Quantitative palaeotemperature estimates based on fossil chydorid ephippia: calibration and validation of a novel method for northern lakes

To fully utilize palaeolimnological archives for tracking past environmental changes, methodological advances are necessary. We present a novel method to quantitatively reconstruct past summer air temperatures based on fossil chydorid (Cladocera: Chydoridae) ephippia assemblages. We examined a 76-lake training set from Finland for chydorid ephippia distribution to develop a transfer function for summer air temperatures. Subsequently, we tested its usability in downcore reconstructions by inferring Holocene temperatures from Lake Arapisto in southern Finland. Significant climate-related variation was found in the distribution and abundance of chydorid ephippia in the training set. A transfer…