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To: Bluedot Living
From: Gail Walker, founder and president of Nantucket Lights
Subject: The Glow Below: How Light Pollution Disrupts Marine Life
Most people think of light pollution as a land-based problem — light shining into bedroom windows, spoiling the view of the stars, causing unsafe glare, and disrupting the natural rhythms of animals that live on land. But artificial light doesn’t stop at the water’s edge, nor does its harm.
Recent studies have found that the man-made light that spills into our oceans and harbors is also affecting the marine ecosystem. From bay scallops and oysters to the whales and striped bass that patrol our coasts, marine life depends on natural darkness in ways we are only beginning to understand.
The Threat to Marine Life
Stated simply, light pollution refers to the unnatural brightening of the night with artificial light. For years, scientists have documented how this disrupts the growth cycles, behavior, and physiology of plants, insects, and animals on land. Now, growing evidence suggests that marine life — from the tiniest zooplankton to the mightiest of whales — can be compromised as well, in large part because the blue and green wavelengths in the LED lights commonly used today penetrate deeper into the ocean than traditional incandescent and halogen lights.
A few examples:
- Artificial light has been found to disrupt spawning behavior of fish and interfere with how they feed and mate. It also makes them more visible to predators, and thus more vulnerable, and causes them to become more — or less — active at night, which can change hunting patterns and interactions among different species.
- Zooplankton, perhaps one of the most important ocean creatures, are also affected. These microscopic organisms, vital to aquatic food chains, normally rise to the surface at night to feed and descend during the day to avoid predators. Artificial light interferes with this rhythm, causing many to stay in deeper, darker water at night. This in turn affects their feeding cycles and could potentially lead to a collapse of fish populations that feed on them.
- It was recently discovered that artificial light at night disrupts oyster behavior and alters the activity of the genes that keep their internal clocks ticking. Even low levels of light were enough to throw off the oysters’ circadian rhythm. While more research into the consequences of this is needed, the worry is that this could make them more susceptible to disease.
In short, there is reason to be concerned about the pervasive artificial light at night near our ocean and harbors.
Keep Nantucket Waters Dark: Principles for Responsible Outdoor Lighting
The artificial light at night that affects the marine life near Nantucket comes from a variety of sources, both on land and on water, most notably building lights, lighthouses, streetlights, marinas and docks, the many boats that are lit up at night, and infrastructure in the ocean, such as the wind turbines. To be sure, some of this light is required for safety, but there are some easy ways to minimize the harm.
- Use light only if there is a clear purpose for it.
- Direct the light so it falls only where it is needed.
- Use the lowest level of light required.
- Use light only when it is needed.
- Use warmer color lights where possible to minimize the amount of blue light.
- If you own property on land, at a minimum please comply with the outdoor lighting bylaw that was adopted in 2023. Free guidance is available at nantucketlights.org.
- If you’re a boat owner, please be especially mindful of lights shining directly into the water, as that is the most harmful of all to marine life. Most importantly, turn them off when not needed.
Nantucket Lights is an all-volunteer 501(c)(3) nonprofit exclusively dedicated to preserving Nantucket’s nighttime environment and heritage of dark skies by raising awareness about light pollution on the island and advocating for environmentally responsible outdoor lighting.
