Light pollution threatens coastal marine systems

A new study suggests light pollution’s effects on coastal marine ecosystems are negatively impacting everything from whales and fish to coral and plankton.

The paper identifies key gaps in knowledge in the study of marine light pollution ecology and recommends research and management for future study.

“Sea creatures have evolved over millions of years to adapt to natural light intensity and patterns,” said lead author Colleen Miller, Ph.D. ’23, who did the research while a doctoral student affiliated with the Cornell Lab of Ornithology. “But now they face an ever-increasing flood of light from human development along the coasts and, except for a few case studies, we have a limited understanding about how it affects many species and entire ecosystems.”

The new research on marine light pollution science, “A Synthesis of the Risks of Marine Light Pollution across Organismal and Ecological Scales,” published Sept. 5 in Aquatic Conservation: Marine and Freshwater Ecosystems.

Moonlight and starlight serve as important cues for marine organisms, and their glow can easily be overwhelmed by artificial light. Studies on marine light pollution found shifts in hormonal cycles, interspecies behavior and reproduction. One classic example is the sea turtle.

“Artificial light at night is harmful to sea turtles in two ways, ” Miller said. “Females trying to find a quiet dark spot to lay their eggs avoid light and may end up not coming ashore at all. Hatchlings head toward inland lights instead of moonlight on the water and then die of dehydration or starvation.”

The widespread use of LED lighting is exacerbating the problem. LEDs typically produce light with shorter wavelengths than older technologies and penetrate deeper into the water.

The good news is that land-based Lights Out efforts – local, state and regional campaigns to darken skies to help migrating birds that are drawn to light at night – will also benefit marine systems near coastal cities. Using as much red light as possible is another option, because it doesn’t penetrate as far into the water. It’s even possible to put up barriers that would shield the coastline from artificial light.

“We also need to look at artificial light at night on a broader scale,” Miller said. “We need much more data from a larger geographic area and over a broader range of organisms. We should be urgently concerned about how artificial light at night is affecting marine ecosystems.”

Pat Leonard is writer for the Cornell Lab of Ornithology.

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