inhabits the intertidal zone down to the subtidal zone, to a depth of 15-20 metres.Sessile, forming seaweds.Primary Producer.In Australia, where it has been introduced, Undaria pinnatifida
has few grazing consumers (some fish and sea urchins). Annual species with two separate life stages. A macroscopic stage (the sporophyte), which produces microscopic zoospores that can settle, germinate and grow into microscopic gametophytes. This stage is usually present through the spring and summer months and once all the spores are released (up to 100 million spores over the spring/summer period), it dies. The microscopic stage (the gametophyte), releases sperm and eggs, when conditions are favourable, which then fertilise and grow into a macroscopic plant. It is present during the colder months. Temperature, light and depth are important variables affecting development.
Plants reach to 1.5-2 m in (even up to 3 m) in length in less than a year. Its growth rate has been measured at 1cm per day.It is found mostly on sheltered reef areas which are subject to oceanic influence, rarely in highly exposed areas. It does not tend to become established successfully in areas with high wave action and an abundance of local vegetation.