Long-term ecological changes in Mediterranean mountain lakes linked to recent climate change and Saharan dust deposition revealed by diatom analyses

Carmen Pérez-Martínez; Kathleen M Rühland; John P Smol; Vivienne J Jones; José M Conde-Porcuna

doi:10.1016/j.scitotenv.2020.138519

Long-term ecological changes in Mediterranean mountain lakes linked to recent climate change and Saharan dust deposition revealed by diatom analyses

Sci Total Environ. 2020 Jul 20:727:138519. doi: 10.1016/j.scitotenv.2020.138519. Epub 2020 Apr 13.

Authors

Carmen Pérez-Martínez¹, Kathleen M Rühland², John P Smol², Vivienne J Jones³, José M Conde-Porcuna⁴

Affiliations

¹ Institute of Water Research, University of Granada, 18071 Granada, Spain; Department of Ecology, Faculty of Science, University of Granada, 18071 Granada, Spain. Electronic address: cperezm@ugr.es.
² Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen's University, Kingston, ON K7L 3N6, Canada.
³ Environmental Change Research Centre, Department of Geography, University College London, Pearson Building, Gower Street, London WC1E 6BT, UK.
⁴ Institute of Water Research, University of Granada, 18071 Granada, Spain; Department of Ecology, Faculty of Science, University of Granada, 18071 Granada, Spain.

PMID: 32498206
DOI: 10.1016/j.scitotenv.2020.138519

Abstract

Anthropogenic climate change and the recent increase of Saharan dust deposition has had substantial effects on Mediterranean alpine regions. We examined changes in diatom assemblage composition over the past ~180 years from high-resolution, dated sediment cores retrieved from six remote lakes in the Sierra Nevada Mountains of Southern Spain. In all lakes, changes in diatom composition began over a century ago, but were more pronounced after ~1970 CE, concurrent with trends in rising regional air temperature, declining precipitation, and increased Saharan dust deposition. Temperature was identified as the main predictor of diatom assemblage changes, whereas both Saharan dust deposition drivers, the Sahel precipitation index and the winter North Atlantic Oscillation, were secondary explanatory variables. Diatom compositional shifts are indicative of lake alkalinization (linked to heightened evapoconcentration and an increase in calcium-rich Saharan dust input) and reduced lake water turbulence (linked to lower water levels and reduced inflows to the lakes). Moreover, decreases in epiphytic diatom species were indicative of increasing aridity and the drying of catchment meadows. Our results support the conclusions of previous chlorophyll-a and cladoceran-based paleolimnological analyses of these same dated sedimentary records which show a regional-scale response to climate change and Saharan dust deposition in Sierra Nevada lakes and their catchments during the 20th century. However, diatom assemblages seem to respond to different atmospheric and climate-related effects than cladoceran assemblages and chlorophyll-a concentrations. The recent impact of climate change and atmospheric Saharan deposition on lake biota assemblages and water chemistry, as well as catchment water availability, will have important implications for the valuable ecosystem services that the Sierra Nevada provides.

Keywords: Alkalinization; Aridity; Ca atmospheric input; Drought; Paleolimnology; Sierra Nevada.

MeSH terms

Africa, Northern
Climate Change
Diatoms*
Dust
Ecosystem
Lakes*
Spain

Substances

Dust