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Effects of sodium formaldehyde bisulfite on ammonia detoxification and biological responses in Koi (Cyprinus rubrofuscus)
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Samaneh Adibi   , Mehdi Ramezani1 , Shapour Kakoolaki , Reza Kazempoor |
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Abstract: (9 Views) |
Introduction
In fish and other aquatic animal farming systems, ammonia is produced by protein metabolism and bacterial activity on excreta and ingested or unabsorbed nutrients (Zhang and Perschbacher, 2003). Exposure to ammonia can cause many toxic effects on fish, affecting physiological and biochemical functions. Ammonia accumulation in fish tissue causes disruption of the circulatory system and various hematological parameters related to lipid metabolism, the immune defense system, blood coagulation, and molecular transport. Exposure to ammonia also causes tissue damage, including to fish gills, liver, and kidneys, through oxidative damage and physiological toxicity. For this reason, in this study, it was decided to use sodium formaldehyde bisulfite (sodium hydroxymethanesulfonate) to reduce nitrogen compounds in reservoir water and some liver and immune blood indices of koi fish, for example, Cyprinus rubrofuscus (Xu et al., 2021). The present study aimed to evaluate the toxic effects of high ammonia (1.5 mg/L) on koi carp and the potential protective role of FBS. Specifically, the objectives were: (1) to assess the impact of severeSodium formaldehyde bisulfite (CH₃NaO₄S; FBS) is widely used to mitigate ammonia toxicity in aquaculture. It functions by chelating free ammonia, reducing its bioavailability and harmful effects. FBS has been approved by the U.S. Food and Drug Administration (FDA) for use in edible aquatic species since 1989 and is effective across a broad range of water temperatures, including near-freezing conditions. Its application has been documented in fish, bivalves, and crustaceans, making it a versatile and cost-effective solution for ammonia management in diverse aquaculture settings.
Methodology
A total of 360 koi Fish (Cyprinus rubrofuscus) with an average weight of 50 g were randomly assigned to 24 aquaria, following a completely randomized design. Six treatments were established, but this study focuses on the highest ammonia exposure (T4, 1.5 mg/L) and two control groups: a positive control (FBS only) and a negative control (no additives). Each treatment had four replicates with 15 fish per tank. FBS was administered proportionally to ammonia concentration. The experiment continued until 50% mortality occurred in T4. Water quality parameters—including ammonia, nitrite, nitrate, pH, hardness, dissolved oxygen, and temperature—were monitored daily, in line with standard aquaculture management guidelines (Boyd and Tucker, 1998). Fish were sampled at mortality checkpoints; two individuals per tank were collected for hematological, serum, and histopathological analyses. Blood was analyzed for RBC and WBC counts, hemoglobin, hematocrit, lymphocyte percentages, and neutrophil percentages. Serum complement proteins C3 and C4 and enzyme activities including ALT (SGPT), AST, and ALP were measured .Tissue samples from gills, liver, and kidneys were fixed, sectioned, and examined microscopically for histopathological changes. Data were analyzed using one-way ANOVA followed by Duncan’s multiple range test at p<0.05.
Results
Exposure to high ammonia (T4, 1.5 mg/L) caused significant negative impacts on koi rubrofuscus. Final body weights in T4 were significantly lower than controls, with a negative specific growth rate (SGR) indicating growth suppression. Survival was 100% in +C and -C, but lower in higher ammonia treatment4. Table 1 summarizes biometric differences.
Table 1: Investigating the differences in biometric and growth indices of koi fish
| Treatment |
Initial weight(grams) |
Secondary weight (gram) |
Specific growth rate (SGR) |
Weight gain (gram) WG |
Initial length
(cm) |
Secondary length
(cm) |
Survival rate
SR |
| T4 |
48.58±0.26 |
48.12±0.45 a |
-0.032±0.04 |
46.58±0.0 |
16.51±0.18 ab |
16.48±0.18 |
77/98±3/85 a |
| C+ |
48.26±0.26 |
48.96±0.14 b |
0.048±0.016 |
0.71±0.22 |
16.7±0.14 b |
16.9±0.12 |
100±0 c |
| C- |
48.14±0.23 |
48.71±0.28 ab |
0.039±0.034 |
0.57±0.49 |
16.4±0.27 ab |
16.6±0.21 |
100±0 c
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| p-value |
0.199 |
0.036* |
0.045 |
0.041 |
0.053 |
0.064 |
0/041* |
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Water quality in treatmentT4 . The results revealed no significant difference in pH between experimental treatments based on the days of study. the study, the highest and the lowest pH was related to the main treatment3 and negative control treatment, respectively. Also on the sixth day, the highest and the treatment4. Hematological analysis revealed significant stress in T4 fish. Hemoglobin and hematocrit decreased, and RBC and WBC counts were significantly lower than in controls., with C3 and C4 complement proteins elevated, alongside increased ALT, AST, and ALP, indicating hepatic disturbance.
Histopathology showed epithelial hyperplasia and lamellar fusion in gills, tubular degeneration in kidneys, and vacuolated hepatocytes in the liver. Positive control fish maintained nearly normal tissue architecture, supporting the protective role of FBS. Overall, T4 ammonia exposure induced multi-level disturbances affecting growth, hematology, serum chemistry, and tissue integrity. FBS mitigated these effects, maintaining better survival, growth, and physiological health.
Discussion and conclusion
High ammonia levels are a significant stressor for koi carp, causing hematological, enzymatic, and histopathological abnormalities Decreased hemoglobin and hematocrit impair oxygen transport, while elevated liver enzymes indicate metabolic dysfunction. Histopathological changes in the gills, kidney and liver indicate direct tissue damage and confirm the multi- organ toxicity of ammonia (Das et al., 2004; Gao et al., 2020). Research has shown that exposure of fish to nitrite will decrease the amount of immunoglobulin IgM and lysozyme (Ciji and Akhtar, 2020). This is also agrees with the findings of this study (Table4). it was found that the change in the results of some researchers (Garcia et al., 2020) showed that the decrease in MDA levels after exposure of lamprey fish to diesel oil contaminants is likely to indicate a relationship between increased antioxidant protection, MDA metabolism and MDA excretion in water. There was no significant difference between the control and 1 groups in terms of MDA content, but it increased with increasing ammonia content. This indicates that FBS has been able to inhibit the negative effects of ammonia, but this problem has shown itself in groups 3 and 4.
According to the research, it is necessary to conduct additional research on the removal of FBS on other fish, in larger scale and for a longer period of storage. It is obvious that since nitrogenous substances are one of the main problems of aquaculture farms, this additional research can be effective in reducing such toxic substances. Ammonia nitrogen is a common environmental limiting factor in aquaculture that can accumulate rapidly in water and reach toxic concentrations. In most aquatic environments, fish are vulnerable to the toxic effects of high levels of ammonia nitrogen. It has been determined that the toxic effects of ammonia nitrogen on fish are multi-mechanistic. Therefore, the aim of this review is to investigate the various toxic effects of ammonia nitrogen on fish, including oxidative stress, neurotoxicity, tissue damage, and immune response.
Conflict of interest
The authors declare no conflict of interest.
Acknowledgment
The authors thank the ornamental fish breeding center for providing experimental fish and laboratory staff for technical assistance with water analysis, blood sampling, and histopathology.
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| Keywords: Ammonia, Antibody-enzyme, Bioaccumulation, Liver indices, Toxicity, FBS |
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Full-Text [PDF 1128 kb]
(3 Downloads)
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Type of Study: case report |
Subject:
آلودگي محيطهاي آبي
Received: 2024/09/14 | Accepted: 2025/12/31
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