Holocene changes in moisture source and temperature revealed by the oxygen isotopic composition of fossil Daphnia ephippia in Sierra Nevada, southern Spain López-Blanco, Charo García-Alix Daroca, Antonio Sánchez Almazo, Isabel María Jiménez Moreno, Gonzalo Anderson, R. Scott This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 892487 to CLB. This work has been also supported by the project PID2021-125619OB-C21 funded by Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación/ 10.13039/501100011033/, by ERDF A way of making Europe / EU Union and by the research group RNM-190 (Junta de Andalucía). The study of oxygen isotopes in chitin and its use as a paleoclimatic proxy is still under development. The low oxygen content of chitin and the low sample weight of fossils have hindered this research topic, even though there is evidence of a strong correlation between the oxygen isotopic composition of chitin and the isotopic composition of the host water. In order to further this research we present a paleoclimatic reconstruction based on δ18O of cladoceran remains from the lake sediments of Laguna de Río Seco, Sierra Nevada, Spain. Here, modern water isotopic data were used as a modern analogue to establish an important influence on evaporative enrichment as the ice-free season advances. The oxygen isotope signal from Daphnia resting eggs was used as a proxy for autumn snapshots of the water isotopic composition at millennial time scales. Long-term changes were controlled by the moisture source and the summer insolation. Between deglaciation and 4.2 kyr BP, δ18O measurements exhibited generally depleted values only interrupted by a peak at ∼ 7.2 kyr BP, concurrent with a temperature maximum inferred from earlier quantitative reconstructions. A predominantly Atlantic moisture source and changes in the evaporation related to seasonality explained the isotopic variability at that time. From 4.2 kyr BP onwards, a notable enrichment in this isotopic signal occurred, which was consistent with greater influence of a Mediterranean precipitation source and higher evaporation at lower lake levels. This new isotope record provides a unique application of paleoclimates from cladocerans, which goes beyond the taxonomic and numerative methodology traditionally used in subfossil cladoceran analysis. 2025-04-30T06:20:48Z 2025-04-30T06:20:48Z 2025-06-30 journal article C. López-Blanco et al. Holocene changes in moisture source and temperature revealed by the oxygen isotopic composition of fossil Daphnia ephippia in Sierra Nevada, southern Spain. Catena 254 (2025) 108984. https://doi.org/10.1016/j.catena.2025.108984 https://hdl.handle.net/10481/103848 10.1016/j.catena.2025.108984 eng info:eu-repo/grantAgreement/EC/H2020/892487 http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Elsevier