Species description: This bryozoan forms encrusting colonies made up of individual elongate zooids. The colony is rigid but easily broken. The zooids occasionally form lobes or erect sections, giving a more three-dimensional structure than most other encrusting bryozoans. Older colonies can even grow into rose-shaped formations. The colony is usually an orange-red, especially where there is new growth but can take on a dark brown to black or even dark purple colouration when mature and where growing has stopped. Each individual zooid is markedly elongate with a distinctive operculum visible as a black spot. They have no avicularia or ovicells.

Habitat: Hard substrata in shallow water, especially marinas and harbours but now also spreading to boulders and hard substrata on rocky shores. Growth there can be quite extensive.

Distribution: First recorded in Northern Ireland in 2012, in Ardglass marina. Now known to be present in Bangor marina and Carrickfergus marina. Recorded from several sites around Britain and Ireland. Originating in marinas and harbours it has now spread to shores. Any new sightings should be reported, especially outside of marinas/harbours.

Similar Species: There are several other orange or red coloured encrusting bryozoans but most do not have the three-dimensional form aside from Schizoporella japonica, and the elongate zooids with distinctive dark spot of operculum in Watersipora subatra are diagnostic.

Key Identification Features:

• Rigid but fragile encrusting bryozoan, that may have some three-dimensional lobes or erect sections. Red-orange colouration, especially at new growth points.
• Can turn black, brown or dark purple where growing has stopped and zooids are more mature.
• Elongate zooids with operculum visible as distinctive dark spot.

iNaturalist: Watersipora subatra at iNaturalist World Species Observations database.

WoRMS: Watersipora subatra at World Register of Marine Species. Accepted name: Watersipora subatra (Ortmann, 1890). AphiaID: 816025.

Classification: Biota; Animalia; Bryozoa; Gymnolaemata; Cheilostomatida; Flustrina; Smittinoidea; Watersiporidae; Watersipora