A temperate reef builder: an evaluation of the growth, morphology and composition of Sabellaria alveolata (L.) colonies on carbonate platforms in South Wales

Sabellaria alveolata (Linné) (Polychaeta: sabellariidae) is a sedentary polychaete that builds wave-resistant reefs from sand-sized particles. Reefs are formed in areas with a large, continuous supply of sand-sized sediment and turbulent water, such as the Bristol Channel, UK. Although several studies have documented the extent, growth, form and geological importance of Sabellariidae, their bioconstructive role has not been adequately assessed. S. alveolata occurs rarely in the UK and is classified as a distinct ecological unit by the Marine Nature Conservation Review, yet it has been little studied. Thus, there is a need for greater understanding of the species’ role in UK coastal ecology and geomorphology. An evaluation of reef development in terms of composition, growth and extent of S. alveolata constructions on carbonate shore platforms in South Wales is presented here. Results indicate that S. alveolata is a fast-growing species capable of juvenile settlement, tube formation and growth of 2.5–5.0 cm in as little as two months after installation of exposure blocks of artificial substrata. Particle size analysis of 24 randomly selected reefs and ten adjacent sand samples shows a significant difference in mean grain size, with worms consolidating particles of a coarser size distribution than the mean particle size of surrounding sand. Preliminary scanning electron microscope observations indicate preferential use of flat, platy and elongate particles in the worm tubes. This research forms part of a larger study concerned with quantifying the bioconstructive capability of S. alveolata