Wakame

Overview

Wakame (Undaria pinnatifida) is a large, opportunistic brown kelp native to East Asia that has become widely established in temperate waters globally. Often found in sheltered, rocky areas, this annual seaweed is known for its rapid growth and ability to colonize both natural substrates and artificial structures like ship hulls and buoys.

Appearance

This kelp typically features a broad, golden-brown, lanceolate blade with a distinct midrib and wavy, corrugated margins. Mature individuals can reach lengths of one to three meters. A key identification feature is the presence of two convoluted, frilled sporophylls located at the base of the stipe, just above the branched, root-like holdfast.

Biology & behavior

Undaria pinnatifida exhibits a heteromorphic life cycle, alternating between a large, macroscopic sporophyte stage and a microscopic gametophyte stage. The visible sporophyte typically appears in winter and reaches its maximum size by spring. As an invasive species in many regions, it can form dense forests that compete with native seaweed for light and space, sometimes displacing local flora and altering ecosystem dynamics.