Light pollution is transforming nightlife on coral reefs

In the quiet stillness of the ocean, when the sun dips below the horizon, marine creatures on coral reefs experience a significant shift.

As daytime creatures retreat into the safety of corals, nocturnal predators begin their evening hunt.

This fascinating cycle is as routine as the setting sun – until the intrusion of artificial light disrupts the natural order.

A study on coral reef nightlife

A recent press release revealed the details of an insightful study on the effects of light pollution on coral reef communities.

The research is recognized as the first, large-scale experiment addressing the influence of light pollution on coral reef nightlife.

The study was conducted by researchers from the University of Bristol, the Centre de Recherches Insulaires et Observatoire de l’Environnement (CRIOBE) in French Polynesia, and Chile’s Pontificia Universidad Católica.

Artificial light: A silent intruder

“When the sun sets, coral reefs undergo a dramatic transformation,” noted Dr. Emma Weschke, the study’s lead author from the University of Bristol’s School of Biological Sciences.

The vibrant fish that command our attention during the day retreat to rest among the corals, and elusive nocturnal species emerge from caves and crevices in pursuit of prey.

“The night usually brings a veil of darkness that allows marine life to hide from nocturnal predators. But artificial light generated by human activities exposes coral reef inhabitants to unexpected danger,” explained Professor Andy Radford, the study’s senior author.

The night vision experiment

The team utilized specially designed underwater infrared cameras to observe a coral reef at night.

These cameras allowed the researchers to film the marine ecosystem without altering fish behavior since fish cannot see in the infrared spectrum.

What they discovered was quite alarming. Compared to control sites that lacked artificial light, a larger number of different fish species were present on artificially illuminated reefs at night.

Further investigation revealed these species to be predatory fish feeding on zooplankton, small fish, and invertebrates.

Dangers of light pollution

Dr. Weschke explained that many species detected on artificially lit reefs were not nocturnal. Instead, these fish are usually active during the day.

“Finding that light pollution can cause fish to stay awake later than usual is concerning because sleep – like for us – is likely essential for regenerating energy and maintaining fitness,” said Dr. Weschke.

“Artificial light makes it much easier for predators to locate and capture prey, reducing their foraging effort. Which is why we think that greater numbers are being attracted to artificially illuminated coral reefs at night,” noted Professor Radford.

Reducing the impacts of artificial light

However, the situation isn’t completely bleak. The researchers observed changes in the reef’s nightlife after an average of 25 consecutive nights of being exposed to artificial light.

Brief periods of exposure didn’t cause noticeable changes in fish communities. This suggests that implementing low-cost solutions rapidly could have a positive impact.

“Reducing the impacts of artificial light could help build resilience on valuable coral reefs,” noted study co-author Professor Steve Simpson.

“Unlike greenhouse gases and plastics, artificial light is a pollutant that doesn’t leave a residue when switched off. Limiting artificial light in both its intensity and duration, prioritizing it for essential needs and reducing aesthetic use, will help re-establish naturally dark nights that marine ecosystems evolved with.”

Preserving coral reefs in a brightening world

Coral reefs, often referred to as the “rainforests of the sea,” are among the most diverse and vital ecosystems on the planet.

They support nearly 25% of all marine species, provide coastal protection, and serve as critical sources of food and income for millions of people globally.

However, the increasing intrusion of artificial light adds another stressor to already vulnerable coral reef systems, which are struggling against threats such as climate change, overfishing, and pollution.

Mitigating light pollution is one of the easiest ways to support coral reef health. By prioritizing low-impact lighting technologies and implementing targeted lighting practices near reef habitats, significant strides can be made in preserving these ecosystems.

Reinstating natural light-dark cycles by limiting artificial light exposure provides reefs a better chance to recover and thrive.

As urban expansion and tourism increase near coastal regions, innovative solutions to minimize light pollution are becoming essential to ensure the survival of these ecological treasures.

The full study was published in the journal Global Change Biology.

Image Credit: Emma Weschke

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–