Knotted Wrack

Knotted wrack, also called egg wrack or rockweed and known scientifically as Ascophyllum nodosum, is a large, common cold water brown alga of the family Fucaceae and the only species in its genus. Its long, tough, leathery fronds grow up to two meters long, occasionally to six meters, and carry regularly spaced egg-shaped air bladders that help disperse broken pieces and improve access to light for photosynthesis, with color ranging from olive-green to olive-brown and young shoots starting yellow before darkening. It dominates sheltered, mid-shore rocky sites from the White Sea to Portugal in Europe and from Labrador to Long Island in North America, and is harvested for fertilizer, alginates, and seaweed meal.