Researchers from the Scottish Association for Marine Science have built upon previous findings that Arctic marine creatures in one Arctic fjord stay active during the dark and frigid winter months and discovered that this activity can be applied to the entire Arctic. Furthermore, they also found that the moonlight is what guides the vertical migrations of small marine animals when no sunlight is present. The researchers believe this behavior evolved in zooplankton in order to avoid predators that use the moonlight to aid in their hunting.
"During the permanently dark and extremely cold Arctic winter, [these] tiny marine creatures, like mythical werewolves, respond to moonlight by undergoing mass migrations," said Kim Last, who participated in the research, in a press release.
During the winter period, the researchers found that the marine creatures shift their lunar activities from the standard 24-hour solar cycle to the 24.8-hour lunar day. Furthermore, their vertical migrations take place when the moon is above the horizon and, approximately every 29.5 days, which coincides with the full moon, a mass sinking of zooplankton takes place where they sink to the depths of the waters approximately 50 meters down.
"The most surprising finding is that these migrations are not rare or isolated to just a few places," said Last. "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."
The findings will help scientists better understand the carbon cycle, which plays a huge role in 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," said Last. "Since there is no photosynthesis during the polar night, carbon is only moved into the deep by predators feeding on prey."
The findings were published in the Jan. 7 issue of Current Biology.