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The release of contaminants of environmental concern including heavy metals and metalloids, and contaminants of emerging concern including organic micropollutants from processing industries, pharmaceuticals, personal care, and anthropogenic sources is a growing threat worldwide due to their toxicity, persistence, and bioaccumulative nature and adversely affect the aquatic environment, crops, animals, fisheries, and human health. There is a big challenge to mitigate inorganic and organic contaminants, which together can be coined as contaminants of environmental and emerging concern (CEECs). The physicochemical properties of several CEECs, reveal that they cannot be easily removed by traditional physicochemical processes and are not economically viable for managing mixed contaminants of low concentrations. As a result, low-cost materials must be designed to provide high CEEC removal efficiency. One of the environmentally viable and energy-efficient approaches is biosorption, which involves using either biomass or biopolymers isolated from plants or animals for decontaminating heavy metals in contaminated environments using inherent biological mechanisms. Among chemical constituents in plant biomass, cellulose, lignin, hemicellulose, proteins, polysaccharides, phenolic compounds, and animal biomass include polysaccharides and other compounds to bind heavy metals covalently and non-covalently. These functional groups include - carboxyl, hydroxyl, carbonyl, amide, amine, sulfhydryl, and other groups. Cation-exchange capacities of these bioadsorbents can be improved by applying the chemical modifications. The relevance of chemical constituents and bioactives in animal, as well as plant-derived biosorbents, is highlighted in this comprehensive review for sequestering and bioremediation of CEECs including as many as ten different heavy metals and metalloids co-contaminated with other organic micropollutants.

Global agriculture is facing tremendous challenges due to climate change. The most predominant amongst these challenges are abiotic and biotic stresses caused by increased incidences of temperature extremes, drought, unseasonal flooding, and pathogens. These threats, mostly due to anthropogenic activities, resulted in severe challenges to crop and livestock production leading to substantial economic losses. It is essential to develop environmentally viable and cost-effective green processes to alleviate these stresses in the crops, livestock, and fisheries. The application of nanomaterials in farming practice to minimize nutrient losses, pest management, and enhance stress resistance capacity is of supreme importance. This paper explores innovative methods for synthesizing nanostructured materials using plants, animals, and fisheries wastes and their valorization to mitigate abiotic and biotic stresses and input use efficiency in climate-smart, and stress-resilient agriculture including crop plants, livestock, and fisheries.

Global agriculture is facing tremendous challenges due to climate change. The most predominant amongst these challenges are abiotic and biotic stresses caused by increased incidences of temperature extremes, drought, unseasonal flooding, and pathogens. These threats, mostly due to anthropogenic activities, resulted in severe challenges to crop and livestock production leading to substantial economic losses. It is essential to develop environmentally viable and cost-effective green processes to alleviate these stresses in the crops, livestock, and fisheries. The application of nanomaterials in farming practice to minimize nutrient losses, pest management, and enhance stress resistance capacity is of supreme importance. This paper explores innovative methods for synthesizing metallic and non-metallic nanoparticles using plants, animals, and fisheries wastes and their valorization to mitigate abiotic and biotic stresses and input use efficiency in climate-smart and stress-resilient agriculture including crop plants, livestock, and fisheries.

This paper evaluates the biosorption of toxic metal ions onto the bioadsorbents derived from mango (Mangifera indica) and guava (Psidium guiag) barks and their metal fixation mechanisms. Maximum metal biosorption capacities of the mango bioadsorbent were found in the following increasing order (mg/g): Hg (16.24) < Cu (22.24) < Cd (25.86) < Pb (60.85). Maximum metal biosorption capacities of guava bioadsorbent follow similar order (mg/g): Hg (21.48) < Cu (30.36) < Cd (32.54) < Pb (70.25), but with slightly higher adsorption capacities. The removal mechanisms of heavy metals using bioadsorbents have been ascertained by studying their surface properties and functional groups using various spectrometric, spectroscopic, and microscopic methods. Whewellite (C2CaO4·H2O) has been identified in bioadsorbents based on the characterization of their surface properties using X-ray techniques (XPS and XRD), facilitating the ion exchange of metal ions with Ca2+ bonded with carboxylate moieties. For both the bioadsorbents, the Pb2+, Cu2+, and Cd2+ are biosorbed completely by ion exchange with Ca2+ (89–94%) and Mg2+ (7–12%), whereas Hg2+ is biosorbed partially (57–66%) by ion exchange with Ca2+ (38–42%) and Mg2+ (19–24%) due to involvement of other cations in the ion exchange processes. Bioadsorbents contain lignin which act as electron donor and reduced Cr(VI) into Cr(III) (29.87 and 37.25 mg/g) in acidic medium. Anionic Cr(VI) was not adsorbed onto bioadsorbents at higher pH due to their electrostatic repulsion with negatively charged carboxylic functional groups.

Penaeid shrimp culture has become an important economic activity in many countries, particularly in Asia. However, environmental challenges and bacterial and viral disease outbreaks are being increasingly recognized as significant constraints on aquaculture production and trade worldwide. Diverse bacterial genera have been associated with infections of penaeid shrimp, but vibriosis is one of the mainly severe bacterial diseases which cause mortality, have been reported in penaeid shrimp culture systems. Tiger shrimp Penaeus monodon and white shrimp Penaeus vannamei are susceptible to fatal effects of luminous vibriosis in India, creating economic losses. There is always a need to control Vibrio harveyi in brackish water shrimp aquaculture. Green water culture system is a biological approach, which integrates the culture of economically important euryhaline finfish as bioaugmentors in the reservoir or net cages/pens in the shrimp growing ponds through zero-water exchange and recirculatory system. The secretions of slime enhance the production of green water which not only suppress the proliferation of luminous bacteria, but also improves the water quality by removing nutrient. In this paper, a hypothesis has been proposed to utilize green water technology as a bioaugmentation technology based on integration of fish green slime beneficial bacteria and their bioactives for controlling priority pathogens in freshwater and brackish water shrimp aquaculture systems for achieving higher shrimp production and enhancing farmers income and livelihood.

This study evaluated the effect of different potassium supplementation dosages on the physiological responses of Pangasianodon hypophthalmus reared in an aquaponic system with Spinacia oleracea L. for 60 days. The system comprised of a rectangular fish tank of 168 l capacity (water volume = 100 l) with nutrient film technique (NFT)-based hydroponic component with fish to plant ratio of 2.8 kg m

A 60-day experimental trial was conducted to investigate the effect of different dosages of potassium supplementation on Spinacia oleracea L. and Pangasianodon hypophthalmus in an aquaponic system. The system consisted of 168 l rectangular fish tanks (0.78 × 0.54 × 0.40 m) with 100 l water volume stocked with P. hypophthalmus at 2.8 kg m-3 and Nutrient Film Technique (NFT) hydroponics with spinach at 28 plants m-2. Four dosages of potassium viz., 90, 120, 150, and 180 mg l-1 were assigned as T1, T2, T3, and T4 and compared with control C (0 mg l-1) to determine the most efficient potassium dosage for the aquaponic system. The physico-chemical parameters and nutrient dynamics were within the permissible range with no marked variation between the control and treatments. The spinach was harvested twice. The first harvest before potassium supplementation showed no significant difference. In the second harvest, the potassium supplementation had a significant (P 0.05) and followed the order: C (33.23 ± 0.52 g)>T1 (33.07 ± 0.45 g)>T2 (32.94 ± 0.40 g)>T3 (32.23 ± 0.37 g)>T4 (32.15 ± 0.35 g). The plant analysis revealed that potassium supplementation triggered the nutrient synergism resulting in higher nitrogen, potassium, phosphorus, iron, and sulfur content in T4 followed by T3, T2, T1, and C. The evaluation of the physiological response of P. hypophthalmus showed higher plasma glucose in T4. Considering the water quality parameters, fish growth, physiological response, spinach yield, and nutrient content, a dose of 150 mg l-1 K+ (T3) could be recommended as an optimum potassium dosage for P. hypophthalmus-Spinacia oleracea L. aquaponic system.

An environment friendly and sustainable approach is being emerged in the area of nanotechnology for accelerated growth and development of culturable aquatic animals hence green chemistry is gaining momentum in recent years. The present study has been carried out to delineate the effects of selenium nanoparticles (Se-NPs) on growth performance, antioxidative status and immunity of fish reared under lead (Pb) and high temperature (34 °C). Three hundred and fifteen fish were equally distributed in seven treatments in triplicates. Three isocaloric and isonitrogenous experimental diets viz. control (Se-NPs-0 mg/kg), Se-NPs at 1 mg/kg and Se-NPs at 2 mg/kg were formulated. The fish were reared under lead (Pb, 1/21st of LC50 (4 ppm)) and high temperature (34 °C) stress and fed with or without dietary Se-NPs. The effects of dietary Se-NPs were studied in terms of growth performance (Weight gain %, feed conversion ratio, protein efficiency ratio and specific growth rate), antioxidative status (catalase, superoxide dismutase, glutathione-S-transferase and glutathione peroxidase), neurotransmitter enzymes (AChE), stress biomarkers (heat shock protein 70, serum cortisol, blood glucose, vitamin C), immunological status (total protein, A/G ratio and respiratory burst activity) in Pangasinodon hypophthalmus post challenge with Aeromonas veronii biovar sobria. Results of the investigation demonstrated significant improvement of growth performance, antioxidative status, neurotransmitter enzyme activity, stress markers and more importantly enhanced immunity of the fish with dietary incorporation of Se-NPs at 1 mg/kg. In addition, post bacterial infection, the relative % survival increased and cumulative mortality % decreased in the group fed with Se-NPs at 1 mg/kg diet. Pb and high temperature treated and fed with control diet group showed devastating impact on the growth performance, antioxidative status, stress markers and immunity of the fish. Similarly, application of Se-NPs at 2 mg/kg showed poor growth performance and elevated level of oxidative stress and other stress biomarkers including other biochemical attributes. Inclusive results indicated that, Se-NPs at 1 mg/kg has capability to enhance overall performance and alleviate multiple stresses in P. hypophthalmus. Hence, Se-NPs at optimum level have ability to develop green chemistry in feed industry for better growth performance of the fish.

A preliminary study was conducted to delineate the ameliorating effect of dietary zinc nanoparticles (Zn-NPs) against thermal stress in Pangasius hypophthalmus reared under concurrent exposure to lead (Pb) and elevated temperature (34 °C). Three diets were formulated such as control (no Zn-NPs), Zn-NPs 10 and 20 mg/kg diet. Two hundred and thirty four fish were randomly distributed in to six treatments groups in triplicates; such as control group (no Zn-NPs in diet and unexposed to Pb and temperature, Ctr/Ctr), control diet with concurrent exposure to Pb and temperature (Pb-T/Ctr), Zn-NPs 10 and 20 mg/kg without stressors (Zn-NPs 10 mg/kg, Zn-NPs 20 mg/kg), Zn-NPs 10 and 20 mg/kg diet with concurrent exposure to Pb and temperature (Pb-T/Zn-NPs 10 mg/kg, Pb-T/Zn-NPs 20 mg/kg). The Pb in treated water was maintained at the level of 1/21th of LC50 (4 ppm) at 34 °C temperature in stressors groups. Post 60 days feeding trial, critical thermal minimum (CTmin), lethal thermal minimum (LTmin), and critical thermal maximum (CTmax), lethal thermal maximum (LTmax) and biochemical attributes on P. hypophthalmus were evaluated. The results indicated that, dietary supplementation of Zn-NPs increased the CTmin, LTmin and CTmax, LTmax in P. hypophthalmus. Positive correlations were observed between CTmin LTmin (Y = − 0.495 + 10.08x, R2, 0.896) and CTmax LTmax (Y = − 0.872 + 4.43x, R2, 0.940). At the end of the thermal tolerance study, oxidative stress and lipid peroxidation (LPO) were significantly reduced and neurotransmitter enzyme was significantly increased in the groups fed with Zn-NPs @ 10 mg and 20 mg/kg diet. Overall results indicated that dietary Zn-NPs can confer protection against thermal stress in P. hypophthalmus.

Water pollution is a serious challenge to the public health. Among different forms of aquatic pollutants, chemical and biological agents create paramount threat to water quality when the safety standards are surpassed. There are many conventional remediatory strategies that are practiced such as resin-based exchanger and activated charcoal/carbon andreverse osmosis. Newer technologies using plants, microorganisms, genetic engineering, and enzyme-based approaches are also proposed for aquatic pollution management. However, the conventional technologies have shown impending inadequacies. On the other hand, new bio-based techniques have failed to exhibit reproducibility, wide specificity, and fidelity in field conditions. Hence, to solve these shortcomings, nanotechnology ushered a ray of hope by applying nanoscale zinc oxide (ZnO), titanium dioxide (TiO2), and tungsten oxide (WO3) particles for the remediation of water pollution. These nanophotocatalysts are active, cost-effective, quicker in action, and can be implemented at a larger scale. These nanoparticles are climate-independent, assist in complete mineralization of pollutants, and can act non-specifically against chemically and biologically based aquatic pollutants. Photocatalysis for environmental remediation depends on the availability of solar light. The mechanism of photocatalysis involves the formation of electron-hole pairs upon light irradiations at intensities higher than their band gap energies. In the present review, different methods of synthesis of nanoscale ZnO, TiO2, and WO3 as well as their structural characterizations have been discussed. Photodegradation of organic pollutants through mentioned nanoparticles has been reviewed with recent advancements. Enhancing the efficacy of photocatalysis through doping of TiO2 and ZnO nanoparticles with non-metals, metals, and metal ions has also been documented in this report.

Climate change and pollution are the most vulnerable stressors that are anticipated increasingly to affect all living organisms including fishes. The aquatic ecosystems are the most affected ecosystem due to contamination and global increasing temperature. In view of the above, the present study delineates 96-h median lethal concentration of heavy metal, lead alone and in combination with high temperature (34 °C) by conducting static non-renewable acute toxicity bioassay in Pangasius hypophthalmus (average weight 3.65 ± 0.75 g). Further, the effect of different definitive doses (80, 82, 84, 86, 88 and 90 mg/L) of lead alone and high temperature on cellular metabolic response was probed. The LC50 of lead was found to be 84.93 mg/L, whereas in combination with high temperature it was 83.10 mg/L in P. hypophthalmus. Catalase, superoxide dismutase and glutathione-S-transferase were noticeably higher (p

Antioxidative status, cellular metabolic stress and neurotransmitter enzyme assay as a pollution biomarker in Oreochromis mossambicus collected from Bhima river were investigated. O. mossambicus was collected from 18 different sites of Bhima river, which differ in their extent and type of contamination load. The antioxidative status were determined such as catalase (CAT), superoxide dismutase (SOD) and glutathione-s-transferase (GST) in the liver, gill, brain, gonad and kidney. All the studied parameters indicated potent signals for contamination of the aquatic water body. The antioxidative status was substantially high (p

Vibrio species are the most dominant multidrug-resistant opportunistic bacterial pathogens in coastal aquaculture environments. There is an urgent need for biocontrol strategy to enhance commercially viable shrimp production. In the present study, eight strains of Bacillus were isolated and characterised from surface mucus of milk fish maintained in greenwater system and their antagonistic effects were evaluated against shrimp pathogenic bacteria Vibrio harveyi, by agar well diffusion and co-culture methods. Promising organisms were immobilised onto a matrix for preparation of bioaugmentor and again tested for antagonistic activity against V. harveyi.

In the present study, we have designed and synthesized a short compositionally simple peptide RY12WY having potent antimicrobial activity. The molecular docking study results showed that peptide has a strong affinity towards two protein targets of A. sobria; aerolysin and outer membrane protein (OMP). The MIC values ranged from 0.98 to 500 μM and MBC values ranged from 4 to 650 μM against the selected bacterial and fungal pathogens. The intense antimicrobial activity of RY12WY is reported against A. sobria, A. hydrophila, E. tarda, S. aureus, V. parahaemolyticus, P. aeruginosa and E.coli at low concentration.The peptide also showed good activity against A. salmonicida and S. parasitica zoospores. The peptide retained its antimicrobial activity at higher temperatures. Besides, it was active in the presence of physiological salts and serum.The peptide showed negligible haemolytic activity at 125 μM and HC50 was found to be 1437.10 μM. The DNA binding assay indicated that peptide can bind with the genetic material of the bacteria and may inhibit its replication. The bacterial viability assay reported that the peptide interferes with bacterial membrane integrity. To conclude, the results suggest that RY12WY could be a promising therapeutic agent in aquaculture and has possible application in food processing industry which warrants higher temperatures.

This study investigated 96h median lethal concentration of endosulfan (99%, pure α: β ratio of 7:3) by conducting static non-renewable acute toxicity bio-assay in Chanos chanos juvenile with average weight (110±5.65g). Further, the effect of different definitive doses (18.5, 19.5, 20.5, 21.5 and 22.5µg/L) of endosulfan on metabolic, heamato-immunoligcal and histopathological response were probed. Anti-oxidative enzymes CAT, SOD and GST showed significant (p

The amelioration effect of water-soluble vitamin pyridoxine against stress was evaluated in milkfish, Chanos chanos exposed to endosulfan. Two hundred and twenty-five fish were distributed randomly into five treatments, each with three replicates. Four isocaloric and isonitrogenous diets with graded levels of pyridoxine feed were as follows: normal water and fed with control diet (En0/PY0); endosulfan-treated water and fed with control diet (En/PY0); and endosulfan-treated water and fed with 50 (En/PY 50 mg/kg), 75 (En/PY 75 mg/kg) and 100 mg/kg (En/PY 100 mg/kg) pyridoxine-supplemented feed. The endosulfan in treated water was maintained at a level of 1/40th of LC50 (0.52 ppb). The effect of dietary pyridoxine supplementation was studied in terms of antioxidative enzymes (catalase, superoxide dismutase, glutathione-S-transferase), stress markers [heat-shock protein 70, caspase-3, cortisol, acetylcholine esterase (AChE), blood glucose], immunohaematological parameters (total protein, albumin, globulin and A/G ratio, nitroblue tetrazolium, RBC, WBC, Hb), gill histopathology and a subsequent challenge study with Vibrio parahaemolyticus. The antioxidative enzymes, stress markers, albumin and A/G ratio were significantly (p < 0.01) elevated, brain AChE and immunohaematological parameters were significantly (p < 0.01) decreased, and chromosome aberration and gill histopathology were also altered due to endosulfan exposure. The relative survival % was reduced due to the combined effect of endosulfan stress and bacterial challenge. Fish fed the diet supplemented with pyridoxine at 75 and 100 mg/kg was found to restore the studied parameter towards normal compared with control and indicated protection against endosulfan-induced stress significantly (p < 0.01). Results obtained in the present study indicate that the supplementation of 75 and 100 mg/kg of pyridoxine in the diet has a definitive role in the mitigation of the endosulfan-induced stress in milkfish, C. chanos fingerlings.

Halotolerant bacteria associated with Psoralea corylifolia L., a luxuriantly growing annual weed in salinity-affected semi-arid regions of western Maharashtra, India were evaluated for their plant growth-promoting activity in wheat. A total of 79 bacteria associated with different parts viz., root, shoot and nodule endophytes, rhizosphere, rhizoplane, and leaf epiphytes, were isolated and grouped based on their habitat. Twelve bacteria isolated for their potential in plant growth promotion were further selected for in vitro studies. Molecular identification showed the presence of the genera Bacillus, Pantoea, Marinobacterium, Acinetobacter, Enterobacter, Pseudomonas, Rhizobium, and Sinorhizobium (LC027447-53; LC027455; LC027457, LC027459, and LC128410). The phylogenetic studies along with carbon source utilization profiles using the Biolog® indicated the presence of novel species and the in planta studies revealed promising results under salinity stress. Whereas the nodule endophytes had minute plant growth-promoting (PGP) activity, the cell free culture filtrates of these strains enhanced seed germination of wheat (Triticum aestivum L). The maximum vigor index was monitored in isolate Y7 (Enterobacter sp strain NIASMVII). Indole acetic acid (IAA) production by the isolates ranged between 0.22 and 25.58 μg mL-1. This signifies the need of exploration of their individual metabolites for developing next-generation bio-inoculants through co-inoculation with other compatible microbes. This study has potential in utilization of the weed-associated microbiome in terms of alleviation of salinity stress in crop plants.

An attempt was made to assess the effect of dietary pyridoxine supplementation on growth performance and cellular metabolic enzymes of Chanos chanos fingerlings under endosulfan induced stress. Two-hundred and twenty-five fish were randomly distributed into five treatments, each with three replicates and fed four isocaloric and isonitrogenous diets with graded levels of pyridoxine for 45 days. Endosulfan concentration in the water was maintained at sublethal level of 1/40th of 96 h LC50 (0.52 ppb). Dietary pyridoxine supplementation significantly enhanced growth performance viz. weight gain (%), specific growth rate, feed conversion ratio and protein efficiency ratio of fish compared to control diet fed group. The results of this experiment revealed that the activities of digestive and metabolic enzymes were significantly improved after feeding with dietary pyridoxine supplementation in C. chanos. Significantly increased muscle and brain ascorbic acid content was observed in fish fed diets containing pyridoxine. Histological studies on liver of fish fed pyridoxine-supplemented diet showed the normal architecture of hepatocytes compared to non-pyridoxine fed group. The results obtained in this study revealed that the inclusion of pyridoxine in diet has a protective effect against endosulfan induced stress in C. chanos fingerlings through metabolic enzyme activities and vitamin C content. This study has a potential in ameliorating the toxic effect of endosulfan induced stress using dietary supplementation of pyridoxine.

The present study delineate the various biochemical and histopathological tool to evaluate as strong biomarker in the field condition for detection of the least and maximize level of pollution and contamination. We have collected Labeo rohita from 13 different sites from East Kolkata wetland to determine biochemical and histopathological status to analyse metal contamination in the significant biological hot spot EKW. The biochemical marker as antioxidative status, i.e., catalase, superoxide dismutase (SOD), and glutathione-S-transferase (GST) in liver and gill, were remarkably higher (p 0.01) at some of the sampling sites, but catalase in brain, SOD in kidney, GST in brain and kidney, and neurotransmitter as acetylcholine esterase (AChE) in brain were not significant (p 0.05) among the sampling sites. The glycolytic enzymes, such as lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) in liver, gill, and muscle, and protein metabolic enzymes, such as alanine amino transferase (ALT) and aspartate amino transferase (AST) in liver, gill, muscle, and kidney, were noticeably higher (p 0.01) at some of the sampling sites. The histopathology of the liver and gill were altered at different sampling sites, such as blood congestion, leucocyte infiltration with parenchymal vacuolisation, nucleus with blood vessels, hepatocytes granular degeneration, haemorrhage, karyorrhexis, shrink nucleus, and pyknotic nuclei in liver. In the gill, structural changes, such as complete destruction and shortening of secondary gill lamellae, blood vessel in gill arch, curling of secondary gill lamellae, aneurism in gill lamellae, and neoplasia, were observed. Most of the metals were found within the safe limit all along the 13 sampling sites, indicating that fishes are safe for the consumption. Based on our finding, we could recommend that a rational application of biochemical profiles, such as oxidative and metabolic stress parameters, including histopathology to be used as biomarkers for biomonitoring the metal contamination in the aquatic environment.

Unexpected fluctuations in weather parameters due to global climate change have been observed in all ecosystems worldwide. The aquatic ecosystem shelters a great diversity of fishes in the upper region of the ecosystem which adversely get affected due to their poikilothermic nature. The present study was designed to elucidate the impact of critical temperature minima (CTMin), lethal temperature minima (LTMin), critical temperature maxima (CTMax), and lethal temperature maxima (LTMax) on Channa striatus. Biologically synthesized silver nanoparticles (Ag-NPs) were evaluated for their potential to enhance thermal tolerance and improve the activities of biochemical enzymes of C. striatus reared under lead (Pb) and high temperature (34 °C) for 50 days. Three iso-caloric and iso-nitrogenous diets which included a basal diet and two supplemented diets with Ag-NPs @ 0.5 mg/kg, and 1 mg/kg were used in the study. Results suggested that CTMin and LTMin were significantly (p 0.01) reduced and CTMax and LTMax were enhanced in the group fed with 0.5 mg/kg Ag-NPs supplemented feed. Pre-exposure to high temperature led to enhanced CTMax and LTMax in C. striatus. The biochemical enzymes involved in protein metabolism, carbohydrate metabolism, acetylcholine esterase and antioxidant activities were found to be normal in fish fed with 0.5 mg/kg Ag-NPs supplemented diet. Bioaccumulation of silver and Pb was determined in different fish tissues and experimental water. Overall, the incorporation of Ag-NPs at 0.5 mg/kg in diet can confer protection to fish against Pb and thermal stress and enhance thermal tolerance of C. striatus.

Inland waterbodies are environmentally impacted with the wastes generated through industries and domestic sewage resulting in pollution and complex ecosystem changes. Sustainable green technology has been emerging as an important tool for remediation of perturbed waterbodies as well as wastewater-fed aquaculture ponds. Various methods for bioremediation such as biostimulation, bioaugmentation, plant-based-assisted bioremediation, phytoremediation, biofilm-/periphyton-based bioremediation, biofloc technology, biodegradation, biotransformation, nano(bio)-remediation, enzymatic bioremediation/recombinant DNA technology, biosorption and nutriremediation for alleviation of the contamination in waterbodies have been discussed. In addition, improved technology interventions in terms of abiotic and biotic stress management, environmental enhancement, stock enhancement/replenishment, species enhancement/selection of the right species, environmentally sound enclosure culture technologies, management enhancement and integrated multi-trophic aquaculture have been explored.

In recent years, metagenomics has emerged as a powerful tool for mining of hidden microbial treasure in a culture independent manner. In the last two decades, metagenomics has been applied extensively to exploit concealed potential of microbial communities from almost all sorts of habitats. A brief historic progress made over the period is discussed in terms of origin of metagenomics to its current state and also the discovery of novel biological functions of commercial importance from metagenomes of diverse habitats. The present review also highlights the paradigm shift of metagenomics from basic study of community composition to insight into the microbial community dynamics for harnessing the full potential of uncultured microbes with more emphasis on the implication of breakthrough developments, namely, Next Generation Sequencing, advanced bioinformatics tools, and systems biology.

The aim of this work was to define the bioaccumulation mechanism of metals onto the non-living biomaterial prepared from an extensively available plant bark biomass of neem (Azadirachta indica). Based on maximum ultimate fixation capacities (mmol/g) of the product, metals ions could be arranged as Hg(2+) < Cd(2+) < Pb(2+) ≅ Cu(2+). Surface properties of the biomaterial were characterized by X-ray photoelectron spectroscopy and X-ray diffraction techniques for their sorption mechanism. Whewellite (C2CaO4 · H2O) was identified in the biomaterial, which indicated that calcium ions are electrovalently bonded with carboxylate ions facilitating the ion exchange mechanism with metal ions. Bioaccumulation of metal ions was also studied by Fourier transform infrared spectroscopy, which indicated the presence of functional groups implicated in adsorbing metal ions. Biomaterial did not adsorb anionic As(III), As(V) and Cr(VI), because of their electrostatic repulsion with carboxylic functional groups. Neem bark can be used as bioindicators, bioaccumulators and biomonitors while determining environmental pressures. Metal bioaccumulative properties and structural investigation of plant bark has potential in providing quantitative information on the metal contamination in the surrounding environment.

The authors have reported the use of nanopolymers for the inhibition of shrimp pathogenic bacteria for aquaculture use. The antimicrobial activity of polyethylene glycols based amphiphilic polymers have different linker molecules such as suberic acid, adipic acid, glutaric acid and dimethyl-5-hydroxyisophthalate on Vibrio harveyi. It was examined by drawing growth curves using optical density measurements. Concentration dependent antimicrobial effects of nanopolymers were tested against V. harveyi which were further confirmed by agar well diffusion for determining minimum inhibitory concentra- tions. The increased concentrations of nanopolymer ef- fectively reduced the bacterial growth and increased the diameter of inhibition zone. This study has important im- plications for disease management in coastal aquaculture.

Endosulfan is an organochlorine pesticide commonly found in aquatic environments that has been found to reduce thermal tolerance of fish. Lipotropes such as the food additive, Lecithin has been shown to improve thermal tolerance in fish species. This study was conducted to evaluate the role of lipotropes (lecithin) for enhancing the thermal tolerance of Chanos chanos reared under sublethal low dose endosulfan-induced stress. Two hundred and twenty-five fish were distributed randomly into five treatments, each with three replicates. Four isocaloric and isonitrogenous diets were prepared with graded levels of lecithin: normal water and fed with control diet (En0/L0), endosulfan-treated water and fed with control diet (En/L0), endosulfan-treated water and fed with 1% (En/L1%), 1.5% (En/L 1.5%) and 2% (En/L 2%) lecithin supplemented feed. The endosulfan in treated water was maintained at the level of 1/40th of LC50 (0.52ppb). At the end of the five weeks, critical temperature maxima (CTmax), lethal temperature maxima (LTmax), critical temperature minima (CTmin) and lethal temperature minima (LTmin) were Determined. There was a significant (P0.01) effect of dietary lecithin on temperature tolerance (CTmax, LTmax, CTmin and LTmin) of the groups fed with 1, 1.5 and 2% lecithin-supplemented diet compared to control and endosulfan-exposed groups. Positive correlations were observed between CT max and LTmax (R(2)=0.934) as well as between CTmin and LTmin (R(2)=0.9313). At the end of the thermal tolerance study, endosulfan-induced changes in cellular stress enzymes (Catalase, SOD and GST in liver and gill and neurotansmitter enzyme, brain AChE) were significantly (p0.01) improved by dietary lecithin. We herein report the role of lecithin in enhancing the thermal tolerance and protection against cellular stress in fish exposed to an organochlorine pesticide.

Global warming due to increasing temperature and contamination in aquatic environment has been found to be inducing cellular metabolic stress in fish. The present study focused on temperature and contamination in aquatic ecosystems and its alleviation/mitigation. Hence, this study was conducted to evaluate the role of zinc to improve growth performance, cellular metabolic stress, and digestive enzymes of the Pangasianodon hypophthalmus reared under lead (Pb) and high temperature. Two hundred and seventy-three fishes were distributed randomly into seven treatments, each with three replicates. Three isocaloric and isonitrogenous diets with graded levels of zinc at 0 mg/kg, 10 mg/kg, and 20 mg/kg were prepared. The Pb in treated water was maintained at the level of 1/21th of LC50 (4 ppm) and maintained at a temperature of 34 °C in exposure groups. The growth performance in terms of weight gain (%), protein efficiency ratio (PER), and specific growth rate (SGR) was found to be inhibited, and the feed conversion ratio (FCR) was enhanced in the Pb and high temperature–exposed group, whereas zinc supplementation has improved weight gain (%), FCR, PER, and SGR. The liver, gill, muscle, and kidney tissues of carbohydrate metabolic enzymes (LDH and MDH), protein metabolic enzymes (ALT and AST), and liver, gill, and muscle G6PDH and ATPase as well as intestinal digestives enzymes (proteases, amylase, and lipase) and intestinal ALP were significantly affected (p < 0.01) by Pb and high temperature exposure to P. hypophthalmus. We herein report the role of zinc in mitigating cellular metabolic stress in fish exposed to Pb and high temperature.

Zinc is one of the essential micronutrients that can be obtained via water and diet in aquatic animals to meet their physiological needs. The present study was designed to understand the effect of the supplementation of zinc nanoparticles (Zn-NPs) in mitigating abiotic and biotic stress in Pangasius hypophthalmus. Two zinc nanoparticle-incorporated diets with 10 and 20 mg/kg nanoparticles and a control without zinc nanoparticles were formulated. To study the effect of formulated feeds on stress tolerance, fish were exposed to sublethal dose (4 ppm) of Pb (lead) and temperature at 34 °C. Two hundred and seventy-three fish were randomly distributed into seven treatment groups in triplicates, namely a control group (no Zn-NPs and no Pb and temperature exposure, Ctr/Ctr), control diet fed and exposed to Pb (Ctr/Pb), control diet fed and concurrently exposed to Pb and temperature (Pb-T/Ctr), and Zn-NPs 10 and 20 mg/kg diet with or without stressors (Zn-NPs 10 mg/kg, Zn-NPs 20 mg/kg, Pb-T/Zn-NPs 10 mg/kg, Pb-T/Zn-NPs 20 mg/kg). The effect of Zn-NPs on growth performance, stress biomarkers, biochemical and immunological responses, and survival of P. hypophthalmus following challenge with pathogenic bacteria were evaluated. The growth performance was noticeably (p

There is strong relation between nutrition and thermal tolerance of fish in terms of improved critical temperature minima (CTmin), lethal temperature minima (LTmin), critical temperature maxima (CTmax), and lethal temperature maxima (LTmax). Fishes act as quantifying indicators of the climate change due to their critical thermal limits in nature and ability to adjust thermal sensitivity to maintain their homeostasis. In the present study, biologically synthesised selenium nanoparticles (Se-NPs) from fisheries waste (fish gill) were used to evaluate its efficacy for enhancement of thermal tolerance of Pangasius hypophthalmus reared under lead (Pb) and high temperature (34°C) for 72days. At the end of the experimental period, CTmin, LTmin, and CTmax, LTmax and cellular metabolic stress were evaluated. The CTmin, LTmin were noticeably (p

Recent studies have demonstrated that selenium (Se) and selenium nanoparticles (Se-NPs) exhibited toxicity at a higher concentration. The lethal concentration of Se and Se-NPs was estimated as 5.29 and 3.97 mg/L at 96 h in Pangasius hypophthalmus. However, the effect of different definite concentration of Se (4.5, 5.0, 5.5, and 6.0 mg/L) and Se-NPs (2.5, 3.0, 3.5, and 4.0 mg/L) was decided for acute experiment. Selenium and Se-NPs alter the biochemical attributes such as anti-oxidative status [catalase (CAT), superoxide dismutase (SOD), and glutathione-S-transferase (GST) activities], neurotransmitter enzyme, cellular metabolic enzymes, stress marker, and histopathology of P. hypophthalmus in a dose- and time-dependent manner. CAT, SOD, and GST were significantly elevated (p

Nanotechnology is a novel arena with promising applications in the field of medicine, industry, and agriculture including fisheries. Cross-disciplinary interactions and the application of this technology in biological systems have led to the innovation of novel nanoparticle antioxidants, which are the subject of our study. In context with above background, we designed an experiment on nano-silver to elucidate its role for mitigation of abiotic and biotic stress. Three diets were formulated viz. silver nanoparticles (Ag-NPs) incorporated at 0.5 and 1 mg/kg diet and control diet (Ag-NPs at 0 mg/kg). Fish were exposed to sublethal level of 1/25th of LC50 (4 ppm) of lead (Pb) and temperature at 34 °C. The effect of Ag-NPs on productive performance (weight gain %, feed conversion ratio, protein efficiency ratio, and specific growth rate), stress biomarkers (catalase, super oxide dismutase, glutathione-s-transferase, acetylcholine esterase, cortisol, heat shock protein), biochemical and immunological response (protein and carbohydrate metabolic enzymes, phagocytic activity, serum total protein and albumin: globulin ratio), histopathology alterations in the liver and gill as well as survival of Channa striatus, following challenge with pathogenic bacteria were evaluated. Dietary Ag-NPs at 0.5-mg supplementation improved growth performance, immunity, survival, and reduced stress biomarker such as HSP 70, cortisol, and blood glucose in various fish tissues. Exposure to Pb and high temperature and group fed with Ag-NPs (1 mg/kg diet) demonstrated remarkable changes in the histo-architect of liver such as pyknotic nuclei, pyknosis, leucocyte infiltration, hemorrhage and karyokinesis, blood vessels with nucleated, lipid vacuoles in the liver tissue. Histology of gill displayed hyperplasia, aneurism, blood congestion, severe telengiectiasis, epithelial lifting, curling of secondary lamella, hyperplasia of epithelial cell of secondary lamella in the group exposed to lead and high temperature and supplemented with Ag-NPs at 1 mg/kg diet. In addition to histopathology, feeding with Ag-NPs at 1 mg/kg diet deteriorated and altered all studied parameters including reduced growth performance. Results obtained in the present study suggest that supplementation of Ag-NPs at 0.5 mg/kg diet has a definitive role to play in the mitigation of abiotic and biotic stress in C. striatus.

The concentrations of 14 metals, namely, chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), selenium (Se), arsenic (As), strontium (Sr), cadmium (Cd), tin (Sn), antimony (Sb), mercury, (Hg), and lead (Pb), have been studied in freshwater mollusk Lamellidens marginalis collected from Dhimbe reservoir. In addition, also studied the cellular and antioxidative status to assess metal contamination as pollution biomarkers. The levels of all the 14 metals were elevated in different sampling sites of Dhimbe reservoir. The level of metals in the L. marginalis was followed as Mn > Zn > Ni > Sr > Cr > Cu > Hg > Se > Sn > Pb > As > Co > Cd > Sb. The oxidative biomarkers viz. catalase (CAT), superoxide dismutase (SOD), and glutathione-S-transferase (GST); glycolytic enzymes viz. lactate dehydrogenase (LDH) and malate dehydrogenase (MDH); and protein metabolic enzymes viz. aspartate amino transferase (AST), alanine amino transferase (ALT), and lipid peroxidation (LPO) were significantly (p

Determination of early life stages of fish for thermal tolerance, optimum temperature for growth, rate of oxygen consumption is becoming essential for aquaculture industry in the climate change scenario due to long-term and short term (seasonal and diurnal) variability in temperature. Emphasis was made to understand the response of early of rohu (0.09 to 0.1 g) to thermal acclimation. Three hundred early fry stage rohu, Labeo rohita (initial weight 0.097±0.01 g) were equally distributed at four different temperatures (28, 30, 32 and 34°C) each with three replicates for a period of 40 days. Highest body weight gain was between 30 and 32°C and lowest feed conversion ratio (FCR) was at 30°C. The percentage weight gain and specific growth rate at 30°C were 382±8.01 and 0.88±0.03% respectively, significantly higher than other acclimation temperatures. Thermal tolerance and oxygen consumption rate were analyzed to determine the temperature tolerance limits and metabolic activity at four acclimation temperatures. Critical thermal maxima (CTmax) was 42.86±0.04, 43.3±0.02, 44.45±0.02 and 45.42±0.03; critical thermal minima (CTmin) was 13.07±0.04, 14.35±0.02, 14.92±0.04 and 15.64±0.03 and oxygen consumption rate was 110.75±0.44, 126.57±0.60, 146.22±0.68, 166.47±0.86 mgO2 kg-1h-1 at 28, 30, 32 and 34°C respectively and increased with increasing acclimation temperatures. Oxygen consumption rate for four acclimatization temperatures increased significantly, 110.75±0.44, 126.57±0.60, 146.22±0.68, 166.47±0.86 mgO2 kg-1h-1 at 28, 30, 32 and 34°C respectively. Temperature preference of the early fry of rohu derived from relationship between acclimation temperatures and Q10 values for 28 to 30°C, 30 to 32°C, 32 to 34°C were 1.94, 2.05, and 1.91 respectively. The optimum temperature range for growth was 30 to 32°C and Q10 value was 32 to 34°C. Survival at different acclimation temperatures was between 98.7±2.31, 96.0±4.0, 93.3±2.31 and 94.7±4.62%, from lower to higher acclimation temperatures. Key words: Acclimation temperature, critical temperature, critical thermal maxima (CTmax), critical thermal minima (CTmin), Labeo rohita.

Silver is a noble metal with antique values and antimicrobial property. Being its colloidal form, silver nanoparticles have wide commercial application. They are being used extensively in the aquaculture industry. Considering their dumping and leaching in water, experiments were conducted to estimate their toxicity on zebrafish (Danio rerio). Silver nanoparticles were synthesized using sodium borohydrate (chemical synthesis) and Guava (Psidium guajava) leaf-extract (biological synthesis) as reductants. UV–Visible spectroscopy exhibited a confirmatory surface plasmonic range of 390–410 nm and transmission electron microscopy data projected a homogenous, round (11–45 nm) and polygonal (17–40 nm) particles of the silver nanoparticles synthesized in chemical and phyto-synthesis routes respectively. Acute toxicity study of these chemicals was conducted in static bioassay method. 96 h LD50 dose for silver nitrate was 100 μg l−1 where as it was 80 and 400 μg l−1 for chemically and biologically synthesized silver nanoparticles respectively. The calculated safe concentration values in water were 0.020, 0.033 and 0.153 mg l−1 for silver nitrate, chemically synthesized nanoparticles and biologically synthesized silver nanoparticles respectively. These candidate chemicals had not influenced any significant alterations in water quality. Current investigations confer that chemically synthesized silver nanoparticles are more toxic than silver nitrate to zebrafish. Biologically synthesized silver nanoparticles are least toxic among all. These trends of impact were also evaluated and reconfirmed through histological assessment of ovarian tissue at sublethal dose (1/10 th of LD50 value). Thus, the potentiality of plant derived nanoparticles should be investigated in different fish models for their sustainable application in aquaculture and water technology.

The abiotic and biotic stress is an episode that effect on regulatory, neuro-endocrine and immune systems of animals including fish. The stress creates stimulatory and suppressive of immune system resulting in increases the incidence of infection. In view of these points, we have conducted an experiment to mitigate the stress through a nutritional approach through Zinc (Zn) supplementation in Pangasius hypophthalmus (initial weight-3.65 ± 0.75 g). Three isocaloric and isonitrogenous diets with graded levels of zinc 0, 10 and 20 mg/kg were prepared and fed to seven different groups with each in triplicate. The experimental group as follows as normal water with control diet (Ctr/Ctr), lead (Pb) exposed and fed with control diet (Ctr/Pb), control diet and exposed to Pb and temperature (Ctr/Pb-T), Zn 10 mg/kg fed without stressors (Zn- 10 mg/kg), Zn 20 mg/kg fed without stressors (Zn-20 mg/kg), Zn 10 mg/kg fed and Pb and temperature exposed (Pb-T/Zn 10 mg/kg) and Zn 20 mg/kg fed and exposed to Pb and temperature (Pb-T/Zn 20 mg/kg). The Pb in treated water was maintained at the level of 1/20th of LC50 (4 ppm) and temperature at 34 °C in exposure groups. The neutraceuticals role of dietary Zn was studied in terms of antioxidative enzymes (catalase, superoxide dismutase, glutathione-S-transferase), stress markers (Heat shock protein 70, cortisol, acetylcholine esterase, blood glucose, Vitamin C), immunological parameters (Total protein, albumin, globulin, A/G ratio and NBT) and subsequent challenge with Aeromonas veronii biovar sobria. The antioxidative enzymes, stress markers, albumin were significantly (p

In the present study, we have analyzed various biochemical and histopathological biomarkers in the Oreochromis mossambicus collected from 18 sites at Bhima River. The biochemical biomarkers viz. antioxidative enzymes in muscle viz. catalase, SOD, and GST, glycolytic enzymes in kidney viz. LDH and MDH, protein metabolic enzymes in liver, gill, brain, gonad and muscle viz. ALT and AST, neurotransmitter enzymes in muscle AChE, lipid peroxidation and histopathology in the liver and gill have been evaluated. The oxidative biomarkers, glycolytic enzymes, protein metabolic enzymes and lipid peroxidation were significantly (p

We herein report the protective role of pyridoxine in enhancing thermal tolerance of Milkfish Chanos chanos reared under endosulfan-induced stress. Four isocaloric and isonitrogenous diets were prepared with graded levels of pyridoxine (0, 50, 75 and 100 mg/kg). Two hundred and twenty five fishes were randomly distributed into four treatment groups in triplicate, reared under endosulfan-treated water, which were fed with pyridoxine supplemented diet, while the negative control group was reared without endosulfan-treatment and control fed. The concentration of endosulfan in treated water was maintained at a level of 1/40th of LC50 i.e. 0.52 μg/L. Dietary pyridoxine supplementation had significant (p 0.01) effect on temperature tolerance viz. CTmax (Critical temperature maxima), LTmax (Lethal temperature maxima), CTmin (Critical temperature minima) and LTmin (Lethal temperature minima) of milkfish. The positive correlation was observed between CT max and LTmax (Y = -1.54 + 15.6x, R(2), 0.943) as well as CTmin and LTmin (Y = -1.44 + 1.021x, R(2), 0.941). At the end of the thermal tolerance study, antioxidative status and HSP 70 were significantly reduced in pyridoxine supplemented groups, whereas brain AChE was significantly (p 0.01) elevated compared to positive and negative control. It is concluded that CTmax, LTmax, CTmin and LTmin, antioxidative status, neurotransmitter enzyme and HSP 70 strengthened the enhancement of thermal tolerance of Milkfish.

Agricultural and industrial practices more than doubled the intrinsic rate of terrestrial N fixation over the past century with drastic consequences, including increased atmospheric nitrous oxide (N 2 O) concentrations. N 2 O is a potent greenhouse gas and contributor to ozone layer destruction, and its release from fixed N is almost entirely controlled by microbial activities. Mitigation of N 2 O emissions to the atmosphere has been attributed exclusively to denitrifiers possessing NosZ, the enzyme system catalyzing N 2 O to N 2 reduction. We demonstrate that diverse microbial taxa possess divergent nos clusters with genes that are related yet evolutionarily distinct from the typical nos genes of denitirifers. nos clusters with atypical nosZ occur in Bacteria and Archaea that denitrify (44% of genomes), do not possess other denitrification genes (56%), or perform dissimilatory nitrate reduction to ammonium (DNRA; (31%). Experiments with the DNRA soil bacterium Anaeromyxobacter dehalogenans demonstrated that the atypical NosZ is an effective N 2 O reductase, and PCR-based surveys suggested that atypical nosZ are abundant in terrestrial environments. Bioinformatic analyses revealed that atypical nos clusters possess distinctive regulatory and functional components (e.g., Sec vs. Tat secretion pathway in typical nos ), and that previous nosZ -targeted PCR primers do not capture the atypical nosZ diversity. Collectively, our results suggest that nondenitrifying populations with a broad range of metabolisms and habitats are potentially significant contributors to N 2 O consumption. Apparently, a large, previously unrecognized group of environmental nosZ has not been accounted for, and characterizing their contributions to N 2 O consumption will advance understanding of the ecological controls on N 2 O emissions and lead to refined greenhouse gas flux models.

The antimicrobial activity of silver-zeolite against Escherichia coli , Vibrio harveyi , Vibrio cholerae and Vibrio parahaemolyticus was examined in liquid medium and agar well diffusion assays. The minimum inhibitory concentration for silver ion-exchanged zeolite against E. coli and V. harveyi was 40 μg/ml, and 50–60 μg/ml for V. cholerae and V. parahaemolyticus . The diameter of the inhibition zones for E. coli , V. harveyi , V. cholerae and V. parahaemolyticus , respectively, increased from 0.5 to 2.3 cm, 0.6 to 2.4 cm, 0.3 to 1.65 cm and 0.3 to 1.7 cm with increasing concentrations of silver ion-exchanged zeolite from 10 to 400 μg. Silver-zeolite removed 20–37% ammonia from aqueous solutions. This study suggests that silver ion-exchanged zeolite could impact disease and environmental management in shrimp aquaculture.

Soil and water interactions and their influence on growth and production in different densities (SD8 & SD16) under zero water exchange were studied in two successive crops of Penaeus monodon in Tamil Nadu, India during 2007 and 2008. Scraping and tilling during pond preparation increased the mineralization rate than scraping only. During crop, there was no significant difference in soil organic carbon and total nitrogen between the SDs. However, as the crop progressed, organic carbon and total nitrogen content of the soil showed significant difference under both the SDs. Between the SDs, nitrate and phosphate content in water significantly differed, whereas the progress of the crop significantly increased both available and total nutrients. Mass balance of nitrogen indicated that applied feed contributed to 97.4–98.5% of input nitrogen, of which nitrogen in sediment accounted for 16.5–27.3%, nitrogen recovery in shrimp was 34.2–43.6% and the nitrogen lost through denitrification and volatilization varied from 4.7% to 34.7%. Zero water exchange system is highly efficient as nitrogen recovery is higher in shrimp and lower in discharge water. Lack of significant difference in metabolites between the SDs indicates the role of aeration and probiotics in sustaining SD16 cultures.

Molecular techniques based on sequencing of metagenomic clone libraries provide an insight into the diversity of microbial populations. Using nucleic acid-based methods, the diversity of soxB genes was examined to detect and characterize sulphur-oxidizing bacteria in Indian coastal aquaculture environments. Gene-specific degenerate primers were used to amplify various fragments (710, 753, 483–503, 280 and 239 bp) of soxB genes. Metagenomic clone libraries were constructed for 753, 483–503 and 239 bp fragments of soxB genes. The abundance of soxB revealed the presence of sulphur-oxidizing organisms. Amino acids in parts of the soxB-encoded proteins were aligned to known conserved amino acid residues. The level of conservation ranged from 23% to 30%. A phylogenetic tree constructed from aligned amino acid sequences of SoxB revealed different clusters associated with the branches of phototrophic α- and γ-proteobacteria. In general, soxB is widespread among the various phylogenetic groups, although this does not necessarily mean that the organism can use sulphur compounds. Our results suggest that the chemolithoautotrophy based on sulphur oxidation in coastal aquaculture is primarily sustained by the presence of sulphur oxidizers, which involve the soxB gene. This study aids identification of the phylogenetic characteristics related to sulphur bioremediation in poorly characterized coastal aquaculture environments.

There is a need to quantify autotrophic nitrifiers in coastal aquaculture systems for evolving a bioremediation strategy. Autotrophic nitrifiers are extremely slow-growing organisms, which cannot be detected by traditional methods as they are notoriously difficult to culture. Molecular techniques based on functional genes could be deployed for the detection of nitrifiers. Ammonia monooxygenase (amoA), that catalyses the oxidation of ammonia to hydroxylamine in the rate-determining step of nitrification is largely unique to ammonia-oxidizing bacteria (AOB). In the present study, a quantitative real-time polymerase chain reaction assay targeting amoA was developed to estimate AOB population size in coastal soil, ammonia-removing bioaugmentors and the solid matrix. To achieve this objective, different set of primers and a dual labelled probe have been designed for SYBR Green and TaqMan real-time assays. The abundance of AOB ranged from 104 to 106 order of magnitude in the samples. In the present study, biofilm formation of the consortium of nitrifying bacteria onto bagasse has also been quantified. The results demonstrate that the developed method is a rapid and sensitive tool for the quantitative detection of nitrifying bacteria in aquatic and related environment. This helps in making the bioremediation approach for ammonia removal by immobilization of nitrifying bacteria onto the natural substrate.

Nucleic acid methods based on sequencing of clone libraries provide sequence and the phylogenetic information of an individual clone. In the present study, ammonia monooxygenase (amoA), nitrite-oxido-reductase(norB), nitrite reductase (nirS) and nitrous oxide reductase (nosZ) genes are chosen to detect nitrifiers and denitrifiers in coastal aquaculture using gene-specific primers. The abundance of these functional genes revealed the presence of nitrifying and denitrifying organisms in coastal aquaculture. Nitrifying and denitrifying communities were analyzed by parallel DNA extractions and clone library construction for amoA, norB, nirS and nosZ obtained from coastal aquaculture soil. Amino acids in parts of the amoA, norB, nirS and nosZ encoded proteins were aligned to know conserved amino acid residues. The amoA genes exhibited 81–82% identity to Nitrosomonas europaea, Nitrosococcus mobilis and Nitrosomonas eutropha which were also similar to particulate methane monooxygenase (pmoA) gene sequences. The norB genes are closely affiliated with Nitrobacter winogradskyi and other uncultured beta-proteobacteria. The nosZ genes exhibited 78–82% identity with Marinobacter sp. and other uncultured denitrifying gamma-proteobacteria. The present study could be useful for making bioremediation strategy for nitrogenous metabolites and understanding of nitrogen fluxes generated through these two functional groups in coastal shrimp aquaculture.

Reduced sulfur compounds produced by the metabolism are the one of the major problems in aquaculture. In the present study, herbivorous fishes have been cultured as biomanipulators for secretions of slime, which enhanced the production of greenwater containing beneficial bacteria. The genes encoding soxB which is largely unique to sulfur-oxidizing bacteria (SOB) due to its hydrolytic function has been targeted for examining the diversity of SOB in the green water system of coastal aquaculture. Novel sequences obtained based on the sequencing of metagenomic clone libraries for soxB genes revealed the abundance of SOB in green water system. Phylogenetic tree constructed from aligned amino acid sequences demonstrated that different clusters have only 82-93% match with Roseobacter sp., Phaeobacter sp., Roseovarius sp., Sulfitobacter sp., Ruegeria sp., and Oceanibulbus sp. The level of conservation of the soxB amino acid sequences ranged from 42% to 71%. 16S rRNA gene analyses of enrichment culture from green water system revealed the presence of Pseudoxanthomonas sp., which has 97% similarity with nutritionally fastidious Indian strain of Pseudoxanthomonas mexicana-a sulfur chemolithotrophic gamma-proteobacterium. Our results illustrate the relevance of SOB in the functioning of the green water system of coastal shrimp aquaculture for oxidation of reduced sulfur compounds, which in turn maintain the sulfide concentration well within the prescribed safe levels.

In the present study, molecular methods based on sequencing of clone libraries have been used to provide sequence and the phylogenetic information of ammonia oxidizing bacteria (AOB). Ammonia monooxygenase (amoA) gene, which catalyzed the oxidation of ammonia to hydroxyl amine in the initial rate-determining step of nitrification was targeted for detection and characterization of AOB using gene-specific primers. The amoA genes obtained through the clone library construction are closely affiliated with Nitrosomonas sp. and other uncultured beta proteobacteria. The levels of nucleotide similarity and amino acid similarity ranged from 85-99% and 83-88%, respectively. The level of conservation of the amino acid sequences is 73%. The use of a matrix prepared from abundantly available lignocellulosic agrowaste-bagasse has successfully been demonstrated for biostimulation of AOB in aquaculture environment by supplementing nutritional requirement facilitating the biofilm mode of growth of the autotrophic consortia. Present study is useful in predictability and reliability of the treatment of ammonia in brackishwater aquaculture.