What is the impact of a marine heatwave on the UK seas?
- Published
In the UK we've been experiencing several heatwaves recently, but did you know these can also have an impact in the sea?
The Met Office, which monitors UK weather, has said that a marine heatwave could reach "extreme" levels around parts of the UK later this week.
This raises concerns for marine life as long periods of sea heat can lead to more deaths than normal among some seagrasses, shellfish and other species.
Important marine habitats such as seagrasses and kelp forests are suited to cooler waters and can experience high levels of heat stress when temperatures increase quickly
Heat-health alerts for England with very hot weather forecast
- Published21 hours ago
Researchers have also noticed how temperature changes have had knock on effects for other marine life.
Cool-adapted species such as cod are generally moving further north and while natural cycles and fishing practices also play a role, many scientists have been pointing to the role of warming seas.
Some warm-water species such as octopus have also risen in number around south-west England.
Prof Matt Frost of the Plymouth Marine Laboratory said that while "it can be exciting to see new species arrive" there are also "negative impacts of that".
He added: "We're seeing a decline in the numbers of cod and other key species… you're also getting other species that could displace native species. That could bring disease [and] all sorts of problems."
Bluefin tuna and octopuses were some of the species spotted in UK waters in 2025 due to warmer seas
The heatwave is currently strongest off the coasts of eastern and southern England.
In some areas it's thought sea temperatures could reach 4-5C higher than average.
Experts say the marine heatwave has been caused by the "heat domes" that brought record-breaking air temperatures in May and June.
The UK's seas have been getting steadily warmer since the 1980s, driven by human-caused climate change.
Dr Zoe Jacobs of the National Oceanography Centre in Southampton said: "We're starting to see temperatures now that we would expect to see at the height of summer, [at the] end of August.
"So, if this event keeps coming… we might start seeing some serious impacts on ecological systems."
