Significance of algal borings and Acmaea grazing traces on molluscan shells from Ardyne (west Scotland) postglacial sediments

Molluscan shells from Postglacial beds (younger than 11,000 years B.P.) of Ardyne Point, southwest Scotland show evidence of algal borings attributed to the chlorophytes Eugomontia sacculata and Ostreobium quekettii. The shells also bear grazing traces similar to those inscribed by the Recent limpet Acmaea virginea on microendolithic algal-infested shells dredged from the shallow sublittoral shelf environment in the Clyde Sea area.

Radula marks of Lepidopleurus which occasionally occur alongside those of Acmaea in the Clyde Sea have not been encountered; they are palaeoecologically less significant since a modern chiton's diet is not clearly defined. Unlike the limpet, it is not exclusively dependent on algae. Biting traces attributed to regular echinoids are common on the Ardyne shells.

Intensity of algal boring is high. This and the bioabrasive traces of the limpet suggest deposition in a shallow (< 12 m) low-energy environment, thus offering a potential palaeoecological tool.