SAMS news room

Into the night with lunartick zooplankton

“But are you sure those blobs are real?” asked Jørgen Berg (project leader of the CIRCA project) after looking quizzically at the coloured data chart lying on the table in front of us.

I fidgeted, the data was showing something that we hadn’t expected during the Polar Night. The “blobs” represented zooplankton that seemed to be migrating in response to moonlight, not sunlight. “Probably,” I replied.

Jorgen paused and in typical Norwegian no-nonsense fashion said, “Well then, let’s go find out”. Little did I know I had inadvertently started a whole field campaign, based on some coloured “blobs”!

For the last few years we have been studying zooplankton migrating up and down in the water in response to sunlight.

Using acoustics, patterns are emerging that show very clear synchronised migrations in the autumn and spring but limited activity during the darkest months of December and January. Now, using new data analysis and visualisation techniques (normally associated with studying biological rhythms in flies, mice and humans) we are seeing patterns in zooplankton migration which are quite new.

During the time of the full moon these small organisms appear to migrate with a new cycle, not the 24 hour cycle of the rising and setting of the sun which we are so familiar with, but one of the rising and setting of the moon, a lunar-day or lunidian cycle close to 25 hours!

The main aim of the field campaign this December is to go “fishing” during the time of the full and new moon with various types of nets and cameras to find out who is doing the migrating. Specifically how deep do they migrate, and how fast, and can they anticipate the rising and setting of the moon? To this end, we also want to know: do zooplankton have a biological clock?

We already know that just about every animal and plant possesses an in-built clock, the best known being the circadian clock. Many of us are even familiar with its workings, or rather when it stops working so well when it becomes re-set during long-haul flights and we experience jet-lag as a consequence. So we can hypothesis that the migrating zooplankton may also have a clock.

Therefore another aim of this trip is to catch some live zooplankton and study them in the lab under constant conditions without moonlight. If they still behave as though they were out in the sea by becoming active when they “think” the moon is up, then we will know that they possess a lunar clock. This would help explain how they manage to migrate to the surface from the dark ocean depths where currently our light sensors cannot detect any light.

Working in the Arctic during the polar night is no mean feat with total darkness 24 hours a day and often the thermometer falls to -20^oC for weeks on end. Although Jørgen is a toughened Polar scientist, I am not, and as I sit here on the flight to Svalbard in December clutching my laptop with the infamous “blobs”, I am experiencing just a little trepidation.

Looking out the window of the plane to the north I can see the night stretching out in front of me, like a big heavy blanket, the last of the sunshine left behind somewhere over mainland Norway. I wonder perhaps whether my own clock may become a little dysfunctional over the next weeks without any form of solar re-setting and I look up and see the moon as only a silver sickle and wonder what is going on down there in the deep dark waters… well, it’s time to find out!

Kim S. Last

Other people involved from SAMS: Finlo Cottier, Collin Griffiths and our student Laura Hobbs

Links:

http://www.mare-incognitum.no/index.php/circa
http://www.sams.ac.uk/finlo-cottier/panarcive
http://www.sams.ac.uk/news-room/new-project-to-investigate-arctic-plankton-dynamics/