Complexities in interpreting chironomid-based temperature reconstructions over the Holocene from a lake in Western Ireland

摘要

Investigation of Holocene climate variability remains challenging. This is largely due to chronological uncertainties and complexities associated with proxies and their relationship with climatic drivers. Pertinent questions still exist regarding the Holocene climate in Ireland, particularly in the early Holocene. We present a mean July air temperature reconstruction based on fossil chironomidae (non-biting midge flies), along with an assessment of chironomid functional traits from five guilds (based on their feeding habits) from Lough Nakeeroge, a small glacial lake in western Ireland. These records span the early to late Holocene (c. 10,000-1500 cal yr BP). The chironomid record is supplemented with pollen data to determine landscape vegetation dynamics, and compared to climate model simulations of the same period. As reliable models are essential for robust analysis of long-term climate change, we critically assess the value of the chironomid transfer function and explore the use of chironomid functional traits to infer past climate variability. While this study demonstrates the complexities of chironomid-based temperature reconstruction in Irish lakes, it endeavours to i) disentangle a complicated Holocene climate history through the exploration of other long-term Holocene records from the island; and ii) improve our understanding of environmental responses to climate variability in Ireland. The findings of this study suggest that the interpretation of chironomid-based temperature transfer functions can be challenging. However, our results demonstrate the influence of climate on the functioning of lake ecosystems over the Holocene, with the promising performance of the collector-filterer feeding guild as a palaeothermometer. (C) 2019 Elsevier Ltd. All rights reserved.