Overview
This controlled aquaculture study evaluated mercury (Hg²⁺) bioaccumulation in muscle tissue of Nile tilapia (Oreochromis niloticus) exposed to a sub-lethal concentration of HgCl₂ (0.3 mg/L; ¼ LC₅₀) for 21 days, and assessed whether dietary supplementation with Nannochloropsis oculata microalga (5% or 10% of feed) could reduce Hg muscle deposition. Hg²⁺ toxicity led to significant musculature bioaccumulation, inhibited acetylcholinesterase (AChE) activity, downregulated antioxidant- and stress-related genes, and caused histopathological changes in gills and intestine. Supplementation with 10% N. oculata upregulated antioxidative genes, downregulated stress-apoptotic genes, and produced minor to no histopathological lesions. The study quantifies Hg accumulation in the muscle of a globally consumed aquaculture fish species under controlled contamination conditions and demonstrates a dietary mitigation strategy.
Key numbers
- n = 120 Nile tilapia; 4 groups × 3 replicate tanks × 10 fish/tank (10 fish/tank)
- Hg exposure: 0.3 mg/L HgCl₂ (sub-lethal, = ¼ LC₅₀ = 1.21 mg/L at 96h)
- Duration: 21 days
- Hg²⁺ bioaccumulation in muscle tissue: significantly elevated in Hg-exposed groups vs. control; specific concentration values in source tables
- N. oculata 10% diet lowered Hg residues in muscle; N. oculata 5% less effective
- AChE activity significantly inhibited by Hg exposure; restored by dietary N. oculata
- Histopathological changes in gills and intestine reduced/eliminated by 10% N. oculata
- 96h LC₅₀ for Hg in Nile tilapia: 1.21 mg/L
- Study conducted at Aquatic Animal Medicine Laboratory, Mansoura University, Egypt
- Journal: Environmental Science and Pollution Research
Methods (brief)
Static-renewal aquarium system with daily HgCl₂ dosing (1000 mg/L stock, diluted to 0.3 mg/L). Three tissues assayed for Hg but muscle is the food-relevant matrix. Antioxidant and stress-gene expression (RT-PCR); histopathology. AChE activity measured in serum. Egypt (Mansoura University).
Implications
Certification: Nile tilapia muscle accumulates measurable Hg under simulated aquaculture contamination conditions; tilapia is one of the most globally consumed aquaculture species and a relevant food-safety matrix for Hg. Courses: Demonstrates dose-dependent Hg accumulation in a commercial food fish species; dietary microalgae as a novel mitigation approach in aquaculture is a timely emerging topic. App: Tilapia from aquaculture settings with water quality risks should carry Hg flags; mitigation via feed additives is not yet standard practice and cannot be assumed. Microbiome: Not applicable.
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Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 6 sections added; narrative text revised |