Environmental changes affecting light climate in Andean Patagonian mountain lakes: implications for the plankton community

MODENUTTI, B.; BALSEIRO, E.; BASTIDAS NAVARRO, M.; SOUZA, M.S.; LASPOUMADERES, C.; CUASSOLO, F.

Perth, Scotland, UK

Congreso; Global Change and the World’s Mountains; 2010

In North-Patagonian Andean lakes (both alpine and deep subalpine) the verylow concentrations of DOC lead to high UV exposure levels. In these lakes, thethermal structure, together with the low nutrient concentrations and the highUV transparency exert a strong effect on the composition and function ofplankton communities. Here we analysed a dataset of lakes from thePatagonian Andes located between 750 m and 1700 m a.s.l. discussing thechanges in their optical characteristics and the effect on plankton communities.Stratification depth can alter the light supply to phototrophic plankton since thedeepening of termocline, which increases thickness of the mixing layer, candrag down planktonic organisms to low light level. Variations in glacial melt canalso alter the plankton distribution in particular the deep chlorophyll maxima.Temperature is expected to increase in alpine areas in the next years, thusalpine lakes from the region (> 1600 m a.s.l.) will change their physicalstructure with co-occurring modification in the surrounding vegetation. Thischanges may occur in a scenario were anthropogenic deposition of nitrogenwas not recorded, therefore increase in carbon:nutrient ratios may beenhanced in the region.