Artificial light can disturb resting fish and attract predators, altering the dynamics of coral reef communities during the night, based on new findings from innovative underwater infrared cameras.
Artificial light can disturb resting fish and attract predators, altering the dynamics of coral reef communities during the night, based on new findings from innovative underwater infrared cameras.
This research, which has been published today in Global Change Biology, was carried out by an international group of scientists from the UK, France, French Polynesia, and Chile. It represents the first large-scale investigation into how light pollution affects coral reef nightlife.
Dr. Emma Weschke, the lead author from the University of Bristol’s School of Biological Sciences, commented, “When night falls, coral reefs experience a significant change. The colorful fish visible during the day retreat to rest among the corals while shy nocturnal species come out from their hiding spots to hunt for food.”
Senior author, Professor Andy Radford, also from Bristol, noted, “Nighttime typically offers a cloak of darkness that allows marine life to evade night-time predators. However, artificial light created by human activities reveals coral reef residents to unforeseen threats.”
The researchers utilized specially designed underwater infrared cameras to observe the reef at night without affecting the behavior of the fish, as they cannot perceive infrared light.
The study found that more fish species were present on reefs illuminated by artificial light at night compared to unlit control sites. Further analysis identified these as predatory fish feeding on zooplankton, small fish, and invertebrates.
Dr. Weschke noted, “Many species found on these illuminated reefs were actually not nocturnal. Instead, they are usually active during the day. This discovery that light pollution might keep fish awake longer than normal is alarming since sleep is crucial for energy regeneration and overall health, just like it is for us.”
Professor Radford elaborated, “Artificial lighting significantly simplifies the task for predators to find and catch their prey, making their foraging efforts less demanding. This likely explains the increased numbers of predators drawn to artificially lit coral reefs at night.”
Changes in the reef’s nighttime ecosystem were recorded after an average of 25 nights of exposure to artificial lighting, while only a few nights of exposure resulted in no significant change in fish communities compared to control areas.
“This is encouraging news as it indicates that there may be cost-effective solutions that can be quickly applied,” said co-author Professor Steve Simpson, also from Bristol’s School of Biological Sciences. “Reducing the impact of artificial light could help enhance the resilience of vital coral reefs.”
Dr. Weschke added, “Unlike greenhouse gases and plastics, artificial light is a pollutant that does not leave a lasting mark when turned off.”
“By limiting the intensity and duration of artificial lighting, focusing it on essential needs, and reducing its aesthetic use, we can help restore the naturally dark nights that marine ecosystems have evolved alongside.”
This research was carried out by scientists from the University of Bristol, UK, the Centre de Recherches Insulaires et Observatoire de l’Environnement (CRIOBE) in French Polynesia, and the Pontificia Universidad Católica de Chile.
