If you’re watching our show, chances are that you’ve looked up a light pollution map at least once or twice. A good dark-sky site can make all the difference when you want to do some nighttime observing, but finding one can be no easy feat! You might think a simple way to escape the glare of city lights would be sailing out on the water some clear evening, but recent research has revealed that we’re making the future – and the oceans – so bright that even phytoplankton want to wear shades.

Light pollution is a major problem for human populations the world over, but we’re beginning to learn that the glow of our cities, towns, and infrastructure even affects life beneath the waves. Factors like the time of year or sedimentary runoff into water sources cause different species of plankton to react to environmental light in different ways. To account for this, researchers focused primarily on copepods — tiny, plentiful shrimp-like plankton that form a significant piece of numerous marine food webs.

Copepods, like many other species of plankton, utilize the light of our day/night cycle to inform their daily journey from the deep to the top of the waves; rising from the ocean floor during the night, then diving to seek safety from surface predators as the Sun begins to light the upper layer of the sea. But the light from human infrastructure is affecting those biological cues, causing a disturbance in copepod behavior across an area of our oceans that is roughly the size of Mexico.

The deeper you dive, the less impact our global brightness appears to have – biologically impactful levels of light pollution begin to level off around 50meters deep – but even at twenty meters down, the affected areas only appear to shrink by about half.

Gaining an understanding of how human light pollution affects marine life is an important step forward on the path to determining our overall impact on the global ecosystem, something this research is well-equipped to help us with.

More Information

Even the sea has light pollution. These new maps show its extent (Science News)

“A global atlas of artificial light at night under the sea,” T. J. Smyth et al., 2021 December 13, Elementa: Science of the Anthropocene