Today’s Image of the Day from NASA Earth Observatory features a blue-green algae bloom on Lake Villarrica in Chile. The image was captured on May 2, 2023 by the Operational Land Imager (OLI) on the Landsat 8 satellite.
According to NASA, ground-based observations and satellite images suggest that cyanobacteria make up the colorful swirls.
“Lake Villarrica, which sits downslope of the volcano of the same name, attracts visitors with its scenic beaches and recreational opportunities. The lake is flanked by small cities and resort areas on its southern shore, with agricultural areas further afield,” says NASA.
“Runoff from development and agriculture carries nutrients such as nitrogen and phosphorous into the lake. When populations of microscopic cyanobacteria spike in response, the blooms often show up in satellite images.”
Lien Rodríguez-López is a researcher at San Sebastián University who studies Chilean lakes using remote sensing. She noted that blooms in freshwater lakes are occurring more and more frequently.
In a recent study, Rodríguez-López analyzed Landsat 8 images to estimate the amount of chlorophyll-a in Lake Villarrica from 2014 to 2021. Chlorophyll-a is the primary type of chlorophyll found in algae.
Levels of chlorophyll-a were found to be highest near the cities of Villarrica and Pucón. As a result, Rodríguez-López determined that runoff from urban pollution is the greatest source of nutrients for algae blooms in Lake Villarrica.
According to Rodríguez-López, the urban pollution is significant enough that the lake is transitioning from an oligotrophic state, with low nutrient levels and high clarity, to a mesotrophic one, with intermediate nutrient and biological-productivity levels.
Furthermore, a warming trend in Lake Villarrica and other Chilean mountain lakes has increased the potential for toxic cyanobacterial blooms in recent years.
Image Credit: NASA Earth Observatory
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