Coral maerl

Lithothamnion corallioides


Coral maerl (Lithothamnion coralliodies) © Lin Baldock

Coral maerl is a slow-growing red seaweed that looks like pink coral.  It has a hard, chalky skeleton and grows many irregular branches, or nodules. Like all seaweeds, coral maerl needs sunlight to grow, and is usually found in shallow water to a depth of 20m.  Individual plants grow, unattached, on top of each other forming dense beds on sand, mud or gravel.  Maerl only grows in areas that are protected from strong wave action but have moderate to strong currents – the conditions have to be just right.   Occasionally it is found on the lower shore at the low water mark. 

Coral maerl is usually found together with the common maerl, and together they make up maerl beds.

Maerl beds are an important habitat for many different kinds of animals and seaweeds, which live amongst or are attached to its branches, or burrow in the coarse gravel of dead maerl beneath the top living layer.

The most serious threats to maerl beds, and the communities of marine creatures they support, come from scallop dredging and pollution.


European distribution

Locations include the west and south-west of Ireland, the south-west corner of Wales and a few sites off the south coast of England.


Conservation status/need

  • Coral Maerl FactThis is a UK BAP Priority Species (BAP species are now Species of Principal Importance/Priority Species).
  • Species of principal importance for the purpose of conservation of biodiversity under the Natural Environment and Rural Communities Act 2006
  • Nationally scarce species
  • Listed on Annex V of the Habitats Directive 
  • Maerl beds are a UKBAP Priority Habitat and are listed in Annex I of the Habitats Directive as a sub-feature of sandbanks and on the OSPAR List of Threatened and/or Declining Species and Habitats


Further information

Marine Life Information Network

JNCC - UK BAP Priority Species and Habitats 

Case Reports for the OSPAR List of threatened and/or declining species and habitats