The life cycle of harpoon weed, Asparagopsis armata, has two morphologically distinct phases. The sexual (gametophyte) plant is rosy, yellowish pink or whitish pink, erect and spreading, with many feathery branches; up to 30 cm tall with some branches developing as conspicuous harpoon-like barbed structures up to 10 mm long. This stage of the harpoon weed is only common in south western locations in the UK.
The asexual (tetrasporophyte) plant, previously known as known as Falkenbergia has spread north as far as Shetland. It is rosy pink, filamentous, and forms fine woolly balls 10 - 20mm in diameter and occurs all year round. It is epiphytic or sometimes free living, typically found subtidally and sometimes tangled up in other seaweeds.
Harpoon weed was first recorded in Britain and Ireland in the 1940s probably spread from alien populations already established in Europe. It is reported to dominate algal assemblages in some locations; forming bloom-like outbreaks during winter in the NW Mediterranean and at such times economic losses to fisheries have been reported due to harpoon weed clogging fishing nets. In Ireland, harpoon weed has recently been identified as a commercially important species for the production of cosmetics.
Information and Identification Sheets: Harpoon Weed