Improving water quality using settleable microalga Ettlia sp. and the bacterial community in freshwater recirculating aquaculture system of Danio rerio

Increasing fish production in recirculating aquaculture system by integrating a biofloc-worm reactor for protein recovery

Aquaculture, producing half of global fish production, offers a high-quality protein source for humans. Improving nitrogen use efficiency (NUE) through microbial protein recovery is crucial for increasing fish production and reducing environmental footprint. However, the poor palatability and high moisture content of microbial protein make its utilization challenging. Here, a biofloc-worm reactor was integrated into a recirculating aquaculture system (BW_RAS) for the first time to convert microbial protein into Tubificidae (Oligochaeta) biomass, which was used as direct feed for culturing fish. Batch experiments indicated that an aeration rate of 0.132 m3 L -1 h -1 and a worm density of 0.3 g cm-2 on the carrier were optimal for microbial biomass growth and worm predation, respectively. Compared to the biofloc reactor-based recirculating aquaculture system (B_RAS), the BW_RAS improved water quality, NUE, and fish production by 17.1 % during a 120-day aquaculture period. The abundance of heterotrophic aerobic denitrifier Deinococcus in BW_RAS was one order of magnitude higher than in B_RAS, while heterotrophic bacteria Mycobacterium was more abundant in B_RAS. Denitrifiers cooperated with organic matter degraders and nitrogen assimilation bacteria for protein recovery and gaseous nitrogen loss while competing with predatory bacteria. Function prediction and qPCR indicated greater aerobic respiration, nitrate assimilation, nitrification (AOB-amoA), and denitrification (napA, nirK, nirS, nosZI), but lower fermentation in BWR compared to BR. This study demonstrated that BW_RAS increased microbial protein production and aerobic nitrogen cycling through ongoing worm predation, further enhancing fish production to a commercially viable level.

Anorexia nervosa and bulimia nervosa: a Mendelian randomization study of gut microbiota

Background

Anorexia nervosa (AN) and bulimia nervosa (BN) poses a significant challenge to global public health. Despite extensive research, conclusive evidence regarding the association between gut microbes and the risk of AN and BN remains elusive. Mendelian randomization (MR) methods offer a promising avenue for elucidating potential causal relationships.

Materials and methods

Genome-wide association studies (GWAS) datasets of AN and BN were retrieved from the OpenGWAS database for analysis. Independent single nucleotide polymorphisms closely associated with 196 gut bacterial taxa from the MiBioGen consortium were identified as instrumental variables. MR analysis was conducted utilizing R software, with outlier exclusion performed using the MR-PRESSO method. Causal effect estimation was undertaken employing four methods, including Inverse variance weighted. Sensitivity analysis, heterogeneity analysis, horizontal multivariate analysis, and assessment of causal directionality were carried out to assess the robustness of the findings.

Results

A total of 196 bacterial taxa spanning six taxonomic levels were subjected to analysis. Nine taxa demonstrating potential causal relationships with AN were identified. Among these, five taxa, including Peptostreptococcaceae, were implicated as exerting a causal effect on AN risk, while four taxa, including Gammaproteobacteria, were associated with a reduced risk of AN. Similarly, nine taxa exhibiting potential causal relationships with BN were identified. Of these, six taxa, including Clostridiales, were identified as risk factors for increased BN risk, while three taxa, including Oxalobacteraceae, were deemed protective factors. Lachnospiraceae emerged as a common influence on both AN and BN, albeit with opposing effects. No evidence of heterogeneity or horizontal pleiotropy was detected for significant estimates.

Conclusion

Through MR analysis, we revealed the potential causal role of 18 intestinal bacterial taxa in AN and BN, including Lachnospiraceae. It provides new insights into the mechanistic basis and intervention targets of gut microbiota-mediated AN and BN.

Potential applications of microalgae-bacteria consortia in wastewater treatment and biorefinery

The use of microalgae-bacteria consortia (MBC) for wastewater treatment has garnered attention as their interactions impart greater environmental adaptability and stability compared with that obtained by only microalgae or bacteria use, thereby improving the efficiency of pollutant removal and bio-product productivity. Additionally, the value-added bio-products produced via biorefineries can improve economic competitiveness and environmental sustainability. Therefore, this review focuses on the interaction between microalgae and bacteria that leads to nutrient exchange, gene transfer and signal transduction to comprehensively understand the interaction mechanisms underlying their strong adaptability. In addition, it includes recent research in which MBC has been efficiently used to treat various wastewater. Moreover, the review summarizes the use of MBC-produced biomass in a biorefining context to produce biofuel, biomaterial, high-value bio-products and bio-fertilizer. Overall, more effort is needed to identify the symbiotic mechanism in MBC to provide a foundation for circular bio-economy and environmentally friendly development programmes.

The Assembly Process of Free-Living and Particle-Attached Bacterial Communities in Shrimp-Rearing Waters: The Overwhelming Influence of Nutrient Factors Relative to Microalgal Inoculation

The ecological functions of bacterial communities vary between particle-attached (PA) lifestyles and free-living (FL) lifestyles, and separately exploring their community assembly helps to elucidate the microecological mechanisms of shrimp rearing. Microalgal inoculation and nutrient enrichment during shrimp rearing are two important driving factors that affect rearing-water bacterial communities, but their relative contributions to the bacterial community assembly have not been evaluated. Here, we inoculated two microalgae, Nannochloropsis oculata and Thalassiosira weissflogii, into shrimp-rearing waters to investigate the distinct effects of various environmental factors on PA and FL bacterial communities. Our study showed that the composition and representative bacteria of different microalgal treatments were significantly different between the PA and FL bacterial communities. Regression analyses and Mantel tests revealed that nutrients were vital factors that constrained the diversity, structure, and co-occurrence patterns of both the PA and FL bacterial communities. Partial least squares path modeling (PLS-PM) analysis indicated that microalgae could directly or indirectly affect the PA bacterial community through nutrient interactions. Moreover, a significant interaction was detected between PA and FL bacterial communities. Our study reveals the unequal effects of microalgae and nutrients on bacterial community assembly and helps explore microbial community assembly in shrimp-rearing ecosystems.

Microbiome dataset of bacterial and fungal communities in anthosphere of twelve different wild plants in South Korea

This dataset provides detailed profiles of bacterial and fungal communities associated with flowers (anthosphere) of 12 different plant species collected from remote and secluded locations characterized by a flourishing and diverse plant ecosystem. In total, 144 flower samples were collected from 12 different wild plants. Bacterial 16S rRNA and fungal ITS genes obtained using the Illumina Miseq approach were used to describe the anthosphere. Metadata and raw sequences obtained in this study are available from the National Center for Biotechnology Information (BioProject ID: PRJNA983070). Amplicon Sequence Variants (ASVs) of bacteria and fungi were analyzed using the DADA2 pipeline. After quality filtering, trimming, and removing the chimeric sequences, 2076 bacterial and 2152 fungal ASVs were identified in the anthosphere. Burkholderiales and Enterobacterales in bacteria, and Pleosporales in fungi were the predominant groups in the anthosphere regardless of the plant species. Among the twelve different plant species, Forsythia koreana exhibited the highest abundance of both bacterial and fungal groups. This dataset represents a detailed exploration of the anthosphere in the most abundant and commonly observed plant species in South Korea, and provides new insights into the microbial communities and interactions of the anthosphere.

Exploring the mechanism of a novel recirculating aquaculture system based on water quality parameters and bacterial communities

To mitigate the serious environmental problems caused by aquaculture wastewater discharge, the development of improved aquaculture systems with more self-purification capacity and less environmental impact has become essential. A novel recirculating aquaculture system (RAS) with ecological ponds was introduced. However, the mechanism of how the ecological ponds decompose the nutrients from the residual feed and excrement of fish is still unclear. Therefore, we designed a seven-week field experiment to explore the dynamic of water quality and the shift of bacterial communities during the initial stage of the RAS ecosystem to maintain the stability of the system. According to the result, the dissolved oxygen concentration maintained at 5.63 to 10.22 mg·L^-1 in aquaculture water, and electrical conductivity increased by 100% to over 800 μs·cm^-1. High-throughput sequencing showed that the abundance and diversity of the bacterial communities in sediment samples were significantly higher than in water samples, and the Proteobacteria, Bacteroidetes, Cyanobacteria, and Actinobacteria were dominant phyla in all samples. The relative abundance of ammonia-oxidizing archaea, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria was lower than 0.10, but rising. Redundancy analysis suggested that TOC, EC, NO₃^-, and NO₂^- were the most important factors shaping the bacterial communities in aquaculture water. Our studies assessed the RAS with ecological ponds for the first time based on water quality parameters and bacterial communities, which indicates that decomposition capacity is insufficient but improved at the initial stage of the operation, and potential risks like eutrophication require attention.

Threats, challenges and sustainable conservation strategies for freshwater biodiversity

Increasing human population, deforestation and man-made climate change are likely to exacerbate the negative effects on freshwater ecosystems and species endangerment. Consequently, the biodiversity of freshwater continues to dwindle at an alarming rate. However, this particular topic lacks sufficient attention from conservation ecologists and policymakers, resulting in a dearth of data and comprehensive reviews on freshwater biodiversity, specifically. Despite the widespread awareness of risks to freshwater biodiversity, organized action to reverse this decline has been lacking. This study reviews prospective conservation and management strategies for freshwater biodiversity and their associated challenges, identifying current key threats to freshwater biodiversity. Engineered nanomaterials pose a significant threat to aquatic species, and will make controlling health risks to freshwater biodiversity increasingly challenging in the future. When fish are exposed to nanoparticles, the surface area of their respiratory and ion transport systems can decline to 60% of their total surface area, posing serious health risks. Also, about 50% of freshwater fish species are threatened by climate change, globally. Freshwater biodiversity that is heavily reliant on calcium perishes when the calcium content of their environments degrades, posing another severe threat to world biodiversity. To improve biodiversity, variables such as species diversity, population and water quality, and habitat are essential components that must be monitored continuously. Existing research on freshwater biota and ecosystems is still lacking. Therefore, data collection and the establishment of specialized policies for the conservation of freshwater biodiversity should be prioritized.

Capabilities and mechanisms of microalgae on nutrients and florfenicol removing from marine aquaculture wastewater

The regulations governing the discharge of marine aquaculture wastewater are becoming increasingly stringent, and the problems of nitrogen and phosphorus pollution and antibiotic residues in wastewater are serious. Microalgae-based treatment with the dual benefits of wastewater purification and microalgae resource recycling was regarded as the most promising technology in aquaculture wastewater treatment. Isochrysis galbana and Chlorella sp. were chosen to investigate antibiotic and nutrient removal mechanisms from aquaculture wastewater. FLO addition stimulated microalgae growth at low FLO concentrations (0.1 and 1 mg/L) but inhibited growth at 10 mg/L. The removal efficiency of DIN by Chlorella sp. and I. galbana after 7 days of cultivation was 66.4% and 25.8%, respectively. Linear curves were obtained between DIN concentration and cultivation duration, remove constant (k) increased as FLO concentration increased from 0 to 10 mg/L, and the highest value of k was obtained in both the Chlorella sp. and I. galbana groups at 10 mg/L. DIP concentrations in FLO-contained simulated aquaculture wastewater decreased sharply with the cultivation of Chlorella sp. and I. galbana, and DIP removal rate increased as FLO concentration increased. When the initial concentration of FLO was 0.1 mg/L, biodegradation by I. galbana accounted for 86.67% of FLO removal. In contrast, FLO removal with biodegradation and biosorption by Chlorella sp. was 89.74% and 3.72%, respectively. Furthermore, Chlorella sp. grown in MPBR demonstrated superior capability for antibiotic-containing marine aquaculture wastewater purification, with average removal rates of DIN and DIP of 81.2% and 100%, respectively. The high removal rate is related to membranes which can improve microalgae performance by decoupling SRT and HRT. For microalgae-based aquaculture wastewater, ammonia was the most crucial nitrogen source, followed by nitrate. These findings serve as a theoretical foundation for developing microalgae-based aquaculture wastewater treatment technology and eliminating antibiotics in aquaculture.

Improvement of aquaculture water quality by mixed Bacillus and its effects on microbial community structure

Microbial remediation, especially the application of probiotics, has recently gained popularity in improving water quality and maintaining aquatic animal health. The efficacy and mechanism of mixed Bacillus for improvement of water quality and its effects on aquatic microbial community structure remain unknown. To elucidate these issues, we applied two groups of mixed Bacillus (Bacillus megaterium and Bacillus subtilis (A0 + BS) and Bacillus megaterium and Bacillus coagulans (A0 + BC)) to the aquaculture system of Crucian carp. Our results showed that the improvement effect of mixed Bacillus A0 + BS on water quality was better than that of A0 + BC, and the NH₄⁺-N, NO₂^--N, NO₃^--N, and total phosphorus (TP) concentrations were reduced by 46.3%, 76.3%, 35.6%, and 80.3%, respectively. In addition, both groups of mixed Bacillus increased the diversity of the bacterial community and decreased the diversity of the fungal community. Microbial community analysis showed that mixed Bacillus A0 + BS increased the relative abundance of bacteria related with nitrogen and phosphorus removal, such as Proteobacteria, Actinobacteria, Comamonas, and Stenotrophomonas, but decreased the relative abundance of pathogenic bacteria (Acinetobacter and Pseudomonas) and fungi (Epicoccum and Fusarium). Redundancy analysis showed that NH₄⁺-N, NO₂^--N, and TP were the primary environmental factors affecting the microbial community in aquaculture water. PICRUST analysis indicated that all functional pathways in the A0 + BS group were richer than those in other groups. These results indicated that mixed Bacillus A0 + BS addition produced good results in reducing nitrogenous and phosphorus compounds and shaped a favorable microbial community structure to further improve water quality.

Metagenomics and network analysis elucidating the coordination between fermentative bacteria and microalgae in a novel bacterial-algal coupling reactor (BACR) for mariculture wastewater treatment

To achieve the goal of treating mariculture wastewater economically and efficiently, a novel bacterial-algal coupling reactor (BACR) integrating acidogenic fermentation and microalgae cultivation was firstly investigated for mariculture wastewater treatment. Volatile fatty acids (VFAs) generated in the dark chamber migrated into the photo chamber for microalgal utilization, which alleviated the pH drop and feedback inhibition of the acidogenic fermentation. The maximum dry cell weight (DCW) of microalgae was 1.46 g/L, and pollutants such as chemical oxygen demand (COD), ammonium (NH₄⁺-N) and total phosphorus (TP) in the BACR were effectively removed under the mixotrophic culture condition. Furthermore, bacterial community profiles and functional genes in the BACR and single acidogenic fermentation reactor were identified. Compared with the single acidogenic fermentation reactor, most of the fermentative bacteria (e.g., Ruminococcus, Christensenellaceae R-7 group, Exiguobacterium, Pseudomonas and Levilinea) were enriched by the BACR. From the genetic perspective, the abundances of dominant genes (ackA, acs and atoD) associated with acetic, propionic and butyric acid production were greatly enhanced in the BACR. In the fatty acid biosynthesis pathway (ko00061), three kinds of high-abundance acetyl-CoA carboxylase genes and eight kinds of downstream functional genes were up-regulated in the BACR. Finally, based on co-occurrence network analysis, the coordination between fermentative bacteria and microalgae in the BACR was revealed. This study provided a deep insight into the advantage and potential of the BACR in mariculture wastewater treatment.

Nitrogen Removal Performance of Novel Isolated Bacillus sp. Capable of Simultaneous Heterotrophic Nitrification and Aerobic Denitrification

The control of nitrogenous pollutants is a key concern in aquaculture production. Bacillus spp. are commonly used as probiotics in aquaculture, but only a few reports have focused on the simultaneous heterotrophic nitrification and aerobic denitrification (SND) capacity of Bacillus sp. strains. In order to improve nitrogen biodegradation efficiency in the aquaculture industry, the SND capacity of Bacillus sp. strains was evaluated using both individual and mixed nitrogen sources and different sources of organic carbon. Twelve Bacillus sp. isolates were screened from aquaculture pond sediments and shrimp guts for nitrogen biodegradation. Six strains exhibited especially efficient inorganic nitrogen removal capacities in media with individual and mixed nitrogen sources. These strains comprise K8, N2, and N5 (B. subtilis), HYS (B. albus), H4 (B. amyloliquefaciens), and S1 (B. velezensis). The strains grew better when the sole nitrogen source was NH₄⁺-N, but degraded nitrogen in the following order: nitrite nitrogen (NO₂^--N), ammonium nitrogen (NH₄⁺-N), and nitrate nitrogen (NO₃^--N). There was no associated NO₂^--N accumulation, regardless of the nitrogen source. The optimal carbon source for nitrogen removal varied based on different nitrogen sources and associated metabolic pathways. The optimal carbon sources for the removal of NO₃^--N, NO₂^--N, and NH₄⁺-N were sodium citrate, sodium acetate, and sucrose, respectively. The application of H4 in recirculating aquaculture water further demonstrated that NO₂^--N and NH₄⁺-N could be effectively removed. This study thus provides valuable technical support for the bioremediation of aquaculture water.

Using physicochemical and biological parameters for the evaluation of water quality and environmental conditions in international wetlands on the southern part of Lake Urmia, Iran

The Kani Barazan and Yadegarlou wetlands in the southern part of Lake Urmia (Iran) have been substantially modified due to human activities and anthropogenic use. In recent years, freshwater-based eco-biological studies to recognize the quality of water resources have been greatly expanded. Microalgae and Cyanophyta are considered important bioindicators for the evaluation of water quality and wetland health worldwide. Herein, 22 microalgae and 5 Cyanophyta genera were identified in both wetlands, in which Cyanophyta has mainly caused blooms. Principal components analysis (PCA) was carried out based on links between the distribution of microalgae and Cyanophyta with physical and chemical parameters. The data showed that depth, turbidity, and the temperature had a significant influence on the microalga and Cyanophyta communities in both wetlands. Based on the biological properties, it seems that the Kani Barazan and Yadegarlou international wetlands experience meso-eutrophic conditions. The integration of the physical, chemical and biological parameters with the water quality index (WQI) revealed that both wetlands were polluted as a consequence of human activities. Moreover, a close relationship between WQI and the biological parameters was documented. Thus, we concluded that microalgae and Cyanophyta communities, their abundance patterns, and water quality changes could provide valuable data for the conservation of the Kani Barazan and Yadegarlou international wetlands.

Analysis of micropollutants in a marine outfall using network analysis and decision tree

The presence of micropollutants (MPs), including pharmaceutical, industrial, and pesticidal compounds, threatens both human health and the aquatic ecosystem. The development and extensive use of new chemicals have also inevitably led to the accumulation of MPs in aquatic environments. Recreational beaches are especially vulnerable to contamination, affecting humans and aquatic animals via the absorption of MPs in water during marine activities (e.g., swimming, sailing, and windsurfing). Additionally, marine outfalls in an urbanized coastal city can cause serious chemical and microbial pollution on recreational beaches, leading to an increase in adverse effects on public health and the ecological system. Therefore, the aim of this study was to, with the use of network and decision tree analyses, identify the features and factors that influence the change in MP concentrations in a marine outfall. These analyses were conducted to inspect the relationship between each MP and its hierarchical structure as well as hydrometeorological variables. Additionally, a risk analysis was conducted in this study in which the MPs were prioritized based on their optimized risk quotient values. During our monitoring of MP concentrations over time at the marine outfall, high concentrations of pharmaceutical and industrial compounds were detected when the tide level was low after rainfall. Furthermore, results of the risk analysis and the prioritization revealed that a total of 18 substances identified in our study posed a risk to the ecosystem; these include major ecotoxicologically hazardous substances such as telmisartan, mevinphos, and methiocarb. Results of the network analysis demonstrated distinct trends for pharmaceutical and industrial substances, whilst those for pesticide compounds were irregular. Additionally, the hierarchical structures for most MPs consisted of rainfall, tide level, and antecedent dry hours; this implies that these factors influence MP dynamics. These findings will be helpful for establishing chemical contamination management plans for recreational beaches in the future.

Integrating Microbial Protein Production and Harvest Systems into Pilot-Scale Recirculating Aquaculture Systems for Sustainable Resource Recovery: Linking Nitrogen Recovery to Microbial Communities

In aquaculture, it is important to raise the nitrogen recovery efficiency (NRE) to improve sustainability. To achieve this, recovery of microbial protein (RMP), instead of nitrification/denitrification in conventional wastewater treatment, is a promising approach whose microbiological mechanisms must be characterized. Here, periodic RMP was conducted in an in situ biofloc-based aquaculture system (IBAS) and a separating assimilation reactor-based recirculating aquaculture system (SRAS). Kinetic analysis indicated that a microbial biomass level of 3 g L^-1 was optimal for inorganic N removal, and excess biomass was harvested to improve the NRE. Unlike the IBAS, the SRAS eliminated the fluctuation in water quality caused by the RMP. Periodic RMP significantly increased the NRE to 44-57% by promoting the filamentous bacterium Herpetosiphon and suppressing anaerobic denitrifiers. Aerobic chemoheterotrophy was the main microbial metabolic process for energy. After RMP, nitrate reductase-encoded functional genes (napA and narG) significantly decreased, while nitrite reductase-encoded functional genes, especially nirK, significantly increased. Co-occurrence networks analysis indicated that the cooperation and competition among organic matter degraders, filamentous bacteria, nitrifiers, and denitrifiers determined the microbial protein yield. These results provide fundamental insights into the influence of the RMP on microbial communities and functions, which is important for realizing sustainable aquaculture.

Cigarette smoking status alters dysbiotic gut microbes in hypertensive patients

Smoking not only is one of the most important risk factors of hypertension (HTN), but also alters the composition of gut microbiota (GM) in previous studies. Although dysbiosis of GM has been implicated in HTN, how GM alters in patients with HTN under smoking status is still not clear. This study aimed to explore the difference in intestinal microflora among smokers with HTN (S-HTN), nonsmokers with HTN (NS-HTN), and smokers without HTN (S-CTR) and identify whether cigarette smoking led to disordered intestinal microbiota in patients with HTN. Metagenomic sequencing analysis of fecal specimens was conducted in nonsmokers without HTN (NS-CTR, n = 9), S-CTR (n = 9), NS-HTN (n = 18), and S-HTN (n = 23). Compared with S-CTR or NS-HTN, the GM in S-HTN was disordered, with lower microbial α-diversity and significant difference of β-diversity on axes as compared to S-CTR at genus and species level. The microbial enterotype in S-HTN was inclined to Prevotella-dominant type. Dramatic changes in the intestinal genera and species composition were observed in S-HTN, including reduced enrichment of Phycisphaera and Clostridium asparagiforme. Moreover, the intestinal function altered in S-HTN. Therefore, the findings of the present study revealed GM disorders in S-HTN and clarified the role of smoking in impairing the intestinal microbiome in HTN. Tobacco control is particularly important for improving GM in patients with HTN, and might be beneficial in preventing future cardiovascular events.

Rearing water microbiomes in white leg shrimp (Litopenaeus vannamei) larviculture assemble stochastically and are influenced by the microbiomes of live feed products

The development of effective management strategies to reduce the occurrence of diseases in aquaculture is hampered by the limited knowledge on the microbial ecology of these systems. In this study, the dynamics and dominant community assembly processes in the rearing water of Litopenaeus vannamei larviculture tanks were determined. Additionally, the contribution of peripheral microbiomes, such as those of live and dry feeds, to the rearing water microbiome were quantified. The community assembly in the hatchery rearing water over time was dominated by stochasticity, which explains the observed heterogeneity between replicate cultivations. The community undergoes two shifts that match with the dynamics of the algal abundances in the rearing water. Source tracking analysis revealed that 37% of all bacteria in the hatchery rearing water were introduced either by the live or dry feeds, or during water exchanges. The contribution of the microbiome from the algae was the largest, followed by that of the Artemia, the exchange water and the dry feeds. Our findings provide fundamental knowledge on the assembly processes and dynamics of rearing water microbiomes and illustrate the crucial role of these peripheral microbiomes in maintaining health-promoting rearing water microbiomes.

Simultaneous removal of nutrient and sulfonamides from marine aquaculture wastewater by concentrated and attached cultivation of Chlorella vulgaris in an algal biofilm membrane photobioreactor (BF-MPBR)

Microalgae based wastewater treatment has attracted increasing attention for its many advantages in recent years. In this study, a novel microalgae biofilm membrane photobioreactor (BF-MPBR) was developed for the efficient microalgae cultivation and the removal of nutrient and sulfonamides (SAs) from marine aquaculture wastewater. Two BF-MPBRs with hydraulic retention time (HRT) of 1 day and 2 days respectively were continuously operated for 70 days without harvesting microalgae. Concentrated and attached culture of marine Chlorella vulgaris was achieved in these continuous flow BF-MPBRs due to the suspended solid carriers and microfiltration membrane module in the reactors. The algal biomass productivity achieved in BF-MPBRs with HRT of 1 day and 2 days were 14.02 and 22.03 mg L^-1 day^-1, respectively. In addition, at the end of the cultivation, 60.4% and 45.0% of microalgae were fixed into algal biofilm in BF-MPBRs with 1 day and 2 day HRT, respectively. Compared with batch cultivation, more efficient nutrient and SAs removal performance was achieved in BF-MPBRs, although the HRT of the BF-MPBRs used in this study was only 1 or 2 days. During the stable operation stage of the BF-MPBRs, the reduction in dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), sulfadiazine (SDZ), sulfamethazine (SMZ) and sulfamethoxazole (SMX) were found in the range of 91.0-99.6%, 92.1-98.4%, 61.0-79.2%, 50.0-76.7% and 60.8-82.1%, respectively. Therefore, nutrient and SAs were simultaneously and efficiently removed from marine aquaculture wastewater by microalgae cultivation in BF-MPBR.

Integration of Marine Macroalgae (Chaetomorpha maxima) with a Moving Bed Bioreactor for Nutrient Removal from Maricultural Wastewater

Rather than direct nutrient removal from wastewaters, an alternative approach aimed at nutrient recovery from aquacultural wastewaters could enable sustainable management for aquaculture production. This study demonstrated the feasibility of cultivating marine macroalgae (Chaetomorpha maxima) with a moving bed bioreactor (MBBR-MA), to remove nitrogen and phosphorus in aquaculture wastewater as well as to produce macroalgae biomass. MBBR-MA significantly increased the simultaneous removal of nitrate and phosphate in comparison with only MBBR, resulting in an average total nitrogen (TN) and total phosphorus (TP) removal efficiency of 42.8 ± 5.5% and 83.7 ± 7.7%, respectively, in MBBR-MA while MBBR had no capacity for TN and TP removal. No chemical oxygen demand (COD) removal was detected in both reactors. Phosphorus could be a limiting factor for nitrogen uptake when N : P ratio increased. The recovered nitrogen and phosphorus resulted in a specific growth rate of 3.86%–10.35%/day for C. maxima with an uptake N : P ratio of 6. The presence of macroalgae changed the microbial community in both the biofilter and water by decreasing the relative abundance of Proteobacteria and Nitrospirae and increasing the abundance of Bacteroidetes. These findings indicate that the integration of the macroalgae C. maxima with MBBR could represent an effective wastewater treatment option, especially for marine recirculating aquaculture systems.

Biological filters regulate water quality, modulate health status, immune indices and gut microbiota of freshwater crayfish, marron (Cherax cainii, Austin, 2002)

Water quality has significant impacts on the health and immune responses of aquaculture species. This study aimed to analyse and compare the effects of two biological filters namely, gravel and, Bio-Ball with a recently developed filter called Water-cleanser on regulation of water quality parameters, health and immune response of marron reared in plastic tanks for 60 days. Results showed that addition of Bio-Ball significantly (P < 0.05) reduced the concentration of ammonia, nitrate and phosphate while Water-cleanser showed the ability to reduce ammonia and nitrate from water in aquaculture tanks. Although the biological filters had no significant effect on marron growth but inclusion of Bio-Ball and Water-cleanser positively influenced the biochemical composition of tail muscle and some haemolymph parameters of marron. The next generation sequence data demonstrated higher bacterial diversity in the hindgut of marron with Water-cleanser, followed by Bio-Ball and gravel, respectively. In addition, the predicted metabolic pathways revealed a significantly higher bacterial activity and gene function correlated to metabolism and biosynthesis of protein, energy and secondary metabolites in Bio-Ball and Water-cleanser. Bio-Ball and Water-cleanser were also associated with up-regulation of innate immune responsive genes of marron gut. Overall, Bio-Ball and Water-cleanser proved to have higher water remediation and immune response modulation capabilities, and therefore could be used as preferred filters for growth of beneficial bacteria in crayfish culture.

Bacterial community enhances flocculation efficiency of Ettlia sp. by altering extracellular polymeric substances profile

This study examined the effects of a bacterial community and extracellular polymeric substances (EPS) on Ettlia sp. flocculation. The growth rate, flocculation efficiency (FE), bacterial community, and EPS profile of axenic and xenic Ettlia cultures were monitored during 46 days of cultivation. For the xenic culture, with a great abundance of growth-promoting and flocculation-inducing bacteria, the biomass density was 18.75% higher and its FE reached 100% in the mid-stationary phase. Moreover, microscopic observation and a quantitative analysis of the EPS revealed the exclusive presence of long filamentous EPS and more compact structure in the xenic Ettlia culture, possibly explaining its better FE. Notwithstanding, for the axenic culture, despite a lower biomass density and reduced abundance of EPS, its FE reached 92.54% in the mid-stationary phase. Thus, the role of the bacterial community was found to be supportive rather than vital for the high settleability of the self-flocculating Ettlia microalgal culture.

Administration of Probiotics in the Water in Finfish Aquaculture Systems: A Review

Over the last few decades, the contribution of aquaculture to animal protein production has increased enormously, and the sector now provides almost half of the fish and shellfish consumed worldwide, making it a major food producer. Nevertheless, many factors, including infections, pollution, and stress, may result in significant economic losses. The aquaculture industry will not be totally successful without the therapeutic and preventive means to control all these factors. Antibiotics (long used in aquaculture practice) have tended to aggravate the problem by increasing antibiotic resistance. Concomitantly, probiotics have widely been suggested as eco-friendly alternatives to antibiotics. However, the way in which probiotics are applied in aquaculture is a key factor in their favorable performance. The aim of this review was to examine the current state of probiotics administration through the water in finfish aquaculture. The review also attempts to cover the research gaps existing in our knowledge of this administration mode, and to suggest the issues that need to be investigated in greater depth.