Knotted Wrack Seaweed

• knotted wrack is perhaps the best known of all the seaweeds of Northern Ireland
• it is very common on most rocky shores, except those most exposed to wave action
• although common, it has undergone rapid decline which may be an indicator of changes in the habitat
• knotted wrack is one of the most important seaweeds on the more sheltered shores
• it is a large brown alga, which can grow to 2m long and live for several decades
• the large egg-shaped air bladders occur in series along the frond making it easy to recognize
• ‘hold-fasts’ attach it firmly to rocks and boulders
• these hold-fasts simply attach the plant to the rock but unlike roots they do not in any way ‘feed’ the plant
• the bladders are up to 5cm long and are not easily ‘popped’, but can be used by children to spray water or as whistles
• knotted wrack is harvested for use in fertilisers and for the manufacture of seaweed meal for animal and human consumption with an extensive range of medicinal and dental use
• knotted wrack can be found all year round on most rocky shores, especially the more sheltered sea loughs such as Strangford Lough
• you can have a look out for knotted wrack at our rock pooling event at Portrush on Saturday the 7 August 2010