Algae has covered large amounts of unique 4,000-year-old maerl beds, which are crucial to marine life and carbon storage
Irreplaceable 4,000-year-old coral beds off the Cornish coast could be killed after being smothered in algae caused by sewage pollution and run-off from farms.
Marine scientists and conservationists were left shocked by the state of the ancient beds of rare pink calcified seaweeds, known as maerl, which are crucial to supporting fragile underwater ecosystems and act as a nursery for commercial fish and shellfish.
The rose pink of a maerl bed is a very rare sight in English waters, with few thought to exist outside Cornwall, where it particularly thrives in clear waters, estuaries and tide-swept bays.
Maerl are a critical habitat, food source and carbon sink
CORNWALL WILDLIFE TRUST
The maerl beds of the Fal and Helford estuaries in Cornwall were designated as a Marine Protected Area in 2005 but a recent dive revealed a “worrying deterioration” in the ecosystems in the Fal estuary, Cornwall Wildlife Trust said.
Matt Slater, a marine conservation officer at the trust, said what they found was “a massive concern” and improvement to the water quality in the Fal estuary was needed urgently.
“It was a shocking sight,” Slater said. “The area, which was previously purple and beautiful, is now covered with a thick layer of brown, fluffy algae.
“We’ve surveyed here regularly for the past eight years and I have never seen the maerl beds looking like this. It was a very sombre atmosphere.
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“It’s a massive concern and shows, yet again, why it is urgent that we do all we can to improve water quality in the Fal estuary.”
Although often referred to as a coral, maerl is a red seaweed, best described as a coralline algae. Each nodule is hard to the touch due to a calcium carbonate skeleton. Maerl nodules are very fragile and very slow growing — just 1mm per year.
The beds, which also act as a carbon store, were recently classified as irreplaceable marine habitats by Natural England because of their almost complete inability to recover from damage. If they are hit by high levels of pollution and start to wither and die, nothing can save them.
The deteriorating state of the maerl beds in the Fal estuary was discovered last month at the end of the UK Maerl Forum, the first international event of its kind where European experts came together to create an action plan to protect Cornwall’s maerl beds.
In 2021, the same maerl was much healthier, but pollution has worsened
CORNWALL WILDLIFE TRUST
An organised dive took place at the end of the forum to see the densest maerl bed in English waters, which scientists at Exeter University have found to be genetically unique from other maerl in UK and European waters.
“Maerl is a coralline seaweed and this algae could potentially harm or kill the maerl bed,” Slater said. “There have been small amounts of algae on them in the past but this was completely covering the entire maerl bed. It was devastating to see.
“In Milford Haven [in Pembrokeshire] they have seen this kind of algae bloom damage maerl. It’s down to nutrient levels in the water.
“The Fal has a very large catchment. We can’t point fingers at people but if something is going to be done it’s going to have to be a big project working in multiple ways.”
Cornwall Wildlife Trust said mobile fishing gear was also damaging maerl beds, as was a deterioration in water quality.
Scallop dredges and beam trawls, which could destroy up to 70 per cent of the live maerl nodules, were of “particular concern”.
The Fal estuary is protected from damaging fishing equipment
WILL PERRETT/GETTY IMAGES
In other parts of the UK, such as Lamlash Bay on the Isle of Arran, fishing has been banned to protect maerl beds.
The trust said it was working with farmers to reduce agricultural run-off and with fishers on sustainable management practices.
Mobile fishing gear and maerl extraction are both banned in the Fal estuary. However, the conference highlighted that water quality was also a key threat.
In other areas, such as Milford Haven and Brittany, algal blooms caused by raised nutrient levels have reportedly led to severe decline, and in some cases complete loss, of maerl habitats.
The Times is demanding faster action to improve the country’s waterways. Find out more about the Clean It Up campaign.
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