Biology

A.nodosum is easily recognised as it’s frond has no midrib and is slightly rounded with a single vesicle swelling to the full width of the frond. It has long fronds up to 1.8m in length which provide excellent shelter for numerous intertidal species. This is the only species that regularly sheds it’s outer skin which appears to have the effect of preventing a build up of epiphytes.

Growth occurs from the tip at a rate of up to 15cm per year in adult individuals and re-growth can occur from the holdfast if the frond is torn off. A.nodosum produces it’s first vesicle in it’s fifth year then annually from then on.

A.nodosum grows in a wide band on the mid-shore on relatively sheltered coasts. It has an elasticity that enables it to cope with the up and down swell but does not cope well with strong wave action and in such locations is replaced by Fucus vesiculosus.

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References.

Collins pocket guide, Seashore of Britain & Europe, Peter Hayward, Tony Nelson-Smith, Chris Shields, 1996.

Handbook of the Marine Fauna of North-West Europe, Eds P.J.Hayward & J.S.Ryland, 2006.

Hill, J.M. & White, N., 2006. Ascophyllum nodosum. Knotted wrack. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 05/02/2007]. Available from: <http://www.marlin.ac.uk/species/Ascophyllumnodosum.htm>