Species composition and biodiversity

Characterising species

For IGS.Mrl in the UK % Frequency Faithfulness Typical abundance
Cerianthus lloydii Frequent
Pagurus bernhardus Occasional
Liocarcinus depurator Occasional
Gibbula magus Occasional
Asterias rubens Occasional
Echinus esculentus Occasional
Lithothamnion glaciale Frequent
Phymatolithon calcareum Common
Polyides rotundus Occasional
Halarachnion ligulatum Occasional
Nitophyllum punctatum Occasional
Brongniartella byssoides Occasional
Dictyota dichotoma Occasional
Laminaria saccharina Frequent
For IMX.MrlMx in the UK % Frequency Faithfulness Typical abundance
Suberites ficus Rare
Cerianthus lloydii Frequent
Anemonia viridis Occasional
Anthopleura ballii Occasional
Sagartiogeton undatus Frequent
Terebellidae indet. Occasional
Myxicola infundibulum Common
Liocarcinus depurator Occasional
Gibbula magus Occasional
Asterias rubens Occasional
Marthasterias glacialis Occasional
Dudresnaya verticillata Frequent
Lithophyllum dentatum Common
Lithophyllum fasciculatum Common
Lithothamnion corallioides Common
Phymatolithon calcareum Frequent
Phymatolithon purpureum Occasional
Gracilaria gracilis Frequent
Halarachnion ligulatum Frequent
Rhodophyllis divaricata Frequent
Dictyota dichotoma Frequent

The maerl beds of Brittany and of the Mediterranean have long been recognised as communities with a particularly high diversity of plant and animal species. In the British Isles, there may be somewhere in the range of 150-200 or more macroalgal species found on maerl, and perhaps over 500 benthic faunal species. Amongst the associated organisms are many rare species which are unusual, rare or poorly known: a recent report on maerl beds in the sound of Arisaig, Scotland by Davies & Hall-Spencer (1996) revealed four species of polychaete and an isopod species likely to be new to science, in addition to large numbers of the isopod Paramunna bilobata, previously described as a rare gravel-dwelling species.

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