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 LC
50
(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.
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 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 (C
2
CaO
4
·H
2
O) 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 Ca
2+
bonded with carboxylate moieties. For both the bioadsorbents, the Pb
2+
, Cu
2+
, and Cd
2+
are biosorbed completely by ion exchange with Ca
2+
(89–94%) and Mg
2+
(7–12%), whereas Hg
2+
is biosorbed partially (57–66%) by ion exchange with Ca
2+
(38–42%) and Mg
2+
(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.
In this work, herbivorous fish
Mugil cephalus
has been cultured to secrete protein rich green slime, which helps nitrifying and oxygen tolerant denitrifying bacteria to grow and colonize. Four ...strains representing
Alcaligenaceae
family have been isolated from greenwater system and characterized using biochemical test, fatty acid methyl ester (GC-FAME) analysis, 16S rRNA and functional gene approaches. They were tested for an ability to nitrify ammonia and nitrite aerobically. Two strains showed notable nitrification activity, when grown in a mineral salts medium containing ammonium sulfate and potassium nitrite. Functional gene analysis confirmed the presence of nitrous oxide reductase (
nosZ
) gene showing that they have an oxygen-tolerant denitrification system. It has been proposed that
Alcaligenes faecalis
strains heterotrophically nitrify ammonia into nitrite via formation of hydroxyl amine, which is oxidized to nitrous oxide using oxygen or nitrite as electron acceptor. These results provide a possible advantage of having nitrification and denitrification capabilities in the same organism, which plays an important role in biological wastewater system.
Abstract
Climate change is an inevitable event that obstructs the output of aquaculture farms and culture-based fisheries in open waters. It poses a serious threat to global food security, altering ...biodiversity, ecosystems, and global fish output by displacing fish stocks from their natural habitats. When compared to freshwater aquaculture, marine/coastal aquaculture is more affected. To combat the effects of climate change, several mitigation methods and adaptations are being implemented, emphasizing future demands of affordable protein. Selective breeding, species diversification, and aquaculture systems like integrated multi-trophic aquaculture, aquaponics, and recirculating aquaculture system are some of the most widely accepted and adapted solutions. Further research on intervention in seed and feed in terms of quality improvement, bioresource utilization, and technological and genetic improvement is required. Climate change policies from the government are also essential. The present study differs from previous reviews by portraying the various abiotic stress factors contributing to the drastic climate change, encompassing adaptation strategies followed in distinct aquaculture sources such as freshwater, inland saline water, brackish water, coastal waters, and culture-based capture fisheries with its future implications.
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
< 0.01) when exposed to Se and Se-NPs, and similarly, a neurotransmitter enzyme (acetylcholine esterase (AChE)) was significantly inhibited in a time- and dose-dependent manner. Further, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and malate hydrogenase were noticeably (
p
< 0.01) affected by Se and Se-NPs from higher concentration to lower concentration. Stress markers such as cortisol and HSP 70 were drastically enhanced by exposure to Se and Se-NPs. All the cellular metabolic and stress marker parameters were elevated which might be due to hyperaccumulation of Se and Se-NPs in the vital organ and target tissues. The histopathology of liver and gill was also altered such as large vacuole, cloudy swelling, focal necrosis, interstitial edema, necrosis in liver, and thickening of primary lamellae epithelium and curling of secondary lamellae due to Se and Se-NP exposure. The study suggested that essential trace element in both forms (inorganic and nano) at higher concentration in acute exposure of Se and Se-NPs led to pronounced deleterious alteration on histopathology and cellular and metabolic activities of
P. hypophthalmus.
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
< 0.01) enhanced, and anti-oxidative stress (catalase, superoxide dismutase, and glutathione-s-transferase) significantly reduced in the Zn-NPs supplemented groups. Similarly, immunological parameters such as total protein, albumin, globulin, and A/G ratio significantly improved, and stress biomarkers such as blood glucose, cortisol, and HSP 70 were reduced in Zn-NPs supplemented groups. Overall, the results suggest that supplementation of dietary Zn-NPs with less concentration in the diet has a definitive role in the mitigation of abiotic and biotic stress in
P. hypophthalmus
.
A 120 days' experiment was conducted in a hybrid biofloc-RAS culture system with varied stocking densities of Nile tilapia (Oreochromis niloticus) viz., 150 fish/m3 (HBR-150), 200 fish/m3 (HBR-200), ...250 fish/m3 (HBR-250) and 300 fish/m3 (HBR-300) in triplicates. The average initial weight of Nile tilapia was 4.79 ± 0.05 g. Tapioca flour was employed to maintain the C: N ratio at 15:1 in HBR units. At the end of the experiment; the growth, digestive enzyme, and serum biochemical enzyme were analysed from the experimental fish. After 120 days of culture period, the fish were challenged with Aeromonas hydrophila. As compared to two controls with RAS-150 (150 fish/m3) and BFT-150 (150 fish/m3), all HBR treatments showed significant improvement in growth and feed utilization. The HBR-150 and HBR-200 had significantly higher digestive enzymes, albumin, globulin, and total protein; least in RAS-150. The liver and muscle tissue of Nile tilapia were analysed for LDH, MDH, AST, and ALT; and these values were found to be significantly higher at increased stocking density (HBR-300) as compared to the controls. The quadratic regression model fitted to stocking density of HBR groups {Biomass gain (y) = −0.1854 × 2 + 84.731× - 4793.3} revealed that a stocking density of 229 fish/m3 is the maximum for HBR culture system. After the challenge against Aeromonas hydrophila, significantly better survivals were observed in HBR-150 followed by HBR-200. Enhanced zootechnical performance, serum biochemical parameters, and metabolic enzyme responses were found in HBR-150 and HBR-200, and lower in the HBR-300 and RAS-150 experimental units. Profitability assessment of HBR and control groups describes low profit in high density comprared that of low stocking density. Thus, it may be concluded that a stocking density of Nile tilapia at 229 fish/m3 is ideal for a hybrid biofloc-RAS culture system (HBR) with better growth, immunity, physiological responses, and survival.
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•Nile tilapia were stocked at 150, 200, 250, and 300 fish/m3 in HBR system.•Enhanced digestive enzyme response of Nile tilapia observed in HBR system.•229/m3 stocking density is recommended for culture of Nile tilapia in HBR system.
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 γ-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.
