Watersipora subtorquata is a highly invasive bryozoan, only known from the British Isles in recent years.
The species can form either extensive encrusting sheets (20 cm in diameter or more) with broad spreading lobes, often overgrowing older layers; or erect slightly foliaceous colonies with lobes composed of autozooids arranged back-to-back. The colour of the colony is highly variable. On occasion, colonies form a broad and extensive orange-red region around the edge of the colony, becoming paler and greyish towards the centre. Alternatively, colonies may be dark sepia, black or deep purple with a narrow orange margin.
Autozooids are sub-rectangular or slightly hexagonal, sometimes narrower proximally (closest to the colony origin). They are relatively large (approx. 1mm in length)
Watersipora subtorquata is highly invasive and has become common on coastlines throughout cool-temperate waters since the 1980s. It now known from Guernsey, Plymouth, Poole Harbour and in France from Brittany and Bordeaux
The species is able to colonise a range of substrates including brown algae, Fucus serratus, Laminaria fronds, stones, shells, artificial substrates.