During Arctic Winters, Active Marine Creatures Migrate By Moonlight

Amid frigid-cold temperatures, tiny Arctic marine creatures busy themselves with their daily vertical migrations, relying on the moon's light to guide them.

"During the permanently dark and extremely cold Artic winter, [these] tiny marine creatures, like mythical werewolves, respond to moonlight by undergoing mass migrations," Kim Last, a researchers from the Scottish Association for Marine Science in Scotland, explained in a news release.

In the latest study, researchers explored a variety of marime Arctic habitats – fjord, shelf, slope, and open sea – during winter months and found the same behaviors among all inhabitants: they had shifted their activities from following the 24-hour solar day to following the 24.8-hour lunar day.

During the Arctic winter, zooplankton begin their vertical migrations when the moon rises above the horizon. In addition to this daily cycle, researchers found zooplankton collectively sink to depths of about 50 meters every 29.5 days, coinciding with the full moon cycle. (Scroll to read more...)

"The most surprising finding is that these migrations are not rare or isolated to just a few places," Last added. "The acoustic database used for our analysis cumulatively spans 50 years of data from moorings that cover much of the Arctic Ocean. The occurrences of lunar migrations happen every winter at all sites, even under sea ice with snow cover on top."

Researchers believe their study, recently published in the journal Current Biology, has implications for understanding the carbon cycle, which is particularly relevant in the face of climate change.

"The daily vertical migration of zooplankton contributes significantly to the carbon pump by moving fixed carbon from the surface into the deep ocean," Last explained. "Since there is no photosynthesis during the polar night, carbon is only moved into the deep by predators feeding on prey."

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