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Marine biology in the polar night: the dark side of life in the polar seas

Posted on 26. March 2014 by Rolf Stange

As so many other activities in the Arctic, most research activities are very seasonal and largely concentrated in the summer, when working conditions are – well, not easy, but easier than in the polar winter, which brings cold, bad weather and darkness 24 hours a day.

So far it was largely believed that it would somehow be similar with animal life, largely. Of course, polar bears don’t hibernate and reindeer have to look for food 12 months a year, and most animals who can move long distance make sure they spend the winter somewhere more pleasant. But whoever stays, reduces his activity, from movement to metabolism, to a minimum. At least according to common assumptions, largely based on a lack of better knowledge.

Some „light“ has now been shed into this darkness during a research expedition of the Norwegian vessel Helmer Hanssen (formerly known as the Jan Mayen), just a few weeks ago in Kongsfjord. The idea was to make observations and collect data to verify or correct those old assumptions.

In times of a normal day-night-cycle, plankton will move towards the surface to feed during darkness and back into lower, darker water layers at daytime to keep away from predators. This regular movement between food-rich surface waters and the darkness of the deep is the biggest natural movement of biomass on Earth. One of the research questions is if a similar movement is still taking place in times of 24 hour darkness. Even if it will take time for data to be analysed and results to be published, it is already now clear that there is much more activity in the water, including movement, than believed so far.

Predatory fish species are appearently able to find food to a higher degree than assumed. This is one result of analysis of stomach content of fish caught during the expedition with Helmer Hanssen. Fish had prey in their stomach which requires at least a minimum of visual perception to be caught. This indicates that these fish have some kind of night vision, at least to some degree. Eyes of such fish will now be analysed to find out how this might work.

Quite heavy equipment was used for oceanographic work including the movement of organisms in the water column. As a first result, the assumption that arctic fjords are a sleepy place in the polar night can safely be put aside. It is already clear that marine biologists who don’t mind cold and darkness will have a lot of work to do in the years to come.

Similar investigations in the Antarctic have already shown that there is much more activity during the polar night in the south polar sea, too.

Another important research field is the question of the reaction of marine organisms to environmental changes, ranging from low concentrations of oil in the water to climate change which will reduce the ice cover in space, thickness and time and bring higher water temperatures. These questions will involve a lot of laboratory work on fish and plankton caught alive during months and years to come.

The work on Helmer Hanssen in Kongsfjord was coordinated by Norwegian scientists, but involved international researchers. Marine biologists and specialists from all over the world are looking forward to the results.

Quite mysterious already at daylight: arctic plankton..

Source: Svalbardposten

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