Physiological Responses of Marine Bivalves to Climate Change

Marine bivalves face a suite of climate-driven stressors including ocean warming, acidification and hypoxia. Warming elevates metabolic rates and shifts the balance between aerobic and anaerobic pathways, often leading to greater energy expenditure and reduced growth. Acidification impairs shell formation by altering carbonate chemistry and can disrupt acid–base homeostasis, enzyme function and cellular ion regulation. Hypoxia, often associated with eutrophication and temperature-dependent oxygen solubility, limits aerobic metabolism and can trigger metabolic depression or the upregulation of anaerobic glycolysis. Many bivalves mitigate these challenges through enhanced antioxidant defences, adjustments in mitochondrial electron transport capacity and the synthesis of stress proteins. In early life stages, combined stressors frequently act synergistically, reducing survival, growth and metamorphic success. At the molecular level, shifts in gene expression mediate changes in heat shock proteins, ion transporters and apoptotic pathways. Collectively, these physiological responses determine species’ resilience, influence community composition and underpin the sustainability of shellfish aquaculture under future climate scenarios.

Research from Nature Portfolio

Recent studies have demonstrated that brief exposure to sub-lethal heat allows Mediterranean mussels to enhance their thermal tolerance through a process known as hardening. Heat-hardened individuals exhibit increased activity of the mitochondrial electron transport system and elevated antioxidant enzyme capacity in mantle tissue, resulting in reduced reactive oxygen species accumulation and lower mortality when subsequently exposed to higher temperatures. This work elucidates the cellular and mitochondrial pathways that underpin thermal resilience and offers a practical framework for improving stock performance in aquaculture operations subject to rising seasonal temperatures.

Physiological Responses of Marine Bivalves to Climate Change publication trend

The graph below shows the total number of articles in physiological responses of marine bivalves to climate change across all publications each year (not limited to Nature Index journals).

Technical terms

Reactive oxygen species (ROS): Chemically reactive molecules derived from oxygen that can damage lipids, proteins and DNA if not neutralised by antioxidants.

Oxidative stress: Imbalance between ROS production and antioxidant defences, leading to cellular damage.

Electron transport system (ETS): Mitochondrial protein complexes that transfer electrons to oxygen, driving ATP synthesis.

Heat shock proteins (HSPs): Molecular chaperones that stabilise and refold damaged proteins under stress conditions.

Ocean acidification: Decrease in seawater pH and carbonate ion availability resulting from uptake of atmospheric CO₂.

Hypoxia: Condition of reduced dissolved oxygen in water that limits aerobic metabolism.

References

1. Antioxidant Activity and Oxidative Damage Associated with Seeding Surgery for Pearl Culture in the Winged Pearl Oyster Pteria sterna. Antioxidants (2024).
2. Hypoxia and Acidification Have Additive and Synergistic Negative Effects on the Growth, Survival, and Metamorphosis of Early Life Stage Bivalves. PLOS ONE (2014).
3. Heat hardening enhances mitochondrial potential for respiration and oxidative defence capacity in the mantle of thermally stressed Mytilus galloprovincialis. Scientific Reports (2021).
4. Are Marine Heatwaves Responsible for Mortalities of Farmed Mytilus galloprovincialis? A Pathophysiological Analysis of Marteilia Infected Mussels from Thermaikos Gulf, Greece. Animals (2022).