Integrated Multi-trophic Aquaculture Research Articles

Selection of marine fish for integrated multi-trophic aquaponic production in the Mediterranean area using DEXi multi-criteria analysis

Producing food according to the sustainability and “circular economy” principles is considered a strategic goal by several world Institutions. Integrated Multi-Trophic Aquaculture (IMTA) responds to these criteria and stemming from it, the “Self-sufficient Integrated Multitrophic AquaPonic” (SIMTAP) aims to drastically reduce production inputs and waste outputs while maximizing the total food production. In order to succeed, proper selection of the most suitable fish, intermediate organisms and plant species to be grown in the system plays a fundamental role. To validate the SIMTAP concept and experimental prototype, the biological characteristics of fish and other species should be assessed taking into account their complementarity and adaptability to the physical and technical traits of the considered system.This study aimed to identify the most suitable marine organisms for food production within the SIMTAP system and to create a decision model via the DEXi decision support system. Hence, in the present work a brief description of the SIMTAP concept, as well as the biological, zootechnical and commercial characteristics of several candidate fish species, are discussed. The criteria considered to address the species selection were: natural geo-distribution, domestication degree, environmental requirements, feeding regime, growth performances, and market value. The candidate species were: Sparus aurata, Dicentrarchus labrax, Mugil cephalus, Diplodus puntazzo, Seriola dumerili, Umbrina cirrosa, Argyrosomus regius, Psetta maxima, Acipenser spp., Solea spp., Octopus vulgaris. Finally, it seems that the DEXi approach increased the objectivity of the species selection process. Gilthead Sea Bream, European Sea Bass and Flathead Grey Mullet resulted to be the most suitable species for SIMTAP production.

Effects of a lagoon on performances of a freshwater fishpond in a multi-trophic aquaculture system

Integrated multi-trophic aquaculture (IMTA) is a way to help preserve the environment while maintaining a good level of total production. An ecologically semi-intensive pond system was designed in which a polyculture fishpond was associated with a lagoon planted with macrophytes to bioremediate the water. The properties of this “semi-intensive coupled” system (SIC) were compared to those of semi-intensive (SI) and extensive (E) systems, each of which was contained in a single fishpond with the same fish polyculture (common carp (Cyprinus carpio), roach (Rutilus rutilus), and perch (Perca fluviatilis)) as SIC. E differed in that it had half the initial density of fish, and the fish were not fed. Fish growth performances, water quality (chemical and biological indicators), chlorophyll concentrations, and invertebrate production were measured. The systems were compared based on fish production performances and physicochemical and biological characteristics, and were then described using principal component analysis (PCA). Carp and roach in the two fed systems had higher growth performances than those in E. Compared to SI, the planted lagoon in SIC, induced a decrease of 15% in fish growth performances and of 83% in total chlorophyll concentration (a proxy for phytoplankton) but improved water quality (−34%, −60% and −80%, for the concentrations of total nitrogen, total phosphorus, and blue green algae (for micro-algae in class Cyanophyceae), respectively). According to the PCA, SIC clearly differed from SI in benthic macro-invertebrate production and concentrations of total nitrogen, total phosphorus, and brown algae (for micro-algae in class Dinophyceae or a branch of Bacillariophyta) in the water. SIC differed from E in oxygen parameters (dissolved and saturation), estimated annual zooplankton production, and pH. In conclusion, the properties of a lagoon reveal perspectives for environmentally friendly practices, while using biodiversity and secondary production in order to enhance fish production.

Perceived social welfare as a driver of green products consumption: Evidences from an integrated multi-trophic aquaculture production

This study investigated consumers' perceptions of green products derived from a circular economy production, by shedding light on the role of perceived social welfare. Furthermore, the paper considered two moderators: perceptual variables on green products and psychological variables on the environment. The analysis was performed in the aquaculture sector—specifically referring to Integrated Multi-Trophic Aquaculture (IMTA) production as a research setting. Respondents received a structured questionnaire containing scales that measured perceived social welfare, environmentalism, green product's perception (in terms of price, quality and usefulness), purchase intention, and word-of-mouth. The results revealed an inverse relationship between perceived social welfare and the behavioral variables. Consumers were more attracted to and focused on the green product's usefulness than its price and quality. Moreover, the study found that environmentalism (in terms of environmental concern and perceived consumer effectiveness) moderate the effect of perceived social welfare on dependent variables. By exploring the role of perceived social welfare as a regressor, this study improves our understanding of consumers' behavior toward green products.

Transformation of phosphorus in an experimental integrated multitrophic aquaculture system using the media filled beds method in plant cultivation

The objective of this study was to trace the transformations of phosphorus in an integrated multitrophic aquaculture (IMTA) system and to determine whether the method of plant breeding influenced the dynamics of these changes. In the experiment, the media filled beds (MFB) method of plant cultivation was applied. Fish tanks were stocked with 200 common carp Cyprinus carpio, and hydroponic terraces were planted with 49 zantedeschia Zantedeschia sp. bulbs. Water samples were taken directly from the fish tanks immediately after each type of filtration (mechanical, biological and hydroponic). The basic forms of orthophosphates in the IMTA system included some H2PO4- ions but mostly HPO42-. The higher supply of reactive phosphorus that occurred over time in the experiment may have contributed to a decrease in calcium ion concentration due to the formation of Ca3(PO4)2 and CaHPO4 salts, thus inactivating some of the phosphorus available to plants. Phosphorus may have also been inactivated in the sediment due to the formation of Mg3(PO4)2 and MgHPO4 salts after decreasing the concentration of calcium ions as a result of their precipitation in sediments. Mineralization of organic matter took place under aerobic conditions. Organic matter was a source of biogenic substances in the IMTA system. Experimental results showed that IMTA systems have significant potential to reduce phosphorus in aquaculture wastewater and thus provide a good environment for fish farming by improving water quality.

Wastewater Valorisation in an Integrated Multitrophic Aquaculture System; Assessing Nutrient Removal and Biomass Production by Duckweed Species

Wastewater Valorisation in an Integrated Multitrophic Aquaculture System; Assessing Nutrient Removal and Biomass Production by Duckweed Species

Testing the hydroponic performance of the edible halophyte Halimione portulacoides, a potential extractive species for coastal Integrated Multi-Trophic Aquaculture

Sea purslane Halimione portulacoides (L.) Aellen is a candidate extractive species for coastal Integrated Multi-Trophic Aquaculture (IMTA) to recycle the dissolved inorganic nitrogen (DIN) and phosphorus (DIP) wasted by excretive species. To test its suitability, saline aquaculture effluents were simulated in the laboratory using a hydroponics approach to cultivate the plants. Nutrient extraction efficiency, growth performance and nutritional profile were assessed under a range of DIN and DIP concentrations representing three different aquaculture intensification regimes and using Hoagland's solution as a control. Over a 10-week period, hydroponic units under non-limited N and P conditions displayed daily extraction rates between 1.5 and 2.8 mg DIN-N L−1 day−1 and 0.1–0.2 mg DIP-P L−1 day−1 and yielded between 63.0 and 73.0 g m−2 day−1 of H. portulacoides biomass. Relatively to biomass produced, H. portulacoides extracted between 2.6 and 4.2 mg DIN-N g−1 and 0.1–0.4 mg DIP-P g−1. The treatment with low-input of DIN and DIP (6.4 mg N L−1 and 0.7 mg P L−1) induced some degree of nutrient limitation, as suggested by the extremely high extraction efficiencies of DIN extraction (99%) in parallel with lower productivity. The nutritional profile of H. portulacoides leaves is comparable to that of other edible halophytes and leafy greens and could be a low-sodium alternative to salt in its lyophilized form. From the present study, we conclude that the edible halophyte H. portulacoides can be highly productive in hydroponics using saline water irrigation with non-limiting concentrations of DIN and DIP and is, therefore, a suitable extractive species for coastal IMTA in brackish waters.

Integrated Multi-Trophic Aquaculture (IMTA) system combining the sea urchin Paracentrotus lividus, as primary species, and the sea cucumber Holothuria tubulosa as extractive species

Sea cucumbers and sea urchins are promising candidates for aquaculture since they are high market value and low-trophic organisms. However, although they often co-exist in many marine habitats showing feeding interactions, there is currently a lack of investigations available regarding the co-culture of these organisms in Integrated Multi-Trophic Aquaculture (IMTA). The present study investigated, for the first time, the laboratory-scale feasibility of an integrated aquaculture between P. lividus and H. tubulosa, two of the most valuable Mediterranean echinoderms, through a four-month experiment.More specifically, three food sources with different fish meal concentrations were tested separately to sustain the integrated production in a land-based RAS (Recycling aquaculture system) of both co-cultured species: 1) completely vegetable diet (D-0), 2) vegetable diet with 20% of fish meal (D-20) and 3) vegetable diet with 40% of fish meal (D-40). Among these experimental diets D-20 (with 20% of fish meal supplement) was consumed more efficiently and sustained high growth rates for both co-cultured species. However, significant growth was detected with all experimental diets, indicating successful integrated aquaculture between sea urchins and sea cucumbers. The present study, therefore, suggested the existence of substantial benefits of an integrated aquaculture between these echinoderm species, that could promote the environmental and economic sustainability of their production on a large-scale. Our results showed, in fact, that less than 24% of the organic matter administered with the food remained as waste in our IMTA system after being ingested by the two trophic levels. The sea urchins ingested 87% of the food administered, absorbing 64% of the organic matter, whilst in the second step, the sea cucumbers consumed 54% of organic matter present in the sea urchin feces. Hence the aquaculture model investigated here was highly effective in reducing the total waste, at the same time providing added value in the form of sea cucumber biomass.

Lamellidens and Wolffia canopy improves growth, feed utilization and welfare of Labeo rohita (Hamilton,1822) in integrated multi-trophic freshwater aquaculture system

A 90 days' trial on integrated multi-trophic aquaculture (IMTA) incorporating floating weed Wolffia globosa as inorganic extractive and a bivalve Lamellidens marginalis as organic extractive was conducted to assess the growth, survival, yield, water quality and welfare of Labeo rohita (Rohu) in an outdoor tank culture system. Twelve cement tanks (20 m3) were randomly allocated into four treatments (in triplicate) where L. rohita was used as fed species. The treatments were assigned as control (C) only rohu, T1: Rohu and partitioned Wolffia canopy, T2: Rohu, L. marginalis and T3: Rohu, Wolffia and L. marginalis. The stocking densities for rohu and L marginalis were 30,000 fingerlings ha−1 and 750 kg ha−1 while Wolffia was transplanted to cover 30% of the tank surface area, and fish to mussel biomass ratio maintained was 2:1. The fish were fed with a sinking pelleted feed (30% Crude Protein) at the rate of 4% body weight. It is observed that total biomass, survival, net fish yield (NFY) was significantly highest in T3 as compared to T1, control and T2. The total protein and lipid content of rohu (whole-body) differ significantly between the treatments. Among the welfare parameters, the nitroblue tetrazolium (NBT) activity was significantly higher in T1 and T3 while superoxide dismutase (SOD) was highest in T1. The catalase (CAT) activity lowest in T3 among all the treatment groups. The water quality parameters like NH4-N, NO3-N, PO4-P were significantly lower in T3 among all treatment groups. Higher water transparency was observed with no algal bloom in T3 and T1. The results suggest that co-culture of L. rohita with W. globosa and L. marginalis can improve water quality, welfare parameters, enhancing fish survival and productivity.

Bio-economic evolution of snakeheads and Indian major carps culture in IMTA system

An experimental study was carried out for a period of six months to assess the commercial culture potentiality of striped snakehead (Channa striatus) over Indian Major Carps (IMCs) in improved Integrated Multi-Trophic Aquaculture (IMTA) system. Characteristics of snakehead (Channa striatus) make it a desirable culturable fish in IMTA system. The experiment was done in two stepsnursery stage (2 months) and grow-out stage (4 months). In the nursery stage, the stocking density was 30 nos/m3 (2.3±0.42 g). Larvae were fed with finely granule formulated feed containing 43.4% protein at 5% body weight which had FCR of 1.3. The survival rate was 67% in this stage. After two months, 20 nos/m3 fry were collected from the larval rearing tank and their average body weight was 25.6±1.9 g. The collected fishes were transferred into grow-out pond and to utilize all the trophic level of the water, 5 tilapia (Oreochromis mossambicus), 2 silver carp (Hypophthalmichthys molitrix), 1 sarpunti (Barbonymus gonionotus) and 1 rui (Labeo rohita) of comparatively larger size than snakeheads were added in each pond. Stinging catfish (Heteropneustes fossilis) was cultured in cages at 100 nos/ft3 stocking density where snails produced in the bottom were used as a major feed ingredient for catfish. Four floating trays, each 0.11 m2 in surface area, were placed in the ponds for growing lettuce. In grow-out stage, formulated pelleted feed (FCR 1.4) with 34.95% protein was fed at 3% body weight. Here about 93% survival rate was found in grow-out phase. At the end, 25 Kg snakehead/decimal was harvested from improved IMTA system where IMCs were produced at 20 Kg/decimal in traditional IMTA system. But no significant difference (P <0.05) was found in production of stinging catfish and vegetables between the improved and traditional IMTA system. The improved IMTA system possessed a significantly lower (P <0.05) operating ratio (59%) than the traditional IMTA system (65%). Return on sales ratio was 41.18% in improved IMTA which was significantly higher (P <0.05) and confirmed the system to bear the burden of increased cost of production but the profit margin was also higher. Benefit-Cost Ratio (BCR) was 1.7 in improved IMTA system which was significantly higher (P <0.01) than traditional IMTA system (1.54). The innovated improved IMTA system can provide around 16% more profit compared to traditional IMTA system from per decimal pond area. This suggests that IMTA can be promoted through action research and field trial with potential fish farmers towards sustaining economic viability and food security of the poor people.

Planktonic and sediment bacterial communities in an integrated mariculture system.

An integrated multi-trophic aquaculture (IMTA) system, with one fish cage model surrounded by an island and shellfish rafts, was used in the current study. Planktonic and sediment bacterial communities in the IMTA system were monitored over four seasons in 2019. In both plankton and sediment samples, the most dominant phyla were Proteobacteria and Bacteroidota. Sediment bacterial samples were more similar and had higher levels of biodiversity than planktonic bacterial samples. Obvious seasonal variations were found in plankton samples, but not in sediment samples. No obvious inter-site variations in planktonic and sediment bacteria (fish cages, shellfish rafts and control sites) were found and the results suggested that no obvious impact of feeding operations in fish culture cage model on bacterial communities in the IMTA system was observed in this study. Based on the sequence data, some faecal indicator bacteria and potentially pathogenic bacterial species were detected. According to the results, the bacterial water quality in the IMTA system was acceptable. PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) analysis revealed that the primary difference in potential functional roles of planktonic and sediment bacteria was amino acid transport and metabolism, which was active in different seasons.

Performance of polychaete assisted sand filters under contrasting nutrient loads in an integrated multi-trophic aquaculture (IMTA) system

Polychaete assisted sand filters (PASFs) allow to combine a highly efficient retention of particulate organic matter (POM) present in aquaculture effluent water and turn otherwise wasted nutrients into valuable worm biomass, following an integrated multi-trophic aquaculture (IMTA) approach. This study evaluated the bioremediation and biomass production performances of three sets of PASFs stocked with ragworms (Hediste diversicolor) placed in three different locations of an open marine land-based IMTA system. The higher organic matter (OM) recorded in the substrate of the systems which received higher POM content (Raw and Df PASFs – filtered raw and screened by drum filter effluent, respectively) likely prompted a superior reproductive success of stocked polychaetes (final densities 2–7 times higher than initial stock; ≈1000–3000 ind. m−2). Bioremediation efficiencies of ≈70% of supplied POM (≈1.5–1.8 mg L−1) were reported in these systems. The PASFs with lower content of OM in the substrate (Df + Alg PASFs – filtered effluent previously screened by drum filter and macroalgae biofilter) differed significantly from the other two, with stocked polychaetes displaying a poorer reproductive success. The PASFs were naturally colonized with marine invertebrates, with the polychaetes Diopatra neapolitana, Terebella lapidaria and Sabella cf. pavonina being some of the species identified with potential for IMTA.

Kelp in IMTAs: small variations in inorganic nitrogen concentrations drive different physiological responses of Saccharina latissima

Kelps can be included in integrated multitrophic aquaculture (IMTA) where their growth and quality might benefit from the nutrient load released by other species like finfish and mussels transforming effluents from the cultured animals into valuable products. We studied how different nutrient concentrations affect growth, photosynthesis, chemical composition and pigment content of the kelp Saccharina latissima. We exposed kelps to natural seawater, water enriched to levels of ammonium and nitrate simulating finfish cage waste (IMTA1) and a combination of such enrichment with natural effluents coming from mussels (IMTA2). The algal biomass was higher and produced elevated total organic content when exposed to both IMTA1 and IMTA2. The photosynthetic responses in terms of relative electron transfer rate (rETRmax), PSII saturation irradiance (Ek) and total nitrogen content were also positively affected by both IMTA1 and IMTA2. We found a significant enhancement in pigment content only when algae were exposed to the strongest enrichment of our study (IMTA2). Finally, we found a positive relationship between rETRmax and growth, and the content of chlorophyll a and fucoxanthin. Our results show significant physiological responses of S. latissima to nutrient enrichment mimicking IMTA settings, as well as the benefit of added nutrients through a boost in photosynthetic activity that leads to higher kelp biomass and pigment production. This study suggests that modest nitrogen enrichment such as the one in our IMTA2 setup is enough to generate not only higher kelp biomass, but also an increased biomass quality with potentially higher market value.

Effects of mussel-kelp ratios in integrated mariculture on the carbon dioxide system in Sanggou Bay

The ocean is the largest carbon reservoir on Earth. The shellfish-seaweed mode of Integrated Multi-trophic Aquaculture (IMTA) can be optimized to enhance carbon removal from the sea. In this study, the effects of different mussel-kelp ratios (i.e. 6:3, 6:2, 6:1, 4:3, 4:2, 4:1, 2:3, 2:2, and 2:1) on water quality and the carbon dioxide (CO2) system were 6:3, 6:2, 6:1, 4:3, 4:2, 4:1, 2:3, 2:2, and 2:1, were investigated using experimental enclosures in Sanggou Bay, China. The results showed that the DO decreased significantly when ratios were 4:1, 6:2 and 6:1. With the exception of ratio 4:3, there was no significant change in pH in any treatment. The highest of DO, pH, and CO32− values occurred when the mussel-kelp ratio was 2:3, the highest proportion of kelp, while the lowest occurred in ratio 6:1, with the highest proportion of mussels. The highest levels of pCO2, CO2 and HCO3− were observed in ratio 6:1, and the lowest when the ratio was 2:3. Both DIC and HCO3− significantly decreased by the end of the experiment for ratios 2:1 and 6:3, while the concentration of CO2 significantly decreased for ratios 2:3 and 6:3. Considering the measured parameters, the mussel-kelp ratios of 2:1, 2:2, 4:2 and 4:3 were identified as the best net carbon sinks with the smallest negative environmental impacts. This study revealed how the IMTA shellfish-seaweed modes can be optimized to mitigate ocean acidification using specific proportions of species.

Biomonitoring of the Application of Monoculture and Integrated Multi-Trophic Aquaculture (IMTA) Using Macrobenthic Structures at Tembelas Island, Kepulauan Riau Province, Indonesia

Sustainable aquaculture needs to be considered when it comes to the utilization of water resources. The aim of this study was to apply biomonitoring using macrobenthic structures on both spatial and temporal applications of monoculture and integrated multi-trophic aquaculture (IMTA) at Tembelas Island, Kepulauan Riau Province, Indonesia. Samples of sediment were taken from three fish farm locations, namely from an IMTA site, a monoculture site, and a reference site. Macrobenthic organisms obtained through rinsing, sieving, and sorting were then identified under a stereo-microscope. Diversity of the macrobenthic assemblages was analyzed with a Shannon-Wiener index (H’). Equitability was expressed through Pielou’s evenness index. Finally, Bray-Curtis’ non-metric multi-dimensional scaling (NMDS) was used for similarities derived from log (X+1) transformed macrobenthic abundance to provide a visual representation of differences in their structure between sites over time. Results showed polychaetes exhibited differences in both variation and abundance of genera between the farm and reference site. The assemblage of macrobenthos at the IMTA site consisted of 9 genera of gastropods, 3 genera of bivalves, 5 genera of polychaetes, and 2 genera of crustaceans. At the monoculture site, 12 genera of gastropods, 4 genera of bivalves, 8 genera of polychaetes, 1 genera of crustaceans, and 1 genera of ophiuroid were observed. A relatively high abundance was observed at the reference site, with 27 genera of gastropods, 11 genera of bivalves, 3 genera of polychaetes, and 1 genera of crustacean. The favorable water conditions and possible absence of waste input from aquaculture resulting in a more suitable habitat for macrobenthic life may explain this relative abundance. Some of them were recognised as opportunistic taxa, i.e., Capitella sp., Heteromastus sp., and Lumbrinereis sp. Based on the diversity and evenness indices and the MNDS ordination, it can be concluded that the application of IMTA systems results in a suppressed or reduced potential impact on environmental disturbance due to aquacultural activities.

Biochemical transformations of nitrogen compounds in the integrated multi–trophic aquaculture the using media filled beds in plant cultivation

Quantitative and qualitative transformations of nitrogen compounds in the Integrated Multi-Trophic Aquaculture (IMTA) system using the Media Filled Beds (MFB) method in plant cultivation was investigated experimentally. Three fish tanks were populated with 200 individuals of common carp (Cyprinus carpio L.) in each. The experiment lasted over three months. The following parameters were determined on the weekly basis: ammonium nitrogen, nitrate (III) nitrogen, nitrate (V) nitrogen, total nitrogen, mineral nitrogen, organic nitrogen and dissolved oxygen, according to commonly adopted methods. Water samples for the analyses were taken directly from the fish tanks and locations directly after each type of filtration (mechanical, biological and hydroponic). The presence of all determined forms of nitrogen was established including the mineral nitrogen which concentration remained at levels sufficient for a normal growth and development of plants. Active nitrification process was detected. Loss of nitrogen from the system was not only due to absorption by plants. Initiation of the anaerobic ammonia oxidation (anammox) and denitrification processes was observed.

Integrated multi-trophic aquaculture systems: energy transfers and food web organization in coastal earthen ponds

Three Ecopath models were built to reproduce 3 experimental treatments carried out in earthen ponds located in Olhão, southern Portugal, to understand the energy transferred and the ecosystem state in integrated multi-trophic aquaculture (IMTA). These earthen ponds behave as simplified ecosystems or mesocosms, with well-defined borders, where the relationships between trophic groups can be described through ecosystem modeling. Different combinations of species were produced in these ponds, corresponding to the 3 treatments: (1) fish, oysters and macroalgae (FOM); (2) fish and oysters (FO); and (3) fish and macroalgae (FM). The managed species were meagre Argyrosomus regius, white seabream Diplodus sargus, flathead grey mullet Mugil cephalus, Japanese oyster Crassostrea gigas and sea lettuce Ulva spp. The results showed that the total amount of energy throughput was 15 to 17 times higher when compared with an equivalent naturalized system. The high biomass and low recycling indicated an immature system with low resilience and low stability that demands high rates of water renewal and aeration to maintain good water-quality levels for finfish production. The addition of oysters and macroalgae in the FOM treatment appeared to improve the water quality, since oysters controlled the excess of phytoplankton produced in the ponds by ingesting a fair amount of the phytoplankton, while the macroalgae helped in the absorption of excess nutrients and created a habitat for periphyton and associated macroinvertebrates. Some ecosystem attributes of the FOM ponds approached the values of the naturalized model, suggesting a possible path towards more sustainable aquaculture.

Low-technology recirculating aquaculture system integrating milkfish Chanos chanos, sea cucumber Holothuria scabra and sea purslane Sesuvium portulacastrum

Closed recirculation aquaculture systems (RAS) in combination with integrated multi-trophic aquaculture (IMTA) are considered best management practices, but high material costs and difficult maintenance still hinder their implementation, especially in developing countries and the tropics. Few case studies of such systems with tropical species exist. For the first time, an extremely low-budget system was tested combining the halophyte sea purslane Sesuvium portulacastrum and a detritivore, sandfish Holothuria scabra, with finfish milkfish Chanos chanos over 8 wk on Zanzibar, Tanzania. In a 2 m3 RAS, milkfish and sea purslane showed good growth, producing an average (±SD) of 1147 ± 79 g fish and 1261 ± 95 g plant biomass, while sea cucumber growth was variable at 92 ± 68 g. The system operated without filter units and did not discharge any solid or dissolved waste. Water quality remained tolerable and ammonia levels were reliably decreased to <1 mg l-1. A NO2- peak occurred within the first 30 d, indicating good biofilter performance of the different system compartments. Changes in dissolved inorganic nitrogen (DIN) species support the notion that the sea cucumber tank was the main site of nitrification, while the hydroponic halophyte tank acted as a net sink of NO3-. A nitrogen budget accounted for 63.7 ± 5.3% of the nitrogen added to the system as fish feed. Increasing the plant to fish biomass ratio to 5:1 would fully treat the DIN load. The experiment provides proof-of-concept of a simple pilot-scale RAS, integrating tropical species at 3 trophic levels.

European lobsters utilise Atlantic salmon wastes in coastal integrated multi-trophic aquaculture systems

In this study, we investigated if juvenile European lobstersHomarus gammaruswould eat waste from Atlantic salmonSalmo salarcages in a coastal integrated multi-trophic aquaculture (IMTA) setup and if there were any impacts on growth. Trophic interactions between salmon and lobsters were assessed using δ15N and δ13C stable isotope analysis and fatty acid profiling from fish feed as indicators of nutrient flow. Analysis revealed that lobsters directly utilised particulate waste from salmon production, as levels of indicator fatty acids from salmon feed were significantly higher in lobster tissues near the fish cages compared to the control site. Route of uptake may have been direct consumption of waste feed or faecal material or indirectly through fouling organisms. Stable isotope analysis did not indicate nutrient transfer to lobsters, suggesting that the duration of the study and/or the amount of waste consumed was not sufficient for stable isotope analysis. Lobsters grew significantly over the trial period at both sites, but there was no significant difference in lobster growth between the sites. Our results show a trophic relationship between salmon and lobsters within this IMTA system, with no apparent advantage or disadvantage to growth.

Screening of Surface-associated Bacteria from the Mexican Red Alga Halymenia floresii for Quorum Sensing Activity

Macroalgae host a dense bacterial epibiome forming surface biofilms, which act as a biological defense by protecting the surface from macrofoulers. During experimental cultivation of Halymenia floresii (Rhodophyta, Halymeniales) under Integrated MultiTrophic Aquaculture (IMTA), the culture tanks remained clean of any exogenous algal colonization, and the surface of the H. floresii thalli was remarkably free from any fouling organisms. The presence of Halymenia also appeared to restrict the establishment of opportunist green algae and the colonization of barnacles usually impairing the cultures. To date, nothing is known about the diversity and biological potential of H. floresii epibionts. Hence, to better understand their epiphytic bacterial community, surface-associated bacteria from distinct H. floresii samples, beach-cast, integrated multi trophic aquaculture cultivar, and cultivar cylinders, were isolated. Thirty-one axenic bacterial strains belonging to 3 phyla, 20 genera, and 25 species were identified by 16S rRNA gene sequencing. Following isolation, they were screened for the production of quorum sensing (QS) signals, since these communication signals play a vital role in biofilm formation. All, except one, isolates were identified as gram-negative; hence, acylated homoserine lactones (AHLs) were focused upon. Using the reporter strain Escherichia coli pSB406, the isolates were screened for their ability to induce luminescence. Of 31 isolates screened, 17 strains, including Pseudoalteromonas arabiensis, Pseudoalteromonas sp. (B5BC and B6.1BC), Pseudoalteromonas mariniglutinosa, Vibrio owensii, Tenacibaculum sp., Maribacter sp., Spongiimicrobium salis, Aquimarina sp., Kordiimonas sp., Alteromonas sp. (B12CC and B16CC), Roseobacter sp., Erythrobacter sp., Ruegeria lacuscaerulensis, and Epibacterium sp., exhibited the presence of extracellular QS signals. Thus, the presence of QS bacteria on the surface of H. floresii was demonstrated for the first time. Our results may open a new direction to investigate the host—QS bacteria interactions.

Aquaculture waste as food for amphipods: the case of Gammarus insensibilis in marsh ponds from southern Spain

Amphipods are emerging as an alternative food resource for fishes and cephalopods in aquaculture. Gammarus insensibilis (Stock, 1996), one of the dominant amphipods inhabiting marsh ponds in southern Spain, has been recently proposed as a promising candidate for being intensively cultured due to its adequate nutritional profile, large body size, and high natural densities. The main aim of this study was to determine whether waste products of aquaculture (such as detritus in the form of fish feces or Ulva sp.) provided an adequate diet for the amphipod in comparison to other traditional diets, such as Artemia nauplii or phytoplankton. G. insensibilis was cultured twice in tanks with 5 treatments: 4 experimental diets (detritus, Ulva sp., Artemia nauplii, and phytoplankton) were used, and one no-feed treatment. Amphipods fed with the two alternative diets, detritus and Ulva, showed promising survival higher than 40% and high concentrations of palmitic acid (16:0), oleic acid (18:1n9), arachidonic acid (20:4n6) (ARA), eicosapentaenoic acid (20:5n3) (EPA), and docosahexaenoic acid (22:6n3) (DHA). Therefore, large-scale culture of this amphipod using inexpensive diets in indoor facilities could provide a nutritious product for aquaculture. The potential development of a sustainable culture using this species in marsh ponds is also discussed in the context of Integrated Multi-Trophic Aquaculture (IMTA).