Ammonia Stress Responses in Aquatic Organisms

Ammonia is a ubiquitous by-product of protein metabolism that readily accumulates in aquatic environments, particularly under intensive farming or eutrophic conditions. At elevated concentrations, un-ionised ammonia permeates epithelial surfaces, disrupting ion regulation and mitochondrial function, and provoking oxidative damage. Aquatic invertebrates and fish mount a suite of physiological and molecular responses to mitigate this stress. Primary defence mechanisms include the upregulation of ammonia-metabolising enzymes such as glutamine synthetase and glutamate dehydrogenase, facilitating the incorporation of toxic ammonia into non-toxic compounds. Concurrent activation of antioxidant systems—superoxide dismutase, catalase and glutathione peroxidases—serves to neutralise reactive oxygen species generated under ammonia challenge. At the cellular level, prolonged exposure can trigger endoplasmic reticulum stress, unfolded protein responses and apoptotic pathways, leading to tissue damage in critical organs such as the gills and hepatopancreas. Recent multi-omics studies have revealed alterations in gene networks controlling immunity, energy metabolism and cellular homeostasis, while microbiome analyses have underscored shifts in gut bacterial communities that exacerbates host vulnerability. Understanding the interplay between these mechanisms is essential for devising strategies to enhance ammonia tolerance, optimise aquaculture practices and safeguard wild populations exposed to pollution.

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Ammonia Stress Responses in Aquatic Organisms publication trend

The graph below shows the total number of articles in ammonia stress responses in aquatic organisms across all publications each year (not limited to Nature Index journals).

Technical terms

Hepatopancreas: A dual-function digestive and detoxification organ in crustaceans analogous to liver and pancreas.

Transcriptomics: Genome-wide profiling of RNA transcripts to assess gene expression changes under stress.

Oxidative stress: Cellular damage caused by imbalance between reactive oxygen species production and antioxidant defence.

Apoptosis: Programmed cell death activated by severe cellular dysfunction or stress.

Gut microbiota: Community of micro-organisms residing in the digestive tract influencing host health and disease resistance.

Endoplasmic reticulum stress: Disturbance of protein folding capacity in the endoplasmic reticulum triggering adaptive responses or cell death.

References

1. Immune and physiological responses in Penaeus monodon to ammonia-N stress: a multi-omics approach. Frontiers in Immunology (2024).
2. Acute Ammonia Causes Pathogenic Dysbiosis of Shrimp Gut Biofilms. International Journal of Molecular Sciences (2024).
3. Differential Toxicity Responses between Hepatopancreas and Gills in Litopenaeus vannamei under Chronic Ammonia-N Exposure. Animals (2023).