Eating seaweeds

Seaweeds are found throughout the world's oceans and seas and none is known to be poisonous. An exception that should be considered is possibly Desmarestia, a widespread genus in colder waters, has sulphuric (sulfuric) acid in its cells, which can have a pH as low as 1, which will certainly not encourage anybody to eat beyond the first mouthful! Many are actually nice to eat and even considered a great delicacy in Asian countries.

Seaweeds are used in many maritime regions for industrial applications and as a fertiliser. The major direct use of these plants as food is in Japan, China and Korea, where seaweed cultivation has become a major coastal industry.

The main food species grown by aquaculture in these countries are Nori or Zicai (Porphyra or Pyropia, a red alga), Kombu, Kunbu or Haidai (Laminaria or Saccharina: brown algae) and Wakame (Undaria, also a brown alga). In Japan alone, the total annual production value of nori amounts to >US$1 billion, one of the most valuable crops produced by aquaculture in the world. In most western countries seaweed consumption is relatively restricted and there has not been any great pressure to develop mass cultivation techniques. On this site, seaweed aquaculture, particularly nori, a Japanese red seaweed, is described in detail.

 Porphyra umbilicalis(left) was probably the species studied by Kathleen Drew-Baker  (1901–1957, below) of the University of  Manchester in the 1950s which led to the discovery of the "Conchocelis" phase of nori, which can be cultivated in shells. This led in turn to the devlopment of a reliable method of seeding nets in Japan and elsewhere.