Biology Biotech
Research carried out in the Svalbard archipelago in recent years has shown that ecosystems that were previously thought to lie dormant during the long polar night are actually still very much active during this period. Investigations are now taking place in order to try and characterise exactly what is happening and what the implications of this previously undiscovered activity might be for the Artic ecosystem
Mysteries of the polar night
Diel vertical migration (DVM) has been said to be the largest synchronised movement of biomass on the planet. It is a common feature of all the world’s oceans (and most of the
lakes) in which
zooplankton migrate up to the surface layers of the water to feed under cover of darkness at night, and then return down into the deep to avoid being eaten during the day. This process is, unsurprisingly, regulated
by light. In most parts of the world, the rise and fall of the sun each day mediates DVM. However, a 2009 paper demonstrated that synchronised DVM was occurring in two fjords within the Arctic Circle during the polar night, a time when there is no direct light to control the behaviour. This discovery challenged the long-lasting paradigm of ecosystems at high altitudes becoming dormant during the polar night due to low food availability and lack of light, and prompted the creation of
the
CircA project by the paper’s authors. Professor Jørgen Berge of the University
of Tromsø and leader of CircA explains the objectives of the project: “Our previous results provided strong evidence that zooplankton were carrying out DVM during the polar night,” he says. “We set ourselves
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a few basic questions to build upon what we had found. We wanted to find which species are doing it, why they are doing it, and why it is important for the local ecosystem. We also set ourselves the goal of developing a new set of tools to set these questions into a Pan-Arctic perspective.” The first goal for the team was to confirm
that their original observations were not anomalous. “We have deployed a number of acoustic instruments to try and monitor the potential migration of zooplankton,” says Berge. “We are using ADCPs – acoustic Doppler current profilers – that detect not only the strength of echoes being emitted, but also the Doppler shift.” Doppler shift is the phenomenon in which the frequency of a wave changes for an observer moving relative to the source (commonly experienced as the change in frequency of a siren as an ambulance or police car drives past), and so detecting the changing frequency of the echoes provides crucial
information to Berge about the movement – or migration – of the zooplankton. In order to find out which organisms
actively migrate during the polar night, the team has carried out extensive field campaigns using an array of sampling devices. “When we are sampling the organisms from the fjords, we always note down the prevailing light climate,” says Berge. “One of the most fascinating things we have noticed during this project is the importance of the moon. During the polar night, the zooplankton are no longer on a solar rhythm, and so during full moon –
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