Climatic fluctuations over the Holocene in southern Iberia (Sierra Nevada, Spain) reconstructed by fossil cladocerans

Abstract

A combination of microfossil assemblages, abundance of fossil ephippia and mean body size provides the longest paleoclimatic reconstruction based on cladoceran subfossils in the Iberian Peninsula. Species turnover in Laguna de Río Seco (Sierra Nevada, southern Spain) was controlled by changes in lake levels in response to fluctuations in hydroclimatic variability over the last ~8600 years. Our archive documents a wet period in the Early and Middle Holocene (~8600–5000 cal yr BP), characterized by eurytopic and plant-associated species. A drier stage occurred from ~5000 cal yr BP and implied a reduction in lake level and higher occurrence of species highly adapted to more ephemeral environments. Proportions of total chydorid ephippia (TCE), indicating rates between asexual and sexual reproduction, are well-correlated with a progressive trend towards aridification. Lower TCE was registered before ~5000 cal yr BP as a result of a favourable environment under higher lake level, while higher TCE started with the upcoming arid stage (~5000 cal yr BP) due to environmental stress. Besides these hydrological signatures, data on Daphnia size broadly indicate a warmer period ~8600–4000 cal yr BP and a colder stage ~4000–255 cal yr BP. Further investigations using this indicator in the Sierra Nevada will provide more precise reconstructions of past climatic conditions in southern-latitude and alpine ecosystems.