Chironomid-climate continentality conundrum

PLOS One | https://doi.org/10.1371/journal.pone.0327780 August 5, 2025 1 / 18 OPEN ACCESS Citation: Bakumenko V, Poska A, Birks HJB, Huser B, Veski S (2025) Chironomid-climate continentality conundrum. PLoS One 20(8): e0327780. https://doi.org/10.1371/journal. pone.0327780 Editor: Walter Finsinger, Centre National de la Recherche Scientifique, FRANCE Received: December 2, 2024 Accepted: June 20, 2025 Published: August 5, 2025 Copyright: © 2025 Bakumenko et al . This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data availability statement: All relevant data are within the paper and its Supporting Information files. Funding: : This study was financially supported by the Estonian Research Council grants PRG1993 and TK215. Varvara Bakumenko was supported by the Doctoral School of Earth Sciences and Ecology, supported by RESEARCH ARTICLE Chironomid-climate continentality conundrum Varvara Bakumenko 1, Anneli Poska1,2*, H. John B. Birks 3, Brian Huser4, Siim Veski1 1 Department of Geology, Tallinn University of Technology, Tallinn, Estonia, 2 Department of Physical Geography and Ecosystem Science, Lund University, Sweden, 3 Department of Biological Sciences and Bjerknes Centre for Climate Research, University of Bergen, Norway; Environmental Change Research Centre, University College London, London, United Kingdom, 4 Department of Aquatic Sciences and

Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden * anneli.poska@nateko.lu.se Abstract It is predicted that continentality, a climate parameter representative of a region’s annual temperature and precipitation range, will undergo significant changes in the future. The lack of past continentality reconstructions makes it impossible to decipher any long-term patterns of continentality changes. Here, we investigate the extent to which continentality influences modern chironomid assemblages and evaluate their ecological relevance for palaeolimnological data-based reconstructions of past continentality. We selected 53 lakes along a longitudinal gradient covering the East European Plain (Western part of Russia, Estonia, Latvia) and southern Scandinavia (Sweden and Norway). We analysed the dependency of chironomid assemblages on a variety of environmental parameters including two continentality indices (annual temperature range (ATR) and the Kerner Oceanity Index (KOI)), growing degree days at base temperature 5 °C, mean air temperatures of July, April, and October, number of ice-cover days, lake-water pH, loss-of-ignition and water depth using redundancy analysis. Correlations between all variables were tested to check for possible con- founding effects. KOI had the highest explanatory power of 18.4% in the dataset and an absence of collinearity (correlation index < 0.7) with all the other tested variables. Further, we estimated weighted average optima to investigate the distribution of

the morphotypes along the continentality gradient in the dataset. Glyptotendipes pallens-type, Neozavrelia, Polypedilum sordens-type, and Microchironomus showed a preference for a continental climate, while Paratanytarsus penicillatus-type, Pseu- dorthocladius, Thienemannimyia, and Limnophyes were found mainly in samples from oceanic areas. Weighted averaging-partial least squares regression was used for a trial test of the data, resulting in a promising KOI-based model performance with R2 = 0.73 and RMSEP = 5.1. Despite the relatively small dataset, our study suggests that chironomid data have the potential for further development as a tool for recon- structing palaeocontinentality.