Biodiversity & Conservation

Ascophyllum nodosum ecad mackaii beds on extremely sheltered mid eulittoral mixed substrata



Image Sue Scott - A dense mat of Ascophyllum nodosum mackaii. Image width ca 40 cm.
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Distribution map

LR.LLR.FVS.Ascmac recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats
  • UK_BAP

Marine natural heritage importance

Listed under EC Habitats Directive
UK Biodiversity Action Plan
National importance Scarce
Habitat Directive feature (Annex 1) Reefs
Large shallow inlets and bays

Biotope importance

Fish such as young common eels Anguilla anguilla and viviparous blennies Zoarces viviparous may shelter in the weed.


  • The attached form of Ascophyllum nodosum is harvested in most areas of its distribution. The unattached mackaii ecad is easy to collect, as it needs no cutting from the rocks, and it has been collected along with the attached form in the past.
  • In the west Highlands many roads run alongside loch shores where the biotope is present. Road improvements or construction or new roads, often involve 'straightening' the shoreline or building causeways across small embayments. In this way the biotope can be destroyed or cut off from the sea.
  • Most Ascophyllum nodosum ecad mackaii beds are in remote, unpolluted sites, and in a natural condition. The rarity of the habitat, the small size of many of the beds, and the importance of the UK populations in an international context have resulted in a Biodiversity Action Plan for this species (Anonymous, 1999(t)).

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This review can be cited as follows:

Hill, J.M. 2001. Ascophyllum nodosum ecad mackaii beds on extremely sheltered mid eulittoral mixed substrata. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 27/11/2015]. Available from: <>