Artificial Light Pollution: A Growing Threat to Marine Life and Coastal Ecosystems

artificial light pollution marine life

Artificial light shining from coastlines around the world is posing a significant threat to young fish, who are drawn to the light and then eaten by predators attracted by the brightness, according to a recent study. The study, conducted by Jules Schligler at the international coral ecosystem research center in Mo’orea, French Polynesia, highlights the detrimental effects of light pollution on marine ecosystems.

While the harmful impact of light pollution on people’s ability to see the night sky and on migrating birds, insects, and other animals is well-known, its effects on marine life have been less studied. Schligler’s research sheds light on this overlooked issue, revealing that nearly a quarter of the world’s coastline is artificially lit, and this number is likely higher now than it was a decade ago.

The study involved creating 12 coral test sites in the waters off Mo’orea and shining an underwater light on half of them. The results were striking: the artificially lit corals attracted two to three times more fish larvae compared to naturally lit control sites. However, this influx of fish larvae also attracted more predators, creating a dangerous environment for the young fish.

“The coral with the [artificial] light is a bad environment for the larval fish because there are more predators, opportunistic fish passing by, that ate them,” Schligler told the Guardian. He emphasized that artificial light should be seen as “another threat to marine animal populations and coastal ecosystems.”

The study did not determine why larval fish are drawn to artificial light, but Schligler suggested two possibilities. The light might attract plankton, which in turn attract the larvae, or both the light and the prospect of food might draw them. Regardless, the light causes all the marine animals to behave unnaturally.

Schligler’s findings, presented at the Society for Experimental Biology conference in Prague, focused on two species – yellowtail dascyllus (Dascyllus flavicaudus) and blue-green chromis (Chromis viridis) – but he believes the implications could be broader. He noted that similar tests on crab and shrimp indicated that marine animals are generally attracted to artificial light.

Oren Levy, head of the laboratory for molecular marine ecology at Israel’s Bar-Ilan University, welcomed the findings. He highlighted that artificial light not only increases the risk of young fish being eaten but also affects their aging and health. Additionally, artificial light harms coral reefs by interfering with reproduction and causing coral collapse.

Both Schligler and Levy stressed that preventing light pollution is not difficult. Using timers and shades can mitigate the impact of artificial light on marine life. “We can start to take light into account for things like marine protected areas,” Schligler suggested, indicating a path forward to protect marine ecosystems from the harmful effects of light pollution.

As coastal development continues, addressing light pollution is crucial to safeguarding marine life and maintaining the health of coastal ecosystems. This study serves as a call to action for policymakers, researchers, and the public to consider the broader ecological impacts of artificial lighting on our oceans.