Very rare and unusual sea species discovered off Scotland's west coast.

April 2007. One of the world's rarest coral-like structures, which in Scotland was previously thought to exist in only one sea loch, has been discovered in Loch Teacuis in Morvern. Beyond Scotland it is only recorded growing sparsely in three other places in the world - in coastal lagoons near Taranto in Italy and in Ardbear Lough and Killary Harbour in Ireland.

The structures, which house colonies of vibrantly coloured red, orange and pink worms, were found on the seabed during a recent marine survey for Scottish Natural Heritage (SNH). Further investigations indicated their presence in a narrow band most of the way around the upper basin of the loch, where the water is shallow. They also extend deeper in places where there is a suitable hard substrate on which to grow.

The structures are built by the tubeworm Serpula vermicularis, which is widespread around Britain in its solitary form, depositing the white tubes often seen on rocks and shells on the beach. Each tube houses a single worm that emerges to feed on passing plankton. In certain conditions, which are not yet understood, the worm tubes can grow up off the seabed, twisting around each other and branching to form coral-like structures. In the right environment these can become very dense and form reefs, known as serpulid reefs. Such reefs provide living space and food for many other marine organisms such as hermit crabs, feather stars and starfish, but had previously only been recorded at one location in Scotland, at Loch Creran in Argyll. In Loch Creran, individual worm colonies are up to 75cm high and 1m in width, merging in places to form reef-like structures up to 200m wide, covering in total around 108ha of the seabed. Though the structures in Loch Teacuis are not as dense, the clusters of tubes are still remarkably well developed, reaching 45cm in height and up to 47cm in width.

 

Jane Dodd, Marine Project Officer for SNH in Argyll and Stirling, said: ‘It's really exciting that we've found another example of this remarkable habitat. Serpulid reefs are very rare in international terms. The structures in Loch Teacuis don't seem to be as extensive as they are in Loch Creran, occurring at a lower density in a band of shallow water around the edge of the loch, but we did find some large worm colonies more than a metre in circumference. We had to move large kelp fronds from around these in order to measure them and found they were growing on the kelp holdfasts, the claw-like structure which anchors the kelp to rocks. We don't see that in Loch Creran where the reefs generally start growing on empty shells in deeper water.

‘When the worms feed a feathery double-horseshoe of crimson tentacles emerges from each tube.’ she added. ‘It's an amazing and colourful spectacle. You might expect to see something this exotic in the Caribbean but I think it will come as a surprise to most people that this is found so close to home.’

Loch Teacuis lies within the Sunart Special Area of Conservation, which is protected under the EC Habitats Directive for its reefs. The newly discovered serpulid structures add to the great diversity of marine communities that make the site special.