Strontium/lithium ratio in aragonitic shells of Cerastoderma edule (Bivalvia) — A new potential temperature proxy for brackish environments.

Quantitative reconstruction of water temperature from shells of bivalve mollusks is still a very challenging task. For example, in highly variable environments such as intertidal zones, shell oxygen isotope values can only provide reliable temperature estimates if the δ 18 O water signature during the time of growth is known. Furthermore, trace element-to-calcium ratios such as Sr/Ca or Mg/Ca often do not serve as reliable paleothermometers, because their incorporation into bivalve shells is known to be strongly biologically controlled. Here, we present a potential novel temperature proxy which is based on the Sr/Li shell ratio of the intertidal bivalve Cerastoderma edule . Up to 81% of the variability in Sr/Li shell is mathematically explained by water temperature. It is suggested that vital effects on the incorporation of Sr and Li into the aragonitic shells are largely eliminated by normalizing Sr/Ca to Li/Ca. Growth rate does not control the incorporation of Sr or Li into the shell of C. edule . By using this new proxy, it was possible to estimate water temperature from C. edule with an uncertainty of ± 1.5 °C. Future studies are required to test if Sr/Li shell also serves as a reliable temperature proxy in other bivalve species and in other environments. [ABSTRACT FROM AUTHOR]