Membranipora membranacea forms flat, single-layered colonies of rectangular zooids arranged in a regular grid — the effect looks like fine lacework, which gives the species its common name. Colonies are pale, semi-transparent, and can spread at 3–5 cm per month under good conditions, eventually covering areas of several hundred square centimetres. The species is abundant from arctic Norway through the North Sea and British Isles, and it is the dominant bryozoan fouler on kelp blades in cold-temperate waters.
On aquaculture nets and ropes, Membranipora sheets stiffen flexible materials, reducing the net’s ability to deform under current and wave loading. This transfers more force to cage frames and mooring systems, increasing the risk of structural failure in storms. The calcareous zooid walls also roughen the net surface, raising drag coefficients and accelerating wear on twine. Because Membranipora commonly co-occurs with barnacles and spirorbid worms, the combined hard-fouling layer can be 3–5 mm thick and very difficult to remove without damaging the net underneath.
Air-drying kills colonies within 12–24 hours; the dead crust becomes brittle and breaks away when the net is re-deployed. High-pressure washing at 100+ bar removes established colonies but scatters calcareous fragments into the water column. Anti-fouling coatings reduce settlement during the summer larval release period (June–September in northern Europe). For farms dealing with mixed bryozoan and barnacle fouling, an integrated approach combining coatings with scheduled mechanical cleaning yields the best results. See related bryozoan species in the organisms database.
Control Methods
Air-drying Manual scraping High-pressure washing