The English Channel prevents new rockpool species from reaching the UK

The English Channel prevents many rockpool species from ‘making the leap’ from Europe to the UK, new research has found.

With sea temperatures set to rise due to climate change, many rock pool species in South West England are under threat.

Creatures from warmer waters to the south could replace them – but the study, by the University of Exeter, suggests Channel currents mean many animals and plants cannot survive the crossing.

The study focused on the St Piran hermit crab, which appeared in Cornwall in 2016 and was named by BBC Springwatch viewers.

“The crab larvae almost certainly came from Brittany in northern France,” said Christophe Patterson, from the Center for Ecology and Conservation at the Penryn Campus in Exeter in Cornwall.

We modeled how ocean currents could transport larvae from Brittany to the South West of the UK, and found very few opportunities for this to happen.

“Only once every ten years, the currents would be favorable for the crossing of the English Channel by the tiny crab larvae of St Piran.

Even on these currents the time it takes for the larvae to be transported to the UK is much longer than most larvae of other species can survive.

“Crabs and other crustaceans have the best chance, as many have larvae that could survive the crossing, but other groups like sea snails, sponges and seaweed simply don’t live long enough in open water to get here.”

Over the past 60 years the sea temperature in the south west of the UK has fluctuated. Despite a slight decrease in recent years, average temperatures are expected to increase.

When the temperature rises, species that normally live in colder waters begin to disappear, but when the temperature drops, they may return.

“Our research suggests that as species disappear they will not be replaced by warmer water species moving north, and the wealth of intertidal fauna in the UK will decline,” said Dr Regan Early, also from the University of Exeter.

“Rockpool Animals are not alone in this quest.

“As the world warms, many species will find themselves in environments that are too hot to survive.

“To avoid extinction, species must move to new areas, keeping them in their preferred climate.

“However, physical barriers like the English Channel can prevent species from doing so.”

The study was carried out by the FABiogeography research group in Exeter.

Christophe Patterson won the Sir Geoffrey Holland Prize for academic excellence in a field related to Cornwall.

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Materials provided by University of Exeter. Note: Content may be edited for style and length.