Arctic animals navigate by light of the winter moon

OBAN, Scotland, Jan. 7 (UPI) -- Not all arctic creatures sleep off the winter. New research suggests tiny marine animals remain active through winter, using the light of the moon to guide their vertical migrations.

Scientists first observed winter nighttime activity in a single frigid fjord. Follow-up research proved the activity wasn't isolated, but was instead indicative of behavior throughout the arctic.

"During the permanently dark and extremely cold Arctic winter, [these] tiny marine creatures, like mythical werewolves, respond to moonlight by undergoing mass migrations," Kim Last, a biologist with the Scottish Association for Marine Science, said in a press release.

Zooplankton were found rising with the daily arc of the moon in fjords, as well as in water atop the continental slope and shelf, and even in the open ocean. In addition to their daily migration, the plankton also responded to the lunar cycle -- sinking lower in the water column every 29.5 days when the full moon rises and light penetrates the deepest.

"The most surprising finding is that these migrations are not rare or isolated to just a few places," Last said. "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."

Because the movements of zooplankton affect ocean carbon cycles -- transporting carbon from the surface to the deep ocean -- researchers say climate and ecological models need to be recalibrated to account for their latest discovery.

Scientists also suspect warming temperatures and melting glaciers will encourage more intense wintertime zooplankton activity, but they'll need to collect data before they know for sure.

The latest findings were published in the journal Current Biology.