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August 18, 2026

How Europe’s heatwaves could affect marine life

 

Europe has just experienced another summer of extreme heat. As the fastest-warming continent on Earth, heat related impacts are becoming increasingly visible across the continent. 

While summer heatwaves make headlines on land, an even larger heatwave is unfolding out of sight. This year, July saw the highest sea surface temperatures ever recorded for July. Roughly 90% of the excess heat from human-caused carbon emissions has been absorbed by the ocean, resulting in dreadful consequences for marine life.  

As sea surface temperatures rise at an unprecedented rate, marine life and the habitats they depend on are coming under increasing pressure. 

What happens to marine life when temperatures increase? 

Heat stress for marine life  

Prolonged periods of unusually warm water can place marine animals under significant physiological stress. Research has linked marine heatwaves to mass mortality events and reduced immune function in some marine species, making them more vulnerable to disease and environmental changes.  

Affects migration in marine animals  

Rising ocean temperatures and marine heatwaves have forced many species of fish and marine mammals to alter their migration paths or move towards cooler regions. This migration can have impacts on the food web. Predators may find their prey disappearing from traditional feeding grounds, while species unable to relocate may face increasing pressure. Changes in the availability of prey have already been observed in some whale populations, affecting feeding behaviour and habitat use. 

Affects spawning habitats for many species 

Temperature plays an important role in the reproductive cycles of many marine animals. Fish, eggs, and larvae often require specific conditions to develop, so even small changes can reduce the area where they’re able to reproduce successfully. 

Studies suggest that marine heatwaves can disrupt breeding success, resulting in fewer young fish surviving to adulthood, and potentially affecting future population sizes.  

Habitat impacts  

The impacts of marine heatwaves extend beyond individual animals. Entire habitats can also be damaged by prolonged periods of extreme heat. Kelp forests and other marine forests are vital marine habitats that support biodiversity, provide shelter, store carbon and help stabilise the seafloor. However, marine heatwaves have been identified as contributing directly or indirectly to their decline globally.    

With 30% of plants and animal species in high risk of extinction, we will likely see the collapse of some ecosystems such as corals and reefs if the current changes in ocean conditions continue.  

Why does this matter for Europe’s seas?  

Protection of marine ecosystems is important. Well managed Marine Protected Areas (MPAs) strengthen ecosystem health, support biodiversity recovery and improve the resilience of marine habitats to climate-related pressures.  

The impacts of marine heatwaves affect us all. A healthy ocean helps in regulating the climate by absorbing heat and storing carbon, regulate temperature and buffer the impact of heatwaves on land. They support fisheries, protect coastlines and livelihoods for millions of people.