ABSTRACT This research assessed the environmental changes occurring in two alpine lakes in Mexico, namely Lake El Sol and Lake La Luna. The investigation was based on the analysis of lakes sediment composition, organic matter content, algae predominance, levels of heavy metals and assessment of environmental risks. Sediment composition analysis revealed angular form as a primary particle, increase in the concentration of gravel particles, and decrease of the concentration of silt and sand particles. The dry season and central areas of the lakes showed the highest concentration of organic carbon (<12%). In addition, Lake El Sol showed the largest alterations in algae predominance, resulting from eutrophication changes. The concentration of Pb, Cd and Ni in sediments and algae was variable. The largest contribution was observed in algae from Lake La Luna; however, sediments from Lake El Sol showed the highest concentration of Pb with the maximum affectation in dry and wet seasons. The ecological risks posed by heavy metals indicated intermittent effects of Pb and Cd on organisms, and minor impacts of Ni. The data will be important in assessing the changes observed in Lakes El Sol and La Luna, in establishing future monitoring practices, and in implementing conservation strategies for ecosystems.
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