Artificial light at night, an unsuspected source of pollution for corals

The natural illumination at night is derived from the moon and the stars. This natural light is important for the reefs, in particular for corals, which, for example, synchronize their spawning with the moonlight. However, over the past decades, in many coastal areas, these natural light levels have been significantly altered by anthropogenic light sources emitted by over-lit cities. Coastal habitats have become some of the most vulnerable habitats to light pollution, including coral reef systems in strongly urbanized locations. Therefore, Artificial Light at Night (ALAN) has become acknowledged as a crucial factor altering the structure and functioning of marine ecosystems in ways that urgently need to be explored.

The Ecophysiology team from Centre Scientifique de Monaco and researchers from Bar-Ilan University, Israel, chose two scleractinian corals species representative of the Red Sea, Stylophora pistillata and Turbinaria reniformis, to further investigate the effects of ALAN on a set of relevant physiological (symbionts and chlorophyll content, photosynthesis, respiration, corals pigment profile and skeletal growth) and biochemical (reactive oxygen species production, antioxidant capacity and lipid damage) parameters. At CSM, they exposed corals for 8 weeks to LED lights at an intensity level mimicking ALAN levels received by some of the most light polluted reefs   

Findings from the present study have been published in the Journal Environmental Pollution, and show that light at nighttime impacts the photosynthesis of the algae living in symbiosis with the corals. After few weeks, corals bleach (loss of symbionts). The intensity of bleaching is linked to the severity of the oxidative stress condition faced by the different species. The finding of this work further our knowledge on the threats faced by scleractinian coral species with ALAN, and on the measures to be applied to reduce this source of pollution.

• Levy, O., de Barros Marangoni, L. F., Cohen, J. I., Rottier, C., Béraud, E., Grover, R., & Ferrier-Pagès, C. (2020). Artificial light at night (ALAN) alters the physiology and biochemistry of symbiotic reef building corals. Environmental Pollution, 114987.

For more information, please contact: 

• Dr Laura Marangoni
• Dr Christine Ferrier-Pagès