Microbial diversity across compartments in an aquaponic system and its connection to the nitrogen cycle

Influences of Community Coalescence on the Assembly of Bacterial Communities of the Small-Scale Complex Aquatic System from the Perspective of Bacterial Transmission, Core Taxa, and Co-occurrence Patterns

Recirculating aquaculture and aquaponics are considered sustainable aquaculture models playing important roles in animal-derived protein supply. In these aquaculture systems, microorganisms are crucial for the system stability. The community coalescence by mixing substances and microorganisms from various microhabitats under hydraulic forces is important for shaping the bacterial communities in these small-scale complex systems. However, the influences of community coalescence on bacterial communities remain rarely revealed in these systems. In this study, aquaponics (APS) and recirculating aquaculture (RAS) systems were set up to explore the bacterial community coalescence across different microhabitats, including water, fish feces, biofilter biofilms, and plant rhizosphere environment. Our results showed that diversity and compositions varied across different microhabitats in both systems. However, bacterial transmissions across these microhabitats differed between systems. The core microbiome of the RAS and APS were formed under community coalescence with the highest contribution of bacterial taxa derived from the fish feces. Nevertheless, the plant rhizosphere bacterial community also contributed to the core microbiome of the APS. Furthermore, the core taxa showed a higher average degree than the other nodes in the bacterial community networks in all microhabitats except for the plant rhizosphere environment, implying the important roles of core taxa in maintaining these bacterial community networks. Our results provide new insights into the assembly of bacterial communities under community coalescence in the artificial aquatic ecosystems comprising complex microhabitats, which is vital for developing microbial solutions for regulating the microbial communities to improve system performance in the future.

Longitudinal Survey of Aeromonas hydrophila and Foodborne Pathogens in a Commercial Aquaponics System

Aquaponic production of fresh produce is a sustainable agricultural method becoming widely adopted, though few studies have investigated potential food safety hazards within commercial systems. A longitudinal study was conducted to isolate and quantify several foodborne pathogens from a commercial, aquaponic farm, and to elucidate their distribution throughout. The survey was conducted over 2 years on a controlled-environment farm containing Nile tilapia (Oreochromis niloticus) and lettuce (Lactuca sativa). Samples (N = 1,047) were collected bimonthly from three identical, independent systems, and included lettuce leaves, roots, fingerlings (7-126 d old), feces from mature fish (>126 d old), water, and sponge swabs collected from the tank interior surface. Most probable number of generic Escherichia coli were determined using IDEXX Colilert Quanti-Tray. Enumeration and enrichment were used to detect Shiga toxin-producing E. coli (STEC), Salmonella enterica, Listeria monocytogenes, Aeromonas spp., Aeromonas hydrophilia, and Pseudomonas aeruginosa. Generic E. coli, STEC, L. monocytogenes, and S. enterica were not detected in collected samples. P. aeruginosa was isolated from water (7/351; 1.99%), swabs (3/351; 0.85%), feces (2/108; 1.85%), and lettuce leaves (2/99; 2.02%). A. hydrophila was isolated from all sample types (623/1047; 59.50%). The incidence of A. hydrophila in water (X2 = 23.234, p < 0.001) and sponge samples (X2 = 21.352, p < 0.001) increased over time.

Runoff of foliar-applied natural fungicides in aquaponics: Implications for fish and nitrification

Aquaponics is a method of producing food in a sustainable manner through the integration of aquaculture and hydroponics, which allows simultaneous cultivation of fish and economic crops. The use of natural fungicides are crucial to the sustainable control of diseases in aquaponics. We assessed the potential impacts of natural fungicides, such as clove oil and lecithin, as well as a synthetic fungicide, tebuconazole, following foliar application in aquaponics. This study examined the runoff rates of the fungicides in decoupled aquaponics, and the subsequent effects of the runoffs on nitrification processes and Nile tilapia (Oreochromis niloticus). The runoffs of the foliar-applied fungicides, clove oil, lecithin, and tebuconazole, were detected in aquaponics water at a percentage runoff rate of 0.3 %, 2.3 %, and 0.3-0.8 % respectively. In the biofilter, lecithin altered the ammonium levels by increasing ammonium-nitrogen levels by 7 mg L-1, 6 h post application. Clove oil, on the other hand, showed no significant effect on ammonium, nitrite, and nitrate-nitrogen. Similarly, the toxicity test showed that eugenol had no significant effects on the hematological, biochemical and antioxidative activities of O. niloticus. Conversely, tebuconazole exhibited significant and persistent effects on various biochemical parameters, including lactate, albumin, and total protein, as well as hematological parameters like hemoglobin and MCH. The use of lecithin and tebuconazole should only be limited to decoupled aquaponics.

Integrated hydroponics systems with anaerobic supernatant and aquaculture effluent in desert regions: Nutrient recovery and benefit analysis

Hydroponics is a resource-efficient system that increases food production and enhances the overall sustainability of agricultural systems, particularly in arid zones with prevalent water scarcity and limited areas of arable land. This study investigated zero-waste hydroponics systems fed by agricultural waste streams as nutrient sources under desert conditions. Three pilot-scale systems were tested and compared. The first hydroponics system ("HPAP") received its nutrient source internally from an aquaponic system, including supernatant from the anaerobic digestion of fish sludge. The second system ("HPAD") was sourced by the supernatant of plant waste anaerobic digestion, and the third served as a control that was fed by commercial Hoagland solution ("HPHS"). Fresh weight production was similar in all treatments, ranging from 488 to 539 g per shoot, corresponding to 5.7 to 6.0 kg total wet weight per m2. The recovery of N and P from wastes and their subsequent uptake by plants was highly efficient, with rates of 77 % for N and 65 % for P. Plants that were fed using supernatants demonstrated slightly higher plant quality compared with those grown in Hoagland solution. Over the duration of the full study (3 months), water was only used to compensate for evapotranspiration, corresponding to ~10 L per kg of lettuce. The potential health risk for heavy metals was negligible, as assessed using the health-risk index (HRI < 1) and targeted hazardous quotient (THQ < 1). The results of this study demonstrate that careful management can significantly reduce pollution, increase the recovery of nutrients and water, and improve hydroponics production.

Microbiome study of a coupled aquaponic system: unveiling the independency of bacterial communities and their beneficial influences among different compartments

To understand the microbiome composition and interplay among bacterial communities in different compartments of a coupled freshwater aquaponics system growing flathead grey mullet (Mugil cephalus) and lettuces (Lactuca sativa), 16S rRNA gene amplicon sequencing of the V3-V4 region was analysed from each compartment (fish intestine, water from the sedimentation tank, bioballs from the biological filter, water and biofilm from the hydroponic unit, and lettuce roots). The bacterial communities of each sample group showed a stable diversity during all the trial, except for the fish gut microbiota, which displayed lower alpha diversity values. Regarding beta diversity, the structure of bacterial communities belonging to the biofilm adhering to the hydroponic tank walls, bioballs, and lettuce roots resembled each other (weighted and unweighted UniFrac distances), while bacteria from water samples also clustered together. However, both of the above-mentioned bacterial communities did not resemble those of fish gut. We found a low or almost null number of shared Amplicon Sequence Variants (ASVs) among sampled groups which indicated that each compartment worked as an independent microbiome. Regarding fish health and food safety, the microbiome profile did not reveal neither fish pathogens nor bacterial species potentially pathogenic for food health, highlighting the safety of this sustainable food production system.

An Analytical Framework on Utilizing Various Integrated Multi-Trophic Scenarios for Basil Production

Here, we aim to improve the overall sustainability of aquaponic basil (Ocimum basilicum L.)-sturgeon (Acipenser baerii) integrated recirculating systems. We implement new AI methods for operational management together with innovative solutions for plant growth bed, consisting of Rapana venosa shells (R), considered wastes in the food processing industry. To this end, the ARIMA-supervised learning method was used to develop solutions for forecasting the growth of both fish and plant biomass, while multi-linear regression (MLR), generalized additive models (GAM), and XGBoost were used for developing black-box virtual sensors for water quality. The efficiency of the new R substrate was evaluated and compared to the consecrated light expended clay aggregate-LECA aquaponics substrate (H). Considering two different technological scenarios (A-high feed input, B-low feed input, respectively), nutrient reduction rates, plant biomass growth performance and additionally plant quality are analysed. The resulting prediction models reveal a good accuracy, with the best metrics for predicting N-NO₃ concentration in technological water. Furthermore, PCA analysis reveals a high correlation between water dissolved oxygen and pH. The use of innovative R growth substrate assured better basil growth performance. Indeed, this was in terms of both average fresh weight per basil plant, with 22.59% more at AR compared to AH, 16.45% more at BR compared to BH, respectively, as well as for average leaf area (LA) with 8.36% more at AR compared to AH, 9.49% more at BR compared to BH. However, the use of R substrate revealed a lower N-NH₄ and N-NO₃ reduction rate in technological water, compared to H-based variants (19.58% at AR and 18.95% at BR, compared to 20.75% at AH and 26.53% at BH for N-NH₄; 2.02% at AR and 4.1% at BR, compared to 3.16% at AH and 5.24% at BH for N-NO₃). The concentration of Ca, K, Mg and NO₃ in the basil leaf area registered the following relationship between the experimental variants: AR > AH > BR > BH. In the root area however, the NO₃ were higher in H variants with low feed input. The total phenolic and flavonoid contents in basil roots and aerial parts and the antioxidant activity of the methanolic extracts of experimental variants revealed that the highest total phenolic and flavonoid contents were found in the BH variant (0.348% and 0.169%, respectively in the roots, 0.512% and 0.019%, respectively in the aerial parts), while the methanolic extract obtained from the roots of the same variant showed the most potent antioxidant activity (89.15%). The results revealed that an analytical framework based on supervised learning can be successfully employed in various technological scenarios to optimize operational management in an aquaponic basil (Ocimum basilicum L.)-sturgeon (Acipenser baerii) integrated recirculating systems. Also, the R substrate represents a suitable alternative for replacing conventional aquaponic grow beds. This is because it offers better plant growth performance and plant quality, together with a comparable nitrogen compound reduction rate. Future studies should investigate the long-term efficiency of innovative R aquaponic growth bed. Thus, focusing on the application of the developed prediction and forecasting models developed here, on a wider range of technological scenarios.