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Environment

Artificial light pollution could fuel growth of toxic algal blooms

The "skyglow" produced when light from cities bounces off clouds can help cyanobacteria and other aquatic microbes grow at night

By James Dinneen

18 April 2025

Cyanobacteria, blooming in Lake Windermere, UK

Cyanobacteria blooming in Lake Windermere, UK

Ashley Cooper pics/Alamy

Communities around the world trying to manage blooms of toxic algae and cyanobacteria already know they have to control nutrient pollution. But now it seems they may have another factor to worry about: too much artificial light.

“You have light pollution in urbanised areas where you may also have a nutrient pollution problem,” says Hans-Peter Grossart at the Leibniz Institute of Freshwater Ecology and Inland Fisheries in Germany. “It could be that the combination of both favours cyanobacteria blooms.”

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