Heat Stress Responses in Aquatic Species

Rising water temperatures driven by climate change pose a profound challenge to aquatic organisms, which are typically poikilothermic and thus closely coupled to ambient conditions. Heat stress triggers a cascade of physiological, cellular and molecular responses aimed at maintaining homeostasis. At the cellular level, elevated temperatures disrupt protein folding, leading to the induction of heat shock proteins that act as chaperones to prevent aggregation. Concurrently, overproduction of reactive oxygen species overwhelms antioxidant defences such as superoxide dismutase and catalase, resulting in lipid peroxidation and membrane damage. Key organs including gills, liver, intestine and kidney undergo histological alterations, impairing gas exchange, metabolism, nutrient absorption and osmoregulation. Many species exhibit metabolic reprogramming—shifting from aerobic respiration towards anaerobic pathways—and alterations in lipid composition to preserve membrane fluidity. Heat stress also perturbs host–microbiome interactions, with shifts in bacterial communities on the skin and in the gut influencing barrier integrity and immune status. At the organismal level, prolonged exposure can reduce growth rates, compromise reproduction and increase mortality, with direct implications for biodiversity, fisheries and aquaculture productivity. Integrating these multi-tissue responses provides a comprehensive framework for developing mitigation strategies and selecting heat‐tolerant strains.

Research from Nature Portfolio

Studies of a freshwater catfish under discrete thermal regimes revealed that both heat and cold stress provoke pronounced gill tissue damage, including cell vacuolation, congestion and necrosis. Concurrent analyses of the gut microbiota showed temperature‐dependent shifts in dominant phyla: heat stress enriched Fusobacteriota and Bacteroidota, while cold stress favoured Pseudomonadota and Bacillota. Overall richness declined under thermal extremes, though evenness increased, indicating a loss of specialist taxa. Functional predictions suggested that core processes such as energy metabolism, cofactor biosynthesis and DNA repair were markedly reduced at elevated temperatures. These findings underscore the tight coupling between respiratory structures and microbial homeostasis in thermal adaptation, with direct relevance for aquaculture management under variable climate scenarios.

Heat Stress Responses in Aquatic Species publication trend

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

Technical terms

Heat shock proteins (HSPs): molecular chaperones that stabilise and refold proteins under thermal stress.

Oxidative stress: condition arising from excess reactive oxygen species overwhelming antioxidant defences.

Superoxide dismutase (SOD) and catalase (CAT): enzymatic antioxidants that neutralise reactive oxygen species into less harmful compounds.

Malondialdehyde (MDA): by-product of lipid peroxidation serving as a marker of cellular oxidative damage.

Microbiota: community of microorganisms inhabiting a specific environment such as the gut or skin.

Peroxisome proliferator-activated receptor α (PPARα): nuclear receptor regulating genes involved in lipid metabolism and stress responses.

References

1. Effects of Thermal Stress on the Antioxidant Capacity, Blood Biochemistry, Intestinal Microbiota and Metabolomic Responses of Luciobarbus capito. Antioxidants (2023).
2. Comprehensive Analysis of Microbiome, Metabolome, and Transcriptome Revealed the Mechanisms of Intestinal Injury in Rainbow Trout under Heat Stress. International Journal of Molecular Sciences (2023).
3. Effects of different temperatures on Leiocassis longirostris gill structure and intestinal microbial composition. Scientific Reports (2024).