University of Wollongong Research Online Faculty of Science, Medicine & Health - Honours Theses University of Wollongong Thesis Collections 2019 A Mentum In Time: Chironomids as Palaeotemperature Indicators at Thirlmere Lakes, NSW, Australia E Swallow Follow this and additional works at: https://ro.uow.edu.au/thsci University of Wollongong Copyright Warning You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorise you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part of this work may be reproduced by any process, nor may any other exclusive right be exercised, without the permission of the author. Copyright owners are entitled to take legal action against persons who infringe their copyright. 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For further information contact the UOW Library: [email protected] A Mentum In Time: Chironomids as Palaeotemperature Indicators at Thirlmere Lakes, NSW, Australia Abstract The Thirlmere lakes, within the Blue Mountains Heritage Area, offer excellent potential to provide records of past climate/environmental change for the southeast Australian region where currently few records exist. Palaeo-records provide a longer-term perspective on lake conditions, which is important given the recent lake drying observed in the system. The primary aim of this study was to use chironomids (non- biting midges) to reconstruct temperature through the Holocene at Thirlmere Lakes National Park. Temperature reconstructions over the Holocene are scarce for the southeast Australian region and chironomids can be ideal proxies to enhance our understanding of climatic variation over this period. The unique characteristics of chironomids, including their ability to respond rapidly to climatic fluctuations, makes them ideal tools for reconstructing palaeotemperature. 31 Chironomid taxa were identified from a master core from Thirlmere Lakes and assessed against an existing training set for the region to infer the likely environmental variables effecting the down-core assemblages. However, temperature was identified as having no significant impact on the changing down-core assemblages, disallowing the creation of a temperature reconstruction. Depth, conductivity and productivity explained the most significant ariancev in the assemblages. The training set contained insufficient modern analogues, limiting theeliability r of inferring environmental conditions at Thirlmere through the Holocene. However, the ecology of the chironomid assemblages implied warm shallow eutrophic conditions prevailed, while modern chironomid assemblages indicate that there is a degree of variability between the lakes within the National Park. They also potentially indicate the lakes are characterised by high variability in environmental conditions, as would result from water level fluctuations and drying. Even though the chironomid record failed to supply reliable interpretations of environmental conditions at Thirlmere Lakes through the Holocene, a better understanding of in-lake process has resulted, enabling identification of future research objectives. Degree Type Thesis Degree Name BEnviSci Hons Department School of Earth, Atmospheric & Life Sciences Advisor(s) Tim Cohen Keywords Chironomid, holocene This thesis is available at Research Online: https://ro.uow.edu.au/thsci/178 A Mentum In Time: Chironomids as Palaeotemperature Indicators at Thirlmere Lakes, NSW, Australia by Elizabeth Swallow A research report submitted in partial fulfilment of the requirements for the award of the degree of BACHELOR OF ENVIRONMENTAL SCIENCE (HONOURS) SCHOOL OF EARTH, ATMOSPHERIC AND LIFE SCIENCES THE UNIVERSITY OF WOLLONGONG October (2019) The information in this thesis is entirely the result of investigations conducted by the author, unless otherwise acknowledged, and has not been submitted in part, or otherwise, for any other degree or qualification. - Elizabeth Swallow 21st October 2019 Central Image: A dry Lake Werri Berri captured by author on 28/02/2019 Circling Images: Chironomid head capsules and phantom midge mandible captured in July of 2019 by author using a compound microscope at ANSTO. From the 12 o’clock position moving clockwise: A Pallidicornis at 20x magnification, an SO5 at 40x magnification, a Paramerina at 20x magnification, a phantom midge mandible at 10x magnification, a Kiefferulus martini at 20x magnification and a Dicrotendipes cumberlandsis at 10x magnification. 2 This research is supported by the AINSE Honours Scholarship Program. 3 Acknowledgements Firstly, I would like to thank each of my supervisors, Tim Cohen, Sam Marx, Craig Woodward and Heather Haines. Each of you provided unique and insightful perspectives which helped me look at my project from all possible sides. Your constant encouragement and enthusiasm made this experience extremely enjoyable and it was a pleasure working with you all. A special thanks to Craig and Heather for introducing me to the world of chironomids, you were always friendly and encouraging and always showed the utmost confidence in me. Heather, thankyou for all your help in the lab and for the initial work on LC2, I know how much time that would have taken so thankyou. Craig, thankyou for all the time spent stepping me through this process and the countless days checking over my results. Your enthusiasm for my project and confidence in me was greatly appreciated. A big thankyou to everyone who helped during my fieldwork and everyone who read my writing and provided feedback, Bryce and Jess especially. Special thanks to my sisters for reading and re-reading my work over and over again. Lastly, a special thankyou to my friend Bryce, your support, encouragement and sarcasm was endless and you made this experience a whole lot funnier. 4 Abstract The Thirlmere lakes, within the Blue Mountains Heritage Area, offer excellent potential to provide records of past climate/environmental change for the southeast Australian region where currently few records exist. Palaeo-records provide a longer-term perspective on lake conditions, which is important given the recent lake drying observed in the system. The primary aim of this study was to use chironomids (non-biting midges) to reconstruct temperature through the Holocene at Thirlmere Lakes National Park. Temperature reconstructions over the Holocene are scarce for the southeast Australian region and chironomids can be ideal proxies to enhance our understanding of climatic variation over this period. The unique characteristics of chironomids, including their ability to respond rapidly to climatic fluctuations, makes them ideal tools for reconstructing palaeotemperature. 31 Chironomid taxa were identified from a master core from Thirlmere Lakes and assessed against an existing training set for the region to infer the likely environmental variables effecting the down-core assemblages. However, temperature was identified as having no significant impact on the changing down-core assemblages, disallowing the creation of a temperature reconstruction. Depth, conductivity and productivity explained the most significant variance in the assemblages. The training set contained insufficient modern analogues, limiting the reliability of inferring environmental conditions at Thirlmere through the Holocene. However, the ecology of the chironomid assemblages implied warm shallow eutrophic conditions prevailed, while modern chironomid assemblages indicate that there is a degree of variability between the lakes within the National Park. They also potentially indicate the lakes are characterised by high variability in environmental conditions, as would result from water level fluctuations and drying. Even though the chironomid record failed to supply reliable interpretations of environmental conditions at Thirlmere Lakes through the Holocene, a better understanding of in-lake process has resulted, enabling identification of future research objectives. 5 Table of Contents Acknowledgements .................................................................................................................... 4 Abstract ...................................................................................................................................... 5 List of Figures ............................................................................................................................ 9 List of Tables ..........................................................................................................................