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Daily Archives: 26. March 2014 − News & Stories

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

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..

arctic plankton

Source: Sval­bard­pos­ten


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