Can stable oxygen and hydrogen isotopes from Australian subfossil Chironomus head capsules be used as proxies for past temperature change?

This paper presents the first systematic investigation of stable isotopes (δO and δH) from the subfossil chironomid head capsules (HCs) of a single taxon (Chironomus). The study focuses on sixteen south-eastern Australian lakes and investigates the potential of Chironomus spp. HC stable isotopes to reconstruct past temperature changes from these lakes. The relationship between δO values of Chironomus spp. HCs from Australian oligotrophic to mesotrophic lakes in humid areas and air temperature appears robust (r\ua0=\ua00.88) and in line with results from European lakes. Similar results were obtained for δH values and temperature (r\ua0=\ua00.94). For lakes that are located in semi-arid and sub-humid areas that have high evaporation compared to precipitation, and often long water residence time, the temperature relationship is not robust. This is due to the evaporative enrichment of δO values in lake water and the effect of salinity and higher nutrient status. Vital effects may also play a role. The overall findings of this study are that both Chironomus spp. HC δO and δH are potentially valuable tools for reconstructing temperature in cooler, low nutrient and low salinity lakes of Australia. In warmer, sub-humid to semi-arid regions, δO and δH may provide valuable information about past changes in hydrological conditions