Blue Forests Basics

What is Rockweed?

Rockweed is a macroalgae, and all rockweed species belong within the brown algae group (just as kelp do). The most important rockweed species in Norway are spiral wrack (Fucus spiralis), serrated wrack (Fucus serratus), knotted wrack (Ascophyllum nodosum), bladderwrack (Fucus vesiculosus), and channelled wrack (Pelvetia canaliculat). Since the 1980’s, Japanese species like Japanese wireweed (Sargassum muticum) have also established themselves in the Norwegian algal flora.

Most rockweed species have air-filled bladders that allow them to float upright at low tide.

Though both kelp and rockweed are brown algae, there are some distinguishing characteristics between them. For example, rockweed grows at the top of the coastal zone in shallow water and does not have leaves as large as kelp. Geographic areas where rockweed is found is often referred to as the rockweed belt. This is primarily the equatorial zone that is most affected by waves and currents.  

The species selection of rockweed varies with the degree of exposure in the area. In western and northern Norway in sheltered waters, we find spiral wrack, channelled wrack, serrated wrack, and bladderwrack. On the Skagerrak coast, knotted wrack and Japanese wireweed often grow in the same areas. 

where is Rockweed found?

What benefits does Rockweed provide?

Historically, rockweed and kelp have been harvested and utilised in many ways. Algae are exceptionally nutritious, as they contain high amounts of iodine, calcium, and several essential vitamins. Algae also contain high amounts of protein, carbohydrates, and antioxidants. Because of their nutritional value, algae have traditionally been used as fertiliser for farming and agriculture in Norway. Macroalgae can also be harvested for feed production within the aquaculture industry.

Rockweed and kelp were traditionally also burned to make glass and produce iodine in Norway. More recently, a useful substance called alginate is often extracted from macroalgae, where it is used in the food and pharmaceutical industries. In addition, macroalgae are harvested for feed production for the aquaculture industry.