Phytoplankton “explosions” are increasingly appearing in oceans, seas, bays, channels and lakes. NASA’s Earth Operational Imager captured this image of a massive algae bloom in Lake Villarrica, Chile, in early May. A sight as beautiful as it is toxic: in the lake you can see swirls of blue and green dancing in the wind. Very suggestive, except that those algae blocks literally pollute and suffocate the aquarium.
Lake Villarrica is located in the Andes mountains at the foot of the volcano of the same name and attracts tourists from all over the world with its panoramic beaches. The basin is surrounded by small towns, resort areas and agricultural areas, from which residues of nitrogen and phosphorus arrive, giving the water a typical blue color. But when the numbers of microscopic cyanobacteria increase in response, algal blooms become very prominent It can be seen from space.
“The freshwater lake thrives a lot,” explains Lien Rodríguez-López of the University of San Sebastián, who studies Chilean lakes using remote sensing and estimated chlorophyll amounts on Lake Villarrica from 2014 to 2021. Lake and chlorophyll a values increased near the shore and near the cities of Villarrica and Pucon, and it was concluded that the most important source of nutrients for these blooms came from urban pollution, although agriculture probably also played a role. Significant enough that the lake transitions from an oligotrophic state, with low nutrient levels and high clarity, to a mesotrophic state, with intermediate levels of nutrients and organic productivity.”
Warm water provides a more hospitable environment for algae. Like many bodies of water around the world, Lake Villarrica has warmed along with the climate. In another study, Rodríguez-López used thermal bands from NASA’s Modis to analyze the surface temperature of Chilean mountain lakes and reported statistically significant warming trends in 12 of the 14 lakes studied, including Villarrica. This trend, he wrote, is “consistent with site observations and an increased frequency of toxic cyanobacteria”.
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