A study of the stable carbon and oxygen isotope composition of recent shells of Mytilidae, especially of oxygen values in relation to temperature

Abstract

Analyses of the stable isotopes 18O and 13C were made of modern marine shells of the widely distributed Mytilidae, primarily intertidal species, collected from beaches in Europe and southern Africa, as well as from Australia and Argentina. At sites facing the open sea and where the field data of annual mean sea-surface temperatures have been recorded a comparison could be made between the stable isotope values of the shells and the seawater temperatures. The comparison shows that there is a good negative correlation between the seawater temperatures and the δ18O values of the Mytilidae shells. The analyses of a series of samples from the outer layer of the valves from five different sites, at right angles to the annual increments, reflected the seasonal variations of the seawater temperatures. The recorded amplitudes of the isotope temperatures in the shells based on the δ18O values were similar to the amplitudes of the recorded sea- surface temperatures just outside the beaches, except for Choromytilus in Swakopmund where the relatively shallow water outside the beach was more influenced by the seasonal temperature changes than the seawater outside the coast. Results shown here from the globally distributed records from the Northern and Sout- hern Hemispheres confirm the universal use of stable isotopes (18O) of marine shells (Mytilidae) in palaeoclimatological / -oceanographical studies.

Keywords

• stable isotopes
• Mollusca
• shells
• Mytilidae
• sea water
• paleotemperature
• Holocene