Disasters At Sea: The Consequences of Light Pollution

Introduction

The invention of the light bulb brought massive changes to society. Suddenly, we were no longer inhibited by the hours of daylight or seasonal darkness. Building lights and giant screens made cities become beacons of light. Today, lights from cars, towns, and billboards block out the darkness for miles and even outshine the stars at midnight. However transformational people thought the lightbulb would be, it is unlikely they realized the effect it would have beyond our city limits, even far out at sea. How could these sources of light disturb nature anyway? In this article, we’ll explain what light pollution is exactly, how it affects marine life, and what can be done to redress the disaster. 

The Disaster: Light Pollution

Artificial light at night (ALAN) is a widespread pollution occurring all around the world. Studies show that 22% of the world’s coastal waters are exposed to ALAN – an area equivalent to roughly half the size of China. This light pollution has many sources from cities to offshore oil rigs to seafaring vessels. 

22% of the world’s coastal waters are exposed to artificial light at night (ALAN). Photo credit: Smooth Water/Flickr.

The strongest effects are felt within the first 100 meters of shoreline but light pollution can in some cases reach far beyond this, even miles offshore, particularly on cloudy days or in areas where the water is especially clear. While natural light typically fades rapidly through the water column, ALAN (particularly blue-light) can reach much deeper, up to 40 meters down. Therefore, not only is ALAN creating light at abnormal times, but also in abnormal spaces, brightening otherwise dark hours and places. 

Additionally, while natural light gradually increases and fades with sunrises, sunsets, and weather patterns, artificial light can instead switch on and off abruptly. Marine organisms have adapted to the patterns and intensities of natural light, basing their behavior and lifecycles on it. The introduction of artificial light pollution therefore has major implications for many ocean animals. 

Impacts

The prevalence of ALAN around the globe has significant effects on the marine life it shines on, affecting animal behaviors by disrupting lifestyle habits. This is because many marine species use natural light as cues and/or guides. 

Light is often used for navigation. The marine animal most strongly affected by light pollution is the sea turtle, which uses moonlight to navigate after hatching. Sea turtle eggs are laid on dark, sandy beaches. Once hatched, the baby sea turtles find their way to the open sea using the reflection of moonlight on the water as their guide. With ALAN however, sea turtles are guided away from the water. Bright city lights confuse the hatchlings and lead them to their death. With so much coastal development, it has become harder and harder for sea turtles to find suitable natural beaches for their nests. Seabirds also use natural light to guide their flights, and can become lost by artificial lighting. This may lead them to fly into buildings or boats. 

Sea turtles use moonlight to navigate from their nests to the ocean. ALAN draws them away from the water, often resulting in death. Photo credit: Blair Witherington / Dark Sky

For some animals, lighting plays a role in their reproduction. Coral reef reproduction follows the light cycle of the moon and can also be disrupted by artificial light. Corals release their sperm and eggs based on the moon cycle, which ensures synchronized spawning. When artificial light outshines moonlight, the release of coral gametes can be delayed or unsynchronized, significantly decreasing reproductive success. 

Several marine species use natural light cues for sleeping and eating, with ALAN disturbing these activities along with their associated cycles. One study showed that clownfish exposed to artificial light had shorter lifespans (44% lower survival rate) and grew smaller than clownfish living in natural light conditions. Clownfish rely on anemones and coral reef ecosystems, the majority of which are in shallower coastal waters which are more likely to experience ALAN. This makes them particularly vulnerable to light pollution. In another study, sea urchins were found to eat more kelp under ALAN conditions. For penguin colonies, coastal lights interfere with nightly feeding and chick survival as the penguins avoid coming ashore. 

A photograph of a clownfish belonging to the species Amphiprion ocellaris. Due to their preference for shallow coastal waters, clownfish are on the frontlines when it comes to light pollution. According to a study from the University of Melbourne along with Flinders University, it was found that clownfish eggs exposed to light pollution did not hatch at all, resulting in zero survivorship. To read this full study, please visit https://royalsocietypublishing.org/rsbl/article/15/7/20190272/34722/Artificial-light-at-night-causes-reproductive. Credit to photographer Nick Hobgood.

From navigation to reproduction to the daily habits of marine organisms, light pollution greatly disturbs their life, leading to physical harm and even death. Now that we’ve shed some light on the issue, it’s time we take the steps necessary to flip the switch and protect our seas from light pollution. 

Recovery

While it’s not feasible to simply turn off all our city lights, there are many solutions to the problem of light pollution. For example, coastal developments can opt for warm-colored lights to avoid the more intensive blue light that shines deeper in water. They can also shield their lights by directing them away from the ocean. Of course, turning off all unnecessary lights helps even more. 

In some areas, dark sky marine reserves have been proposed to protect ocean life. These areas would have greater restrictions on artificial light at night as a conservation tactic for the species in the area. 

Conclusion

While the lightbulb revolutionized human society, it also led to a major pollution problem for wildlife. From baby sea turtles to migratory birds to coral reefs, marine species around the world are negatively impacted by light pollution. Going forward, implementing lighting restrictions could create a brighter (darker) future for marine life. 

Directories / Sources

Citation No. 1: “Into the blue: Understanding marine light pollution”, Written by Megan Eaves, Published on June 6th, 2025. Published by Dark Sky. Retrieval Date: August 13th, 2026. https://darksky.org/news/into-the-blue-understanding-marine-light-pollution/ 

Citation No. 2: “Bathed in a Sea of Artificial Light”, Written by Unknown, Published on March 2nd, 2022. Published by NASA. Retrieval Date: August 13th, 2026. https://science.nasa.gov/earth/earth-observatory/bathed-in-a-sea-of-artificial-light-149518/ 

Citation No. 3: “From the beach to the seafloor, light pollution interferes with marine life”, Written by Natasha Chortos, Published on June 8th, 2024. Published by Dark Sky. Retrieval Date: August 14th, 2026.

https://darksky.org/news/from-the-beach-to-the-seafloor-light-pollution-interferes-with-marine-life/ 

Citation No. 4: “Light pollution at night severely disrupts the reproductive cycle of corals”, Written by Bar-Ilan University, Published on November 8th, 2020. Published by Science Direct. Retrieval Date: August 14th, 2026. https://www.sciencedaily.com/releases/2020/11/201105113014.htm