Quantcast
Environmental News for a Healthier Planet and Life

Losing Nemo? Nighttime Light Pollution Can Stop Clownfish From Hatching, Study Shows

Oceans
Losing Nemo? Nighttime Light Pollution Can Stop Clownfish From Hatching, Study Shows
alexmerwin13 / Flickr / CC BY-NC-ND 2.0

Light pollution is increasing near coral reefs as coastal developments expand. Some bungalows are even built above the reef with clear floors, so that tourists can watch the fish at night. But that means the fish can see the light from the bungalows, too.


A group of Australian researchers set out to investigate how that light might impact one of reef's most iconic residents: the clownfish. Their results were dramatic: When clownfish eggs were exposed to artificial light at night (ALAN), not a single one hatched.

"The overwhelming finding is that artificial light pollution can have a devastating effect on reproductive success of coral reef fish," lead study author and Flinders University Research Associate Dr. Emily Fobert said in an email to EcoWatch.

The results, published in Biology Letters Wednesday, show that the fish are very sensitive to even low levels of artificial light.

"When ALAN is present, no eggs hatched but when the light was removed during the recovery period, eggs from the ALAN exposure hatched like normal, so the presence of light is clearly interfering with an environmental cue that initiates hatching in clownfish," Fobert said.

To achieve their results, Fobert and her team examined 10 pairs of common clownfish (Amphiprion ocellaris) in a lab, as National Geographic explained. Each pair had its own tank. Half of the tanks were lit like a natural coral reef: light for 12 hours and dark for 12 hours. The other half were exposed to nighttime light levels similar to those a typical coastal town would emit. The researchers then studied the fish for 60 days to determine how the differing light levels impacted spawning, egg fertilization and egg hatching. They found no change to spawning or fertilization, but a surprisingly extreme change to hatching.

"I wasn't expecting the result [in the paper] to be that nothing hatched," Thomas Davies, a Bangor University in Wales conservation ecologist, told National Geographic. "It's quite worrying … a really big result that speaks to how light pollution can have a really big impact on marine species."

Clownfish are so sensitive to light because they spawn around the full moon and their eggs typically hatch after sunset, according to a Flinders University press release. The nighttime hatching likely keeps the new babies safe from predators, National Geographic explained.

"These findings likely extend to other reef fish as many share similar reproductive behaviors, including the timing of hatching during early evening," Fobert said in the release.

Davies thought the study's implications for clownfish could be severe.

"Zero percent hatching is essentially no recruiting to the next generation and could cause extinction in a species. It's quite profound," he told National Geographic.

The paper authors wrote that more work needed to be done to see how light levels might impact clownfish in the wild, but ALAN is a growing concern. A 2017 study found that the earth area lit by artificial light at night grew by around 2 percent per year from 2012 to 2016.

Senior author, founder of the conservation group Saving Nemo and Flinders Prof. Karen Burke da Silva explained that the clownfish study began to fill an important knowledge gap.

"Artificial light at night is becoming a greater concern among ecologists, as light is spreading globally, and the impacts on organisms can be severe, but very little research has been done around ALAN in the marine environment," she said in the press release.

Correction: A previous version of this article said that 10 clownfish were used in the experiment. It has been corrected to reflect the fact that 10 pairs were used.

David Attenborough narrates "The Year Earth Changed," premiering globally April 16 on Apple TV+. Apple

Next week marks the second Earth Day of the coronavirus pandemic. While a year of lockdowns and travel restrictions has limited our ability to explore the natural world and gather with others for its defense, it is still possible to experience the wonder and inspiration from the safety of your home.

Read More Show Less
EcoWatch Daily Newsletter

By Michael Svoboda

For April's bookshelf we take a cue from Earth Day and step back to look at the bigger picture. It wasn't climate change that motivated people to attend the teach-ins and protests that marked that first observance in 1970; it was pollution, the destruction of wild lands and habitats, and the consequent deaths of species.

Read More Show Less
Trending
An Amazon.com Inc. worker walks past a row of vans outside a distribution facility on Feb. 2, 2021 in Hawthorne, California. PATRICK T. FALLON / AFP via Getty Images

Over the past year, Amazon has significantly expanded its warehouses in Southern California, employing residents in communities that have suffered from high unemployment rates, The Guardian reports. But a new report shows the negative environmental impacts of the boom, highlighting its impact on low-income communities of color across Southern California.

Read More Show Less
Xiulin Ruan, a Purdue University professor of mechanical engineering, holds up his lab's sample of the whitest paint on record. Purdue University / Jared Pike

Scientists at the University of Purdue have developed the whitest and coolest paint on record.

Read More Show Less

Less than three years after California governor Jerry Brown said the state would launch "our own damn satellite" to track pollution in the face of the Trump administration's climate denial, California, NASA, and a constellation of private companies, nonprofits, and foundations are teaming up to do just that.

Read More Show Less