Biodiversity & Conservation

Beds of dead maerl

Dead maerl beds

Beds of dead maerl
Distribution map

Dead maerl beds recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats
  • UK_BAP

For a list of 2004 characterising species please see the JNCC website.

Species indicative of sensitivity

To assess the sensitivity of the biotope, the sensitivity of component species is reviewed. Those species that are considered to be particularly indicative of the sensitivity of the biotope, and for which research has been undertaken in detail are shown below (see selection criteria). The biology of other component species of the biotope is also taken into account wherever information is known to the researcher.

Species found especially in this biotope

  • Cruoria cruoriaeformis

Rare of scarce species associated with this biotope


The key structural species in live maerl beds is the maerl itself. However, in ‘dead’ maerl beds the maerl provides the substratum alone. While grazers are probably important species that keep live maerl free of overgrowing species, this is not relevant in ‘dead’ maerl beds. The maerl bed communities are very dependent on the fauna and flora of the surrounding area, and are highly variable. Therefore, it was not possible to identify particular key or important characterizing species. Therefore, the assessment of sensitivity was based on major functional groups of organisms and representative examples where the evidence allowed. For example, epifloral, epifaunal, infaunal and deep burrowing species. Loss of members of these groups would result in an impoverished community rather than loss of the maerl community itself, so that no one group or species (within ‘dead’ maerl beds) was identified as representative of sensitivity on its own.

Additional information


This review can be cited as follows:

Tyler-Walters, H. 2013. Beds of dead maerl. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 01/12/2015]. Available from: <>