when the moon is at its brightest – they start to synchronise with the lunar rhythm.” In very high latitudes in Arctic waters,
the moon has a special cycle during the polar night. During new moon, it orbits below the horizon 24 hours a day, while during the full moon it stays above the horizon. In the phases in between, there is a daily moonset and moonrise.
This,
combined with the lack of sunlight, creates a unique climate of light during the polar night. “What we see happen is that the zooplankton switch from a 24 hour cycle to a 24.8 hour cycle,” says Berge. “During full moon and on a clear night, the entire community will migrate deeper. It shatters the idea that the polar night is an environment entirely bereft of light and activity. The organisms in the water aren’t going into some kind of hibernation as was imagined – they are actively responding to the prevailing light climate.” Although solar illumination is
undetectable to the human eye during the polar night, the data indicates that the Arctic zooplankton are still responding to the variations in low light levels that exist. This means that there exists a whole suite of food-web interactions and ecosystem structural features that have simply been overlooked until now, and so the CircA project is now looking to establish the basic biological foundation behind the behaviours and their wider ecological impacts. Having studied Arctic DVM throughout
the seasons, Berge’s team are now beginning to see that the idea of a huge mass of
zooplankton moving up and down in absolute
synchrony might be
AT A GLANCE an
oversimplification. “What we have noticed is that different species of zooplankton respond to the changing conditions throughout the year in different ways,” he explains. “The group of species that are migrating extensively during the autumn are not the same as the ones migrating during the polar night.
“What we see happen is that the zooplankton switch from a 24 hour cycle to a 24.8 hour cycle”
The team’s findings have sparked interest
in the field and more research is now being done. Berge believes that one of the most important outcomes of his findings could be the implications that they have in the field of environmental management. Increased levels of shipping as well as oil and gas prospecting pose a threat to all Arctic wildlife, but having solid evidence that organisms are actively migrating during the polar night and are present at the surface rather than hibernating in deeper waters shows that any potential oil spill or similar accident could be highly damaging to the local ecosystem.
★ Project Information
Project Title: Circadian rhythms of Arctic zooplankton from polar twilight to polar night – patterns, processes, and ecosystem implications (CircA)
Project Objective: Determine the primary physical and biological factors that are responsible for the diel vertical migration patterns of zooplankton in the high Arctic during the polar night and twilight period, and to elucidate the resultant ecosystem effects.
Project Duration and Timing: 2012-2015
Project Funding: Norwegian Research Council
Project Partners: Norway: UNIS, UiT, APN, NTNU International: SAMS (UK), IOPAS (Poland), Univ of Delaware (USA)
MAIN CONTACT
Jørgen Berge Professor in marine biology at UiT The Arctic University of Norway and adjunct professor at UNIS. Finished PhD in 2000, and have since 2003 been working on Svalbard with marine ecosystems and ecosystem effects of climate change. Since 2012 leading two larger projects aimed at polar night processes
Contact: Tel: +47 90169125 Email:
Jorgen.berge@
uit.no Web:
www.mare-incognitum.no
www.projectsmagazine.eu.com
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