Chironomid-inferred Holocene climate in the Austrian Alps

Understanding the climatic instability at millennial timescales is very important for determining the background and trend of natural climatic variations. Remote high alpine lakes are particularly sensitive to climatic changes, and their sediments are excellent archives preserving information about past environmental changes. Much of our knowledge of past climate is derived just from the palaeoecological analysis of lake sediments. The main goal of the proposed study is to determine Holocene climatic variability and climate impact on lake ecosystems by means of chironomid analysis of the sediment record from the remote high alpine lake Schwarzsee ob Sölden located in the Austrian Alps. The proposed project will be carried out in the Institute of Ecology, University of Innsbruck, where a multi-proxy palaeoecological investigation including diatoms, pollen, plant macrofossils, geochemistry, mineralogy, etc. from this alpine lake is currently in progress within an ongoing FWF project (R29-N10). Chironomid analysis of sediment records is a young but powerful tool for reconstruction of past environmental conditions, and widely used in palaeoecology and palaeoclimatology within multidisciplinary projects. Quantitative reconstruction of past summer air temperature from chironomid assemblages on the basis of a regional temperature data set will promote our understanding of Holocene climatic variability in the Austrian Alps and contribute to a spatial reconstruction of climate variability through time in the Alpine region. Special attention will be placed on studying the past changes in bottom-water anoxia and mixing regime of the lake. Chironomid-based evidence of these changes will provide independent assessment of the climate impact on in-lake processes over the last 10,000 years. This study will provide the first chironomid-based reconstruction of past climatic and limnological changes throughout the Holocene in the Austrian Alps. The obtained results may serve as background knowledge to predict the response of lake ecosystems to possible future climate changes in the Alpine region.