MOLLUSK SHELLS OF PATELLA CRENATA (GASTROPODA: PATELLIDAE) FROM TENERIFE, CANARY ISLANDS, AS A LOW-LATITUDE PALEOCLIMATIC PROXY

The limpet genus, Patella, has been established as a credible repository of sub-monthly paleotemperature data at high and mid latitudes. However, these shells have not been extensively studied in low-latitude environments, where climatic variations are comparatively subdued and shell growth may be continuous throughout all seasons. The Canary Islands, located 95km from the Atlantic coast of Morocco at 27-29^oN, provide an ideal location for studying these shells at subtropical latitudes considering that (1) Patella is plentiful in the modern rocky intertidal shore and (2) archeological shells are well-preserved and abundant in shell middens expanding back in time ~2,500 years. Moreover, oxygen isotope ratios (δ¹⁸O) of local seawater do vary seasonally allowing us to constrain this parameter for estimating sea surface temperature (SST) from shell carbonate.

We analyzed the δ¹⁸O values of live-collected Patella shells using two different sampling approaches. First, live-collected limpets were sampled using a manual Dremel drill along the calcitic shell margin, which provided bulk (averaged) δ¹⁸O values at the time of specimen collection. Second, several modern limpets were cross-sectioned from anterior to posterior parallel to the maximum growth axis and microsampled sequentially at high resolution using a Merchantek micromill.

Bulk shell margin δ¹⁸O values correlated negatively with observed SST (R²=0.95; p<0.001; n=98). These results suggest that the high-resolution oxygen isotope time series of Patella crenata records seasonal variations in SST. Ongoing oxygen isotope analyses from high-resolution micromilled samples will allow us to reconstruct SST at sub-monthly scale during the late Holocene using archaeological P. crenata from the Canary Islands.