The Met Office has warned that a marine heatwave could reach "extreme" levels around parts of the UK later this week, raising fears for sea life. Prolonged sea heat can trigger mass die-offs among seagrasses, shellfish and other species, while encouraging warm-water creatures such as octopus, so the event matters both for fragile marine habitats and for the fishing communities that depend on them.

The heatwave is strongest off eastern and southern England, with sea temperatures potentially reaching 4-5C above average, and is expected to be especially intense in parts of the English Channel and the southern North Sea. It has been fuelled by the "heat domes" that brought record air temperatures in May and June, layered on top of long-term ocean warming since the 1980s. Scientists note longer-term shifts too, with cool-adapted cod moving north and octopus numbers rising in the south-west, and warn that such conditions could become average by the middle-to-end of the century unless greenhouse gas emissions are cut.