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DescriptionUndaria pinnatifida or wakame is a large brown kelp with a branched holdfast giving rise to a stipe. Just above the holdfast, the stipe has very wavy edges, giving it a corrugated appearance. The stipe gives rise to a blade that is broad, flattened and lanceolate. It has a distinct midrib. The margins of the blade are wavy. Plants can reach an overall length of one to three metres. Undaria pinnatifida is an annual species with two separate life stages.
Wakame is a laminarian kelp indigenous to the temperate regions of Japan, China and Korea (Stuart, 2003). It has been spread around the world by international shipping and mariculture. It has extended its range to include 12 countries on four continents since 1981 (Stuart, 2003). Wakame is a non-native species, which may cause displacement of native species. It was first recorded in the UK from the Hamble Estuary in the Solent on 15 June 1994 (Farell & Fletcher, 2000). It tolerates a wide salinity and temperature range. Its morphological and reproductive characteristics make it a very successful invasive species. Undaria pinnatifida possesses a heteromorphic life cycle with alternation of generations between a diploid sporophyte and a haploid gametophyte (Aguilar-Rosas et al., 2004). It may be confused with Alaria esculenta but the corrugated stipe is distinctive.Wakame is economically important as a food crop but is also a fouling organism. It is able to compete with native kelp species in the shallow sublittoral/infralittoral zone (Farrell & Fletcher, 2000). It is also effective in providing habitats, nursery areas and protective cover for many species. It grows well in estuarine conditions unlike many of the native kelp species (Farrell & Fletcher, 2000) .