Testate amoebae assemblages from two tropical high-mountain lakes in central Mexico during the last ∼60 years

Testate amoebae are bioindicators sensitive to environmental change, which show good preservation in sediments of low pH environments, such as high mountain lakes (LAM). The presence and diversity of testate amoebae were documented in surface sediments and sediment cores, dated with Pb-210, from the only 2 LAMs in Mexico (El Sol and La Luna), which have shown signs of recent human-induced changes. A total of 18 taxa were recorded and the main species observed in both lakes were Difflugia glans "glans" and D. globulosa. Specific richness and Shannon's diversity index were higher in Lake El Sol than in the smaller, acidic and ultraoligotrophic Lake La Luna. The sediment cores recorded changes, during the last 20 to 25 years, in the composition of the testate amoebae communities (El Sol) and in their dominance (La Luna), as well as increased accumulation rate and concentrations of iron and organic carbon. These are signs of anthropogenic impact on the lakes, which should alert us to improve protection measures for these unique ecosystems, not only at the local (crater) level, but also with a more regional perspective.