The dog cockle, Glycymeris glycymeris (L.), a new annually-resolved sclerochronological archive for the Irish Sea

Cross-dated chronologies derived from internal growth increments in the shells of the long-lived bivalve, the dog cockle Glycymeris glycymeris (Linnaeus, 1758), live-collected from two different sites off the east (1997) and south (2009) coasts of the Isle of Man respectively, are described. The chronologies, developed from ten individuals from each site, were found to be statistically robust (Expressed Population Signal (EPS) = 0.87 and 0.94 respectively) with a significant common growth signal despite their location 27 km apart (R = 0.53; N = 49, P = < 0.0001). The period of common growth between the two chronologies is consistent with the 12-year difference in their dates of collection thus providing evidence of an annual periodicity of growth line formation. Significant positive correlations were identified between the chronology indices from both the southern (R = 0.55, N = 58, P = < 0.0001) and eastern sites (R = 0.64, N = 68, P = < 0.0001) and mean January to September sea surface temperatures. A significant positive correlation was also found between the southern site and the winter North Atlantic Oscillation index (R = 0.43; N = 49, P = 0.0009). These data indicate that annual growth increments in the shells of G. glycymeris have the potential to be used as a scleroclimatological archive.