Scotland’s coasts and seas are home to around 8,000 animal and plant species. Priority Marine Features (PMFs) are the  81 species and habitats that we consider to be conservation priorities in our waters. The PMF list is used to help target future marine conservation work in Scotland.

Graham Epstein from our marine team explains why the middle of winter can be a good time to observe one of the rarest features on the list – serpulid reefs.

Diving in icy water and minus temperatures surrounded by snow-white mountains may seem like a bad idea; however, in winter there is far less kelp and seaweed to shield our view of Loch Creran’s special serpulid reefs.

Diving in ice at Loch Creran

The organ-pipe worm (Serpula vermicularis) is a colourful marine tubeworm with a showy crown of feathery tentacles. Individual organ-pipe worms are not uncommon and can be found in most parts of the world. But in just a few special places hundreds of the creatures grow together forming reefs. Each reef starts with one newly settled worm building its tube on a stone or shell on the muddy seabed. More worms settle on the stone and on existing worm tubes, eventually forming a bush-like reef.

Organ-pipe worms (Serpula vermicularis) in Loch Creran (c) Graham Saunders/SNH

By far the best developed and largest known area of serpulid reefs in the world lies at the bottom of Loch Creran Special Area of Conservation (SAC). Here the reefs form a high-rise home for a host of other animals such as sponges, sea firs, crabs, squat lobsters and marine snails.

Serpulid reef in Loch Creran (c) Graham Saunders/SNH

The Heriot-Watt University dive team has been studying the reefs in Loch Creran for 30 years now. A current student is investigating the distribution and status of serpulid reefs around the loch for their final year research project, so a couple of SNH colleagues and I thought we’d head down to the loch to help out on the diving field work.

Serpulid reefs are extremely fragile and vulnerable to seabed disturbance, such as from storms, fishing gear or mooring chains. They may also be sensitive to changes in the water flow and quality. Following recent reports that some reefs had collapsed, the current research attempts to explain patterns in the distribution of damaged and well developed reefs. Together with further diving and acoustic techniques this research should give us a better understanding of the status of the serpulid reefs within the SAC.

So was it as cold as it looks? Probably yes. But the numb fingers and ‘ice-cream headaches’ on hitting the water didn’t dampen our spirits. We had plenty of layers under our drysuits, as well as gloves and hats to keep us warm on deck. We also found that running on the spot helped to keep the blood flowing and the beautiful views around Loch Creran helped distract us from the cold.

Click the links to our website for more information on Priority Marine Features, serpulid reefs and the Loch Creran Marine Protected Area. You can watch a short clip of serpulids in Loch Creran here (taken on a previous survey).