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Night on planet Earth is getting brighter as artificial light illuminates more natural spaces. Scientists know a lot about how this messes with ecosystems on land. New research now shows it can disturb the underwater communities around coral reefs as well. here's NPR's Jonathan Lambert.
JONATHAN LAMBERT, BYLINE: For millennia, life on coral reefs, just like everywhere else, could count on one basic rule - it's light during the day and dark at night. This daily rhythm sets the pace of life underwater. But, says biologist Emma Weschke, artificial light disrupts this rhythm for animals just like it would for humans.
EMMA WESCHKE: If we were trying to sleep in a room that was lit, I don't know, by a lot of artificial light outside or someone switching the light on inside all the time, at the least we'd be pretty groggy and frustrated the following day.
LAMBERT: In addition to keeping animals up, scientists know that light pollution can confuse critters, disrupt migration and flip food webs by changing which species are active. Most of these studies are on land, but light reaches coastal waters, too, brightening an estimated 15% of coral reefs worldwide.
WESCHKE: There has actually not been any study so far that's actually looking at what biological implications artificial light might be having on coral reef ecosystems.
LAMBERT: To find out, University of Bristol's Weschke and her colleagues literally shone a light on this research gap, exposing normally dark reefs in French Polynesia to bright lights and watching how the community changed using infrared cameras. After a few weeks...
WESCHKE: What we found was actually an increase in the number of species by 103%. So that's double the number of species that are active in the illuminated area.
LAMBERT: They found that the light attracted some species that aren't normally found on the reef. They also found lots of daytime fish that should be asleep were out foraging. Perhaps most importantly, the number of predators spiked. That concerns University of Minnesota biologist Colleen Miller.
COLLEEN MILLER: If there's a lot of predators coming in but not necessarily changes in other functional groups, like herbivores or scavengers or something, then that's a real shift in the balance of the community. It could be - but we don't know - massively impactful for that ecosystem.
LAMBERT: Those impacts could be major, Weschke says, because it's forcing daytime and nocturnal species to interact instead of passing like ships in the night.
WESCHKE: That can have consequences for competition for food, for space. Essentially, you know, it's turning the place into a bit of a nightclub.
LAMBERT: It's unclear what the long-term consequences of this new nightclub might be. But the study, published in the journal Global Change Biology, did find some hopeful results. Just a few nights of light pollution didn't seem to faze the community much. That suggests that simple actions, like using motion detectors or just turning off lights that are only for show, can really help.
WESCHKE: All of these things can really just provide the reef that respite from so much brightness.
LAMBERT: Addressing light pollution is a lot simpler than, say, curbing climate change, Weschke says, because a mere flick of a switch brings instantaneous relief to tired critters.
Jonathan Lambert, NPR News.
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