One of UK’s largest seagrass meadows discovered in Cornish Bay

  • Watch Grace Pascoe's report

A meadow of seagrass covering nearly 360 hectares has been discovered under the water in St Austell Bay.

It's one of the largest seagrass meadows in the UK and is home to hundreds of marine species.

Teams from Cornwall Wildlife Trust and the Cornwall Inshore Fisheries and Conservation Authority surveyed and mapped St Austell Bay’s seabed using echo-sounders on boats and by diving underwater.

Abby Crosby from Cornwall Wildlife Trust says the discovery is a cause for celebration.

"We've discovered about 359 hectares of seagrass in this bay alone which makes it the largest bed in Cornwall and maybe one of the largest bays in the whole of the UK.

“A bed that size provides lots of benefits to us as people as well as wildlife.

"It does support extraordinary biodiversity, hundreds of different species of plants and animals will live in that seagrass bed including the well-known seahorse, then of course seagrass is a true plant, it has a roots system.

Volunteer divers found 122 different species of plants and animals living in St Austell Bay's seagrass Credit: Matt Slater

"359 hectares of roots provides really significant coastal stabilisation against changing weather systems and erosion and of course it’s a really valuable blue carbon habitat," she added.

"It’s a habitat which has the ability to capture and store carbon, which at a time of a climate crisis is invaluable and a natural solution that we really do need to focus on.”

Seagrass is often called the 'wonder plant' by conservationists because it can capture carbon 35 times more quickly than a tropical rain forest.

Cornwall Wildlife Trust say work is needed to protect the bed and that further surveys should be carried out to find out if there are other seagrass beds in nearby areas.

According to Abby, the seagrass is under threat despite its importance.

"We’ve lost at least 40% of these habitats across the world.

Conservationists say seagrass is a species-rich 'wonder plant’, it captures carbon 35 times more quickly than a tropical rainforest Credit: Ocean Conservation Trust

"We all have a role to play in protecting sea grass. It's not just about designating marine protected areas, it's about us thinking about what we do at sea or by the coast.

"There are multiple pressures that can face seagrass and so many ways to protect it.

"That could be water quality and how we manage our land better for the rivers and streams that come down into this bay, or whether it's direct impacts from mooring and anchoring in vessels at sea and there's ways of putting it into recovery by restoring it."

Through protection and restoration, it’s hoped these sub-tidal habitats will be able to flourish well into the future.