of Lake Poopó. The lake body is situated on top of Cenozoic deposits, consisting mainly of unconsolidated material. These sediments are the remains of extensive prehistoric lakes, which covered the Altiplano during at least five glaciation periods. Mining and heavy metals There is a long tradition of mining in the Poopó Basin. Extraction of metals was ordered in the 13th century to support the Inca army. After Spanish colonization in the 16th century, the mining operations increased in scale. At this point the region became known as one of the mining centres of Bolivia. The mining districts are situated at the foothills of the Cordillera Oriental along the eastern border of the Poopó basin. The most important minerals to the economy are silver and tin. Studies have shown elevated concentrations of heavy metals in surface and ground waters of the Poopó basin. These metals are naturally present in the bedrock, from which they are released through weathering processes. The mining activities in the area further contributes to the heavy metal pollution. Acid leaching from mines and mechanical processing of ore speed up the process. The major part of the heavy metals transported to Lake Poopó seem to be immobilized in the bottom sediments. But concentrations of arsenic, lead, and cadmium in the lake water exceed Bolivian and World Health Organization guideline values for drinking water. Flora and fauna There are only three fish species in the system: the native pupfish Orestias agassizii and catfish Trichomycterus rivulatus, and the introduced silverside Odontesthes bonariensis. The lake had a relatively large fish population, but by 2017 pollution and the near-complete reduction of water had all but decimated the locally important fishing industry. The aquatic bird life was very diverse, with a total of 34 species. Most famous are the three species of flamingo (Andean, James's and Chilean), which mainly lived in the shallow lagoons in the northern and eastern parts of the lake. An inventory of the bird population, made in 2000 in cooperation with BirdLife International, identified 6 threatened species and others that are near-threatened. Among these are the Andean flamingo and the Andean condor. A total of 17 higher plants and 3 species of algae were identified in and around Lake Poopó. Due to the constant drought and flooding, the littoral zone experiences great disturbances. As a result, there was hardly any vegetation to be found on the shores of the