Paleoenvironmental proxies in echinoid spines (Eucidaris galapagensis, Döderlein 1887) along a natural water temperature gradient

Here we present data on oxygen isotopes (δ18O), carbon isotopes (δ13C), and Mg/Ca ratios measured in Eucidaris galapagensis (Döderlein, 1887) spines, which were sampled along the natural water temperature gradient of the Galápagos archipelago. We found a negative correlation of δ18OCalcite with ambient water temperature following the equation 1000 ln (α) = 23.03 (103T− 1 [K]) − 47.90. We also found δ13CCalcite be positively correlated with water temperature following the equation δ13CCalcite(VPDB) = − 47.585 + (0.164 ∗ T[K]. Mg/Ca ratios also showed a significant correlation with water temperature, however, with a low correlation coefficient. The large scatter of δ18OCalcite values within the upwelling region indicates higher growth rates during seasons of colder water temperatures. Considering this and the observed steeper slope in the temperature-δ18OCalcite relationship, our data suggest that the common assumption of respiration affecting oxygen isotope fractionation does not apply for the tropical species E. galapagensis. Overall, our data show that E. galapagensis spines represent valuable paleoenvironmental archives which might have the potential to provide sub-annually resolved water temperature records if spine architecture and growth pattern are well constrained.