High Quality Content by WIKIPEDIA articles! Ascophyllum nodosum is a large, common brown alga (Phaeophyceae) in the family Fucaceae, being the only species in the genus Ascophyllum. It is seaweed of the northern Atlantic Ocean, also known as rockweed, Norwegian kelp, knotted kelp, knotted wrack or egg wrack. It is common on the north-western coast of Europe (from Svalbard to Portugal) including east Greenland and the north-eastern coast of North America.