Contribution
Annual stratification patterns in tropical mountain lakes reflect altered thermal regimes in response to climate change
Labaj, Andrew L.; Michelutti, Neal; Smol, John P.
Fundamental and Applied Limnology Volume 191 Nr. 4 (2018), p. 267 - 275
publié: Sep 25, 2018
publication en ligne: Jul 13, 2018
manuscrit accepté: Jun 29, 2018
révision final du manuscrit reçu: Jun 7, 2018
révision du manuscrit demandée: May 21, 2018
manuscrit reçu: Apr 9, 2018
ArtNo. ESP141019104000, Prix: 29.00 €
Abstract
Many lakes in the tropical Andes have historically been described as polymictic, experiencing only brief periods of thermal stratification. Recent work in Cajas National Park, in the Southern Sierra of Ecuador, however, shows that lakes presently undergo extended periods of thermal stratification. Nevertheless, questions remain about annual patterns of stratification and the main drivers that influence these new thermal regimes. Here, we present two years of lake temperature profiles from four Cajas-area lakes, which span more than 1,000 m elevation. All lakes experienced prolonged periods of thermal stratification, notably from November to May, when air temperatures were highest and wind speeds were lowest. In the three lakes at lowest elevations, the strength of thermal stratification was significantly positively correlated with air temperature and negatively correlated with wind speed. From May to October, when air temperatures were lowest and wind speeds were highest, each of the lakes experienced isothermal periods. The pattern of thermal stratification in each of the lakes was similar between the two years. Our high-resolution data show that stratification does not breakdown overnight, as has previously been hypothesized. As climate models predict future warming to be greatest with increasing altitude, the strength and duration of stratification in tropical mountain lakes will likely increase over time, with widespread implications for chemical and biological lake processes.
Mots-clefs
tropical Andes • mountain lakes • thermal stratification • anthropogenic climate change