Extraordinary discovery in South Arran MPA

Close up of flame shell. Photograph Paul Kay

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An extensive flame shell bed estimated to be 10,000m2 – about the size of 30 tennis courts – has been discovered in the South Arran Marine Protected Area (MPA) by island recreational divers.

As only the second known remaining flame shell bed in the Clyde marine region, this is a significant and exciting discovery not just for Arran but for biodiversity interests throughout the whole of Scotland. Seabed habitats are the foundation of a healthy marine environment.

Historic records show that 70 to 150 years ago, Scotland’s seas and the Clyde had a wide array of living seabed habitats; seabeds that were literally alive with habitat-forming species of bivalve molluscs, such as horse mussels and flame shells, and worms like the honeycomb worm and tube-worm serpula.

Of these, the flame shell is a particularly amazing species. Gaining their name from the neon orange flame-like tentacles protruding from their shells, flame shells on their own are beautiful and unusual looking creatures rarely seen or even heard of by the public.

This is despite playing a very important role in the marine ecosystem. By producing thin, strong threads (byssus threads), flame shells literally knit the seabed together to build a nest which supports a large variety of other marine life that lives on and within this mass of seabed material.

As a result, living reefs like this create an important habitat and enhance biodiversity in the area; research on the only other known flame shell reef in the Clyde recorded 265 different animal species within samples of the flame shell bed.

These living reefs are not only biodiversity power houses, providing key nursery grounds for juvenile fish and commercially important scallops, they are vital blue carbon stores which can help increase resilience to climate change.

‘It is very encouraging to hear of the discovery of an extensive and previously unknown area of flame shell reef in the Clyde,’ commented Heriot-Watt University’s Dr Dan Harries, whose research focuses on marine benthic communities.

‘These reefs support diverse and abundant communities of marine organisms so it is not just about the discovery of the flame shells themselves – it is a discovery of an entire marine community of exceptional biodiversity.’

The true significance of this find in Arran’s seas is revealed by understanding what the extent of these living reefs used to be in the Clyde prior to the advent of bottom towed scallop dredging and seabed trawl fisheries.

More than a century ago, the Clyde had at least seven large flame shell reefs, covering many dozens of square kilometres; Sanda-Southend, Skelmorie Bank, Stravanan Bay, Tan Buoy, Great Cumbrae, Inchmarnock, Otter Ferry and Lamlash Bay. Five decades of scallop dredging reduced these biodiversity hotspots to just one known remnant reef at Otter Ferry in Loch Fyne, and it has only survived due to high power sub-sea electric cables rendering the ground too dangerous to fish.

Professor Jason Hall-Spencer of Plymouth University has described the discovery of this new flame shell bed off Arran as: ‘Absolutely amazing and very welcome news.’

Hall-Spencer spent years researching the biodiversity associations of a flame shell bed while based at the Millport Marine Biological research station 20 years ago.

He said: ‘This discovery re-ignites the possibility that, with adequate protection, the once widespread Clyde flame shell beds could one day fully recover along with wider marine and fisheries improvements. I cannot commend the community on Arran highly enough for the dogged determination to recover the seas around their island and the wider Firth of Clyde.’

This newly-discovered flame shell bed is sited within the South Arran MPA which was designated following a campaign led by the Community of Arran Seabed Trust (COAST) – a marine conservation charity – supported by the passionate island community.

Although the MPA was designated for other habitats and species, the discovery of this flame shell bed is testament to the importance of the decision in 2016 by the then cabinet secretary, Richard Lochhead, to afford wider protection to the South Arran MPA.

It is an excellent example of why better protection for the marine environment is needed from destructive fishing practices such as bottom trawling and scallop dredging.

COAST’s MPA project officer, Lucy Kay, who was one of the divers who found the reef whilst on a recreational dive said: ‘Important discoveries like this are helping to improve our collective knowledge of Scotland’s seas.

‘This discovery highlights the invaluable contribution of community groups and citizen scientists in helping to survey and monitor the marine environment around our shores, much of which is currently done on a voluntary basis without any financial assistance from Marine Scotland.’

Flame Shell bed biodiversity. Photograph Paul Kay