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Billions of sea creatures were easily fooled

Professor Jørgen Berge with one of the four sonars, measuring activity in the sea the days before and after the solar eclipse. FOTO: Eirik Palm

Billions of sea creatures were easily fooled

Jørgen Berge couldn't let the opportunity go by: What happens in the ocean when it suddenly gets dark? Now he knows the answer.

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28.03.2015 kl 18:58

"It would simply be a crime to let this chance go by," said the professor from The University Centre in Svalbard and The Arctic University of Norway.


Light or clock?
At 11 a.m. Wednesday he took a UNIS boat out into the ice-cold Adventfjorden. On board with him was technical equipment worth a million kroner. Four sonar (echo-sounding) instruments were lowered into the water and their positions plotted via GPS. Twenty meters below sea level the instruments hung between surface buoys and anchors on the seabed. The sonar data will help record the activity of microorganisms before, during and after the total solar eclipse.

Thus, Berge returned home looking forward to the eclipse.

Participating in the project is Colin Griffiths, a doctor and technical oceanographer from the Scottish Association for Marine Science. The two have long researched underwater activity during the polar night. The results show the small marine organisms swim up into the water column when it gets dark in what is the largest synchronized movement of biomass on Earth.

But are they exclusively governed by light, or do they have a built-in biological clock?

"The background is knowledge of animal behavior during eclipses," Berge said. "The birds stop, among other things, singing and it gets quiet when the sun disappears. Our hypothesis is that the opposite happens in the ocean. Then zooplankton begins to come to life and increase their activity."

"And the setting is quite exceptional," he added, noting the March 20 date of the eclipse "It is the spring equinox, and the greatest difference of night and day."


Questions about insight
However, Adventfjorden became colder and icier during the subsequent days, making it impossible to get out using the small boat at UNIS' disposal. But the Norwegian Coast Guard vessel Svalbard docked in Longyearbyen during the weekend in-between two cruises, and the vessel was made available made to the researcher and Arctic Biology students the Saturday after the eclipse.

"The idea was that (the instruments) would remain until Monday, but because of ice in the fjord, and because the K/V Svalbard is here and has the opportunity to go out with us, we are going today," the professor said.

Once the Svalbard reached the fjord, a skiff with the researchers was lowered while the students observed from the coast guard vessel's helipad. In addition to watching the scientists work, the students collected online test data from the water column for further study.

Out on the bay, the sonar instruments were brought up as their connections to the seafloor were severed electronically, causing them to immediate surface. Berge and Griffiths tugged, dragged and finally brought the instruments safely aboard.
What's the point of knowing the data they contain?

"This is basic research in itself, the understanding of how nature works," Berge said. "Then there is the Arctic during warming periods and decreases in ice. The light will increase and there will be greater intensity in the water column. The fact that the organisms that move up and down in the water column, meaning animals that find their food there must look elsewhere. It is a fundamental question about insight into how this works."


Anarchy
It all started with a project about the daily movements of microorganisms during the International Polar Year in 2007. At that time they became aware the movement, or migration, occurs throughout the polar night. From 2011, they received support from The Research Council of Norway, which is when the work investigating the interaction between light and dark, and the microorganisms' movements up and down in the water column, began in earnest.

When it is dark they swim up the water column to find sustenance, but what about when the polar night is over and there is daylight all day, as happens in April?

"Then there is anarchy," Berge said. Quite simply. There is no pattern."

When a difference between night and day happens, however, there are more organized forms. The sonar equipment the researchers have deployed has four frequencies. The various organisms have specific signatures, therefore giving Berge and Griffiths the ability to measure activity before, during and after the eclipse – and determine which marine animals are moving.

"I hope we get to see that not all of them are starting to move up in the water column, but that some of them react," the professor said.

What if nothing happens?

"Then it just means that the organisms are not so controlled by light," Berge said

What does he think is most likely?

"I think it is most likely that most organisms will move from 11 to 11:30 a.m.," Berge said.

"It is a wonderful opportunity to do something and it will be tremendously exciting to look at the data."


Swallowing the bait

On Tuesday morning, an e-mail arrived with a picture from a sonar instrument. "The pattern looks perhaps a bit unclear but, now that push comes to shove, this is a fantastic result that we are going to analyze further during the next few months."

The picture shows it is becoming considerably greener further up the image during the period the solar eclipse is in progress. Exactly at the moments of totality, the fluctuations disappear on the seabed. Those are the small marine animals, causing the scientists much excitement.

"There are fewer animals staying down," Berge said.

So they responded to the eclipse?

"Absolutely," he said. "Without a doubt. Looking to the upper 20 meters we have a light green ribbon that goes upward. These are animals that are responding to the lack of light and migrating upwards."

Is that the result he hoped for?

"Yes, absolutely," Berge said. "It was maybe a little difficult to read the bands that were migrating.

This means the animals are reacting to light and apparently do not have a biological clock. Now the task of collating the data begins.

"It gives us accurate and new information about how marine organisms respond to light and how they migrate in the water, which we can use when we need to predict how they will behave when the ice disappears," Berge said.

Once the solar eclipse was over, the mammals returned to the seabed. Billions of tiny sea creatures in Isfjorden, in other words, swallowed the bait on Friday, March 20.

Translated by Mark Sabbatini

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Se bildet større

Transcript from the sonar showing the small creatures, such as plankton, started migrating upwards during the solar eclipse. FOTO: Norwegian Polar Institute

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