Toward more accurate temperature reconstructions based on oxygen isotopes of subfossil chironomid head-capsules in Australia

Abstract

This study investigates the potential of applying stable oxygen isotopes (δ18O) from head capsules (HCs) of subfossil chironomids (subfamily Tanypodinae) to reconstruct past temperature changes from south-eastern Australia. The study reports δ18O results from Tanypodinae HCs in nine lakes. The relationship between δ18O values of Tanypodinae HCs in lakes and summer (February) air temperature is robust (r = 0.84) supporting its potential to be applied as a temperature proxy in the Australian region. The comparison of these results with the δ18O values measured on Chironomus spp. HCs from the same lakes reveals differences between the two groups. δ18O values of Tanypodinae HCs have a stronger correlation with the δ18O of lake water, δ18O of precipitation and air temperature as compared with Chironomus δ18O values. This suggests that Tanypodinae HCs are superior targets to Chironomus spp. for temperature reconstructions. Our data indicate that the δ18O of Tanypodinae HCs could perform as well as the assemblage based chironomid transfer function from the Australian mainland. We recommend analysis of HCs from additional lakes to develop a more robust calibration curve relating Tanypodinae HC δ18O to temperature.