Characterising Inter-Individual Growth Variability of Patella vulgata Shell Through Calcein Marking Experiments: Consequences for Palaeo-Environmental Studies

Sclerochronological data from archaeological shell middens provides crucial information about past environments and subsistence practices of coastal human populations. These studies rely on a strong knowledge of species-specific growth patterns, as it is the main driver of the quantity and quality of information recorded in biogenic carbonates. The limpet Patella vulgata is highly represented in eastern Atlantic shell middens. In this study, the micro-increment formation of its shell was investigated through in situ marking experiments, using calcein fluorochrome (150 mg.L−1) coupled with cohort study and local SST recording. Calcein-stained growth structures confirmed the efficacy of the fluorochrome, and our results shows a disturbed tidal increment formation, with on average more than one increment per day, but less than one increment per tide. Growth is not mainly influenced by environmental factors, but could be forced by competition among limpets and endogenous factor (age and sex), resulting in a highly heterogenous population in terms of growth rates. Growth interruption could not be detected solely by micro-increment observation, causing a major issue for cross-calibration with recorded temperatures, sclerochronological estimation of growth and isotopic profiles. For palaeo-environmental application, we recommend to consider that there is no general population pattern, even at a micro-habitat scale.