globally asymptotically stable. This implies that fish farming using the IMTA system on Karimunjawa island was still considerably under normal condition.

Domesticated Populations of Codium tomentosum Display Lipid Extracts with Lower Seasonal Shifts than Conspecifics from the Wild-Relevance for Biotechnological Applications of this Green Seaweed.

In the last decades, the use of algae in biotechnology and food industries has experienced an exponential growth. Codium tomentosum is a green macroalgae with high biotechnological potential, due to its rich lipidome, although few studies have addressed it. This study aimed to investigate the seasonal changes in lipid and pigment profiles of C. tomentosum, as well as to screen its antioxidant activity, in order to evaluate its natural plasticity. Samples of C. tomentosum were collected in two different seasons, early-autumn (September/October) and spring (May), in the Portuguese coast (wild samples), and in a land-based integrated multitrophic aquaculture (IMTA) system (IMTA samples). Total lipid extracts were analysed by LC–MS, GC–MS, and HPLC, and antioxidant activity was screened through free radical scavenging potential against DPPH and 2,20-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals. Wild samples showed a high seasonal variability, modifying their lipidome and pigment profiles according to environmental shifts, while IMTA samples showed a relatively stable composition due to early-stage culturing in controlled conditions. The lipids that contributed the most to seasonal discrimination were glycolipids (monogalactosyl diacylglycerol - MGDG and digalactosyl diacylglycerol - DGDG) and the lyso forms of phospholipids and glycolipids. Lipid extracts showed antioxidant activity ranging from 61 ± 2 to 115 ± 35 µmol Trolox g−1 of lipid extract in DPPH assay and from 532 ± 73 to 927 ± 92 µmol Trolox g−1 of lipid extract in ABTS assay, with a more intense antioxidant activity in wild spring samples. This study revealed that wild specimens of C. tomentosum presented a higher plasticity to cope with seasonal environmental changes, adjusting their lipid, pigment, and bioactivity profiles, while IMTA samples, cultured under controlled conditions, displayed more stable lipidome and pigment compositions.

Potential growth and nutrient removal of Kappaphycus alvarezii in a fish floating‐net cage system in Sekotong Bay, Lombok, Indonesia

AbstractThere has been increasing interest in promoting the seaweed Kappaphycus alvarezii as a co‐culture species in an integrated multitrophic aquaculture system. In recent work, we observed the capability of K. alvarezii to grow and remove carbon (C), nitrogen (N), and phosphorus (P) when planted in an intensive fish floating‐net cage system in Sekotong Bay, Lombok, Indonesia. Environmental factors that may influence seaweed bioremediation were investigated. After 42 days, there was a significant difference in the seaweed growth and bioremediation capability while cultivated within the fish cage system compared to the control site. Six kilogram of K. alvarezii incorporated inside the fish cages reduced the inorganic NH4+ and PO43− on average of 22.5–34% and 5–30%, respectively, from morning to afternoon and removed 131 g C g DW−1, 4.6 g N g DW−1, and 1.18 g P g DW−1. The seaweed growth rate inside the fish cages was 3.33% d−1 and higher than at the control site. Water motion was a limiting factor for growth and nutrient bioremediation inside the fish cage system. Our results provide evidence of the potential for K. alvarezii to grow in a fish aquaculture system and reduce the nutrient discharge from fish farms.

Antioxidant activity of extracts from marine macroalgae, wild-collected and cultivated, in an integrated multi-trophic aquaculture system

Methanolic and hydroethanolic extracts of ten common species of marine macroalgae (5 Rhodophyta, 2 Ochrophyta and 3 Chlorophyta) of the intertidal system of the Canary Islands were screened to evaluate their in vitro antioxidant activity by DPPH radical scavenging activity and reducing power. The concentration of bioactives as pigments and phenolic compounds was also determined. Wild-collected algae and these cultivated in an integrated multitrophic aquaculture (IMTA) system during one month, were analyzed. The highest antioxidant activity was observed in Halopithys incurva, Fucus spiralis and Treptacantha abies-marina. The hydroethanolic extracts exhibited higher reducing power than methanolic extracts in most species. However, the differences in DPPH scavenging activity between solvents were not so high, and only the hydroethanolic extracts of some species showed antioxidant activity. The highest concentration of polyphenols was reached in H. incurva, T. abies-marina and F. spiralis. However, compared to collected seaweeds, the percentage of these compounds was lower in cultivated samples. The highest concentrations of chlorophyll a and carotenoids were found in T. abies-marina, Codium intertextum and F. spiralis. In red algae, the phycoerythrin (PE) content was higher in H. incurva, followed by P. capillacea. After culture, pigment content increased in most species, depending on the assimilation capacity of the ammonium from fishpond effluents. C/N ratio in samples collected in the field was high, indicating nitrogen limitation. After cultivation under high nitrogen availability (fishpond effluents), the ratio decreased in all species, especially in C. intertextum, F. spiralis and H. incurva, by the accumaltion of N-compounds. Pearson coefficient only showed significant correlations between the reducing power and some bioactive compounds, particularly polyphenols and PE. In conclusion, culture under IMTA conditions changed the biochemical composition of algae. The antioxidant activity did not decrease after culture in several species, despite the reduction of phenolic compounds, probably due to the benefits of the high N availability in the IMTA.

Digestive microbiota of shrimp Penaeus vannamei and oyster Crassostrea gigas co-cultured in integrated multi-trophic aquaculture system

A current practice of marine aquaculture is to integrate different trophic-level organisms to optimise nutrients uptake, improve water quality, and potentially increase economic income. Even though bacterial communities in the intestine of the Pacific white shrimp Penaeus vannamei and in the digestive gland of the Pacific oyster Crassostrea gigas have been studied, the effect of an integrated multi-trophic aquaculture (IMTA) system in the digestive microbiome of both species is unknown. In the present work, we examined the bacterial communities in the intestine of P. vannamei and digestive gland of C. gigas under monoculture and co-culture in IMTA conditions. The results revealed a higher final weight of shrimp in co-culture compared to monoculture (2.73 ± 0.07 g and 2.47 ± 0.13 g, respectively) (P < .1). The total sedimentable particles in water were significantly reduced in co-culture conditions compared to shrimp monoculture (P < .05). Analysis of oyster gut bacterial communities in co-culture with shrimp showed higher diversity compared to oyster from monoculture and shrimp treatments. We found that Proteobacteria is the most abundant phylum in all treatments, followed by Bacteroidetes and Actinobacteria. Higher abundance of Bacteroidetes and abundance variation in Alphaproteobacteria (Sphingomonodales and Rhodobacterales) of oyster from IMTA were attributed to consumption of shrimp waste and consequently reduction of suspended matter in the system. Moreover, shrimp intestine and oyster digestive gland in the co-culture system showed a lower relative abundance of Vibrionaceae compared to monoculture treatments. These results suggest that IMTA system impose digestive microbiome dynamics changes that could improve water management and shrimp productivity.

Nutraceutical assessment of Solieria filiformis and Gracilaria cornea (Rhodophyta) under light quality modulation in culture

Seaweeds can produce certain pigments under specific light, salinity, and nutrient conditions. These pigments have important biological activities, which have been cited in numerous published literature; thus, they have been considered of nutraceutical importance. Solieria filiformis and Gracilaria cornea (Rhodophyta) have been studied for their ability to produce pigments, polysaccharides, and other nutraceuticals with antioxidant activity. Our group currently cultivates these species under an environmentally friendly integrated multi-trophic aquaculture (IMTA) system. In the present study, the ability of these seaweeds to synthesize carotenoids and phycobiliproteins by light quality modulation in laboratory cultures was determined. The experimental design used light-emitting diodes (LEDs) for the evaluation of individual light quality effects (white, blue, green, and red) and a combination of white + blue light for the combined effect. Five replicates per treatment were implemented. Seaweeds were kept in 800-mL polyethylene culture containers with Provasoli-enriched seawater at 22 °C for 3 weeks. The cultures were irradiated between 100 and 110 μmol photons m−2 s−1 with a 12:12 light:dark cycle. Growth parameters, pigment content, C:N ratio, and antioxidant activity were determined. The growth rate increased significantly when seaweeds were subjected to the combination of white + blue light, whereas chlorophyll a synthesis was improved under the green light treatment. As for phycobiliproteins, blue and green light resulted in the highest synthesis of phycoerythrin in S. filiformis and G. cornea, respectively. The synthesis of carotenoids increased with exposure to white light in both species whereas the antioxidant activity increased with the white + blue combination in G. cornea and with white light in S. filiformis. Light quality can promote growth and synthesis of certain compounds in red macroalgae; understanding these variables would be an advantage to control their nutraceutical quality in culture.

MEC-Ecopath結合モデルを用いた複合養殖システムの解析 ―女川湾を事例として―

MEC-Ecopath結合モデルを用いた複合養殖システムの解析 ―女川湾を事例として―

Feed Types Driven Differentiation of Microbial Community and Functionality in Marine Integrated Multitrophic Aquaculture System

Integrated multi trophic aquaculture (IMTA) improves the production of aquatic animals by promoting nutrient utilization through different tropical levels. Microorganisms play an important role in elements cycling, energy flow and farmed-species health. The aim of this study was to evaluate how feed types, fresh frozen fish diet (FFD) or formulated diet (FD), influence the microbial community diversity and functionality in both water and sediment in a marine IMTA system. Preferable water quality, higher animal yields and higher cost efficiency were achieved in the FD pond. Feed types changed the pond bacterial community distribution, especially in the rearing water. The FFD pond was dominated with Cyanobacteria in the water, which played an important role in nitrogen fixation through photosynthesis due to the high nitrogen input of the frozen fish diet. The high carbohydrate composition in the formulated diet triggered higher metabolic pathways related to carbon and lipid metabolism in the water of the FD pond. Sediment had significantly higher microbial diversity than the rearing water. In sediment, the dominating genus, Sulfurovum and Desulfobulbus, were found to be positively correlated by network analysis, which had similar functionality in sulfur transformation. The relatively higher rates of antibiotic biosynthesis in the FFD sediment might be related to the pathogenic bacteria introduced by the trash fish diet. The difference in microbial community composition and metabolic pathways may be associated with the different pathways for nutrient cycling and animal growth performance. The formulated diet was determined to be more ecologically and economically sustainable than the frozen fish diet for marine IMTA pond systems.

Effect of High-Pressure Processing (HPP) on the Fatty Acid Profile of Different Sized Ragworms (Hediste diversicolor) Cultured in an Integrated Multi-Trophic Aquaculture (IMTA) System.

Ragworms (Hediste diversicolor) cultured under integrated multi-trophic aquaculture (IMTA) conditions display an improved fatty acids (FA) profile than conspecifics from the wild, thus being more suitable for maturation diets of marine fish and shrimp. Nonetheless, their use may represent a potential pathway for pathogens. The objective of the present study was to determine if high-pressure processing (HPP), as an approach to safeguard microbiological safety, could promote significant shifts on the FA profiles of different sized ragworms. An analysis of similarities (ANOSIM) revealed the existence of significant differences in the FA profile and lipid quality indexes (atherogenicity (AI), thrombogenicity (TI) and polyene (PI)) of control and HPP treated ragworms of all tested sizes (small, medium and large). Saturated (SFA) and monounsaturated FA (MUFA) increased after HPP, while polyunsaturated FA (PUFA; FA with 2 or 3 double bonds) and highly unsaturated FA (HUFA; FA with ≥ 4 double bonds) decreased. The amount of docosahexaenoic acid (DHA) in polychaetes exposed to HPP decreased an average of 25%, when compared with the levels recorded in control groups. The values of PI significantly decreased after HPP, while those of AI and TI displayed a significant increase. Despite the shifts in the FA profile of ragworms exposed to HPP, these still display a superior profile to that of wild specimens, namely the presence of DHA. Therefore, HPP can be considered as a suitable approach to safeguard the biosecurity of cultured polychaetes, without compromising their nutritional value, and support the principles of circular economy through the use of IMTA.

Photosynthetic bacteria enhanced water quality and integrity of microbial community composition of integrated multitrophic aquaculture system of milkfish Chanos chanos coastal farming

Aquaculture faces substantial challenges in mitigating the detrimental environmental impacts of intensive farming. Traditional methods have given rise to serious concerns, leading to the search for alternative approaches using probiotics. An indigenously isolated photosynthetic purple bacterium, Rhodovulum sulfidophilum, was introduced into a marine integrated multitrophic aquaculture system cultivating Chanos chanos in southwestern Taiwan. The effects of R. sulfidophilum on water quality parameters, the relative levels of nitrogenase-encoding nifH and nitrous oxide reductase-encoding nosZ genes, the occurrence of sulfonamide resistance, the presence of sulfonamide resistance genes, and microbial community structure were determined. Supplementation with R. sulfidophilum decreased the chemical oxygen demand, the nitrate levels, and the occurrence of sulfonamide-resistant bacteria in the fishpond water compared with that of the control after rearing. The level of the sulfonamide resistance gene sul2 decreased in R. sulfidophilum-supplemented water samples, while the control exhibited an elevated level of sul2 after rearing. Supplementation with R. sulfidophilum also maintained the integrity of the bacterial community structure. In conclusion, our results suggest that R. sulfidophilum is an attractive supplement for enhanced disease emergence control, microbial biodiversity maintenance, and sustainable marine aquaculture practice.

Integrated Multitrophic Aquaculture By-Products with Added Value: The Polychaete Sabella spallanzanii and the Seaweed Chaetomorpha linum as Potential Dietary Ingredients.

Aquaculture expansion is limited by the negative environmental impact of the waste and the need for alternative sources in the diet of reared fish. In this framework, for the first time, the survival rates, biomass gain, and fatty acid profiles of the polychaete Sabella spallanzanii and the macroalga Chaetomorpha linum, reared/cultivated as bioremediators in an integrated multitrophic aquaculture system (IMTA), were evaluated for their potential reuse applications. Results showed that these organisms represent a natural source of omega-3 and omega-6. On account of the overall results and the high biomass obtained as by-products, a preliminary study was performed employing both S. spallanzanii and C. linum as new dietary ingredients to feed different sized Dicentrarchus labrax. Fish survival rate, biomass growth, and specific growth rate were determined resulting in no significant differences between control and treated fishes. Histological analyses showed no alterations of the stomach tunica mucosa and submucosa in treated fishes. The eco-friendly approaches applied in the here-realized IMTA system could guarantee the achievement of sustainable by-products represented by the bioremediators S. spallanzanii and C. linum, as well as their reliability as a natural source of compounds beneficial to fish and human health.

A Microcosm Multitrophic Aquaculture System

Environmental degradation has continued to increase in the last decade, requiring us to put increasing efforts into environmental mitigation, including in terms of food production. Future food production must be able to minimize the use of fresh water, fertilizers and pesticides, and reduce soil erosion. The Multitrophic Aquaculture System (MAS) approach could be one positive solution to this problem, by cultivating multitrophic organisms in the same system. This study aims to present details of the processes involved in implementing MAS on a microcosm scale that is currently underway. In the future, this system will be scaled up to in-situ level using brackish water ponds. In the present study, red seaweed Gracilaria changii was used as an autotrophic organism while the grouper Epinephelus fuscoguttatus as a heterotrophic organism. There are two treatments and one control, each with three replicates. This study shows that the system developed works well enough for seaweed. Seaweed seems to grow well, even though the growth rate is still low. Groupers, which are in the same system, are also in quite good condition, although some groupers showed low appetite, most likely due to low oxygen supply and excessive nutrition in the water. These challenges may be overcome by using higher seaweed stocking density. The system can maintain several water quality parameters, such as pH, at optimal level.

Technical feasibility of integrating Amazon river prawn culture during the first phase of tambaqui grow-out in stagnant ponds, using nutrient-rich water

The aim of this study was to evaluate the feasibility of producing the Amazon river prawn (Macrobrachium amazonicum) with tambaqui (Colossoma macropomum) in integrated multi-trophic aquaculture (IMTA) systems. An experiment was carried out in a completely randomized design with four treatments (types of production systems) and three replicates per treatment (ponds): prawn monoculture (30 prawns. m−2); fish monoculture (3 fish. m−2); IMTA with prawns and fish free-swimming in the same pond (30 prawns. m−2 and 3 fish. m−2); and IMTA with prawns free-swimming and fish in cages placed inside the ponds (30 prawns. m−2 free-swimming and 40 fish. m−3 in net cages). Prawns and tambaqui in the monocultures received commercial pelleted diets, whereas only the tambaqui received the pelleted diet in the integrated cultures. The experiment lasted 5.7 months. Both the prawns and the fish developed well in stagnant ponds while using nutrient-rich water. The mean final body mass, final body length and productivity of the prawns in the monoculture were higher than those of the prawns in the IMTAs. No significant differences were observed for the survival of the prawns and the tambaqui between treatments, and for the mean final mass of the tambaqui between the monoculture and the IMTA systems. Prawn growth and yield were similar whether the tambaqui was reared free-swimming or in cages. Therefore, the prawns and the tambaqui are compatible for IMTA. Yield in IMTA was ∼0.6 t ha−1 prawns, 5 t ha−1 tambaqui in free-swimming and 3 t ha−1 in net-cages. In conclusion, the culture of Amazon river prawn and tambaqui in IMTA is technically feasible in the first grow-out phase of the tambaqui. This system is flexible and permits different management strategies according to the target markets for each species.

Uptake of enrofloxacin from seawater to the macroalgae Ulva and its use in IMTA systems

Integrated multi-trophic aquaculture systems can minimize the environmental impacts of aquaculture, while delivering economical benefits. However, the use of extractive species such as seaweeds can accumulate pharmaceuticals commonly used in these systems. Therefore, this work evaluated the exposure of the seaweed Ulva to enrofloxacin (ENR), a vastly used antimicrobial in aquaculture, at two dosages (C1, 7.5 μg L−1 and C2, 15 μg L−1), and concentrations in water and in Ulva were measured through time. Traditional endpoints such as growth and mortality were assessed as ENR effects in the macroalgae. Enrofloxacin presented good stability in seawater, and degradation rates were influenced by the presence of seaweed at the lowest concentration tested. The seaweed was able to assimilate the antibiotic, reaching internal concentrations of 7.76 ± 1.11 ng g−1 WW after 30 min of exposure for C1, and 14.51 ± 1.22 ng g−1 WW, after 15 min for C2. Lowest concentrations detected at the end of experimental time were 4.08 ± 0.42 ng g−1 WW and 5.09 ± 1.57 ng g−1 WW for C1 and C2, respectively, which nonetheless, corresponds to ∼5% of the maximum residue limit established for fish for ENR by the European regulation. The presence of ENR stimulated Ulva growth, with differences observed 96 h after the beginning of the trial.

Seaweed nutrient physiology: application of concepts to aquaculture and bioremediation

ABSTRACTInorganic carbon, nitrogen and phosphorus are the main elements required by seaweeds for photosynthesis and growth. This review focusses mainly on nitrogen, but the roles of carbon and phosphorus, which may interactively affect seaweed physiological processes, are also explored. Fundamental concepts such as limiting nutrients, sources, and ratios, mechanisms of nutrient uptake, nutrient assimilation and storage, patterns of uptake and preferences for different nitrogen sources are discussed. The roles of abiotic (water motion, light, temperature, salinity and desiccation) and biotic (life stages and age class) factors in nutrient (nitrogen, phosphorous, carbon) uptake are also reviewed. Understanding species-specific nitrogen physiologies and nitrogen source preferences will enable polyculture of different seaweed species and the use of seaweeds as biofilters in integrated multitrophic aquaculture systems.

Analysis of algal growth- and morphogenesis- promoting factors in an integrated multi-trophic aquaculture system for farming Ulva spp.

Analysis of algal growth- and morphogenesis- promoting factors in an integrated multi-trophic aquaculture system for farming Ulva spp.

Understanding the individual role of fish, oyster, phytoplankton and macroalgae in the ecology of integrated production in earthen ponds

In order to demonstrate that IMTA can be profitable and a good alternative to regular semi-intensive fish mariculture production in earthen ponds three different production treatments with distinct combinations of trophic levels were designed: (i) a combination of fish, filter feeders, phytoplankton and macroalgae, (ii) fish, filter feeders and phytoplankton and (iii) fish, phytoplankton and macroalgae, to evaluate the role of each trophic level within an Integrated Multi-Trophic Aquaculture system (IMTA). Each treatment was carried out under semi-intensive conditions with two replicates, in a total of 6 earthen ponds of 500 m2 surface and depth of 1.5 m. The results showed that fish, oyster, phytoplankton and macroalgae integrated aquaculture is a healthy sustainable production system for mariculture in earthen ponds, providing much more fish supply compared with the other two treatments. Ponds with filter feeders had significantly lower turbidity (Nephelometric Formazin unit (FNU) of 13 in the morning and 17 in the afternoon) when compared to ponds without filter feeders (16 FNU in the morning and 20 FNU in the afternoon) with increased light penetration throughout water column (61 and 55 cm transparency in ponds with filter feeders compared to 51 cm in ponds without filter feeders) and consequently higher photosynthetic activity with significantly higher dissolved oxygen (5.4 mg L−1 in the morning and 6.7 mg L−1 in the afternoon in ponds with filter feeders compared to 5.3 mg L−1 in the morning and 6.4 mg L−1 in the afternoon in ponds without filter feeders) and carbon sequestration (0.50 and 0.53 mg L−1 8 h−1 in ponds with filter feeders and 0.43 mg L−1 8 h−1 in ponds without filter feeders). In the fish, filter feeder, phytoplanton and macroalgae IMTA treatment, phytoplankton played a crucial role because they increased DO levels, removed the excess of nutrients from animal excretion, and was used as food by the filter feeders. Almost as important is the presence of filter feeders since they control the density of the microalgae and particulate matter in the ponds contributing to a more constant level of DO and higher transparency of the water column. The increased transparency and pond fertilization by oyster excretion, resulted in higher proliferation of phytoplankton (chlorophyll a concentrations of 16.5 μg L−1 and 20.2 μg L−1 in ponds with filter feeder and 13.3 μg L−1 in ponds without filter feeder) with benefits not only for filter feeders themselves but also for the macroalgae. At the end there was higher water quality and higher savings (14% day−1) in the energy costs for pond aeration. Meagre, white seabream and flathead grey mullet enhance their performance in IMTA systems with the presence of filter feeders with food conversion rates (FCR) of 1.52 when compared with 2.46 in the regular semi-intensive system composed by fish, phytoplankton and macroalgae. Meagre grew significantly more in IMTA systems with controlled macroalgae while white seabream and flathead grey mullet enhance their performance in the presence of macroalgae. The results show that the fish, oyster, phytoplankton and macroalgae integrated production in earthen ponds is an improved system compared to the regular semi-intensive fish production. The enhanced water quality in these systems leads to improved fish performance and higher biomass production, and to reduction in the energy power used, contributing to greater profitability.

Integrated multitrophic aquaculture applied to shrimp rearing in a biofloc system

This study aimed to evaluate the performance of an integrated multitrophic aquaculture (IMTA) system applied to shrimp rearing in biofloc technology (BFT). The IMTA system consisted of shrimp (Litopenaeus vannamei) in a rearing tank (800 L), a tilapia (Oreochromis niloticus) rearing tank (90 L), and a hydroponic bench with 0.33 m2 of planting space for Sarcocornia ambigua culture. A submerged pump constantly pumped water from the shrimp tank to the tilapia tank. Then, by gravity, water flowed through the sarcocornia hydroponic bench and returned to the shrimp tank. The hydroponic bench had enough capacity for 32 plants. Shrimp, tilapia and sarcocornia stock densities were 312 shrimp m−3 (250 shrimps per 800 L tank), 445 tilapia m−3 (40 tilapias per 90 L tank), and 97 sarcocornia plants m−2 (32 plant per system), respectively. The same experimental units were used in the control system which only differed by the absence of sarcocornia. The initial weight was 4.09 ± 0.025 g, 1.16 ± 0.02 g and 1.17 ± 0.175 g for shrimp, fish and sarcocornia, respectively. Shrimps were fed according to the feed table, and the fishes were fed with 1% of fish biomass, stimulating tilapia to use biofloc as a food source. Results show no difference between shrimp and tilapia performance in either treatment. Only IMTA total yield (4.83 ± 0.19 kg m−3) was significantly higher than that in the control system (3.99 ± 0.045 kg m−3). Nitrate was higher in the control system (12.28 ± 1.27 mg L−1) compared to the IMTA system (9.38 ± 1.09 mg L−1).These results demonstrate a yield increase of up to 21.5% by multitrophic integration of L. vannamei, O. niloticus and S. ambigua in a biofloc system.