Abstract

In the western North Atlantic and Gulf of Mexico, isotope sclerochronology and field studies of the hard clams, Mercenaria mercenaria and M. campechiensis, collected across a latitudinal gradient show patterns in the seasonal timing of slow versus fast shell incremental growth. It is unknown, however, if similar patterns exist in the eastern North Atlantic. The European limpet, Patella vulgata, is abundant in rocky shore communities and archaeological deposits along the eastern North Atlantic. As such, it is a potentially valuable archive for paleoclimate and archaeological research. We used isotope sclerochronology to identify the seasonal timing of annual growth line formation in shells from the cold- and warm-temperate zones and at the boundary between these zones. Four shells from the cold-temperate zone (United Kingdom and Norway), five shells from the warm-temperate zone (Spain), and six shells from the boundary (near the English Channel) were analyzed. The isotopic records represent between two and eight years of growth. Cold-temperate shells formed annual lines in winter, and warm-temperate shells produced annual lines in summer. A mixed pattern was found at the boundary. This pattern in the seasonal timing of slowed growth across a latitudinal gradient is similar to that shown in studies of Mercenaria in the western North Atlantic. Thermal tolerance is the most likely mechanism for the observed changes in the timing of annual growth line formation with latitude.

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