A dip in the sea can provide welcome relief after long stretches of hot weather – especially when the water is an inviting 20°C or more, as it has been recently across southern parts of the UK. But such sea temperatures are unusually warm, with UK waters being hit by the third major marine heatwave in four years.

Aside from obvious negative consequences for people, such as more drownings in open water, marine heatwaves can affect sea life of all sizes, from microscopic plankton to huge whales.

Around the world, such instances of unusually warm sea temperatures for five days or more have caused die-back of key species such as kelp, seagrass and corals.

Marine heatwaves have also caused death or changes to the life cycles of marine mammals and shellfish, as well as other species that depend on them, such as seabirds. They have caused species to migrate or shift their geographic range. These changes all disrupt ecosystems, with disastrous ramifications for oceanic food webs.

The UK’s first major marine........

© The Conversation