This study conducted in the IGB LakeLab, a unique facility for large-scale experiments on freshwater ecosystems, found that artificial light at night (skyglow) stimulates the growth and metabolic processes of cyanobacteria, also known as blue-green algae, in lakes. The experiment showed that even very low light levels of 0.06 lux, which is typical of urban skyglow, were sufficient to significantly increase the abundance of cyanobacteria and other light-using bacteria, as well as to alter the overall carbon cycling in the lake ecosystem. These findings suggest that light pollution could be a contributing factor to the increasing risk of potentially toxic cyanobacterial blooms in lakes.
Artificial Skyglow and its Effects
- Artificial light that scatters in the atmosphere and brightens the night sky is known as artificial skyglow.
- Skyglow can affect biodiversity and ecosystems over long distances.
- The effects of skyglow on freshwater ecosystems were largely unknown until this study.
Experiment in the IGB LakeLab
- The IGB LakeLab is a unique facility that can be described as a suite of experimental lakes, allowing for large-scale experiments on lake ecosystems.
- In this experiment, 10 out of 15 enclosures were dimly lit at night using a specifically designed lighting system, with illuminance levels ranging from 0.06 lux (typical skyglow) to 6 lux (highest documented skyglow), while 5 control enclosures were left unlit.
Impact on Cyanobacteria and Carbon Cycling
- The abundance of cyanobacteria and other light-using bacteria (anaerobic oxygenic phototrophs) was on average 32 times higher under lit conditions than under dark control conditions.
- Even very low light intensities of 0.06 lux were sufficient to stimulate the growth of cyanobacteria and other phototrophs.
- Skyglow also stimulated the bacterial decomposition of organic matter produced by algae, thus altering the overall carbon cycling in the lake ecosystem.
Implications and Future Directions
- One of the consequences of the dramatic increase in light pollution observed worldwide could be an increasing risk of potentially toxic cyanobacterial blooms.
- Light pollution should be considered as a possible factor in explaining algal blooms that cannot be explained at present.
- Remote sensing methods can be used for early detection of cyanobacterial blooms caused by light pollution.
