English: A large bloom of cyanobacteria, more commonly known as blue-green algae, spread across the lake in green filaments and strands that are clearly visible in this simulated-natural-colour image. According to local news reports, the nutrients feeding the bloom in Lake Atitlán come from sewage, agricultural run off, and increased run off as a result of deforestation around the lake basin. The image reveals clearly why run-off would end up in the lake. Mountains and volcanoes encircle Lake Atitlán, ensuring that all rain that falls in the basin flows into the bowl-like lake. Silver-gray settlements, another source of pollution, ring the lake. Deforestation is a little bit more difficult to see. The forest is a darker shade of green than agricultural fields. The contrast between forested land and agriculture is most evident on the slopes of the San Pedro Volcano on the south-west shore of the lake. Large pale green squares cut into the dark green crown over the peak of the volcano.