Researching the sea caves of St Kilda



A team of marine biologists from Heriot-Watt has shed light on some of the fascinating species found in sea caves in the remote Scottish islands of St Kilda and North Rona, setting the baseline for future environmental monitoring in this challenging and previously poorly studied marine environment.

A picture of a rich, vibrant and healthy biological community.
Dan Harries

The team worked with staff from Scottish Natural Heritage, who had commissioned the project and with staff from National Museums Scotland, who took charge of the extensive collection of specimens.

The scenery of St Kilda is breathtakingly wild and rugged with giant sea cliffs and sea stacks supporting dense colonies of seabirds. Many sea caves and tunnels penetrate the rocky reefs and cliffs around the coasts of the islands but the almost continuous presence of waves prevents entry to the caves on most days. The team faced considerable challenges in terms of exposure and the weather, but succeeded in surveying several spectacular sea caves. 

Dan Harries, a marine biologist in the School of Life Sciences, said, “The upper walls of the caves are typically blanketed by a diverse, complex and colourful mosaic of filter feeding animals including sponges, sea squirts and tube worms. The cave floors and lower walls bear evidence of the power of the waves, with rock surfaces worn smooth and bare by the continuous movement of the cobbles and boulders over the cave floor. 

“We returned with many hundreds of high resolution photographs and specimens which together paint a picture of a rich, vibrant and healthy biological community. The identity of many of the species is still to be determined but it appears that they include a possible new species of soft coral. The specimens will be incorporated into the collections of National Museums Scotland and represent a valuable extension of our physical records of Scottish marine biodiversity.”