Looking a little more closely, the worm so dominating the Llanddona beach now is the Sand Mason Worm – Lanice conchilega. These worms glue sand and shell grains together to create the long tubes in which they live. On top of the tubes they construct a characteristic fringe and feed by grasping particles from the water with tentacles. Normally you see these scattered fringe tops just protruding from the sand, but when there has been a mass recruitment there can be so many that they modify the topography of the beach or nearshore seabed. I did not have time to explore the full extent of the area covered by the unusual density of tubes, but the feature must have spread over 1.5 Km along the shore by 300 to 400 metres wide.
The muddy sand offshore area in Red Wharf Bay has been sampled on an almost annual basis for over 25 years. Experience shows that it is particularly liable to substantial changes in the species that dominate the fauna and are capable of modifying the conditions for others. Having visited Llanddona beach for many years, I do not recall seeing quite such a mass takeover of the lower shore by quite such a hugely successful recruitment of Sand Mason Worms.
|Red Wharf Bay with worms - lots!|