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Maerl - Phymatolithon calcareum

Phymatolithon calcareum

Image Keith Hiscock - Phymatolithon calcareum forming a maerl bed. Loch Carron, West Scotland. Image width ca 20 cm.
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Distribution map

Phymatolithon calcareum recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

Sightings Have you seen Phymatolithon calcareum?
If so please submit your record.

  • EC_Habitats
  • UK_BAP

Key identification features Key identification features

  • Pink to mauvish brown.
  • Calcareous branching nodules up to 3 cm across and 6 mm thick.
  • Commonly resembles stag's horns.
  • The surface can be smooth or flaky.
  • Phymatolithon calcareum is the most common species but there are several others.

Habitat Habitat

  • Depth of less than 20 metres on sheltered sand, mud or gravel.
  • Usually found as unattached plants forming beds of coral gravel (maerl).
  • Slow growing. Provides an important habitat for other species.

Species facts Species facts

  • Unusual collection of species present in maerl beds.
  • Dead maerl beds are more common than live ones.
  • Live maerl is a thin crust over dead material that may be 8,000 years old.
  • Extracted for use as a soil conditioner on farm land.
  • Damaged by heavy bottom fishing gear, especially scallop dredgers.
  • Included in UK Biodiversity Action Plan and EC Habitats Directive.

Want to read more?

Have a look at the intermediate review or the advanced review.

Sightings Have you seen a maerl? If so please submit your record.