title: Climate change forces new ecological states in tropical Andean lakes.
abstract: Air temperatures in the tropical Andes have risen at an accelerated rate relative to the global average over recent decades. However, the effects of climate change on Andean lakes, which are vital to sustaining regional biodiversity and serve as an important water resource to local populations, remain largely unknown. Here, we show that recent climate changes have forced alpine lakes of the equatorial Andes towards new ecological and physical states, in close synchrony to the rapid shrinkage of glaciers regionally. Using dated sediment cores from three lakes in the southern Sierra of Ecuador, we record abrupt increases in the planktonic thalassiosiroid diatom Discostella stelligera from trace abundances to dominance within the phytoplankton. This unprecedented shift occurs against the backdrop of rising temperatures, changing atmospheric pressure fields, and declining wind speeds. Ecological restructuring in these lakes is linked to warming and/or enhanced water column stratification. In contrast to seasonally ice-covered Arctic and temperate alpine counterparts, aquatic production has not increased universally with warming, and has even declined in some lakes, possibly because enhanced thermal stability impedes the re-circulation of hypolimnetic nutrients to surface waters. Our results demonstrate that these lakes have already passed important ecological thresholds, with potentially far-reaching consequences for Andean water resources.
authors: Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
authors: Neal
authors: N
authors: Michelutti
authors: Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.
authors: Alexander P
authors: AP
authors: Wolfe
authors: Department of Environment and Sustainable Resource Development, Government of Alberta, Edmonton, AB T5K 2M4, Canada.
authors: Colin A
authors: CA
authors: Cooke
authors: Washington State Department of Ecology, Olympia, WA, 98504-7600, United States of America.
authors: William O
authors: WO
authors: Hobbs
authors: Department of Atmospheric and Environmental Sciences, University at Albany, SUNY, Albany, NY, 12222, United States of America.
authors: Mathias
authors: M
authors: Vuille
authors: Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
authors: John P
authors: JP
authors: Smol
mesh_terms: D057231:Climate Change; D017377:Diatoms; D005580:Fossils; D006863:Hydrogen-Ion Concentration; D060106:Lakes / Q000737:chemistry; D013020:South America; D014329:Tropical Climate
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