Small-scale Aquaponic Systems Research Articles

Determination of Phylloplane Associated Bacteria of Lettuce from a Small-Scale Aquaponic System via 16S rRNA Gene Amplicon Sequence Analysis

Fresh vegetables harbour diverse bacterial populations on their surfaces which are important for plant health and growth. Information on epiphytic bacteria is limited to only a few types of vegetables and it is unknown how the lettuce epiphytic bacterial community structure may respond when a probiotic product is added to an aquaponic system. In this study, we evaluated lettuce growth and analysed epiphytic bacterial communities of lettuce based on metabarcoding analysis of the V3-V4 region of the 16S rRNA gene obtained from paired-end Illumina MiSeq reads. The addition of Bacillus probiotics resulted in a significant increase of nitrate and phosphate in the deep-water culture solution, as well as increased vegetative growth of lettuce. Metabarcoding analysis revealed that the most abundant phyla on lettuce leaf surfaces were Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. The in-depth bacterial composition analysis indicated that genera Chryseobacterium, Bacillus, Pantoea, Pseudoduganella, Flavobacterium, Paludibacter, and Cloacibacterium were dominant in leaf samples obtained from Bacillus-treated systems. Analysis of lettuce epiphytic bacterial communities of the fresh lettuce leaf surfaces also indicated the presence of food-borne pathogens belonging to the Shigella and Aeromonas genera, which were less abundant in the probiotic treated systems. This study provides the first characterization of the epiphytic bacterial community structure and how it can be modulated by the addition of a probiotic mixture to the nutrient solution of aquaponic systems.

Economic Sustainability of Small-Scale Aquaponic Systems for Food Self-Production

Aquaponics involves the simultaneous production of plants and fish and it is increasingly being used with a self-consumption purpose. However, there are uncertainties and little information about the economic sustainability of small-scale self-managed aquaponic systems. The objective of this study was to obtain economic information about these systems, including the level of commoditization of food production as a measure of their autonomy. For this purpose, two small-scale aquaponic systems (SAS) based on FAO models were self-constructed using cheap and easy-to-obtain materials and monitored for a year. A total of 62 kg of tilapia and 352 kg of 22 different vegetables and fruits were produced, with an average net agricultural added value of 151.3 €. Results showed positive accounting profit but negative economic profit when labor costs were included. The degree of commoditization was around 44%, which allows a certain autonomy, thanks to the use of family labor force.

Efficiency of pumpkin (Cucurbita pepo), sweet wormwood (Artemisia annua) and amaranth (Amaranthus dubius) in removing nutrients from a smallscale recirculating aquaponic system

In aquaponic systems, plants absorb dissolved nutrients from aquaculture wastewater for their growth. The removal of nutrients allows reuse of water and minimises wastewater discharge to the surrounding environment. This study evaluated the relative nutrient removal efficiencies of three plant species and the performance of Nile tilapia (Oreochromis niloticus) in a small-scale aquaponic system. Three aquaponic systems were assigned as treatments PU (pumpkin), SW (sweet wormwood) and AM (amaranth). Physical-chemical water quality parameters were measured in the fish tanks as well as hydroponic inlets and outlets. Fish sampling was done every 2 weeks for 60 days. Results showed significantly (p < 0.05) lower nutrient concentrations in the hydroponic outlets than the inlets. There was no significant difference in nutrient removal efficiency of the plants (p > 0.05) for all the tested nutrients except for phosphorus. Phosphorus removal was substantially high in PU (75.5 ± 16.8%) than SW (47.36 ± 14.5%) and AM (40.72 ± 13.2%). In addition, the SW system had better (p < 0.05) relative growth rate (0.06 ± 0.00) than that of PU (0.05 ± 0.00) and AM (0.05 ± 0.00). Nitrogen and phosphorus content in plant tissues was significantly high (p < 0.05) in SW and PU plants respectively. Water quality parameters had a significant influence on the growth of fish (p < 0.05). The growth of fish was not different (p > 0.05) in the three treatments. The findings indicate that the tested plants can reduce nutrients in aquaculture discharge water.

Food safety concerns in urban aquaponic production: Nitrate contents in leafy vegetables

Aquaponics is a farming technique that can be used in urban environments for the simultaneous production of plants (hydroponics) and fish (aquaculture). The fish consume the supplied feed and their waste is naturally converted to nitrate and other nutrients, which are then taken up by the plants, acting as a natural water filter. Regarding food safety, there is concern about nitrate accumulation in leafy vegetables produced using this technique. In this study, three different species are tested using a small-scale aquaponic system in order to determine if they are apt for consumption in terms of nitrate levels in their leaves. The nitrate contents observed (613, 2387.8 and 1425.4 mg kg−1 for romaine lettuce, Swiss chard and curly kale, respectively) are below the limits imposed by the European Commission in the existing regulations. They are also within the range of values obtained for the same vegetables cultivated in a conventional way.

Growth and Nutrient Removal Efficiency of Sweet Wormwood (Artemisia annua) in a Recirculating Aquaculture System for Nile Tilapia (Oreochromis niloticus)

The maintenance of optimal water quality for fish production is one of the major challenges in aquaculture. Aquaponic systems can improve the quality of water for fish by removing the undesirable wastes and in turn produce a second marketable crop. However, there is no information on the growth and nutrient removal capability of Artemisia annua in aquaponic systems. This study evaluated the effect of plant density on water quality, the growth of A. annua and Oreochromis niloticus in a small scale aquaponic system in Kenya. The aquaponic system consisted of three treatments representing different plant densities (D1: 48 plants/m2, D2: 24 plants/m2 and D3:0 plants/m2). The high plant density system contributed significantly (p &lt; 0.05) to the removal of all nutrients. The removal efficiency of ammonia was significantly higher in D1 (64.1 ± 14.7%) than in D2 (44.5 ± 6.8%) and D3 (38.0 ± 12.1%). Nitrates and nitrites were inconsistent, whereas phosphorus increased gradually in all treatments. The productivity of plants was higher in D1 than D2. Fish growth rates were significantly higher in D1 (0.35 ± 0.03 g/d) and D2 (0.32 ± 0.02 g/d) than in D3 (0.22 ± 0.04 g/d). The results show that A. annua can be cultivated in aquaponic systems due to its nitrogen removal capabilities.

Suitability and optimization of FAO’s small-scale aquaponics systems for joint production of lettuce (Lactuca sativa) and fish (Carassius auratus)

Aquaponics is a developing technique that combines the simultaneous production of plants (hydroponics) and fish (aquaculture). With it, the use of resources (i.e., water, nutrients, land) is reduced whilst at the same time minimising residues’ discharge to the environment. Among its benefits, it allows the production of healthy vegetables and fish in reduced spaces by means of small-scale systems. In this work, three of them based on FAO models with different hydroponic subsystems (nutrient film technique -NFT-, floating raft, and vertical felt) are tested to produce lettuce (Lactuca sativa) and goldfish (Carassius auratus). Water parameters as well as the growth of plants and fishes were monitored in two different production cycles. The hydroponic subsystem that outperformed the best was the NFT, both in terms of crop production and water consumption. All systems showed similar results in fish production. Further research is needed to corroborate the outputs obtained when using other combinations of plants and fishes. Small-scale aquaponic systems are particularly interesting for self-production and even more so in urban environments with reduced available space.

Vegetable Intercropping in a Small-Scale Aquaponic System

This paper reports the results of the first study of an aquaponic system for Pangasianodon hypophthalmus production that uses Lactuca sativa L. (lettuce) and Cichorium intybus L. rubifolium group (red chicory) intercropping in the hydroponic section. The experiment was conducted in a greenhouse at the Zurich University of Applied Sciences, Wädenswil, Switzerland, using nine small-scale aquaponic systems (each approximately 400 L), with the nutrient film technique (NFT). The intercropping of vegetables did not influence the water temperature, pH, electric conductivity (EC), oxidation–reduction potential, nor O2 content. Intercropping with red chicory increased the lettuce sugar content (+16.0% and +25.3% for glucose and fructose, respectively) and reduced the lettuce caffeic acid content (−16.8%). In regards to bitter taste compounds (sesquiterpene lactones), intercropping reduced the concentrations of dihydro-lactucopicrin + lactucopicrin (−42.0%) in lettuce, and dihydro-lactucopicrin + lactucopicrin (−22.0%) and 8-deoxy–lactucin + dihydro-lactucopicrin oxalate (−18.7%) in red chicory, whereas dihydro-lactucin content increased (+40.6%) in red chicory in regards to monoculture. A significantly higher organic nitrogen content was found in the lettuce (3.9%) than in the red chicory biomass (3.4%), following the intercropping treatment. Anion and cation contents in vegetables were affected by species (Cl−, NO3−, PO43−, SO42−, and Ca2+), intercropping (K+ and Mg2+), and species × intercropping interactions (NO2− and NH4+). Experimental treatments (monoculture vs intercropping and distance from NFT inlet) did not exert significant effects on leaf SPAD (index of relative chlorophyll content) values, whereas the red coloration of the plants increased from the inlet to the outlet of the NFT channel. Intercropping of lettuce and red chicory affected the typical taste of these vegetables by increasing the sweetness of lettuce and changing the ratio among bitter taste compounds in red chicory. These results suggest intercropping as a possible solution for improving vegetable quality in aquaponics. Although the results are interesting, they have been obtained in a relatively short period, thus investigations for longer periods are necessary to confirm these findings. Further studies are also needed to corroborate the positive effect of the presence of red chicory in the system on fish production parameters.

Plant and fish production performance, nutrient mass balances, energy and water use of the PAFF Box, a small-scale aquaponic system

Aquaponics is an integrated farming concept that combines fish and hydroponic plant production in a recirculating water system. This food production system promises a reduced environmental footprint when compared to conventional farming systems. However, questions regarding its sustainability remain and there is a lack of data on its performance. A small-scale aquaponic system named PAFF Box (Plant And Fish Farming Box) consisting of a ship container topped by a greenhouse was studied. Plant yield in ebb-and-flow and deep water culture (DWC) hydroponic beds, lettuce, basil and tilapia production capacity and water and energy consumption were investigated. Additionally, all macro- and micronutrient mass balances were analyzed in order to give a better picture of their dynamics and recycling ability. Thanks to the daily inputs of tap water, and 42g of feed per m2 of plant beds, DWC beds showed 3–10 fold higher plant yields than ebb and flow. The production of 1kg of vegetable in DWC consumed 244L of water and 84.5kWh of electricity and 1kg increase of tilapia consumed 278L and 96.2kWh. The system was very efficient in water use for fish production but alternative solutions for warming the water and fine-tuned pumping setup are required to decrease energy needs. Key nutrients such as potassium, phosphorus, iron, copper, zinc, manganese and molybdenum, remained low in solution. Nitrate, calcium, boron and sodium concentrations increased quickly and only water exchange could control their accumulation meanwhile a low daily water exchange rate of 3.6% implicated a high nutrient loss in the environment. In the willingness to decrease aquaponics environmental footprint, this study indicates that improved designs could be explored such as decoupled aquaponic systems.

WITHDRAWN: Diagnostic hierarchy of radiological features in soft tissue tumours and proposition of a simple diagnostic algorithm to estimate malignant potential of an unknown mass

Aquaponics is an integrated farming concept that combines fish and hydroponic plant production in a recirculating water system. This food production system promises a reduced environmental footprint when compared to conventional farming systems. However, questions regarding its sustainability remain and there is a lack of data on its performance. A small-scale aquaponic system named PAFF Box (Plant And Fish Farming Box) consisting of a ship container topped by a greenhouse was studied. Plant yield in ebb-and-flow and deep water culture (DWC) hydroponic beds, lettuce, basil and tilapia production capacity and water and energy consumption were investigated. Additionally, all macro- and micronutrient mass balances were analyzed in order to give a better picture of their dynamics and recycling ability. Thanks to the daily inputs of tap water, and 42 g of feed per m2 of plant beds, DWC beds showed 3 to 10 fold higher plant yields than ebb and flow. The production of 1 kg of vegetable in DWC consumed 244 L of water and 84.5 kWh of electricity and 1 kg increase of tilapia consumed 278 L and 96.2 kWh. The system was very efficient in water use for fish production but alternative solutions for warming the water and fine-tuned pumping setup are required to decrease energy needs. Key nutrients such as potassium, phosphorus, iron, copper, zinc, manganese and molybdenum, remained low in solution. Nitrate, calcium, boron and sodium concentrations increased quickly and only water exchange could control their accumulation meanwhile a low daily water exchange rate of 3.6% implicated a high nutrient loss in the environment. In the willingness to decrease aquaponics environmental footprint, this study indicates that improved designs could be explored such as decoupled aquaponic systems.

School gardening with a twist using fish: Encouraging educators to adopt aquaponics in the classroom

ABSTRACTTo evaluate the willingness of teachers to incorporate aquaponics in the classroom, we engaged teachers in a 6-week project. Participants in the experimental group maintained small-scale aquaponic systems. All teachers completed pretests and posttests, and exit surveys. Both groups (experimental and control) scored significantly higher on the posttest, but there was no significant score difference between groups. In the exit surveys, participants from the experimental group expressed a greater likelihood to use an aquaponic system at home or in the classroom, believed the system was easy to maintain, and strongly agreed it would help students with math and science.

Energy and water use of a small-scale raft aquaponics system in Baltimore, Maryland, United States

Aquaponics is a form of aquaculture that integrates hydroponics to raise edible plants and fish. There is growing interest in aquaponics because it can be practiced in non-traditional locations for agriculture such as inside warehouses and on marginal lands, and it can provide locally grown products without using synthetic pesticides, chemical fertilizers, or antibiotics. Yet questions remain about the ecological and economic sustainability of aquaponics. The objective of this study was to describe the operating conditions, inputs (energy, water, and fish feed) and outputs (edible crops and fish) and their relationship over two years for a small-scale raft aquaponics operation in Baltimore, Maryland, United States. The system had roughly 1% water loss per day and used an average of 35,950L for replenishment per year. Predicted values suggest rainfall could completely replace the existing water needs. The average energy use was 19,526kWh for propane and electricity per year at a cost of $2055 US dollars. The largest uses of electricity were in-tank water heaters. Comparing inputs to outputs, 104L of water, 0.5kg feed, and 56kWh energy ($6 in energy costs) were needed to produce 1kg of crops; and 292L of water, 1.3kg feed, and 159kWh of energy ($12 in energy costs) were needed to produce a 1kg increase in tilapia. Raising tilapia was a net loss, while raising crops was a net gain when comparing market prices to energy costs. Understanding energy, water, and feed use in aquaponic systems is essential to inform farm business plans. These data can serve as a point of comparison to other small-scale aquaponic systems, and inform future work on life cycle assessments of aquaponics.