Effect of skyglow on lakes

Artificial light propagating towards the night sky can be scattered back to Earth and reach ecosystems tens to hundreds of kilometres away from the original light source. This phenomenon is known as artificial skyglow, and its consequences on freshwaters are largely unknown. In a large-scale lake enclosure experiment, we found that skyglow at the level of 0.06 and 6 lux increased the abundance of anoxygenic aerobic phototrophs and cyanobacteria by 32 (±22) times. Ecosystem metabolome analysis revealed that skyglow increased the production of algal-derived metabolites which appeared to stimulate heterotrophic activities as well. Furthermore, we found that skyglow decreased the number of bacteria-bacteria interactions. Effects of skyglow were more pronounced at night, suggesting that responses to skyglow can occur on short time scales. Overall, our results call for considering skyglow as a reality of increasing importance for aquatic ecosystems and the global carbon cycle.