Experimental determination of the temperature dependence of oxygen-isotope fractionation between water and chitinous head capsules of chironomid larvae

Abstract Oxygen-isotope values of invertebrate cuticle preserved in lake sediments have been used palaeoenvironmental reconstructions, generally with the assumption that fractionation oxygen isotopes between and water ( $$\upalpha_{\text{cuticle}-\text{H}_{2}\text{O}}$$ ? cuticle - H 2 O ) is independent temperature. We cultured chironomid larvae laboratory labelled oxygen-isotope across a range closely controlled temperatures from 5 to 25 °C order test hypothesis head capsules $$\upalpha_{\text{chironomid}-\text{H}_{2}\text{O}}$$ chironomid Results indicate can be rejected, decreases increasing The scatter data suggests further experiments are needed verify relationship. However, these results temperature-dependence should considered when ? 18 O as paleoenvironmental proxy, especially cases where chironomids combined other materials for which temperature dependent, such calcite, derive reconstructions past