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

This study investigates the potential of applying stable oxygen isotopes (δ 18O) from head capsules (HCs) of subfossil chironomids (subfamily Tanypodinae) to reconstruct past temperature changes from southeastern Australia. The study reports δ 18O results from Tanypodinae HCs in nine lakes. The relationship between δ 18O 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 δ 18O values measured on Chironomus spp. HCs from the same lakes reveals differences between the two groups. δ 18O values of Tanypodinae HCs have a stronger correlation with the δ 18O of lake water, δ 18O of precipitation and air temperature as compared with Chironomus δ 18O values. This suggests that Tanypodinae HCs are superior targets to Chironomus spp. for temperature reconstructions. Our data indicate that the δ 18O 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 δ 18O to temperature.