In a new study from the University of Melbourne, experts have discovered that young clownfish exposed to artificial light are struggling to survive. The researchers found that juvenile clownfish living closest to shore are dying faster than those located farther offshore.
The scientists also determined that the surviving clownfish living near artificial light developed more slowly than clownfish under natural lighting conditions by 44 percent.
Professor Stephen Swearer said the team exposed 42 clownfish in their host anemones to either artificial light at night (ALAN) or natural light in the lagoon. The clownfish were monitored for over nearly two years.
“The impacts of light pollution found here are probably underestimated and mitigation measures and policy changes are urgently required,” said Professor Swearer.
Study lead author Jules Schligler is an expert at the École Pratique des Hautes Études PSL Université Paris (EPHE) and the Centre of Island Research and Environmental Observatory (CRIOBE). He noted that clownfish can live in shallow coastal waters and are highly sedentary living in anemones, which means they can be easily impacted by night lights from streetlights, piers. or ports.
“As with many other reef fish, clownfish feed, reproduce, defend their territories and interact with other fish during the day and reset whilst sleeping at night. However, 36 per cent of the clownfish exposed to light pollution were more likely to die than fish under natural light cycles,” said Schligler. “Like humans, fish need a period of inactivity, which is crucial for their well-being.”
According to the researchers, even the fish that survived did not entirely escape the effects of artificial light as they grew less than fish from the control group.
“This is the first time that the impacts of ALAN have been tested on a coral reef fish in the wild and over such a long time,” said study co-author Daphne Cortese.
“As 12 percent of all coral reef fish live in close association with another sedentary species, such as a coral or anemone, light pollution could already be having severe negative impacts on a fifth of fringing reef fish populations.”
The experts hope their research will help raise awareness of the impacts of ALAN on coastal marine ecosystems.
“Many marine protected areas are impacted by light pollution at night, and authorities are not taking this pollution into account,” said study co-author Professor Ricardo Beldade of the Pontificia Universidad Católica de Chile. “We hope that policy makers take this threat much more seriously for future management strategies.”
The study is published in the journal Royal Society Proceedings B.